Fix SQLite query compatibility inside WITH clause

Rename model methods to #succeeding.

.gitignore

@@ -15,6 +15,9 @@
 /config/master.key
 /config/puma.rb
 
+# Ignore test database.
+/db/test.sqlite3
+
 # Ignore all logfiles and tempfiles.
 /log/*
 /tmp/*
@@ -30,7 +33,7 @@
 
 /tmp/restart.txt
 
-# Ignore user files
+# Ignore user files.
 /.bash_history
 /.byebug_history
 /.config
@@ -38,6 +41,7 @@
 /.lesshst
 /.local
 /.mysql_history
+/.sqlite_history
 /.ssh
 /.vim
 /.viminfo

DESIGN.md

@@ -0,0 +1,76 @@
+DESIGN
+======
+
+Below is a list of design decisions. The justification is to be consulted
+whenever a change is considered, to avoid regressions.
+
+### Data type for DB storage of numeric values (`decimal` vs `float`)
+
+* among database engines supported (by Rails), SQLite offers storage of
+  `decimal` data type with the lowest precision, equal to the precision of
+  `REAL` type (double precision float value, IEEE 754), but in a floating point
+  format,
+    * decimal types in other database engines offer greater precision, but store
+      data in a fixed point format,
+* biology-related values differ by several orders of magnitude; storing them in
+  fixed point format would only make sense if required precision would be
+  greater than that offered by floating point format,
+    * even then, fixed point would mean either bigger memory requirements or
+      worse precision for numbers close to scale limit,
+        * for a fixed point format to use the same 8 bytes of storage as IEEE
+          754, precision would need to be limited to 18 digits (4 bytes/9 digits)
+          and scale approximately half of that - 9,
+    * double precision floating point guarantees 15 digits of precision, which
+      is more than enough for all expected use cases,
+        * if a decimal string with at most 15 significant digits is converted to
+          the IEEE 754 double-precision format, giving a normal number, and then
+          converted back to a decimal string with the same number of digits, the
+          final result should match the original string,
+        * if an IEEE 754 double-precision number is converted to a decimal
+          string with at least 17 significant digits, and then converted back to
+          double-precision representation, the final result must match the
+          original number,
+        * single precision floating point only guarntees 6 digits of precision,
+          which is estimated to be too low for some use cases (e.g. storing
+          latitude/longitude with a resolution grater than 100m),
+* double precision floating point (IEEE 754) is a standard that ensures
+  compatibility with majority of database engines,
+    * the same data format is used internally by Ruby as a `Float`; it
+      guarantees no conversions between storage and computation,
+    * as a standard with hardware implementations ensures both: computing
+      efficiency and hardware/3rd party library compatibility as opposed to Ruby
+      custom `BigDecimal` type,
+    * at present, only normalized numbers are used and considered sufficient, in
+      order to avoid potential issues with the cross-platform compatibility of
+      subnormal (denormal) numbers,
+* in the future, the IEEE 754 decimal64 data type may be considered once it is
+  supported by database engines.
+
+### Database layer vs application layer data model constraints
+
+* database constraints are the final guard against data integrity corruption,
+    * they should safeguard against data referential integrity loss under _all_
+      data (not schema) manipulation scenarios, including application level
+      logic errors and direct data manipulation (e.g. through `dbconsole`),
+* application constraints can be as restrictive as database constraints or more,
+  but not less, as it doesn't serve any use case,
+    * proper application level constraints should prevent unhandled database
+      exception occurences, e.g `ActiveRecord::InvalidForeignKey` for operations
+      performed through Models (i.e. not `#delete_all` etc.)
+
+### User interface
+* values provided by user have to be exactly preserved, avoiding any precision
+  loss due to e.g. type casting
+    * when it's not possible to store value without information loss, feedback has to
+      be given at the time of entering value
+    * values can be received using either:
+        * `input[number]` - validates: number format, value against `[min]` and
+          `[max]` attributes; cannot validate precision (no `[pattern]` support);
+          or
+        * `input[text]` - can validate number format and precision with
+          `[pattern]`; cannot validate range (no `[min]`/`[max]` support),
+        * none of the above prevents misinterpretation of values between 0 and
+          Float::MIN as 0.0 - this has to be checked manually,
+        * assuming that user input with _precision > DIG_ is as rare as in
+          the range _(0, MIN)_, the decision is to choose input which requires
+          the least/simplest additional code.

Gemfile

@@ -1,14 +1,14 @@
 source "https://rubygems.org"
 
-# The requirement for the Ruby version comes from Rails
-gem "rails", "~> 7.2.2"
+# The requirement for the Ruby version comes from Rails.
+gem "rails", "~> 8.1.4"
 gem "sprockets-rails"
 gem "puma", "~> 6.0"
 gem "sassc-rails"
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
 gem "tzinfo-data", platforms: %i[ mingw mswin x64_mingw jruby ]
 
-# TODO: select db gems automatically
+# TODO: select db gems automatically?
 #   database_config = ERB.new(File.read("config/database.yml")).result
 #   YAML.load(database_config, aliases: true).values.map { |env| env["adapter"] }.uniq
 group :mysql, optional: true do
@@ -21,7 +21,7 @@ group :sqlite, optional: true do
   gem "sqlite3", "~> 2.7"
 end
 
-gem "devise"
+gem "devise", "~> 5.0.4"
 
 gem "importmap-rails"
 gem "turbo-rails", "~> 2.0"
@@ -43,3 +43,7 @@ group :test do
   gem "capybara"
   gem "selenium-webdriver"
 end
+
+# TODO: remove after upgrade to next version containing PR:
+#   https://github.com/ruby-i18n/i18n/pull/755
+gem "i18n", git: "https://github.com/ruby-i18n/i18n", branch: "delegate-missing-interpolation-handler"

Gemfile.lock

@@ -1,86 +1,97 @@
+GIT
+  remote: https://github.com/ruby-i18n/i18n
+  revision: 8850d979a3a32453123ed744b943ead8751ba73b
+  branch: delegate-missing-interpolation-handler
+  specs:
+    i18n (1.15.2)
+      concurrent-ruby (~> 1.0)
+
 GEM
   remote: https://rubygems.org/
   specs:
-    actioncable (7.2.2.1)
-      actionpack (= 7.2.2.1)
-      activesupport (= 7.2.2.1)
+    action_text-trix (2.1.19)
+      railties
+    actioncable (8.1.4)
+      actionpack (= 8.1.4)
+      activesupport (= 8.1.4)
       nio4r (~> 2.0)
       websocket-driver (>= 0.6.1)
       zeitwerk (~> 2.6)
-    actionmailbox (7.2.2.1)
-      actionpack (= 7.2.2.1)
-      activejob (= 7.2.2.1)
-      activerecord (= 7.2.2.1)
-      activestorage (= 7.2.2.1)
-      activesupport (= 7.2.2.1)
+    actionmailbox (8.1.4)
+      actionpack (= 8.1.4)
+      activejob (= 8.1.4)
+      activerecord (= 8.1.4)
+      activestorage (= 8.1.4)
+      activesupport (= 8.1.4)
       mail (>= 2.8.0)
-    actionmailer (7.2.2.1)
-      actionpack (= 7.2.2.1)
-      actionview (= 7.2.2.1)
-      activejob (= 7.2.2.1)
-      activesupport (= 7.2.2.1)
+    actionmailer (8.1.4)
+      actionpack (= 8.1.4)
+      actionview (= 8.1.4)
+      activejob (= 8.1.4)
+      activesupport (= 8.1.4)
       mail (>= 2.8.0)
       rails-dom-testing (~> 2.2)
-    actionpack (7.2.2.1)
-      actionview (= 7.2.2.1)
-      activesupport (= 7.2.2.1)
+    actionpack (8.1.4)
+      actionview (= 8.1.4)
+      activesupport (= 8.1.4)
       nokogiri (>= 1.8.5)
-      racc
-      rack (>= 2.2.4, < 3.2)
+      rack (>= 2.2.4)
       rack-session (>= 1.0.1)
       rack-test (>= 0.6.3)
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
       useragent (~> 0.16)
-    actiontext (7.2.2.1)
-      actionpack (= 7.2.2.1)
-      activerecord (= 7.2.2.1)
-      activestorage (= 7.2.2.1)
-      activesupport (= 7.2.2.1)
+    actiontext (8.1.4)
+      action_text-trix (~> 2.1.15)
+      actionpack (= 8.1.4)
+      activerecord (= 8.1.4)
+      activestorage (= 8.1.4)
+      activesupport (= 8.1.4)
       globalid (>= 0.6.0)
       nokogiri (>= 1.8.5)
-    actionview (7.2.2.1)
-      activesupport (= 7.2.2.1)
+    actionview (8.1.4)
+      activesupport (= 8.1.4)
       builder (~> 3.1)
       erubi (~> 1.11)
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
-    activejob (7.2.2.1)
-      activesupport (= 7.2.2.1)
+    activejob (8.1.4)
+      activesupport (= 8.1.4)
       globalid (>= 0.3.6)
-    activemodel (7.2.2.1)
-      activesupport (= 7.2.2.1)
-    activerecord (7.2.2.1)
-      activemodel (= 7.2.2.1)
-      activesupport (= 7.2.2.1)
+    activemodel (8.1.4)
+      activesupport (= 8.1.4)
+    activerecord (8.1.4)
+      activemodel (= 8.1.4)
+      activesupport (= 8.1.4)
       timeout (>= 0.4.0)
-    activestorage (7.2.2.1)
-      actionpack (= 7.2.2.1)
-      activejob (= 7.2.2.1)
-      activerecord (= 7.2.2.1)
-      activesupport (= 7.2.2.1)
+    activestorage (8.1.4)
+      actionpack (= 8.1.4)
+      activejob (= 8.1.4)
+      activerecord (= 8.1.4)
+      activesupport (= 8.1.4)
       marcel (~> 1.0)
-    activesupport (7.2.2.1)
+    activesupport (8.1.4)
       base64
-      benchmark (>= 0.3)
       bigdecimal
       concurrent-ruby (~> 1.0, >= 1.3.1)
       connection_pool (>= 2.2.5)
       drb
       i18n (>= 1.6, < 2)
+      json
       logger (>= 1.4.2)
       minitest (>= 5.1)
       securerandom (>= 0.3)
       tzinfo (~> 2.0, >= 2.0.5)
-    addressable (2.8.7)
-      public_suffix (>= 2.0.2, < 7.0)
-    base64 (0.2.0)
-    bcrypt (3.1.20)
-    benchmark (0.4.0)
-    bigdecimal (3.1.9)
+      uri (>= 0.13.1)
+    addressable (2.9.0)
+      public_suffix (>= 2.0.2, < 8.0)
+    base64 (0.3.0)
+    bcrypt (3.1.22)
+    bigdecimal (4.1.3)
     bindex (0.8.1)
     builder (3.3.0)
-    byebug (12.0.0)
+    byebug (13.0.0)
+      reline (>= 0.6.0)
     capybara (3.40.0)
       addressable
       matrix
@@ -90,139 +101,155 @@ GEM
       rack-test (>= 0.6.3)
       regexp_parser (>= 1.5, < 3.0)
       xpath (~> 3.2)
-    concurrent-ruby (1.3.5)
-    connection_pool (2.5.2)
-    crass (1.0.6)
-    date (3.4.1)
-    devise (4.9.4)
+    concurrent-ruby (1.3.8)
+    connection_pool (3.0.2)
+    crass (1.0.7)
+    date (3.5.1)
+    devise (5.0.4)
       bcrypt (~> 3.0)
       orm_adapter (~> 0.1)
-      railties (>= 4.1.0)
+      railties (>= 7.0)
       responders
       warden (~> 1.2.3)
-    drb (2.2.1)
+    drb (2.2.3)
+    erb (6.0.7)
     erubi (1.13.1)
-    ffi (1.17.2-aarch64-linux-gnu)
-    ffi (1.17.2-aarch64-linux-musl)
-    ffi (1.17.2-arm-linux-gnu)
-    ffi (1.17.2-arm-linux-musl)
-    ffi (1.17.2-arm64-darwin)
-    ffi (1.17.2-x86_64-darwin)
-    ffi (1.17.2-x86_64-linux-gnu)
-    ffi (1.17.2-x86_64-linux-musl)
-    globalid (1.2.1)
+    ffi (1.17.4-aarch64-linux-gnu)
+    ffi (1.17.4-aarch64-linux-musl)
+    ffi (1.17.4-arm-linux-gnu)
+    ffi (1.17.4-arm-linux-musl)
+    ffi (1.17.4-arm64-darwin)
+    ffi (1.17.4-x86_64-darwin)
+    ffi (1.17.4-x86_64-linux-gnu)
+    ffi (1.17.4-x86_64-linux-musl)
+    globalid (1.4.0)
       activesupport (>= 6.1)
-    i18n (1.14.7)
-      concurrent-ruby (~> 1.0)
-    importmap-rails (2.1.0)
+    importmap-rails (2.2.3)
       actionpack (>= 6.0.0)
       activesupport (>= 6.0.0)
       railties (>= 6.0.0)
-    io-console (0.8.0)
-    irb (1.15.2)
+    io-console (0.9.4)
+    irb (1.18.0)
       pp (>= 0.6.0)
+      prism (>= 1.3.0)
       rdoc (>= 4.0.0)
       reline (>= 0.4.2)
+    json (3.0.2)
     logger (1.7.0)
-    loofah (2.24.0)
+    loofah (2.25.2)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
-    mail (2.8.1)
+    mail (2.9.1)
+      logger
       mini_mime (>= 0.1.1)
       net-imap
       net-pop
       net-smtp
-    marcel (1.0.4)
-    matrix (0.4.2)
+    marcel (1.2.1)
+    matrix (0.4.3)
     mini_mime (1.1.5)
-    minitest (5.25.5)
-    mysql2 (0.5.6)
-    net-imap (0.5.7)
+    minitest (6.0.6)
+      drb (~> 2.0)
+      prism (~> 1.5)
+    mysql2 (0.5.7)
+      bigdecimal
+    net-imap (0.6.7)
       date
       net-protocol
     net-pop (0.1.2)
       net-protocol
-    net-protocol (0.2.2)
+    net-protocol (0.4.0)
       timeout
-    net-smtp (0.5.1)
+    net-smtp (0.5.2)
       net-protocol
-    nio4r (2.7.4)
-    nokogiri (1.18.8-aarch64-linux-gnu)
+    nio4r (2.7.5)
+    nokogiri (1.19.4-aarch64-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.18.8-aarch64-linux-musl)
+    nokogiri (1.19.4-aarch64-linux-musl)
       racc (~> 1.4)
-    nokogiri (1.18.8-arm-linux-gnu)
+    nokogiri (1.19.4-arm-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.18.8-arm-linux-musl)
+    nokogiri (1.19.4-arm-linux-musl)
       racc (~> 1.4)
-    nokogiri (1.18.8-arm64-darwin)
+    nokogiri (1.19.4-arm64-darwin)
       racc (~> 1.4)
-    nokogiri (1.18.8-x86_64-darwin)
+    nokogiri (1.19.4-x86_64-darwin)
       racc (~> 1.4)
-    nokogiri (1.18.8-x86_64-linux-gnu)
+    nokogiri (1.19.4-x86_64-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.18.8-x86_64-linux-musl)
+    nokogiri (1.19.4-x86_64-linux-musl)
       racc (~> 1.4)
     orm_adapter (0.5.0)
-    pg (1.5.9)
-    pp (0.6.2)
+    pg (1.7.0)
+    pg (1.7.0-aarch64-linux)
+    pg (1.7.0-aarch64-linux-musl)
+    pg (1.7.0-arm64-darwin)
+    pg (1.7.0-x86_64-darwin)
+    pg (1.7.0-x86_64-linux)
+    pg (1.7.0-x86_64-linux-musl)
+    pp (0.6.4)
       prettyprint
     prettyprint (0.2.0)
-    psych (5.2.3)
-      date
-      stringio
-    public_suffix (6.0.1)
-    puma (6.6.0)
+    prism (1.9.0)
+    public_suffix (7.0.5)
+    puma (6.6.1)
       nio4r (~> 2.0)
     racc (1.8.1)
-    rack (3.1.13)
-    rack-session (2.1.0)
+    rack (3.2.7)
+    rack-session (2.1.2)
       base64 (>= 0.1.0)
       rack (>= 3.0.0)
     rack-test (2.2.0)
       rack (>= 1.3)
-    rackup (2.2.1)
+    rackup (2.3.1)
       rack (>= 3)
-    rails (7.2.2.1)
-      actioncable (= 7.2.2.1)
-      actionmailbox (= 7.2.2.1)
-      actionmailer (= 7.2.2.1)
-      actionpack (= 7.2.2.1)
-      actiontext (= 7.2.2.1)
-      actionview (= 7.2.2.1)
-      activejob (= 7.2.2.1)
-      activemodel (= 7.2.2.1)
-      activerecord (= 7.2.2.1)
-      activestorage (= 7.2.2.1)
-      activesupport (= 7.2.2.1)
+    rails (8.1.4)
+      actioncable (= 8.1.4)
+      actionmailbox (= 8.1.4)
+      actionmailer (= 8.1.4)
+      actionpack (= 8.1.4)
+      actiontext (= 8.1.4)
+      actionview (= 8.1.4)
+      activejob (= 8.1.4)
+      activemodel (= 8.1.4)
+      activerecord (= 8.1.4)
+      activestorage (= 8.1.4)
+      activesupport (= 8.1.4)
       bundler (>= 1.15.0)
-      railties (= 7.2.2.1)
-    rails-dom-testing (2.2.0)
+      railties (= 8.1.4)
+    rails-dom-testing (2.3.0)
       activesupport (>= 5.0.0)
       minitest
       nokogiri (>= 1.6)
-    rails-html-sanitizer (1.6.2)
-      loofah (~> 2.21)
+    rails-html-sanitizer (1.7.1)
+      loofah (~> 2.25, >= 2.25.2)
       nokogiri (>= 1.15.7, != 1.16.7, != 1.16.6, != 1.16.5, != 1.16.4, != 1.16.3, != 1.16.2, != 1.16.1, != 1.16.0.rc1, != 1.16.0)
-    railties (7.2.2.1)
-      actionpack (= 7.2.2.1)
-      activesupport (= 7.2.2.1)
+    railties (8.1.4)
+      actionpack (= 8.1.4)
+      activesupport (= 8.1.4)
       irb (~> 1.13)
       rackup (>= 1.0.0)
       rake (>= 12.2)
       thor (~> 1.0, >= 1.2.2)
+      tsort (>= 0.2)
       zeitwerk (~> 2.6)
-    rake (13.2.1)
-    rdoc (6.13.1)
-      psych (>= 4.0.0)
-    regexp_parser (2.10.0)
-    reline (0.6.1)
+    rake (13.4.2)
+    rbs (4.2.0)
+      logger
+      prism (>= 1.6.0)
+      tsort
+    rdoc (8.1.0)
+      erb
+      prism (>= 1.6.0)
+      rbs (>= 4.0.0)
+      tsort
+    regexp_parser (2.13.1)
+    reline (0.7.0)
       io-console (~> 0.5)
-    responders (3.1.1)
-      actionpack (>= 5.2)
-      railties (>= 5.2)
-    rexml (3.4.1)
-    rubyzip (2.4.1)
+    responders (3.2.1)
+      actionpack (>= 7.0)
+      railties (>= 7.0)
+    rubyzip (3.7.0)
     sassc (2.4.0)
       ffi (~> 1.9)
     sassc-rails (2.1.2)
@@ -232,53 +259,52 @@ GEM
       sprockets-rails
       tilt
     securerandom (0.4.1)
-    selenium-webdriver (4.31.0)
+    selenium-webdriver (4.50.0)
       base64 (~> 0.2)
       logger (~> 1.4)
-      rexml (~> 3.2, >= 3.2.5)
-      rubyzip (>= 1.2.2, < 3.0)
+      rubyzip (>= 1.2.2, < 4.0)
       websocket (~> 1.0)
-    sprockets (4.2.2)
-      concurrent-ruby (~> 1.0)
+    sprockets (4.4.1)
+      concurrent-ruby (~> 1.1)
       logger
       rack (>= 2.2.4, < 4)
     sprockets-rails (3.5.2)
       actionpack (>= 6.1)
       activesupport (>= 6.1)
       sprockets (>= 3.0.0)
-    sqlite3 (2.7.3-aarch64-linux-gnu)
-    sqlite3 (2.7.3-aarch64-linux-musl)
-    sqlite3 (2.7.3-arm-linux-gnu)
-    sqlite3 (2.7.3-arm-linux-musl)
-    sqlite3 (2.7.3-arm64-darwin)
-    sqlite3 (2.7.3-x86_64-darwin)
-    sqlite3 (2.7.3-x86_64-linux-gnu)
-    sqlite3 (2.7.3-x86_64-linux-musl)
-    stringio (3.1.7)
-    thor (1.3.2)
-    tilt (2.6.0)
-    timeout (0.4.3)
-    turbo-rails (2.0.13)
+    sqlite3 (2.9.6-aarch64-linux-gnu)
+    sqlite3 (2.9.6-aarch64-linux-musl)
+    sqlite3 (2.9.6-arm-linux-gnu)
+    sqlite3 (2.9.6-arm-linux-musl)
+    sqlite3 (2.9.6-arm64-darwin)
+    sqlite3 (2.9.6-x86_64-darwin)
+    sqlite3 (2.9.6-x86_64-linux-gnu)
+    sqlite3 (2.9.6-x86_64-linux-musl)
+    thor (1.5.0)
+    tilt (2.9.0)
+    timeout (0.6.1)
+    tsort (0.2.0)
+    turbo-rails (2.0.23)
       actionpack (>= 7.1.0)
       railties (>= 7.1.0)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
+    uri (1.1.1)
     useragent (0.16.11)
     warden (1.2.9)
       rack (>= 2.0.9)
-    web-console (4.2.1)
-      actionview (>= 6.0.0)
-      activemodel (>= 6.0.0)
+    web-console (4.3.0)
+      actionview (>= 8.0.0)
       bindex (>= 0.4.0)
-      railties (>= 6.0.0)
+      railties (>= 8.0.0)
     websocket (1.2.11)
-    websocket-driver (0.7.7)
+    websocket-driver (0.8.2)
       base64
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.5)
     xpath (3.2.0)
       nokogiri (~> 1.8)
-    zeitwerk (2.7.2)
+    zeitwerk (2.8.3)
 
 PLATFORMS
   aarch64-linux-gnu
@@ -293,12 +319,13 @@ PLATFORMS
 DEPENDENCIES
   byebug
   capybara
-  devise
+  devise (~> 5.0.4)
+  i18n!
   importmap-rails
   mysql2 (~> 0.5)
   pg (~> 1.5)
   puma (~> 6.0)
-  rails (~> 7.2.2)
+  rails (~> 8.1.4)
   sassc-rails
   selenium-webdriver
   sprockets-rails

README.md

@@ -16,14 +16,10 @@ environment, see the _Contributing_ section below.
 * Server side:
     * Ruby interpreter, depending on the version of Rails used (see _Gemfile_),
         * https://guides.rubyonrails.org/upgrading_ruby_on_rails.html#ruby-versions
-    * database (e.g. MySQL >= 8.0) supporting:
+    * database (e.g. SQLite, MySQL >= 8.0) supporting:
         * recursive Common Table Expressions (CTE) for SELECT/UPDATE/DELETE,
             * MariaDB does not support CTE for UPDATE/DELETE
               (https://jira.mariadb.org/browse/MDEV-18511)
-        * decimal datatype with precision of at least 30,
-            * SQLite3 _flexible typing_ decimal will work, but precision
-              will be limited to 16, making it practical mostly for testing
-              purposes
     * for testing: browser as specified in _Client side_ requirements
 * Client side:
     * browser (e.g. Firefox >= 121) supporting:
@@ -89,14 +85,10 @@ Running
 
 ### Standalone Rails server + Apache proxy
 
-Customize Puma config template:
+Copy and customize Puma config template if required:
 
     cp -a config/puma.rb.dist config/puma.rb
 
-and specify server IP/port, either with `port` or `bind`, e.g.:
-
-    bind 'tcp://0.0.0.0:3000'
-
 #### (option 1) Start server manually
 
     bundle exec rails s -e production
@@ -123,9 +115,26 @@ Contributing
 
 ### Gems
 
-Apart from database adapter, install development and testing gems:
+Install development and testing gems, including at least MySQL and SQLite
+database adapters:
 
-    bundle config --local with mysql development test
+    bundle config --local with development test mysql sqlite
+
+#### Using gems from local git repos
+
+When working on gem PRs, it may be useful to work with proposed changes locally
+until PRs get accepted upstream. To add gem hosted in local git repository:
+
+    bundle config set local.capybara /var/www/tmp/capybara
+
+Add gem to `Gemfile`:
+
+  gem "capybara", git: "https://github.com/teamcapybara/capybara", branch: "branch-name"
+
+and install:
+
+    bundle install
+    bundle show capybara
 
 ### Configuration
 
@@ -138,20 +147,29 @@ assets.
 
 ### Database
 
-Grant database user privileges for development and test environments,
-possibly with different Ruby versions:
+Grant database user privileges for development and test environments. Example
+below shows how to grant privileges to all databases which names start with
+`fixinme-` on MySQL:
 
     > mysql -p
     mysql> create user `fixinme-dev`@localhost identified by '<some password>';
     mysql> grant all privileges on `fixinme-%`.* to `fixinme-dev`@localhost;
     mysql> flush privileges;
 
+Dumping development data before database reset:
+
+    mysqldump -h <address> -u <user> -p --no-create-info --no-tablespaces --complete-insert <database> > tmp/data.sql
+
 ### Development environment
 
 Starting application server in development environment:
 
     bundle exec rails s -e development
 
+Accessing database console when more than one test db is present:
+
+    bundle exec rails dbconsole -e test --db sqlite3
+
 For running rake tasks, prepend command with environment:
 
     RAILS_ENV=development bundle exec rails ...
@@ -164,14 +182,22 @@ Tests need to be run from within toplevel application directory:
 
         bundle exec rails test:system
 
-* system test(s) with seed/test name specified:
+* system test(s) with seed or test name specified:
 
-        bundle exec rails test:system --seed 64690 --name test_add_unit
+        bundle exec rails test:system --include test_add_unit --seed 64690
 
-* all tests from one file, with optional seed:
+* all tests from one file, optionally with seed:
 
         bundle exec rails test test/system/users_test.rb --seed 1234
 
+* system tests for selected database configuration (if multiple present):
+
+        bundle exec rails test:system --include /^test_sqlite3_/
+
+* single system test for all database configurations (if multiple present):
+
+        bundle exec rails test:system --include /^test_\\w+_add_unit$/
+
 ### Icons
 
 Pictogrammers Material Design Icons: https://pictogrammers.com/library/mdi/

app/assets/images/alert-outline.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" id="icon" viewBox="0 0 24 24"><path d="M12,2L1,21H23M12,6L19.53,19H4.47M11,10V14H13V10M11,16V18H13V16" /></svg>

app/assets/images/check-circle-outline.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" id="icon" viewBox="0 0 24 24"><path d="M12 2C6.5 2 2 6.5 2 12S6.5 22 12 22 22 17.5 22 12 17.5 2 12 2M12 20C7.59 20 4 16.41 4 12S7.59 4 12 4 20 7.59 20 12 16.41 20 12 20M16.59 7.58L10 14.17L7.41 11.59L6 13L10 17L18 9L16.59 7.58Z" /></svg>

app/assets/images/chevron-down.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" id="icon" viewBox="0 0 24 24"><path d="M7.41,8.58L12,13.17L16.59,8.58L18,10L12,16L6,10L7.41,8.58Z" /></svg>

app/assets/images/pencil-outline.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" id="icon" viewBox="0 0 24 24"><path d="M14.06,9L15,9.94L5.92,19H5V18.08L14.06,9M17.66,3C17.41,3 17.15,3.1 16.96,3.29L15.13,5.12L18.88,8.87L20.71,7.04C21.1,6.65 21.1,6 20.71,5.63L18.37,3.29C18.17,3.09 17.92,3 17.66,3M14.06,6.19L3,17.25V21H6.75L17.81,9.94L14.06,6.19Z" /></svg>

app/assets/images/pictograms/alert-outline.svg

@@ -1 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" id="icon" viewBox="0 0 24 24"><path fill="#ffffff" d="M12,2L1,21H23M12,6L19.53,19H4.47M11,10V14H13V10M11,16V18H13V16" /></svg>

app/assets/images/pictograms/check-circle-outline.svg

@@ -1 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" id="icon" viewBox="0 0 24 24"><path fill="#ffffff" d="M12 2C6.5 2 2 6.5 2 12S6.5 22 12 22 22 17.5 22 12 17.5 2 12 2M12 20C7.59 20 4 16.41 4 12S7.59 4 12 4 20 7.59 20 12 16.41 20 12 20M16.59 7.58L10 14.17L7.41 11.59L6 13L10 17L18 9L16.59 7.58Z" /></svg>

app/assets/stylesheets/application.css

@@ -15,6 +15,16 @@
  *= require_self
  */
 
+/* Strive for simplicity:
+ * * style elements/tags only - if possible,
+ * * replace element/tag name with class name - if element has to be styled
+ * differently depending on context (e.g. <form>, <table>, <a> as link/button),
+ * * styles with multiple selectors should have all selectors with same
+ * specificity, to allow proper rule specificity vs order management.
+ *
+ * NOTE: style in a modular way, similar to how CSS @scope would be used,
+ * to make transition easier once @scope is widely available. */
+/* TODO: change :root -> <html> ? */
 :root {
   --color-focus-gray: #f3f3f3;
   --color-border-gray: #dddddd;
@@ -46,50 +56,173 @@
 :focus-visible {
   outline: none;
 }
-
-
-/* TODO: collapse gaps around empty rows (`topside`) once possible
- * https://github.com/w3c/csswg-drafts/issues/5813 */
-body {
-  display: grid;
-  gap: 0.8em;
-  grid-template-areas:
-    "header    header  header"
-    "nav       nav     nav"
-    "leftempty topside rightempty"
-    "leftside  main    rightside";
-  grid-template-columns: 1fr auto 1fr;
-  grid-template-rows: repeat(4, auto);
-  font-family: system-ui;
-  margin: 0.4em;
+/* NOTE: move to higher priority layer instead of using !important?; add CSS
+ * @layer requirements in README */
+/* Disable elements with:
+ *  `[aria-disabled=true]` - non-form elements (e.g. links),
+ *  `[disabled]` - form controls, that may be enabled conditionally,
+ *  `[readonly]` - form controls, that stay disabled for form lifetime. */
+[aria-disabled=true],
+[disabled] {
+  border-color: var(--color-border-gray) !important;
+  color: var(--color-border-gray) !important;
+  /* NOTE: cannot set cursor when `pointer-events: none`; can be fixed by setting
+   * `cursor` on wrapping element.
+  cursor: not-allowed; */
+  fill: var(--color-border-gray) !important;
+  pointer-events: none !important;
 }
+/* Styles set `display` without distinguishing between [hidden] elements, making
+ * them visible. */
+[hidden] {
+  display: none !important;
+}
+
+
+/* Color coding of input controls' background:
+ *  blue - target for interaction with pointer,
+ *  gray - target for interaction with keyboard,
+ *  red - destructive, non-undoable action.
+ */
+/* TODO: merge selectors using :is() */
+a,
 button,
+details,
 input,
 select,
+summary,
 textarea {
   background-color: inherit;
   font: inherit;
 }
+details,
 input,
 select {
   text-align: inherit;
 }
+input,
+select,
+summary,
+textarea {
+  border: 1px solid var(--color-gray);
+  border-radius: 0.25em;
+  padding: 0.2em 0.4em;
+}
+svg {
+  height: 1.4em;
+  margin: 0 0.2em 0 0;
+  width: 1.4em;
+}
+svg:last-child {
+  margin-right: 0;
+}
+textarea {
+  margin: 0;
+}
+input[type=checkbox] {
+  accent-color: var(--color-blue);
+  appearance: none;
+  -webkit-appearance: none;
+  display: flex;
+  height: 1.1em;
+  margin: 0;
+  padding: 0;
+  width: 1.1em;
+}
+input[type=checkbox]:checked {
+  appearance: checkbox;
+  -webkit-appearance: checkbox;
+}
+/* Hide spin buttons of <input type=number>. */
+/* TODO: add spin buttons inside <input type=number>: before (-) and after (+) input. */
+input[type=number] {
+  appearance: textfield;
+  -moz-appearance: textfield;
+  text-align: end;
+}
+input::-webkit-inner-spin-button {
+  -webkit-appearance: none;
+}
+input::-webkit-outer-spin-button {
+  -webkit-appearance: none;
+  margin: 0;
+}
+/* Text color of table form controls:
+ *  - black for row/table forms,
+ *  - inherited for internal (column specific) buttons/forms. */
+table input,
+table select,
+table summary,
+table textarea {
+  border-color: var(--color-border-gray);
+}
+table input,
+table select,
+table textarea {
+  padding-block: 0.375em;
+}
+table form input,
+table form select,
+table form summary,
+table form textarea {
+  color: inherit;
+}
+table svg:not(:only-child) {
+  height: 1.25em;
+  width: 1.25em;
+}
+input:focus-visible,
+/* TODO: select:focus-visible is redundant with -within? */
+select:focus-visible,
+select:focus-within,
+/* TODO: how to achieve `summary:focus-within` for `::details-content`? */
+summary:focus-visible,
+textarea:focus-visible {
+  accent-color: var(--color-dark-blue);
+  background-color: var(--color-focus-gray);
+  color: black;
+}
+input:hover,
+select:hover,
+summary:hover,
+textarea:hover {
+  border-color: var(--color-blue);
+  outline: 1px solid var(--color-blue);
+}
+select:hover,
+summary:hover {
+  color: black;
+  cursor: pointer;
+}
+/* TODO: style <details>/<summary> focus to match <select> as much as possible.
+summary:focus-visible::before,
+summary:hover::before {
+  background-color: black;
+}
+ */
+input:invalid,
+select:invalid,
+textarea:invalid {
+  border-color: var(--color-red);
+  outline-color: var(--color-red);
+}
+pre {
+  display: inline;
+  font: inherit;
+}
 
-
-/* blue - target for interaction with pointer */
-/* gray - target for interaction with keyboard */
-/* TODO: remove non-font-size rems from buttons/inputs below */
-a,
-button,
-input[type=submit] {
+/* `.button`: button-styled <a>, <button>, <input type=submit>.
+ * `.link`: any other <a>.
+ * `.tab`: tab-styled <a>.
+ */
+.button,
+.link,
+.tab {
   cursor: pointer;
   text-decoration: none;
   white-space: nowrap;
 }
-/* [hidden] submit controls cannot have `display` set as it makes them visible */
 .button,
-button:not([hidden]),
-input[type=submit]:not([hidden]),
 .tab {
   align-items: center;
   color: var(--color-gray);
@@ -97,66 +230,35 @@ input[type=submit]:not([hidden]),
   fill: var(--color-gray);
   font-weight: bold;
 }
-.button,
-button,
-input[type=submit] {
+.button {
+  border: 1px solid var(--color-gray);
+  border-radius: 0.25em;
   font-size: 0.8rem;
-  padding: 0.4em;
+  padding: 0.6em 0.5em;
   width: fit-content;
 }
-input:not([type=submit]):not([type=checkbox]),
-select,
-textarea {
-  padding: 0.2em 0.4em;
+.link {
+  color: inherit;
+  text-decoration: underline 1px var(--color-border-gray);
+  text-underline-offset: 0.25em;
 }
-.button,
-button,
-input,
-select,
-textarea {
-  border: solid 1px var(--color-gray);
-  border-radius: 0.25em;
+.auxiliary {
+  border-color: var(--color-nav-gray);
+  color: var(--color-nav-gray);
+  fill: var(--color-nav-gray);
 }
-fieldset,
-textarea {
-  margin: 0
-}
-.button > svg,
-.tab > svg,
-button > svg {
-  height: 1.8em;
-  width: 1.8em;
-}
-.button > svg:not(:last-child),
-.tab > svg:not(:last-child),
-button > svg:not(:last-child) {
-  padding-right: 0.4em;
-}
-fieldset {
+table .button {
+  border-color: var(--color-border-gray);
+  font-weight: normal;
+  height: 100%;
   padding: 0.4em;
 }
-legend {
-  color: var(--color-gray);
-  display: flex;
-  gap: 0.4em;
-  width: 100%;
-}
-legend span {
-  align-content: center;
-  flex-grow: 1;
-}
-
-/* TODO: move normal non-button links (<a>:hover/:focus) styling here (i.e.
- * page-wide, top-level) and remove from table.items - as the style should be
- * same everywhere */
 .button:focus-visible,
-button:focus-visible,
-input[type=submit]:focus-visible {
+.tab:focus-visible,
+.tab:hover {
   background-color: var(--color-focus-gray);
 }
-.button:hover,
-button:hover,
-input[type=submit]:hover {
+.button:hover {
   background-color: var(--color-blue);
   border-color: var(--color-blue);
   color: white;
@@ -166,68 +268,42 @@ input[type=submit]:hover {
   background-color: var(--color-red);
   border-color: var(--color-red);
 }
-
-input[type=checkbox] {
-  accent-color: var(--color-blue);
-  appearance: none;
-  -webkit-appearance: none;
-  display: flex;
-  height: 1.1rem;
-  margin: 0;
-  width: 1.1rem;
+.link:focus-visible {
+  text-decoration-color: var(--color-gray);
 }
-input[type=checkbox]:checked {
-  appearance: checkbox;
-  -webkit-appearance: checkbox;
-}
-/* Hide spin buttons in input number fields */
-input[type=number] {
-  appearance: textfield;
-  -moz-appearance: textfield;
-}
-input::-webkit-inner-spin-button {
-  -webkit-appearance: none;
-}
-input::-webkit-outer-spin-button {
-  -webkit-appearance: none;
-  margin: 0;
-}
-input:hover,
-select:hover,
-textarea:hover {
-  border-color: var(--color-blue);
-  outline: solid 1px var(--color-blue);
-}
-input:invalid,
-select:invalid,
-textarea:invalid {
-  border-color: var(--color-red);
-  outline: solid 1px var(--color-red);
-}
-select:hover {
-  cursor: pointer;
-}
-input:focus-visible,
-select:focus-within,
-select:focus-visible,
-textarea:focus-visible {
-  accent-color: var(--color-dark-blue);
-  background-color: var(--color-focus-gray);
-}
-fieldset,
-input[type=text]:read-only,
-textarea:read-only {
-  border: none;
-  padding-left: 0;
-  padding-right: 0;
+.link:hover {
+  color: var(--color-blue);
+  text-decoration-color: var(--color-blue);
 }
 
 
+/* NOTE: collapse gaps around empty rows (`topside`) once possible with
+ * `grid-collapse` property and remove alternative `grid-template-areas`.
+ * https://github.com/w3c/csswg-drafts/issues/5813 */
+body {
+  display: grid;
+  gap: 0.8em;
+  grid-template-areas:
+    "header    header  header"
+    "nav       nav     nav"
+    "leftside  main    rightside";
+  grid-template-columns: 1fr minmax(max-content, 2fr) 1fr;
+  font-family: system-ui;
+  margin: 0.4em;
+}
+body:has(> .topside-area) {
+  grid-template-areas:
+    "header    header  header"
+    "nav       nav     nav"
+    "leftside  topside rightside"
+    "leftside  main    rightside";
+}
+
 header {
   grid-area: header;
 }
 
-
+/* TODO: change .navigation -> <nav> ? */
 .navigation {
   display: flex;
   grid-area: nav;
@@ -236,37 +312,31 @@ header {
   margin-inline-start: 4%;
 }
 .navigation > .tab {
-  border-bottom: solid 2px var(--color-nav-gray);
+  border-bottom: 2px solid var(--color-nav-gray);
   flex: 1;
   font-size: 1rem;
   justify-content: center;
-  padding-block: 0.3em;
-}
-.navigation > .tab:hover,
-.navigation > .tab:focus-visible {
-  background-color: var(--color-focus-gray);
+  padding-block: 0.4em;
 }
 .navigation > .tab.active {
-  border-bottom: solid 4px var(--color-blue);
+  border-bottom: 4px solid var(--color-blue);
   color: var(--color-blue);
   fill: var(--color-blue);
 }
 
-
-.topside {
+.topside-area {
   grid-area: topside;
 }
-.leftside {
+.leftside-area {
   grid-area: leftside;
 }
-.main {
+.main-area {
   grid-area: main;
 }
-.rightside {
+.rightside-area {
   grid-area: rightside;
 }
 
-
 .buttongrid {
   display: grid;
   gap: 0.4em;
@@ -274,14 +344,14 @@ header {
   grid-template-columns: auto 1fr auto;
   grid-template-rows: max-content;
 }
-.tools {
+.tools-area {
   grid-area: tools;
 }
 
 
 #flashes {
   display: grid;
-  gap: 0.2em;
+  row-gap: 0.4em;
   grid-template-columns: 1fr auto auto auto 1fr;
   left: 0;
   pointer-events: none;
@@ -297,281 +367,310 @@ header {
   display: grid;
   grid-column: 2/5;
   grid-template-columns: subgrid;
+  line-height: 2.2em;
   pointer-events: auto;
 }
-.flash.alert:before {
-  content: url('pictograms/alert-outline.svg');
+.flash::before {
+  filter: invert(1);
   height: 1.4em;
   margin: 0 0.5em;
   width: 1.4em;
 }
+.flash.alert::before {
+  content: url('alert-outline.svg');
+}
 .flash.alert {
   border-color: var(--color-red);
   background-color: var(--color-red);
 }
-.flash.notice:before {
-  content: url('pictograms/check-circle-outline.svg');
-  height: 1.4em;
-  margin: 0 0.5em;
-  width: 1.4em;
+.flash.notice::before {
+  content: url('check-circle-outline.svg');
 }
 .flash.notice {
   border-color: var(--color-blue);
   background-color: var(--color-blue);
 }
-.flash > div {
-  grid-column: 2;
-}
-/* NOTE: currently flash button inherits some unnecessary styles from generic
- * button. */
-.flash > button {
-  border: none;
-  color: inherit;
+.flash svg {
   cursor: pointer;
-  font-size: 1.4em;
-  font-weight: bold;
-  grid-column: 3;
+  fill: white;
+  height: 2.2em;
   opacity: 0.6;
-  padding: 0.2em 0.4em;
+  padding: 0.4em 0.5em;
+  width: 2.4em;
 }
-.flash > button:hover {
+.flash svg:hover {
   opacity: 1;
 }
 
 
-/* TODO: Update styling, including rem removal. */
-form table {
-  border-spacing: 0.8rem;
+.labeled-form {
+  align-items: center;
+  display: grid;
+  gap: 0.9em 1.1em;
+  grid-template-columns: 1fr minmax(max-content, 0.5fr) 1fr;
 }
-form tr td:first-child {
+.labeled-form label {
   color: var(--color-gray);
   font-size: 0.9rem;
-  padding-right: 0.25rem;
+  grid-column: 1;
   text-align: right;
+  white-space: nowrap;
 }
-form label.required {
+.labeled-form label.required {
   font-weight: bold;
 }
-form label.error,
-form td.error::after {
+/* Don't style `label.error + input` if case already covered by `input:invalid`. */
+.labeled-form label.error {
   color: var(--color-red);
 }
-form td.error {
-  display: -webkit-box;
-}
-form td.error::after {
-  content: attr(data-content);
-  font-size: 0.9rem;
-  margin-left: 1rem;
-  padding: 0.25rem 0;
-  position: absolute;
-}
-form em {
+.labeled-form em {
   color: var(--color-text-gray);
   font-size: 0.75rem;
   font-weight: normal;
 }
-form input[type=submit] {
-  float: none;
+.labeled-form input {
+  grid-column: 2;
+}
+.labeled-form input[type=submit] {
   font-size: 1rem;
-  margin: 1.5rem auto 0 auto;
-  padding: 0.75rem;
+  margin: 1em auto 0 auto;
+  padding: 0.75em;
+}
+.labeled-form .auxiliary {
+  grid-column: 3;
+  /* If more buttons are needed, `grid-row` can be replaced with
+   * `reading-flow: grid-columns` to ensure proper [tabindex] order. */
+  grid-row: 1;
+  height: 100%;
+  padding-block: 0;
+}
+
+.tabular-form table {
+  border: none;
+  border-spacing: 0;
+}
+.tabular-form table td {
+  border: none;
+  padding-inline-start: 0.4em;
+  vertical-align: middle;
+}
+.tabular-form table td:first-child {
+  padding-inline-start: 0;
+}
+.tabular-form table td:last-child {
+  padding-inline-end: 0;
+}
+.tabular-form table :is(form, input, select, textarea):only-child {
+  margin-inline-start: 0;
 }
 
 
-table.items {
-  border-spacing: 0;
-  border: solid 1px var(--color-border-gray);
+.items-table {
+  border: none;
   border-radius: 0.25em;
+  border-spacing: 0;
   font-size: 0.85rem;
   text-align: left;
 }
-table.items thead {
-  font-size: 0.8rem;
+.items-table:has(tbody > tr > td) {
+  border: 1px solid var(--color-border-gray);
 }
-table.items thead,
-table.items tbody tr:hover {
+.items-table:has(tbody > tr > td) caption {
+  display: none;
+}
+.items-table tbody:not(:has(tr > td)){
+  visibility: collapse;
+}
+.items-table th,
+.items-table tr:where(:hover) {
   background-color: var(--color-focus-gray);
 }
-table.items th {
-  padding-block: 0.75em;
+.items-table th {
+  font-size: 0.8rem;
+  padding: 0.75em 0 0.75em 1em;
   text-align: center;
 }
-table.items th,
-table.items td {
-  padding-inline: 1em 0;
-}
-/* For <a> to fill <td> completely, we use an ::after pseudoelement. */
-table.items td.link {
-  padding: 0;
-  position: relative;
-}
-table.items td.link a {
-  color: inherit;
-  font: inherit;
-}
-table.items td.link a::after {
-  content: '';
-  inset: 0;
-  position: absolute;
-}
-table.items td:first-child {
-  padding-inline-start: calc(1em + var(--depth) * 0.8em);
-}
-table.items td:has(input, textarea) {
-  padding-inline-start: calc(0.6em - 0.9px);
-}
-table.items td:first-child:has(input, textarea) {
-  padding-inline-start: calc(0.6em + var(--depth) * 0.8em - 0.9px);
-}
-table.items th:last-child {
+.items-table th:last-child {
   padding-inline-end: 0.4em;
 }
-table.items td:last-child {
+.items-table td {
+  border-top: 1px solid var(--color-border-gray);
+  height: 2.4em;
+  padding: 0.1em 0 0.1em calc(1em + var(--depth) * 0.8em);
+}
+.items-table td:last-child {
   padding-inline-end: 0.1em;
 }
-table.items td {
-  border-top: solid 1px var(--color-border-gray);
-  height: 2.4em;
-  padding-block: 0.1em;
+.items-table :is(form, input, select, textarea):only-child {
+  margin-inline-start: calc(-0.4em - 0.9px);
 }
-table.items .actions {
-  display: flex;
+/* For <a> to fill table cell completely, we use an `::after` pseudoelement. */
+/* TODO: expand to whole row? will require adjusting z-index on inputs/buttons */
+.items-table td:has(> .link) {
+  position: relative;
+}
+.items-table .link::after {
+  content: '';
+  inset: -1px 0 0 0;
+  position: absolute;
+}
+.items-table .flex {
   gap: 0.4em;
   justify-content: end;
 }
-table.items .actions.centered {
-  justify-content: center;
-}
-table.items tr.dropzone {
+.items-table .dropzone {
   position: relative;
 }
-table.items tr.dropzone::after {
+.items-table .dropzone::after {
   content: '';
   inset: 1px 0 0 0;
   position: absolute;
-  outline: dashed 2px var(--color-blue);
+  outline: 2px dashed var(--color-blue);
   outline-offset: -1px;
   z-index: var(--z-index-table-row-outline);
 }
-table.items td.handle {
-  cursor: move;
+.items-table .handle {
+  cursor: grab;
 }
-table.items tr.form td {
+.items-table .form td {
   vertical-align: top;
 }
-
-/* TODO: replace :hover:focus-visible combos with proper LOVE stye order */
-/* TODO: Update styling, including rem removal. */
-table.items td.link a:hover,
-table.items td.link a:focus-visible,
-table.items td.link a:hover:focus-visible {
-  text-decoration: underline;
-  text-decoration-thickness: 0.05rem;
-  text-underline-offset: 0.2rem;
-}
-table.items td.link a:hover {
-  color: var(--color-blue);
-}
-table.items td.link a:focus-visible {
-  text-decoration-color: var(--color-gray);
-}
-table.items td.link a:hover:focus-visible {
-  color: var(--color-dark-blue);
-}
-
-table.items td:not(:first-child),
+.items-table td:not(:first-child),
 .grayed {
   color: var(--color-table-gray);
-  fill: var(--color-table-gray);
+  fill: var(--color-gray);
 }
-table.items td.hint {
-  color: var(--color-table-gray);
-  font-style: italic;
-  font-size: 0.8rem;
-  padding: 1em;
-}
-table.items svg {
-  height: 1.2rem;
-  vertical-align: middle;
-  width: 1.2rem;
-}
-table.items td.svg {
+.items-table td:has(> svg:only-child) {
   text-align: center;
 }
-table.items td.number {
-  text-align: right;
-}
-table.items .button,
-table.items button,
-table.items input[type=submit] {
-  font-weight: normal;
-  padding: 0.3em;
-}
-table.items input:not([type=submit]):not([type=checkbox]),
-table.items select,
-table.items textarea {
-  padding-block: 0.375em;
-}
-/* TODO: find a way (layers?) to style inputs differently while making sure
- * hover works properly without using :not(:hover) selectors here. */
-table.items .button:not(:hover),
-table.items button:not(:hover),
-table.items input:not(:hover),
-table.items select:not(:hover),
-table.items textarea:not(:hover) {
-  border-color: var(--color-border-gray);
-}
-table.items .button:not(:hover),
-table.items button:not(:hover),
-table.items input[type=submit]:not(:hover),
-table.items select:not(:hover) {
-  color: var(--color-table-gray);
-}
-table.items select:focus-within,
-table.items select:focus-visible {
-  color: black;
-}
 
-form a[name=cancel] {
-  border-color: var(--color-border-gray);
-  color: var(--color-nav-gray);
-  fill: var(--color-nav-gray);
-}
-form table.items {
-  border: none;
-}
-form table.items td {
-  border: none;
-  text-align: left;
-  vertical-align: middle;
-}
-form table.items td:first-child {
-  color: inherit;
-}
 
-.centered {
+.center {
   margin: 0 auto;
 }
-.extendedright {
-  margin-right: auto;
+.hexpand {
+  width: 100%;
 }
-.hflex {
+.flex {
   display: flex;
   gap: 0.8em;
 }
-.vflex {
-  display: flex;
-  gap: 0.8em;
+.flex.reverse {
+  flex-direction: row-reverse;
+}
+.flex.vertical {
   flex-direction: column;
 }
-[disabled] {
-  border-color: var(--color-border-gray) !important;
-  color: var(--color-border-gray) !important;
-  cursor: not-allowed;
-  fill: var(--color-border-gray) !important;
-  pointer-events: none;
+.hint {
+  color: var(--color-table-gray);
+  font-style: italic;
+  font-size: 0.9rem;
+  text-align: center;
 }
-.unwrappable {
+.hmin50 {
+  min-width: 50%;
+}
+.hminnumber {
+  min-width: 5em;
+}
+.hmintext {
+  min-width: 6em;
+}
+.hstretch {
+  /* `width` conflicts with <input>/<textarea> size defined by [size]/[cols]
+   * attributes. It's best to not use these attributes (e.g. set them to 1) when
+   * setting width through stylesheet. */
+  /* NOTE: `field-sizing` can be considered after upgrade do FF >=152 */
+  width: -moz-available;
+  width: stretch;
+}
+.italic {
+  color: var(--color-gray);
+  font-style: italic;
+}
+.ralign {
+  text-align: right;
+}
+.rextend {
+  margin-right: auto;
+}
+
+
+details {
+  align-content: center;
+  position: relative;
+}
+summary {
+  align-items: center;
+  color: var(--color-gray);
+  display: flex;
+  gap: 0.4em;
+  height: 100%;
   white-space: nowrap;
 }
+summary::before {
+  background-color: currentColor;
+  content: "";
+  height: 1em;
+  mask-image: url('chevron-down.svg');
+  mask-size: cover;
+  width: 1em;
+}
+summary:has(.button) {
+  padding-block: 0;
+  padding-inline-end: 0;
+}
+summary .button {
+  border: 1px solid var(--color-border-gray);
+  border-radius: inherit;
+  border-top-left-radius: 0;
+  border-bottom-left-radius: 0;
+  border-style: none none none solid;
+  height: 100%;
+}
+summary span {
+  width: 100%;
+}
+details[open] summary::before {
+  transform: scaleY(-1);
+}
+summary::marker {
+  padding-left: 0.25em;
+}
+/* NOTE: use `details[open]::details-content` once widely available. */
+details[open] ul {
+  background-color: white;
+  border: 1px solid var(--color-border-gray);
+  border-radius: 0.25em;
+  box-shadow: 1px 1px 3px var(--color-border-gray);
+  margin: -1px 0 0 0;
+  padding-left: 0;
+  position: absolute;
+  width: 100%;
+}
+li:hover {
+  background-color: var(--color-focus-gray);
+}
+li label {
+  align-items: center;
+  display: flex;
+  line-height: 1.4em;
+}
+li input[type=checkbox] {
+  margin: 0 0.25em;
+}
+li::marker {
+  content: '';
+}
+/*
+ * TODO:
+ * * disable <label> containing disabled checkbox: `label:has(input[disabled])`,
+ * * disabled label styling,
+ * * focused label styling (currently only checkbox has focus),
+ * * disabled checkbox blue square focus removal.
+ * */
+
+#measurement_form {
+  min-width: 66%;
+  width: max-content;
+}

app/controllers/application_controller.rb

@@ -25,6 +25,18 @@ class ApplicationController < ActionController::Base
   #   Turbo will reload 2nd time with HTML format and flashes will be lost.
   rescue_from *ActionDispatch::ExceptionWrapper.rescue_responses.keys, with: :rescue_turbo
 
+  # Required by #respond_with (gem `responders`) used by Devise controllers.
+  respond_to :html, :turbo_stream
+
+  def after_sign_in_path_for(resource)
+    # TODO: allow setting path per-user or save last path in session and restore
+    units_path
+  end
+
+  def after_sign_out_path_for(resource)
+    new_user_session_path
+  end
+
   protected
 
   def current_user_disguised?
@@ -43,9 +55,9 @@ class ApplicationController < ActionController::Base
 
   private
 
-  def render_no_content(record)
-    helpers.render_errors(record)
-    render html: nil, layout: true
+  def render_errors(record)
+    target = record.new_record? ? [:new, record.parent || record.class] : [:edit, record]
+    render 'errors', assigns: {record: record, target: target}
   end
 
   def rescue_turbo(exception)

app/controllers/default/units_controller.rb

@@ -17,7 +17,7 @@ class Default::UnitsController < ApplicationController
 
   def import
     @unit.port!(current_user)
-    flash.now[:notice] = t('.success', unit: @unit)
+    flash.now.notice = t('.success', unit: @unit)
   ensure
     run_and_render :index
   end
@@ -30,14 +30,14 @@ class Default::UnitsController < ApplicationController
 
   def export
     @unit.port!(nil)
-    flash.now[:notice] = t('.success', unit: @unit)
+    flash.now.notice = t('.success', unit: @unit)
   ensure
     run_and_render :index
   end
 
   def destroy
     @unit.destroy!
-    flash.now[:notice] = t('.success', unit: @unit)
+    flash.now.notice = t('.success', unit: @unit)
   ensure
     run_and_render :index
   end

app/controllers/measurements_controller.rb

@@ -1,5 +1,7 @@
 class MeasurementsController < ApplicationController
   def index
+    @measurements = []
+    #@measurements = current_user.units.ordered.includes(:base, :subunits)
   end
 
   def new

app/controllers/quantities_controller.rb

@@ -19,9 +19,9 @@ class QuantitiesController < ApplicationController
   def create
     @quantity = current_user.quantities.new(quantity_params)
     if @quantity.save
-      @before = @quantity.successive
+      @before = @quantity.succeeding
       @ancestors = @quantity.ancestors
-      flash.now[:notice] = t('.success', quantity: @quantity)
+      flash.now.notice = t('.success', quantity: @quantity)
     else
       render :new
     end
@@ -33,7 +33,7 @@ class QuantitiesController < ApplicationController
   def update
     if @quantity.update(quantity_params.except(:parent_id))
       @ancestors = @quantity.ancestors
-      flash.now[:notice] = t('.success', quantity: @quantity)
+      flash.now.notice = t('.success', quantity: @quantity)
     else
       render :edit
     end
@@ -43,18 +43,22 @@ class QuantitiesController < ApplicationController
     permitted = params.require(:quantity).permit(:parent_id)
     @previous_ancestors = @quantity.ancestors
 
-    # Until UI blocks all disallowed reparents, render error messages if present
-    render_no_content(@quantity) unless @quantity.update(permitted)
-
-    @ancestors = @quantity.ancestors
-    @self_and_progenies = @quantity.with_progenies
-    @before = @self_and_progenies.last.successive
+    if @quantity.update(permitted)
+      @ancestors = @quantity.ancestors
+      # TODO: simplify into 1 query (see #succeeding comment)
+      @quantities = @quantity.with_progenies
+      @before = @quantities.last.succeeding
+    else
+      # Until UI blocks all disallowed reparents, render error messages if present.
+      flash.now.alert = @quantity.errors.full_messages
+      render :nothing
+    end
   end
 
   def destroy
     @quantity.destroy!
     @ancestors = @quantity.ancestors
-    flash.now[:notice] = t('.success', quantity: @quantity)
+    flash.now.notice = t('.success', quantity: @quantity)
   end
 
   private

app/controllers/readouts_controller.rb

@@ -1,37 +1,33 @@
 class ReadoutsController < ApplicationController
-  before_action :find_quantity, only: [:new, :discard]
+  before_action :find_quantities, only: [:new]
+  before_action :find_quantity, only: [:discard]
   before_action :find_prev_quantities, only: [:new, :discard]
 
   def new
-    new_quantities =
-      case params[:scope]
-      when 'children'
-        @quantity.subquantities
-      when 'subtree'
-        @quantity.progenies
-      else
-        [@quantity]
-      end
-    new_quantities -= @prev_quantities
-    @readouts = current_user.readouts.build(new_quantities.map { |q| {quantity: q} })
+    @quantities -= @prev_quantities
+    # TODO: raise ParameterInvalid if new_quantities.empty?
+    @readouts = @quantities.map { |q| q.readouts.build }
 
-    @user_quantities = current_user.quantities.ordered
     @user_units = current_user.units.ordered
 
-    @quantities = @prev_quantities + new_quantities
-#    @common_ancestor = current_user.quantities
-#      .common_ancestors(all_quantities.map(&:parent_id)).first
+    quantities = @prev_quantities + @quantities
+    @superquantity = current_user.quantities
+      .common_ancestors(quantities.map(&:parent_id)).first
   end
 
   def discard
     @prev_quantities -= [@quantity]
 
-    @common_ancestor = current_user.quantities
+    @superquantity = current_user.quantities
       .common_ancestors(@prev_quantities.map(&:parent_id)).first
   end
 
   private
 
+  def find_quantities
+    @quantities = current_user.quantities.find(params[:quantity])
+  end
+
   def find_quantity
     @quantity = current_user.quantities.find_by!(id: params[:id])
   end

app/controllers/units_controller.rb

@@ -1,10 +1,9 @@
 class UnitsController < ApplicationController
-  before_action only: :new do
-    find_unit if params[:id].present?
-  end
-  before_action :find_unit, only: [:edit, :update, :rebase, :destroy]
+  before_action ->{ @unit = current_user.units.find_by!(id: params[:id]) },
+    only: [:new, :edit, :update, :rebase, :destroy],
+    unless: ->{ action_name == "new" && params[:id].nil? }
 
-  before_action except: :index do
+  before_action except: [:index] do
     raise AccessForbidden unless current_user.at_least(:active)
   end
 
@@ -17,12 +16,12 @@ class UnitsController < ApplicationController
   end
 
   def create
-    @unit = current_user.units.new(unit_params)
+    @unit = current_user.units.new(params.expect(Unit::ATTRIBUTES))
     if @unit.save
-      @before = @unit.successive
-      flash.now[:notice] = t('.success', unit: @unit)
+      @before = @unit.succeeding
+      flash.now.notice = t('.success', unit: @unit)
     else
-      render :new
+      render_errors @unit
     end
   end
 
@@ -30,40 +29,32 @@ class UnitsController < ApplicationController
   end
 
   def update
-    if @unit.update(unit_params.except(:base_id))
-      flash.now[:notice] = t('.success', unit: @unit)
+    if @unit.update(params.except(:base_id).expect(Unit::ATTRIBUTES))
+      flash.now.notice = t('.success', unit: @unit)
     else
-      render :edit
+      render_errors @unit
     end
   end
 
   # TODO: Avoid double table width change by first un-hiding table header,
   # then displaying index, e.g. by re-displaying header in index
   def rebase
-    permitted = params.require(:unit).permit(:base_id)
-    permitted.merge!(multiplier: 1) if permitted[:base_id].blank? && @unit.multiplier != 1
+    unit_params = params.expect(unit: :base_id)
+    unit_params.merge!(multiplier: 1.0) if unit_params[:base_id].blank?
 
     @previous_base = @unit.base
-    @unit.update!(permitted)
+    @unit.update!(unit_params)
 
-    @before = @unit.successive
+    @before = @unit.succeeding
     if @unit.multiplier_previously_changed?
-      flash.now[:notice] = t(".multiplier_reset", unit: @unit)
+      flash.now.notice = t(".multiplier_reset", unit: @unit)
     end
   end
 
   def destroy
     @unit.destroy!
-    flash.now[:notice] = t('.success', unit: @unit)
+    flash.now.notice = t('.success', unit: @unit)
   end
 
   private
-
-  def unit_params
-    params.require(:unit).permit(Unit::ATTRIBUTES)
-  end
-
-  def find_unit
-    @unit = current_user.units.find_by!(id: params[:id])
-  end
 end

app/controllers/user/profiles_controller.rb

@@ -1,5 +1,8 @@
-class RegistrationsController < Devise::RegistrationsController
-  before_action :authenticate_user!, only: [:edit, :update, :destroy]
+class User::ProfilesController < Devise::RegistrationsController
+  def destroy
+    # TODO: Disallow/disable deletion for last admin account; update :edit view
+    super
+  end
 
   protected
 

app/controllers/users_controller.rb

@@ -37,7 +37,7 @@ class UsersController < ApplicationController
   end
 
   # NOTE: limited actions availabe to :admin by design. Users are meant to
-  # manage their accounts by themselves through registrations. :admin
+  # manage their accounts by themselves through profiles. :admin
   # is allowed to sign-in (disguise) as user and make changes from there.
 
   protected

app/helpers/application_helper.rb

@@ -1,59 +1,85 @@
 module ApplicationHelper
-  # TODO: replace legacy content_tag with tag.tagname
-  class LabelledFormBuilder < ActionView::Helpers::FormBuilder
-    (field_helpers - [:label]).each do |selector|
+  class LabeledFormBuilder < ActionView::Helpers::FormBuilder
+    (field_helpers - [:label, :hidden_field]).each do |selector|
       class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
         def #{selector}(method, options = {})
-          labelled_row_for(method, options) { super }
+          labeled_field_for(method, options) { super }
         end
       RUBY_EVAL
     end
 
     def select(method, choices = nil, options = {}, html_options = {})
-      labelled_row_for(method, options) { super }
+      labeled_field_for(method, options) { super }
     end
 
-    def submit(value, options = {})
-      @template.content_tag :tr do
-        @template.content_tag :td, super, colspan: 2
-      end
-    end
-
-    def form_for(&block)
-      @template.content_tag(:table, class: "centered") { yield(self) } +
-      # Display leftover error messages (there shouldn't be any)
-      @template.content_tag(:div, @object&.errors.full_messages.join(@template.tag(:br)))
+    def submit(value = nil, options = {})
+      value, options = nil, value if value.is_a?(Hash)
+      options[:class] = @template.class_names('button', options[:class])
+      super
     end
 
     private
 
-    def labelled_row_for(method, options)
-      @template.content_tag :tr do
-        @template.content_tag(:td, label_for(method, options), class: "unwrappable") +
-        @template.content_tag(:td, options.delete(:readonly) ? @object.public_send(method) : yield,
-          @object&.errors[method].present? ?
-            {class: "error", data: {content: @object&.errors.delete(method).join(" and ")}} :
-            {})
-      end
+    def labeled_field_for(method, options)
+      field = if options.delete(:readonly) then
+                value = object.public_send(method)
+                value = @template.l(value) if value.respond_to?(:strftime)
+                value ||= options[:placeholder]
+              else
+                yield
+              end
+      label_for(method, options) + field
     end
 
     def label_for(method, options = {})
-      return '' if options[:label] == false
-
-      text = options.delete(:label)
-      text ||= @object.class.human_attribute_name(method).capitalize
       classes = @template.class_names(required: options[:required],
-                                      error: @object&.errors[method].present?)
-      label = label(method, "#{text}:", class: classes)
-      hint = options.delete(:hint)
+                                      error: object.errors[method].present?)
 
-      label + (@template.tag(:br) + @template.content_tag(:em, hint) if hint)
+      handler = {missing_interpolation_argument_handler: method(:interpolation_missing)}
+      # Label translation search order:
+      #   controller.action.* => helpers.label.model.* => activerecord.attributes.model.*
+      # First 2 levels are translated recursively.
+      label(method, class: classes) do |builder|
+        translation = I18n.with(**handler) { deep_translate(method, **options) }
+        translation.presence || "#{builder.translation}:"
+      end
+    end
+
+    def interpolation_missing(key, values, string)
+      @template.instance_values[key.to_s] || deep_translate(key, **values)
+    end
+
+    # Extension to label text translation:
+    # * recursive translation,
+    # * interpolation of (_relative_) translation key names and instance variables,
+    # * pluralization based on any interpolable value
+    # TODO: add unit tests for the above
+    def deep_translate(key, **options)
+      options[:default] = [
+        :".#{key}",
+        :"helpers.label.#{@object_name}.#{key}_html",
+        :"helpers.label.#{@object_name}.#{key}",
+        ""
+      ]
+
+      # At least 1 interpolation key is required for #translate to act on
+      # missing interpolation arguments (i.e. call custom handler).
+      # Also setting `key` to nil avoids recurrent translation.
+      options[key] = nil
+
+      @template.t(".#{key}_html", **options) do |translation, resolved_key|
+        if translation.is_a?(Array) && (count = translation.to_h[:count])
+          @template.t(resolved_key, count: I18n.interpolate(count, **options), **options)
+        else
+          translation
+        end
+      end
     end
   end
 
-  def labelled_form_for(record, options = {}, &block)
-    options = options.deep_merge(builder: LabelledFormBuilder, data: {turbo: false})
-    form_for(record, **options) { |f| f.form_for(&block) }
+  def labeled_form_for(record, options = {}, &block)
+    extra_options = {builder: LabeledFormBuilder, html: {class: 'labeled-form'}}
+    form_for(record, **merge_attributes(options, extra_options), &block)
   end
 
   class TabularFormBuilder < ActionView::Helpers::FormBuilder
@@ -65,32 +91,36 @@ module ApplicationHelper
     [:text_field, :password_field, :text_area].each do |selector|
       class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
         def #{selector}(method, options = {})
-          options[:maxlength] ||= object.class.type_for_attribute(method).limit
-          if object.errors.include?(method)
-            options[:pattern] = except_pattern(object.public_send(method), options[:pattern])
-          end
+          options[:maxlength] ||= object.type_for_attribute(method).limit
+          # If [cols]/[size] is not set, minimum field width is controlled with
+          # stylesheet. To prevent browser estimating missing [cols]/[size]
+          # based on e.g. [maxlength], set it to 1.
+          options[:#{selector == :text_area ? :cols : :size}] ||= 1
           super
         end
       RUBY_EVAL
     end
 
     def number_field(method, options = {})
-      value = object.public_send(method)
-      if value.is_a?(BigDecimal)
-        options[:value] = value.to_scientific
-        type = object.class.type_for_attribute(method)
-        options[:step] ||= BigDecimal(10).power(-type.scale)
-        options[:max] ||= BigDecimal(10).power(type.precision - type.scale) -
-          options[:step]
-        options[:min] = options[:min] == :step ? options[:step] : options[:min]
-        options[:min] ||= -options[:max]
+      case object.type_for_attribute(method).type
+      when :float, :double
+        options[:min] ||= Float::MIN_15.to_scientific
+        options[:max] ||= Float::MAX_15.to_scientific
+        options[:oninput] = 'numberValidate(event)'
+        options[:size] ||= options[:class]&.split&.include?('hstretch') ? 1 : 6
+        options[:step] ||= :any
+        options[:value] = object.public_send("#{method}_before_type_cast")
       end
       super
     end
 
     def button(value = nil, options = {}, &block)
-      # button does not use #objectify_options
-      options.merge!(@options.slice(:form))
+      # #button does not use #objectify_options/@default_options
+      value, options = nil, value if value.is_a?(Hash)
+      options = options.merge(
+        @default_options.slice(:form),
+        class: @template.class_names('button', options[:class])
+      )
       super
     end
 
@@ -98,11 +128,7 @@ module ApplicationHelper
 
     def submit_default_value
       svg_name = object ? (object.persisted? ? 'update' : 'plus-circle-outline') : ''
-      @template.svg_tag("pictograms/#{svg_name}", super)
-    end
-
-    def except_pattern(value, pattern = nil)
-      "(?!^#{Regexp.escape(value)}$)" + (pattern || ".*")
+      @template.svg_tag(svg_name, super)
     end
   end
 
@@ -111,20 +137,21 @@ module ApplicationHelper
     # [autofocus].  Otherwise IDs are not unique when multiple forms are open
     # and the first input gets focus.
     record_object, options = nil, record_object if record_object.is_a?(Hash)
-    options.merge!(builder: TabularFormBuilder, skip_default_ids: true)
-    render_errors(record_object || record_name)
+    extra_options = {builder: TabularFormBuilder, skip_default_ids: true}
+    options = merge_attributes(options, extra_options)
     fields_for(record_name, record_object, **options, &block)
   end
 
   def tabular_form_with(**options, &block)
-    options = options.deep_merge(builder: TabularFormBuilder,
-                                 html: {autocomplete: 'off'})
-    form_with(**options, &block)
+    extra_options = {builder: TabularFormBuilder, class: 'tabular-form',
+                     html: {autocomplete: 'off'}}
+    form_with(**merge_attributes(options, extra_options), &block)
   end
 
   def svg_tag(source, label = nil, options = {})
-    svg_tag = content_tag :svg, options do
-      tag.use(href: "#{image_path(source + ".svg")}#icon")
+    label, options = nil, label if label.is_a? Hash
+    svg_tag = tag.svg(**options) do
+      tag.use(href: image_path("#{source}.svg") + '#icon')
     end
     label.blank? ? svg_tag : svg_tag + tag.span(label)
   end
@@ -134,12 +161,13 @@ module ApplicationHelper
       ['measurements', 'scale-bathroom', :restricted],
       ['quantities', 'axis-arrow', :restricted, 'right'],
       ['units', 'weight-gram', :restricted],
+      # TODO: display users tab only if >1 user present; sole_user?/sole_admin?
       ['users', 'account-multiple-outline', :admin],
     ]
 
     menu_tabs.map do |name, image, status, css_class|
       if current_user.at_least(status)
-        link_to svg_tag("pictograms/#{image}", t("#{name}.navigation")),
+        link_to svg_tag(image, t("#{name}.navigation")),
           {controller: "/#{name}", action: "index"},
           class: class_names('tab', css_class, active: name == current_tab)
       end
@@ -171,21 +199,19 @@ module ApplicationHelper
 
   def image_link_to_unless_current(name, image = nil, options = nil, html_options = {})
     name, html_options = link_or_button_options(:link, name, image, html_options)
-    html_options = html_options.deep_merge DISABLED_ATTRIBUTES if current_page?(options)
+    if current_page?(options, method: [:get, :post])
+      html_options = html_options.deep_merge DISABLED_ATTRIBUTES
+    end
     link_to name, options, html_options
   end
 
-  def render_errors(records)
-    flash[:alert] ||= []
-    Array(records).each { |record| flash[:alert] += record.errors.full_messages }
-  end
-
-  def render_flash_messages
+  def render_flash
     flash.map do |entry, messages|
+      # Conversion of flash to Array only required because of Devise.
       Array(messages).map do |message|
         tag.div class: "flash #{entry}" do
-          tag.div(sanitize(message)) + tag.button(sanitize("&times;"), tabindex: -1,
-                                                  onclick: "this.parentElement.remove();")
+          tag.span(sanitize(message)) +
+            svg_tag('close-outline', {onclick: "this.parentElement.remove()"})
         end
       end
     end.join.html_safe
@@ -204,8 +230,6 @@ module ApplicationHelper
   private
 
   def link_or_button_options(type, name, image = nil, html_options)
-    name = svg_tag("pictograms/#{image}", name) if image
-
     html_options[:class] = class_names(
       html_options[:class],
       'button',
@@ -216,10 +240,18 @@ module ApplicationHelper
       html_options[:onclick] = "return confirm('\#{html_options[:onclick][:confirm]}');"
     end
 
-    if type == :link && !(html_options[:onclick] || html_options.dig(:data, :turbo_stream))
-      name += '...'
-    end
+    link_is_local = html_options[:onclick] || html_options.dig(:data, :turbo_stream)
+    name = name.to_s
+    name += '...' if type == :link && !link_is_local
+    name = svg_tag(image, name) if image
 
     [name, html_options]
   end
+
+  # Like Hash#deep_merge, but aware of HTML attributes.
+  def merge_attributes(left, right)
+    left.deep_merge(right) do |key, lvalue, rvalue|
+      key == :class ? class_names(lvalue, rvalue) : rvalue
+    end
+  end
 end

app/helpers/quantities_helper.rb

@@ -1,7 +1,11 @@
 module QuantitiesHelper
-  def quantity_options(quantities, selected: nil)
-    values = quantities.map { |q| [sanitize(' ' * q.depth + q.name), q.id] }
-    values.unshift([t('.select_quantity'), nil, {hidden: true}])
-    options_for_select(values, selected: selected)
+  def quantities_check_boxes(quantities)
+    # Closing <details> on focusout event depends on relatedTarget for internal
+    # actions being non-null. To ensure this, all top-layer elements of
+    # ::details-content must accept focus, e.g. <label> needs tabindex="-1" */
+    collection_check_boxes(nil, :quantity, quantities, :id, :to_s_with_depth,
+                           include_hidden: false) do |b|
+      content_tag :li, b.label(tabindex: -1) { b.check_box + b.text }
+    end
   end
 end

app/javascript/application.js

@@ -1,130 +1,188 @@
 // Configure your import map in config/importmap.rb. Read more:
 // https://github.com/rails/importmap-rails
 import "@hotwired/turbo-rails"
+import "./turbo_actions.js"
+// TODO: access `data-` attributes through
+// `keyname in`/`dataset.keyname`/`delete dataset.keyname`
 
 
-/* Hide page before loaded for testing purposes */
+// Show page if hidden for testing purposes.
 function showPage(event) {
   document.documentElement.style.visibility="visible"
 }
 document.addEventListener('turbo:load', showPage)
 
 
-/* Turbo stream actions */
-Turbo.StreamElement.prototype.enableElement = function(element) {
-    element.removeAttribute("disabled")
-    element.removeAttribute("aria-disabled")
-    // 'tabindex' is not used explicitly, so removing it is safe
-    element.removeAttribute("tabindex")
-}
-
-Turbo.StreamActions.disable = function() {
-  this.targetElements.forEach((e) => {
-    e.setAttribute("disabled", "disabled")
-    e.setAttribute("aria-disabled", "true")
-    e.setAttribute("tabindex", "-1")
-  })
-}
-
-Turbo.StreamActions.enable = function() {
-  this.targetElements.forEach((e) => { this.enableElement(e) })
-}
-
-Turbo.StreamActions.hide = function() {
-  this.targetElements.forEach((e) => { e.style.display = "none" })
-}
-
-Turbo.StreamActions.close_form = function() {
-  this.targetElements.forEach((e) => {
-    /* Move focus if there's no focus or focus inside form being closed */
-    const focused = document.activeElement
-    if (!focused || (focused == document.body) || e.contains(focused)) {
-      let nextForm = e.parentElement.querySelector(`#${e.id} ~ tr:has([autofocus])`)
-      nextForm ??= e.parentElement.querySelector("tr:has([autofocus])")
-      nextForm?.querySelector("[autofocus]").focus()
-    }
-    document.getElementById(e.getAttribute("data-form")).remove()
-    if (e.hasAttribute("data-link")) {
-      this.enableElement(document.getElementById(e.getAttribute("data-link")))
-    }
-    if (e.hasAttribute("data-hidden-row")) {
-      document.getElementById(e.getAttribute("data-hidden-row")).removeAttribute("style")
-    }
-    e.remove()
-  })
-}
-
-
-/* Items table drag and drop support */
-function processKey(event) {
-  if (event.key == "Escape") {
-    event.currentTarget.querySelector("a[name=cancel]").click();
+// <details> event handlers.
+function detailsChange(event) {
+  var target = event.currentTarget
+  var count = target.querySelectorAll('input:checked:not([disabled])').length
+  var span = target.querySelector('summary > span')
+  var button = target.querySelector('button')
+  if (count > 0) {
+    span.textContent = count + ' selected';
+    Turbo.StreamElement.prototype.enableElement(button)
+  } else {
+    span.textContent = span.getAttribute('data-prompt')
+    Turbo.StreamElement.prototype.disableElement(button)
   }
 }
-window.processKey = processKey;
+window.detailsChange = detailsChange
 
-var lastEnterTime;
-function dragStart(event) {
-  lastEnterTime = event.timeStamp;
-  var row = event.currentTarget;
-  row.closest("table").querySelectorAll("thead tr").forEach((tr) => {
-    tr.toggleAttribute("hidden");
-  });
-  event.dataTransfer.setData("text/plain", row.getAttribute("data-drag-path"));
-  var rowRectangle = row.getBoundingClientRect();
-  event.dataTransfer.setDragImage(row, event.x - rowRectangle.left, event.y - rowRectangle.top);
-  event.dataTransfer.dropEffect = "move";
+// Close open <details> when focus lost.
+function detailsClose(event) {
+  if (!event.relatedTarget ||
+      event.relatedTarget.closest("details") != event.currentTarget) {
+    event.currentTarget.removeAttribute("open")
+  }
 }
-window.dragStart = dragStart;
+window.detailsClose = detailsClose
+
+window.detailsObserver = new MutationObserver((mutations) => {
+  mutations[0].target.dispatchEvent(new Event('change', {bubbles: true}))
+});
+
+
+// Validation of multiple-submit forms with different field requirements.
+function formValidate(event) {
+  var id = event.submitter.getAttribute("data-validate")
+  if (!id) return;
+
+  var input = document.getElementById(id)
+  if (!input.checkValidity()) {
+    input.reportValidity()
+    event.preventDefault()
+  }
+}
+window.formValidate = formValidate
+
+// Pattern for number precision verification. Should accept all number formats
+// accepted by Kernel#Float. Lookahead checks the number of significant digits
+// in mantissa, following expression makes sure there is only one dot.
+const numberRegExp = /^\-?(?=(?:\.?0)*(?:\.?\d){1,15}?(?:\.?0)*\.?(?:[eE]|$))(?<mantissa>\d*\.?\d+|\d+\.)(?:[eE]\-?\d{1,3})?$/
+
+// Validation of input[type=number] value precision.
+function numberValidate(event) {
+  var input = event.target
+
+  input.setCustomValidity("")
+  if (!input.validity.valid) return
+
+  var match = numberRegExp.exec(input.value)
+  if (!match ||
+      (parseFloat(input.value) == 0.0 && match.groups['mantissa'].match(/[1-9]/))) {
+    // TODO: move message to locales
+    input.setCustomValidity("Please select a value within range of double precision floating-point format.")
+  }
+}
+window.numberValidate = numberValidate
+
+
+// Keyboard event processing handlers.
+function formProcessKey(event) {
+  switch (event.key) {
+    case "Escape":
+      event.currentTarget.querySelector("a[name=cancel]").click()
+      break
+    // TODO: allow new line inside <textarea> (submit with ctrl-enter?)
+    case "Enter":
+      event.currentTarget.querySelector("button[name=button]").click()
+      event.preventDefault()
+      break
+  }
+}
+window.formProcessKey = formProcessKey
+
+function detailsProcessKey(event) {
+  // TODO: up/down arrows to move focus to prev/next line
+  switch (event.key) {
+    case "Escape":
+      if (event.currentTarget.hasAttribute("open")) {
+        event.currentTarget.removeAttribute("open")
+        event.stopPropagation()
+      }
+      break
+    case "Enter":
+      var button = event.currentTarget.querySelector("button:not([disabled])")
+      if (button) {
+        button.click()
+        // Autofocus won't be respected unless target is blurred.
+        event.target.blur()
+        event.preventDefault()
+        event.stopPropagation()
+      }
+      break
+  }
+}
+window.detailsProcessKey = detailsProcessKey;
+
+
+// Items table drag and drop support.
+var lastEnterTime
+function dragStart(event) {
+  lastEnterTime = event.timeStamp
+  var row = event.currentTarget
+  row.closest("table").querySelectorAll("thead tr").forEach((tr) => {
+    tr.toggleAttribute("hidden")
+  })
+  event.dataTransfer.setData("text/plain", row.getAttribute("data-drag-path"))
+  var rowRectangle = row.getBoundingClientRect()
+  event.dataTransfer.setDragImage(row, event.x - rowRectangle.left,
+                                  event.y - rowRectangle.top)
+  event.dataTransfer.dropEffect = "move"
+}
+window.dragStart = dragStart
 
 /*
 * Drag tracking assumptions (based on FF 122.0 experience):
 *   * Enter/Leave events at the same timeStamp may not be logically ordered
 *     (e.g. E -> E -> L, not E -> L -> E),
 *   * not every Enter event has corresponding Leave event, especially during
-*     rapid pointer moves
+*     rapid pointer moves.
 * NOTE: sometimes Leave is not emitted when pointer goes fast over table
 * and outside. This should probably be fixed in browser, than patched here.
+* TODO: replace Leave table with Enter document?
+*   https://www.quirksmode.org/js/events_order.html#link4
 */
 function dragEnter(event) {
-  //console.log(event.timeStamp + " " + event.type + ": " + event.currentTarget.id);
-  dragLeave(event);
-  lastEnterTime = event.timeStamp;
-  const id = event.currentTarget.getAttribute("data-drop-id");
-  document.getElementById(id).classList.add("dropzone");
+  //console.log(event.timeStamp + " " + event.type + ": " + event.currentTarget.id)
+  dragLeave(event)
+  lastEnterTime = event.timeStamp
+  const id = event.currentTarget.getAttribute("data-drop-id")
+  document.getElementById(id).classList.add("dropzone")
 }
-window.dragEnter = dragEnter;
+window.dragEnter = dragEnter
 
 function dragOver(event) {
-  event.preventDefault();
+  event.preventDefault()
 }
-window.dragOver = dragOver;
+window.dragOver = dragOver
 
 function dragLeave(event) {
-  //console.log(event.timeStamp + " " + event.type + ": " + event.currentTarget.id);
-  // Leave has been accounted for by Enter at the same timestamp, processed earlier
-  if (event.timeStamp <= lastEnterTime) return;
+  //console.log(event.timeStamp + " " + event.type + ": " + event.currentTarget.id)
+  // Leave has been accounted for by Enter at the same timestamp, processed earlier.
+  if (event.timeStamp <= lastEnterTime) return
   event.currentTarget.closest("table").querySelectorAll(".dropzone").forEach((tr) => {
-    tr.classList.remove("dropzone");
-  });
+    tr.classList.remove("dropzone")
+  })
 }
-window.dragLeave = dragLeave;
+window.dragLeave = dragLeave
 
 function dragEnd(event) {
-  dragLeave(event);
+  dragLeave(event)
   event.currentTarget.closest("table").querySelectorAll("thead tr").forEach((tr) => {
-    tr.toggleAttribute("hidden");
-  });
+    tr.toggleAttribute("hidden")
+  })
 }
-window.dragEnd = dragEnd;
+window.dragEnd = dragEnd
 
 function drop(event) {
-  event.preventDefault();
+  event.preventDefault()
 
-  var params = new URLSearchParams();
-  var id_param = event.currentTarget.getAttribute("data-drop-id-param");
-  var id = event.currentTarget.getAttribute("data-drop-id").split("_").pop();
-  params.append(id_param, id);
+  var params = new URLSearchParams()
+  var id_param = event.currentTarget.getAttribute("data-drop-id-param")
+  var id = event.currentTarget.getAttribute("data-drop-id").split("_").pop()
+  params.append(id_param, id)
 
   fetch(event.dataTransfer.getData("text/plain"), {
     body: params,
@@ -138,4 +196,4 @@ function drop(event) {
   .then(response => response.text())
   .then(html => Turbo.renderStreamMessage(html))
 }
-window.drop = drop;
+window.drop = drop

app/javascript/turbo_actions.js

@@ -0,0 +1,97 @@
+// Turbo Streams actions.
+
+const FORM_CONTROLS = ["BUTTON", "FIELDSET", "INPUT", "OPTGROUP", "OPTION", "SELECT",
+                       "TEXTAREA"]
+
+Object.assign(Turbo.StreamElement.prototype, {
+  disableElement(element) {
+    if (FORM_CONTROLS.includes(element.tagName)) {
+      element.setAttribute("disabled", "disabled")
+    } else {
+      element.setAttribute("aria-disabled", "true")
+      // NOTE: tabindex should not be disabled?
+      element.setAttribute("tabindex", "-1")
+    }
+  },
+
+  enableElement(element) {
+    if (FORM_CONTROLS.includes(element.tagName)) {
+      element.removeAttribute("disabled")
+    } else {
+      element.removeAttribute("aria-disabled")
+      // Assume 'tabindex' is not used explicitly, so removing it is safe.
+      element.removeAttribute("tabindex")
+    }
+  },
+
+  showElement(element) { element.style.visibility = "visible" }
+})
+
+Object.assign(Turbo.StreamActions, {
+  disable() {
+    this.targetElements.forEach((e) => { this.disableElement(e) })
+  },
+
+  enable() {
+    this.targetElements.forEach((e) => { this.enableElement(e) })
+  },
+
+  hide() {
+    this.targetElements.forEach((e) => { e.style.visibility = "collapse" })
+  },
+
+  show() {
+    this.targetElements.forEach((e) => { this.showElement(e) })
+  },
+
+  unselect() {
+    this.targetElements.forEach((e) => { e.checked = false; this.enableElement(e) })
+  },
+
+  validate_form() {
+    this.targetElements.forEach((form) => {
+      this.templateContent.querySelectorAll("span").forEach((span) => {
+        var control = document.querySelector(
+          `[form="${form.id}"][name="${span.dataset.name}"]`
+        )
+        control.setCustomValidity(span.textContent)
+        // Add event listener in capture phase to clear custom validity before
+        // `[oninput]` or any other bubble phase handler is invoked.
+        //   https://www.quirksmode.org/js/events_order.html
+        // TODO: keep invalidating current value whenever user re-enters it. Store
+        // invalid value and validation message in `[data-invalid-message/value]`
+        // and check input value on "input" event (below) (using `[pattern]` may not
+        // be suitable due to inability to customize validtion message; also
+        // pattern may be used for other, conflicting purposes).
+        // After user executes any other action (while form is open), remove `[data-]`
+        // attributes and custom validation, as value may no longer be invalid.
+        control.addEventListener(
+          "input",
+          function(event) { event.target.setCustomValidity("") },
+          {capture: true, once: true}
+        )
+      })
+      form.reportValidity()
+    })
+  },
+
+  close_form() {
+    this.targetElements.forEach((e) => {
+      // Move focus if there's no focus or focus inside form being closed.
+      const focused = document.activeElement
+      if (!focused || (focused == document.body) || e.contains(focused)) {
+        let nextForm = e.parentElement.querySelector(`#${e.id} ~ tr:has([autofocus])`)
+        nextForm ??= e.parentElement.querySelector("tr:has([autofocus])")
+        nextForm?.querySelector("[autofocus]").focus()
+      }
+      document.getElementById(e.dataset.form).remove()
+      if ('link' in e.dataset) {
+        this.enableElement(document.getElementById(e.dataset.link))
+      }
+      if ('hiddenRow' in e.dataset) {
+        this.showElement(document.getElementById(e.dataset.hiddenRow))
+      }
+      e.remove()
+    })
+  }
+})

app/models/application_record.rb

@@ -1,4 +1,6 @@
 class ApplicationRecord < ActiveRecord::Base
+  include ActionView::Helpers::TagHelper
+
   class << self
     # Cached attribute has non-user assignable value calculated from other
     # attributes' values on create/update. This simplifies and speeds up

app/models/note.rb

@@ -0,0 +1,3 @@
+class Note < ApplicationRecord
+  ATTRIBUTES = [:text]
+end

app/models/quantity.rb

@@ -6,16 +6,21 @@ class Quantity < ApplicationRecord
   belongs_to :parent, optional: true, class_name: "Quantity"
   has_many :subquantities, ->{ order(:name) }, class_name: "Quantity",
     inverse_of: :parent, dependent: :restrict_with_error
+  has_many :readouts, dependent: :restrict_with_error
 
   validate if: ->{ parent.present? } do
     errors.add(:parent, :user_mismatch) unless user_id == parent.user_id
     errors.add(:parent, :self_reference) if id == parent_id
   end
   validate if: ->{ parent.present? }, on: :update do
+    # TODO: should not report error for (parent == self)
     errors.add(:parent, :descendant_reference) if ancestor_of?(parent)
   end
   validates :name, presence: true, uniqueness: {scope: [:user_id, :parent_id]},
     length: {maximum: type_for_attribute(:name).limit}
+  # FIXME: length validation for :text type column is probably wrong; reported
+  # limit is in bytes (at least for MySQL) and check is for #length (i.e.
+  # characters); this doesn't seem to apply to :string (implemented as varchar)
   validates :description, length: {maximum: type_for_attribute(:description).limit}
 
   # Update :depths of progenies after parent change
@@ -60,26 +65,42 @@ class Quantity < ApplicationRecord
   scope :defaults, ->{ where(user: nil) }
 
   # Return: ordered [sub]hierarchy
-  scope :ordered, ->(root: nil, include_root: true) {
-    numbered = Arel::Table.new('numbered')
+  scope :ordered, ->(**kwargs) {
+    with_path(**kwargs).order(arel_table[:path])
+  }
 
-    self.model.with(numbered: numbered(:parent_id, :name)).with_recursive(arel_table.name => [
-      numbered.project(
-        numbered[Arel.star],
-        numbered.cast(numbered[:child_number], 'BINARY').as('path')
-      ).where(numbered[root && include_root ? :id : :parent_id].eq(root)),
-      numbered.project(
-        numbered[Arel.star],
-        arel_table[:path].concat(numbered[:child_number])
-      ).join(arel_table).on(numbered[:parent_id].eq(arel_table[:id]))
-    ]).order(arel_table[:path])
+  # TODO: sort recursive CTE using ORDER BY; it's supported by SQLite, so
+  # drop MySQL until it is available (?)
+  # Only ORDER BY allows proper i.e. not placing limits on user data and
+  # efficient with regard to paging (LIMIT/OFFSET) depth-first search.
+  # Sorting based on numbering is less elegant/efficient (MySQL: ROW_NUMBER cannot
+  # be used inside recursive CTE and needs separate SELECT,
+  # https://bugs.mysql.com/bug.php?id=96538).
+  # Sorting based on pathname requires I) padding to maximum column length or
+  # II) delimiter which a) cannot be used in sorted column and b) sorts before
+  # anything else (this adds complexity; NULL cannot be used when sorting).
+  # Sorting based on ARRAY is only available on PostgreSQL.
+  scope :with_path, ->(root: nil, include_root: true) {
+    with_number = Arel::Table.new('with_number')
+
+    self.model.with(with_number: with_number(:parent_id, :name))
+      .with_recursive(arel_table.name => [
+        with_number.project(
+          with_number[Arel.star],
+          with_number.cast(with_number[:number], 'BINARY').as('path')
+        ).where(with_number[root && include_root ? :id : :parent_id].eq(root)),
+        with_number.project(
+          with_number[Arel.star],
+          arel_table[:path].concat(with_number[:number])
+        ).join(arel_table).on(with_number[:parent_id].eq(arel_table[:id]))
+      ])
   }
 
   # TODO: extract named functions to custom Arel extension
   # NOTE: once recursive queries allow use of window functions, this scope can
   # be merged with :ordered
   # https://gist.github.com/ProGM/c6df08da14708dcc28b5ca325df37ceb#extending-arel
-  scope :numbered, ->(parent_column, order_column) {
+  scope :with_number, ->(parent_column, order_column) {
     select(
       arel_table[Arel.star],
       Arel::Nodes::NamedFunction.new(
@@ -92,12 +113,17 @@ class Quantity < ApplicationRecord
           ).from(arel_table),
           Arel::Nodes.build_quoted('0')
         ],
-      ).as('child_number')
+      ).as('number')
     )
   }
 
   def to_s
-    name
+    tag.pre name
+  end
+
+  def to_s_with_depth
+    # em space, U+2003
+    ' ' * depth + name
   end
 
   def destroyable?
@@ -125,15 +151,17 @@ class Quantity < ApplicationRecord
       .order(arel_table[:depth].desc)
   }
 
-  # Return: successive record in order of appearance; used for partial view reload
-  def successive
+  # Return: succeeding record in order of appearance, used for partial view reload.
+  # TODO: add scope returning succeeding element for multiple records
+  def succeeding
     quantities = Quantity.arel_table
-    Quantity.with(
-      quantities: user.quantities.ordered.select(
-        quantities[Arel.star],
-        Arel::Nodes::NamedFunction.new('LAG', [quantities[:id]]).over.as('lag_id')
-      )
-    ).where(quantities[:lag_id].eq(id)).first
+    Quantity.with(lagging_quantities: user.quantities.with_path.select(
+      quantities[Arel.star],
+      # For SQLite 'OVER () ORDER BY x' is not equivalent to 'OVER (ORDER BY x)'.
+      Arel::Nodes::NamedFunction.new('LAG', [quantities[:id]])
+        .over(Arel::Nodes::Window.new.order(Quantity.ordered.order_values)).as('lag_id')
+    )).from(Arel::Table.new(:lagging_quantities).as(:quantities))
+      .where(quantities[:lag_id].eq(id)).take
   end
 
   def with_progenies

app/models/readout.rb

@@ -4,4 +4,6 @@ class Readout < ApplicationRecord
   belongs_to :user
   belongs_to :quantity
   belongs_to :unit
+
+  # TODO: validate quantity.user_id == unit.user_id != NULL
 end

app/models/unit.rb

@@ -1,9 +1,12 @@
 class Unit < ApplicationRecord
-  ATTRIBUTES = [:symbol, :description, :multiplier, :base_id]
+  ATTRIBUTES = {unit: [:symbol, :description, :multiplier, :base_id]}
 
   belongs_to :user, optional: true
   belongs_to :base, optional: true, class_name: "Unit"
-  has_many :subunits, class_name: "Unit", inverse_of: :base, dependent: :restrict_with_error
+  # TODO: use #alias_attribute after Rails upgrade?
+  alias_method :parent, :base
+  has_many :subunits, class_name: "Unit", inverse_of: :base,
+    dependent: :restrict_with_error
 
   validate if: ->{ base.present? } do
     errors.add(:base, :user_mismatch) unless user_id == base.user_id
@@ -13,8 +16,8 @@ class Unit < ApplicationRecord
   validates :symbol, presence: true, uniqueness: {scope: :user_id},
     length: {maximum: type_for_attribute(:symbol).limit}
   validates :description, length: {maximum: type_for_attribute(:description).limit}
-  validates :multiplier, numericality: {equal_to: 1}, unless: :base
-  validates :multiplier, numericality: {greater_than: 0, precision: true, scale: true}, if: :base
+  validates :multiplier, numericality: {equal_to: 1.0}, unless: :base
+  validates :multiplier, numericality: {greater_than: 0.0}, if: :base
 
   scope :defaults, ->{ where(user: nil) }
   scope :defaults_diff, ->{
@@ -76,23 +79,21 @@ class Unit < ApplicationRecord
       .from(units).group(:base_id, :symbol)
   }
   scope :ordered, ->{
-    left_outer_joins(:base).order(ordering)
+    left_outer_joins(:base).order([
+      arel_table.coalesce(Arel::Table.new(:bases_units)[:symbol], arel_table[:symbol]),
+      arel_table[:base_id].not_eq(nil),
+      arel_table[:multiplier],
+      arel_table[:symbol]
+    ])
   }
 
-  def self.ordering
-    [arel_table.coalesce(Arel::Table.new(:bases_units)[:symbol], arel_table[:symbol]),
-     arel_table[:base_id].not_eq(nil),
-     :multiplier,
-     :symbol]
-  end
-
   before_destroy do
     # TODO: disallow destruction if any object depends on this unit
     nil
   end
 
   def to_s
-    symbol
+    tag.pre symbol
   end
 
   def movable?
@@ -103,21 +104,21 @@ class Unit < ApplicationRecord
     user_id.nil?
   end
 
-  # Should only by invoked on Units returned from #defaults_diff which are #portable
+  # Should only by invoked on Units returned from #defaults_diff which are #portable.
   def port!(recipient)
     recipient_base = base && Unit.find_by!(symbol: base.symbol, user: recipient)
-    params = slice(ATTRIBUTES - [:symbol, :base_id])
+    params = slice(ATTRIBUTES[:unit] - [:symbol, :base_id])
     Unit.find_or_initialize_by(user: recipient, symbol: symbol)
       .update!(base: recipient_base, **params)
   end
 
-  def successive
+  def succeeding
     units = Unit.arel_table
-    lead = Arel::Nodes::NamedFunction.new('LAG', [units[:id]])
-    window = Arel::Nodes::Window.new.order(*Unit.ordering)
-    lag_id = lead.over(window).as('lag_id')
-    Unit.with(
-      units: user.units.left_outer_joins(:base).select(units[Arel.star], lag_id)
-    ).where(units[:lag_id].eq(id)).first
+    Unit.with(lagging_units: user.units.left_outer_joins(:base).select(
+      units[Arel.star],
+      Arel::Nodes::NamedFunction.new('LAG', [units[:id]])
+        .over(Arel::Nodes::Window.new.order(Unit.ordered.order_values)).as('lag_id')
+    )).from(Arel::Table.new(:lagging_units).as(:units))
+      .where(units[:lag_id].eq(id)).take
   end
 end

app/models/user.rb

@@ -12,10 +12,10 @@ class User < ApplicationRecord
     disabled: 0,    # administratively disallowed to sign in
   }, default: :active, validate: true
 
-  has_many :readouts, dependent: :destroy
+  has_many :readouts, dependent: :delete_all
   accepts_nested_attributes_for :readouts
-  has_many :quantities, dependent: :destroy
-  has_many :units, dependent: :destroy
+  has_many :quantities, dependent: :delete_all
+  has_many :units, dependent: :delete_all
 
   validates :email, presence: true, uniqueness: true,
     length: {maximum: type_for_attribute(:email).limit}

app/views/application/errors.turbo_stream.erb

@@ -0,0 +1,7 @@
+<%= turbo_stream.validate_form dom_target(*@target, :form) do %>
+  <% @record.errors.attribute_names.map do |attr| %>
+    <%= tag.span data: {name: field_name(dom_class(@record), attr)} do %>
+      <%- @record.errors.full_messages_for(attr).map { |m| m + '.' }.join(' ') %>
+    <% end %>
+  <% end %>
+<% end %>

app/views/default/units/_unit.html.erb

@@ -5,7 +5,7 @@
   </td>
 
   <% if current_user.at_least(:active) %>
-    <td class="actions">
+    <td class="flex">
       <% unless unit.portable.nil? %>
         <% if unit.default? %>
           <%= image_button_to_if unit.portable?, t('.import'), 'download-outline',

app/views/default/units/index.html.erb

@@ -1,16 +1,17 @@
-<div class="rightside buttongrid">
+<div class="rightside-area buttongrid">
   <% if current_user.at_least(:active) %>
     <%# TODO: implement Import all %>
     <%#= image_button_to t('.import_all'), 'download-multiple-outline',
       import_all_default_units_path, data: {turbo_stream: true} %>
   <% end %>
-  <%= image_link_to t('.back'), 'arrow-left-bold-outline', units_path, class: 'tools' %>
+  <%= image_link_to t('.back'), 'arrow-left-bold-outline', units_path,
+    class: 'tools-area' %>
 </div>
 
-<table class="main items">
+<table class="main-area items-table">
   <thead>
     <tr>
-      <th><%= User.human_attribute_name(:symbol).capitalize %></th>
+      <th><%= Unit.human_attribute_name(:symbol) %></th>
       <% if current_user.at_least(:active) %>
         <th><%= t '.actions' %></th>
       <% end %>

app/views/layouts/application.html.erb

@@ -23,10 +23,10 @@
   </head>
 
   <body>
-    <header class="hflex">
+    <header class="flex">
       <%= image_link_to t(".source_code"), "code-braces", source_code_url %>
       <%= image_link_to t(".issue_tracker"), "bug-outline", issue_tracker_url,
-            class: "extendedright" %>
+        class: "rextend" %>
       <% if user_signed_in? %>
         <%= image_link_to_unless_current(current_user, "account-wrench-outline",
           edit_user_registration_path) %>
@@ -44,10 +44,10 @@
     </header>
 
     <div id="flashes">
-      <%= render_flash_messages %>
+      <%= render_flash %>
     </div>
 
-    <%# Allow overwriting/clearing navigation menu for some views %>
+    <%# Allows overwriting/clearing navigation menu for some views %>
     <nav class="navigation">
       <%= content_for(:navigation) || (navigation_menu if user_signed_in?) %>
     </nav>

app/views/layouts/application.turbo_stream.erb

@@ -1,6 +1,6 @@
-<%= yield %>
-
-<%# Some views may convert ActiveRecord errors to flashes, render at the end. %>
+<%# Render unconditionally, to clear previous flash messages. %>
 <%= turbo_stream.update :flashes do %>
-  <%= render_flash_messages %>
+  <%= render_flash %>
 <% end %>
+
+<%= yield %>

app/views/measurements/_form.html.erb

@@ -1,29 +1,46 @@
-<%= tabular_form_with model: Measurement.new do |form| %>
-  <fieldset>
-    <legend>
-      <%= tag.span id: :measurement_form_legend %>
-      <%= image_link_to '', "close-outline", measurements_path, name: :cancel,
-        class: 'dangerous', onclick: render_turbo_stream('form_close') %>
-    </legend>
-    <table class="items">
-      <tbody id="readouts">
-        <tr id="readouts_form">
-          <td>
-            <%= select_tag :id, quantity_options(@quantities), onchange:
-              "this.form.requestSubmit(document.getElementById('readout_submit'));",
-              class: 'quantity' %>
-            <%= form.submit id: :readout_submit, name: nil, value: nil,
-              formaction: new_readout_path, formmethod: :get, formnovalidate: true,
-              hidden: true, data: {turbo_stream: true} %>
+<%= tabular_form_with model: Measurement.new, id: :measurement_form,
+  class: 'topside-area flex vertical center',
+  html: {onkeydown: 'formProcessKey(event)'} do |form| %>
+
+  <table class="items-table center">
+    <tbody id="readouts">
+      <%= tabular_fields_for @measurement do |form| %>
+        <tr class="italic">
+          <td class="hexpand hmin50"><%= t '.taken_at_html' %></td>
+          <td colspan="3" class="ralign">
+            <%= form.datetime_field :taken_at, required: true %>
           </td>
-          <td></td>
-          <td></td>
-          <td></td>
         </tr>
-        <tr id="measurement_form_actions">
-          <td colspan="4"><div class="actions centered"><%= form.button %></div></td>
-        </tr>
-      </tbody>
-    </table>
-  </fieldset>
+      <% end %>
+    </tbody>
+  </table>
+
+  <%# TODO: right-click selection; unnecessary with hierarchical tags? %>
+  <details id="quantity_select" class="center hexpand" open
+           onkeydown="detailsProcessKey(event)">
+    <summary autofocus>
+      <%# TODO: Set content with CSS when span empty to avoid duplication; or
+        change to disabled input with prompt %>
+      <span data-prompt="<%= t('.select_quantity') %>">
+        <%= t('.select_quantity') %>
+      </span>
+      <%= image_button_tag t(:apply), "update", name: nil, disabled: true,
+        formaction: new_readout_path, formmethod: :get, formnovalidate: true,
+        data: {turbo_stream: true} %>
+    </summary>
+    <ul><%= quantities_check_boxes(@quantities) %></ul>
+  </details>
+
+  <div class="flex reverse">
+    <%= form.button id: :create_measurement_button, disabled: true -%>
+    <%= image_link_to t(:cancel), "close-outline", measurements_path, name: :cancel,
+      class: 'auxiliary dangerous', onclick: render_turbo_stream('form_close') %>
+  </div>
 <% end %>
+
+<script>
+  quantity_select.addEventListener('focusout', detailsClose)
+  quantity_select.addEventListener('change', detailsChange)
+  detailsObserver.observe(quantity_select.querySelector('ul'),
+    {subtree: true, attributeFilter: ['disabled']})
+</script>

app/views/measurements/_form_close.html.erb

@@ -1,2 +1,4 @@
-<%= turbo_stream.update :measurement_form %>
 <%= turbo_stream.update :flashes %>
+<%= turbo_stream.remove :measurement_form %>
+<%= turbo_stream.show :no_items -%>
+<%= turbo_stream.enable :new_measurement_link -%>

app/views/measurements/index.html.erb

@@ -1,5 +1,5 @@
 <%# TODO: show hint when no quantities/units defined %>
-<div class="rightside buttongrid">
+<div class="rightside-area buttongrid">
   <% if current_user.at_least(:active) %>
     <%= image_link_to t('.new_measurement'), 'plus-outline', new_measurement_path,
       id: :new_measurement_link, onclick: 'this.blur();',
@@ -7,4 +7,8 @@
   <% end %>
 </div>
 
-<%= tag.div class: 'main', id: :measurement_form %>
+<table class="main-area">
+  <tbody id="measurements">
+    <%= render(@measurements) || render_no_items %>
+  </tbody>
+</table>

app/views/measurements/new.turbo_stream.erb

@@ -1,4 +1,5 @@
 <%= turbo_stream.disable :new_measurement_link -%>
-<%= turbo_stream.update :measurement_form do %>
+<%= turbo_stream.hide :no_items -%>
+<%= turbo_stream.append_all 'body' do %>
   <%= render partial: 'form' %>
 <% end %>

app/views/quantities/_form.html.erb

@@ -1,19 +1,16 @@
 <%= tabular_fields_for @quantity, form: form_tag do |form| %>
-  <%- tag.tr id: row, class: "form", onkeydown: "processKey(event)",
+  <%- tag.tr id: row, class: "form", onkeydown: "formProcessKey(event)",
     data: {link: link, form: form_tag, hidden_row: hidden_row} do %>
 
     <td style="--depth:<%= @quantity.depth %>">
-      <%= form.text_field :name, required: true, autofocus: true, size: 20 %>
-    </td>
-    <td>
-      <%= form.text_area :description, cols: 30, rows: 1, escape: false %>
-    </td>
+      <%= form.text_field :name, autofocus: true, class: 'hstretch', required: true %>
+    <td><%= form.text_area :description, class: 'hstretch', escape: false, rows: 1 %>
 
-    <td class="actions">
+    <td class="flex">
       <%= form.button %>
-      <%= image_link_to t(:cancel), "close-outline", quantities_path, class: 'dangerous',
-        name: :cancel, onclick: render_turbo_stream('form_close', {row: row}) %>
-    </td>
-    <td></td>
+      <%= image_link_to t(:cancel), "close-outline", quantities_path,
+        class: 'dangerous', name: :cancel,
+        onclick: render_turbo_stream('form_close', {row: row}) %>
+    <td>
   <% end %>
 <% end %>

app/views/quantities/_quantity.html.erb

@@ -1,24 +1,24 @@
-<%= tag.tr id: dom_id(quantity),
-           ondragstart: "dragStart(event)", ondragend: "dragEnd(event)",
-           ondragover: "dragOver(event)", ondrop: "drop(event)",
-           ondragenter: "dragEnter(event)", ondragleave: "dragLeave(event)",
-           data: {drag_path: reparent_quantity_path(quantity), drop_id: dom_id(quantity),
-                  drop_id_param: "quantity[parent_id]"} do %>
+<tr id="<%= dom_target(quantity) %>"
+    ondragstart="dragStart(event)" ondragend="dragEnd(event)"
+    ondragover="dragOver(event)" ondrop="drop(event)"
+    ondragenter="dragEnter(event)" ondragleave="dragLeave(event)"
+    data-drag-path="<%= reparent_quantity_path(quantity) %>"
+    data-drop-id="<%= dom_target(quantity) %>"
+    data-drop-id-param="<%= field_name(:quantity, :parent_id) %>">
 
-  <td class="link" style="--depth:<%= quantity.depth %>">
-    <%= link_to quantity, edit_quantity_path(quantity), onclick: 'this.blur();',
-      data: {turbo_stream: true} %>
-  </td>
-  <td><%= quantity.description %></td>
+  <td style="--depth:<%= quantity.depth %>">
+    <%= link_to quantity, edit_quantity_path(quantity), class: 'link',
+      onclick: 'this.blur();', data: {turbo_stream: true} %>
+  <td><%= quantity.description %>
 
   <% if current_user.at_least(:active) %>
-    <td class="actions">
-      <%= image_link_to t('.new_subquantity'), 'plus-outline', new_quantity_path(quantity),
-        id: dom_id(quantity, :new, :link), onclick: 'this.blur();', data: {turbo_stream: true} %>
+    <td class="flex">
+      <%= image_link_to t('.new_subquantity'), 'plus-outline',
+        new_quantity_path(quantity), id: dom_target(:new, quantity, :link),
+        onclick: 'this.blur();', data: {turbo_stream: true} %>
 
       <%= image_button_to_if quantity.destroyable?, t('.destroy'), 'delete-outline',
         quantity_path(quantity), method: :delete %>
-    </td>
-    <td class="handle" draggable="true">&#x283F</td>
+
+    <td class="handle" draggable="true">&#x283F
   <% end %>
-<% end %>

app/views/quantities/create.turbo_stream.erb

@@ -1,7 +1,5 @@
-<%= turbo_stream.close_form dom_id(@quantity.parent || Quantity, :new) %>
-<%= turbo_stream.remove :no_items %>
+<%= turbo_stream.close_form dom_target(:new, @quantity.parent || :quantity) %>
 <% @ancestors.each do |ancestor| %>
   <%= turbo_stream.replace ancestor %>
 <% end %>
-<%= @before ? turbo_stream.before(@before, @quantity) :
-  turbo_stream.append(:quantities, @quantity) %>
+<%= turbo_stream.before @before || :endmark, @quantity %>

app/views/quantities/destroy.turbo_stream.erb

@@ -2,4 +2,3 @@
   <%= turbo_stream.replace ancestor %>
 <% end %>
 <%= turbo_stream.remove @quantity %>
-<%= turbo_stream.append(:quantities, render_no_items) if current_user.quantities.empty? %>

app/views/quantities/edit.turbo_stream.erb

@@ -1,13 +1,12 @@
-<% ids = {row: dom_id(@quantity, :edit),
-          hidden_row: dom_id(@quantity),
+<% ids = {row: dom_target(:edit, @quantity),
+          hidden_row: dom_target(@quantity),
           link: nil,
-          form_tag: dom_id(@quantity, :edit, :form)} %>
+          form_tag: dom_target(:edit, @quantity, :form)} %>
 
-<%= turbo_stream.append :quantity_form do %>
+<%= turbo_stream.append_all 'body' do %>
   <%- tabular_form_with model: @quantity, html: {id: ids[:form_tag]} do %>
   <% end %>
 <% end %>
 
 <%= turbo_stream.hide ids[:hidden_row] %>
-<%= turbo_stream.remove ids[:row] %>
 <%= turbo_stream.after @quantity, partial: 'form', locals: ids -%>

app/views/quantities/index.html.erb

@@ -1,33 +1,31 @@
-<div class="rightside buttongrid">
+<div class="rightside-area buttongrid">
   <% if current_user.at_least(:active) %>
     <%= image_link_to t('.new_quantity'), 'plus-outline', new_quantity_path,
-      id: dom_id(Quantity, :new, :link), onclick: 'this.blur();',
-      data: {turbo_stream: true} %>
+      id: :new_quantity_link, onclick: 'this.blur();', data: {turbo_stream: true} %>
   <% end %>
-  <%#= image_link_to t('.import_quantities'), 'download-outline', default_quantities_path,
-    class: 'tools' %>
+  <%#= image_link_to t('.import_quantities'), 'download-outline',
+    default_quantities_path, class: 'tools-area' %>
 </div>
 
-<%= tag.div class: 'main', id: :quantity_form %>
+<table class="main-area items-table">
+  <caption class="hint"><%= t '.no_items' %></caption>
 
-<table class="main items">
-  <thead>
+  <tbody>
     <tr>
-      <th><%= Quantity.human_attribute_name(:name).capitalize %></th>
-      <th><%= Quantity.human_attribute_name(:description).capitalize %></th>
-      <% if current_user.at_least(:active) %>
-        <th><%= t :actions %></th>
-        <th></th>
-      <% end %>
-    </tr>
-    <%= tag.tr id: "quantity_", hidden: true,
-               ondragover: "dragOver(event)", ondrop: "drop(event)",
-               ondragenter: "dragEnter(event)", ondragleave: "dragLeave(event)",
-               data: {drop_id: "quantity_", drop_id_param: "quantity[parent_id]"} do %>
-      <th colspan="4"><%= t '.top_level_drop' %></th>
+      <th class="hmintext"><%= Quantity.human_attribute_name(:name) %>
+      <th class="hexpand"><%= Quantity.human_attribute_name(:description) %>
+    <% if current_user.at_least(:active) %>
+      <th><%= t :actions %>
+      <th>
+
+    <tr id="quantity_" hidden
+      ondragover="dragOver(event)" ondrop="drop(event)"
+      ondragenter="dragEnter(event)" ondragleave="dragLeave(event)"
+      data-drop-id="quantity_"
+      data-drop-id-param="<%= field_name(:quantity, :parent_id) %>">
+      <th colspan="4"><%= t '.top_level_drop' %>
     <% end %>
-  </thead>
-  <tbody id="quantities">
-    <%= render(@quantities) || render_no_items %>
-  </tbody>
+
+    <%= render @quantities %>
+    <tr id="endmark" hidden>
 </table>

app/views/quantities/new.turbo_stream.erb

@@ -1,20 +1,15 @@
-<% dom_obj = @quantity.parent || @quantity %>
-<% ids = {row: dom_id(dom_obj, :new),
+<% target_id = dom_target(:new, @quantity.parent || :quantity) %>
+<% ids = {row: target_id,
           hidden_row: nil,
-          link: dom_id(dom_obj, :new, :link),
-          form_tag: dom_id(dom_obj, :new, :form)} %>
+          link: dom_target(target_id, :link),
+          form_tag: dom_target(target_id, :form)} %>
 
 <%= turbo_stream.disable ids[:link] -%>
 
-<%= turbo_stream.append :quantity_form do %>
+<%= turbo_stream.append_all 'body' do %>
   <%- tabular_form_with model: @quantity, html: {id: ids[:form_tag]} do |form| %>
     <%= form.hidden_field :parent_id if @quantity.parent_id? %>
   <% end %>
 <% end %>
 
-<% if @quantity.parent_id? %>
-  <%= turbo_stream.remove ids[:row] %>
-  <%= turbo_stream.after @quantity.parent, partial: 'form', locals: ids %>
-<% else %>
-  <%= turbo_stream.prepend :quantities, partial: 'form', locals: ids %>
-<% end %>
+<%= turbo_stream.after @quantity.parent || :quantity_, partial: 'form', locals: ids %>

app/views/quantities/reparent.turbo_stream.erb

@@ -1,9 +1,7 @@
-<% @self_and_progenies.each do |q| %>
-  <%= turbo_stream.remove q %>
-<% end %>
 <% @previous_ancestors.union(@ancestors).each do |ancestor| %>
   <%= turbo_stream.replace ancestor %>
 <% end %>
-<% @self_and_progenies.each do |q| %>
-  <%= @before ? turbo_stream.before(@before, q) : turbo_stream.append(:quantities, q) %>
+<% @quantities.each do |quantity| %>
+  <%= turbo_stream.remove quantity %>
+  <%= turbo_stream.before @before || :endmark, quantity %>
 <% end %>

app/views/quantities/update.turbo_stream.erb

@@ -1,4 +1,4 @@
-<%= turbo_stream.close_form dom_id(@quantity, :edit) %>
+<%= turbo_stream.close_form dom_target(:edit, @quantity) %>
 <% @ancestors.push(@quantity).each do |ancestor| %>
   <%= turbo_stream.replace ancestor %>
 <% end %>

app/views/readouts/_form.html.erb

@@ -1,28 +1,22 @@
+<%# TODO: add readout reordering by dragging %>
 <%= tabular_fields_for 'readouts[]', readout do |form| %>
-  <%- tag.tr id: dom_id(readout.quantity, :new, :readout),
-             onkeydown: 'processKey(event)' do %>
+  <%- tag.tr id: dom_target(:new, readout.quantity, :readout) do %>
     <td>
-      <%#= readout.quantity.relative_pathname(@common_ancestor) %>
-      <%= form.collection_select :quantity_id, @user_quantities,
-        :id, ->(q){ sanitize('&emsp;' * q.depth + q.name) },
-        {disabled: @quantities.map(&:id).delete!(form.object.quantity.id)},
-        {class: 'quantity'} %>
+      <%# TODO: add grayed readout index (in separate column?) %>
+      <%= readout.quantity.relative_pathname(@superquantity) %>
+      <%= form.hidden_field :quantity_id %>
     </td>
     <td>
-      <%= form.number_field :value, required: true, autofocus: true, size: 10 %>
+      <%= form.number_field :value, required: true, autofocus: readout_counter == 0 %>
     </td>
     <td>
       <%= form.collection_select :unit_id, @user_units, :id,
-        ->(u){ sanitize('&emsp;' * (u.base_id ? 1 : 0) + u.symbol) } %>
+        ->(u){ sanitize('&emsp;' * (u.base_id ? 1 : 0) + u.symbol) },
+        {prompt: '', disabled: '', selected: ''}, required: true %>
     </td>
-
-    <td class="actions">
-      <%= image_button_tag t('.new_children'), 'plus-multiple-outline',
-        formaction: new_measurement_path(readout.quantity, :children),
-        formmethod: :get, formnovalidate: true, data: {turbo_stream: true} %>
-      <%#= image_button_tag t('.new_subtree'), 'plus-multiple-outline',
-        formaction: new_measurement_path(:subtree), **common_options -%>
-      <%= image_button_tag '', 'delete-outline', class: 'dangerous',
+    <td class="flex">
+      <%# TODO: change to _link_ after giving up displaying relative paths %>
+      <%= image_button_tag '', 'delete-outline', class: 'dangerous', name: nil,
         formaction: discard_readouts_path(readout.quantity),
         formmethod: :get, formnovalidate: true, data: {turbo_stream: true} %>
     </td>

app/views/readouts/_form_discard.html.erb

@@ -1,2 +0,0 @@
-<%= turbo_stream.remove dom_id(@quantity, :new, :readout) %>
-<%= render partial: 'form_repath' %>

app/views/readouts/_form_repath.html.erb

@@ -1,7 +1,7 @@
-<%= turbo_stream.update(:measurement_form_legend) { @common_ancestor&.pathname } %>
+<%= turbo_stream.update(:measurement_form_legend) { @superquantity&.pathname } %>
 
 <% @prev_quantities.each do |pq| %>
-  <%= turbo_stream.update dom_id(pq, nil, :pathname) do %>
-    <%= pq.relative_pathname(@common_ancestor) %>
+  <%= turbo_stream.update dom_target(pq, :pathname) do %>
+    <%= pq.relative_pathname(@superquantity) %>
   <% end %>
 <% end %>

app/views/readouts/discard.turbo_stream.erb

@@ -0,0 +1,4 @@
+<%= turbo_stream.disable :create_measurement_button if @prev_quantities.one? %>
+<%= turbo_stream.remove dom_target(:new, @quantity, :readout) %>
+<%= render partial: 'form_repath' %>
+<%= turbo_stream.unselect dom_target(@quantity) %>

app/views/readouts/new.turbo_stream.erb

@@ -1,8 +1,8 @@
-<%#= render partial: 'form_repath' %>
-
 <% @readouts.each do |r| %>
-  <%= turbo_stream.disable_all "select.quantity option[value='#{r.quantity_id}']" %>
+  <%= turbo_stream.disable dom_target(r.quantity) %>
 <% end %>
-<%= turbo_stream.before :readouts_form do %>
+<%= render partial: 'form_repath' %>
+<%= turbo_stream.append :readouts do %>
   <%= render partial: 'form', collection: @readouts, as: :readout %>
 <% end %>
+<%= turbo_stream.enable :create_measurement_button if @prev_quantities.empty? %>

app/views/units/_form.html.erb

@@ -1,22 +1,19 @@
 <%= tabular_fields_for @unit, form: form_tag do |form| %>
-  <%- tag.tr id: row, class: "form", onkeydown: "processKey(event)",
+  <%- tag.tr id: row, class: "form", onkeydown: "formProcessKey(event)",
     data: {link: link, form: form_tag, hidden_row: hidden_row} do %>
 
     <td style="--depth:<%= @unit.base_id? ? 1 : 0 %>">
-      <%= form.text_field :symbol, required: true, autofocus: true, size: 12 %>
-    </td>
+      <%= form.text_field :symbol, autofocus: true, class: 'hstretch', required: true %>
     <td>
-      <%= form.text_area :description, cols: 30, rows: 1, escape: false %>
-    </td>
-    <td class="number">
-      <%= form.number_field :multiplier, required: true, size: 10, min: :step if @unit.base_id? %>
-    </td>
+      <% if @unit.base_id? %>
+        <%= form.number_field :multiplier, class: 'hstretch', required: true %>
+      <% end %>
+    <td><%= form.text_area :description, class: 'hstretch', escape: false, rows: 1 %>
 
-    <td class="actions">
+    <td class="flex">
       <%= form.button %>
       <%= image_link_to t(:cancel), "close-outline", units_path, class: 'dangerous',
         name: :cancel, onclick: render_turbo_stream('form_close', {row: row}) %>
-    </td>
-    <td></td>
+    <td>
   <% end %>
 <% end %>

app/views/units/_unit.html.erb

@@ -1,31 +1,32 @@
-<%= tag.tr id: dom_id(unit),
-           ondragstart: "dragStart(event)", ondragend: "dragEnd(event)",
-           ondragover: "dragOver(event)", ondrop: "drop(event)",
-           ondragenter: "dragEnter(event)", ondragleave: "dragLeave(event)",
-           data: {drag_path: rebase_unit_path(unit),
-                  drop_id: dom_id(unit.base || unit),
-                  drop_id_param: "unit[base_id]"} do %>
+<tr id="<%= dom_target(unit) %>"
+    ondragstart="dragStart(event)" ondragend="dragEnd(event)"
+    ondragover="dragOver(event)" ondrop="drop(event)"
+    ondragenter="dragEnter(event)" ondragleave="dragLeave(event)"
+    data-drag-path="<%= rebase_unit_path(unit) %>"
+    data-drop-id="<%= dom_target(unit.base || unit) %>"
+    data-drop-id-param="<%= field_name(:unit, :base_id) %>">
 
-  <td class="link" style="--depth:<%= unit.base_id? ? 1 : 0 %>">
-    <%= link_to unit, edit_unit_path(unit), onclick: 'this.blur();', data: {turbo_stream: true} %>
-  </td>
-  <td><%= unit.description %></td>
-  <td class="number"><%= unit.multiplier.to_html %></td>
+  <td style="--depth:<%= unit.base_id? ? 1 : 0 %>">
+    <%= link_to unit, edit_unit_path(unit), class: 'link', onclick: 'this.blur();',
+      data: {turbo_stream: true} %>
+  <%# Closing <td> tag required to avoid whitespace inclusion for testing. %>
+  <td class="ralign"><%= unit.multiplier.to_html if unit.base_id? %></td>
+  <td><%= unit.description %>
 
   <% if current_user.at_least(:active) %>
-    <td class="actions">
+    <td class="flex">
       <% unless unit.base_id? %>
         <%= image_link_to t('.new_subunit'), 'plus-outline', new_unit_path(unit),
-          id: dom_id(unit, :new, :link), onclick: 'this.blur();', data: {turbo_stream: true} %>
+          id: dom_target(:new, unit, :link), onclick: 'this.blur();',
+          data: {turbo_stream: true} %>
       <% end %>
 
-      <%= image_button_to_if unit.movable?, t('.destroy'), 'delete-outline', unit_path(unit),
-        method: :delete %>
-    </td>
+      <%= image_button_to_if unit.movable?, t('.destroy'), 'delete-outline',
+        unit_path(unit), method: :delete %>
+
     <% if unit.movable? %>
-      <td class="handle" draggable="true">&#x283F</td>
+      <td class="handle" draggable="true">&#x283F
     <% else %>
-      <td></td>
+      <td>
     <% end %>
   <% end %>
-<% end %>

app/views/units/create.turbo_stream.erb

@@ -1,4 +1,3 @@
-<%= turbo_stream.close_form dom_id(@unit.base || Unit, :new) %>
-<%= turbo_stream.remove :no_items %>
+<%= turbo_stream.close_form dom_target(:new, @unit.base || :unit) %>
 <%= turbo_stream.replace @unit.base if @unit.base_id? %>
-<%= @before ? turbo_stream.before(@before, @unit) : turbo_stream.append(:units, @unit) %>
+<%= turbo_stream.before @before || :endmark, @unit %>

app/views/units/destroy.turbo_stream.erb

@@ -1,3 +1,2 @@
 <%= turbo_stream.replace @unit.base if @unit.base_id? %>
 <%= turbo_stream.remove @unit %>
-<%= turbo_stream.append(:units, render_no_items) if current_user.units.empty? %>

app/views/units/edit.turbo_stream.erb

@@ -1,13 +1,12 @@
-<% ids = {row: dom_id(@unit, :edit),
-          hidden_row: dom_id(@unit),
+<% ids = {row: dom_target(:edit, @unit),
+          hidden_row: dom_target(@unit),
           link: nil,
-          form_tag: dom_id(@unit, :edit, :form)} %>
+          form_tag: dom_target(:edit, @unit, :form)} %>
 
-<%= turbo_stream.append :unit_form do %>
+<%= turbo_stream.append_all 'body' do %>
   <%- tabular_form_with model: @unit, html: {id: ids[:form_tag]} do %>
   <% end %>
 <% end %>
 
 <%= turbo_stream.hide ids[:hidden_row] %>
-<%= turbo_stream.remove ids[:row] %>
 <%= turbo_stream.after @unit, partial: 'form', locals: ids -%>

app/views/units/index.html.erb

@@ -1,32 +1,33 @@
-<div class="rightside buttongrid">
+<div class="rightside-area buttongrid">
   <% if current_user.at_least(:active) %>
     <%= image_link_to t('.new_unit'), 'plus-outline', new_unit_path,
-      id: dom_id(Unit, :new, :link), onclick: 'this.blur();', data: {turbo_stream: true} %>
+      id: :new_unit_link, onclick: 'this.blur();', data: {turbo_stream: true} %>
   <% end %>
-  <%= image_link_to t('.import_units'), 'download-outline', default_units_path, class: 'tools' %>
+  <%= image_link_to t('.import_units'), 'download-outline', default_units_path,
+    class: 'tools-area' %>
 </div>
 
-<%= tag.div id: :unit_form %>
+<table class="main-area items-table">
+  <caption class="hint"><%= t '.no_items' %></caption>
 
-<table class="main items">
-  <thead>
+  <tbody>
     <tr>
-      <th><%= User.human_attribute_name(:symbol).capitalize %></th>
-      <th><%= User.human_attribute_name(:description).capitalize %></th>
-      <th><%= User.human_attribute_name(:multiplier).capitalize %></th>
-      <% if current_user.at_least(:active) %>
-        <th><%= t :actions %></th>
-        <th></th>
-      <% end %>
-    </tr>
-    <%= tag.tr id: "unit_", hidden: true,
-               ondragover: "dragOver(event)", ondrop: "drop(event)",
-               ondragenter: "dragEnter(event)", ondragleave: "dragLeave(event)",
-               data: {drop_id: "unit_", drop_id_param: "unit[base_id]"} do %>
-      <th colspan="5"><%= t '.top_level_drop' %></th>
+      <th class="hmintext"><%= Unit.human_attribute_name(:symbol) %>
+      <th class="hminnumber"><%= Unit.human_attribute_name(:multiplier) %>
+      <th class="hexpand"><%= Unit.human_attribute_name(:description) %>
+    <% if current_user.at_least(:active) %>
+      <th><%= t :actions %>
+      <th>
+
+    <tr id="unit_" hidden
+      ondragover="dragOver(event)" ondrop="drop(event)"
+      ondragenter="dragEnter(event)" ondragleave="dragLeave(event)"
+      data-drop-id="unit_" data-drop-id-param="<%= field_name(:unit, :base_id) %>">
+      <th colspan="5"><%= t '.top_level_drop' %>
     <% end %>
-  </thead>
-  <tbody id="units">
-    <%= render(@units) || render_no_items %>
-  </tbody>
+
+    <%= render @units %>
+    <%# Hidden rows with IDs allow simplier row insertion by using only
+      turbo_stream #after/#before instead of #after + #prepend/#before + #append. %>
+    <tr id="endmark" hidden>
 </table>

app/views/units/new.turbo_stream.erb

@@ -1,20 +1,15 @@
-<% dom_obj = @unit.base || @unit %>
-<% ids = {row: dom_id(dom_obj, :new),
+<% target_id = dom_target(:new, @unit.base || :unit) %>
+<% ids = {row: target_id,
           hidden_row: nil,
-          link: dom_id(dom_obj, :new, :link),
-          form_tag: dom_id(dom_obj, :new, :form)} %>
+          link: dom_target(target_id, :link),
+          form_tag: dom_target(target_id, :form)} %>
 
 <%= turbo_stream.disable ids[:link] -%>
 
-<%= turbo_stream.append :unit_form do %>
+<%= turbo_stream.append_all 'body' do %>
   <%- tabular_form_with model: @unit, html: {id: ids[:form_tag]} do |form| %>
     <%= form.hidden_field :base_id if @unit.base_id? %>
   <% end %>
 <% end %>
 
-<% if @unit.base_id? %>
-  <%= turbo_stream.remove ids[:row] %>
-  <%= turbo_stream.after @unit.base, partial: 'form', locals: ids %>
-<% else %>
-  <%= turbo_stream.prepend :units, partial: 'form', locals: ids %>
-<% end %>
+<%= turbo_stream.after @unit.base || :unit_, partial: 'form', locals: ids %>

app/views/units/rebase.turbo_stream.erb

@@ -1,4 +1,5 @@
+<% [@previous_base, @unit.base].uniq.compact.each do |unit| %>
+  <%= turbo_stream.replace unit %>
+<% end %>
 <%= turbo_stream.remove @unit %>
-<%= turbo_stream.replace @previous_base if @previous_base %>
-<%= turbo_stream.replace @unit.base if @unit.base_id? && (@previous_base.id != @unit.base_id) %>
-<%= @before ? turbo_stream.before(@before, @unit) : turbo_stream.append(:units, @unit) %>
+<%= turbo_stream.before @before || :endmark, @unit %>

app/views/units/update.turbo_stream.erb

@@ -1,3 +1,3 @@
-<%= turbo_stream.close_form dom_id(@unit, :edit) %>
+<%= turbo_stream.close_form dom_target(:edit, @unit) %>
 <%= turbo_stream.replace @unit.base if @unit.base_id? %>
 <%= turbo_stream.replace @unit %>

app/views/users/confirmations/create.turbo_stream.erb

@@ -0,0 +1 @@
+<% flash.discard %>

app/views/users/confirmations/new.html.erb

@@ -1,8 +0,0 @@
-<div class="main">
-  <%= labelled_form_for resource, url: user_confirmation_path do |f| %>
-    <%= f.email_field :email, required: true, size: 30, autofocus: true, autocomplete: "email",
-      value: (resource.pending_reconfirmation? ? resource.unconfirmed_email : resource.email) %>
-
-    <%= f.submit t(:resend_confirmation) %>
-  <% end %>
-</div>

app/views/users/index.html.erb

@@ -1,36 +1,32 @@
-<table class="main items" id="users">
+<table class="main-area items-table" id="users">
   <thead>
     <tr>
-      <th><%= User.human_attribute_name(:email).capitalize %></th>
-      <th><%= User.human_attribute_name(:status).capitalize %></th>
-      <th><%= User.human_attribute_name(:confirmed_at).capitalize %></th>
-      <th>
-        <%= User.human_attribute_name(:created_at).capitalize %>&nbsp;<sup>UTC</sup>
-      </th>
+      <th><%= User.human_attribute_name(:email) %></th>
+      <th><%= User.human_attribute_name(:status) %></th>
+      <th><%= User.human_attribute_name(:confirmed_at) %></th>
+      <th><pre><%= User.human_attribute_name(:created_at) %> <sup>(UTC)</sup></pre></th>
       <th><%= t :actions %></th>
     </tr>
   </thead>
   <tbody>
     <% @users.each do |user| %>
       <tr>
-        <td class="link"><%= link_to user, user_path(user) %></td>
+        <td><%= link_to user, user_path(user), class: 'link' %></td>
         <td>
           <% if user == current_user %>
             <%= user.status %>
           <% else %>
             <%= form_for user do |u| %>
-              <%= u.select :status, User.statuses.keys, {}, autocomplete: "off",
-                onchange: "this.form.requestSubmit();" %>
+              <%= u.select :status, User.statuses.keys, {}, autocomplete: 'off',
+                onchange: 'this.form.requestSubmit();' %>
             <% end %>
           <% end %>
         </td>
-        <td class="svg">
-          <%= svg_tag "pictograms/checkbox-marked-outline" if user.confirmed_at.present? %>
-        </td>
-        <td><%= user.created_at.to_fs(:db_without_sec) %></td>
-        <td class="actions">
+        <td><%= svg_tag 'checkbox-marked-outline' if user.confirmed_at.present? %></td>
+        <td><pre><%= l user.created_at, format: :without_tz %></pre></td>
+        <td class="flex">
           <% if allow_disguise?(user) %>
-            <%= image_link_to t(".disguise"), "incognito", disguise_user_path(user) %>
+            <%= image_link_to t('.disguise'), 'incognito', disguise_user_path(user) %>
           <% end %>
         </td>
       </tr>

app/views/users/mailer/confirmation_instructions.html.erb

@@ -1,5 +1,5 @@
 <p>Welcome <%= @email %>!</p>
 
 <p>You can confirm your account email through the link below:</p>
-
+<!-- FIXME: is confirmation_url valid route prefix? -->
 <p><%= link_to 'Confirm my account', confirmation_url(@resource, confirmation_token: @token) %></p>

app/views/users/passwords/create.turbo_stream.erb

@@ -0,0 +1 @@
+<% flash.discard %>

app/views/users/passwords/edit.html.erb

@@ -1,13 +1,12 @@
-<div class="main">
-  <%= labelled_form_for resource, url: user_password_path, html: {method: :put} do |f| %>
-    <%= f.hidden_field :reset_password_token, label: false %>
+<%= labeled_form_for resource, url: user_password_path,
+  html: {method: :put, class: 'main-area', data: {turbo: false}} do |f| %>
 
-    <%= f.password_field :password, label: t(".new_password"), required: true, size: 30,
-      minlength: @minimum_password_length, autofocus: true, autocomplete: "new-password",
-      hint: t("users.minimum_password_length", count: @minimum_password_length) %>
-    <%= f.password_field :password_confirmation, label: t(".password_confirmation"),
-      required: true, size: 30, minlength: @minimum_password_length, autocomplete: "off" %>
+  <%= f.hidden_field :reset_password_token %>
 
-    <%= f.submit t(".update_password") %>
-  <% end %>
-</div>
+  <%= f.password_field :password, required: true, size: 30, autofocus: true,
+    minlength: @minimum_password_length, autocomplete: 'new-password' %>
+  <%= f.password_field :password_confirmation, required: true, size: 30,
+    minlength: @minimum_password_length, autocomplete: 'off' %>
+
+  <%= f.submit t('.update_password') %>
+<% end %>

app/views/users/passwords/new.html.erb

@@ -1,7 +0,0 @@
-<div class="main">
-  <%= labelled_form_for resource, url: user_password_path do |f| %>
-    <%= f.email_field :email, required: true, size: 30, autofocus: true, autocomplete: "email" %>
-
-    <%= f.submit t(:recover_password) %>
-  <% end %>
-</div>

app/views/users/profiles/edit.html.erb

@@ -0,0 +1,30 @@
+<% content_for :navigation, flush: true do %>
+  <%= link_to svg_tag('arrow-left-bold-outline', t(:back)),
+    request.referer.present? ? :back : root_path, class: 'tab' %>
+<% end %>
+
+<div class="rightside-area buttongrid">
+  <%#= TODO: Disallow/disable deletion for last admin account, image_button_to_if %>
+  <%= image_button_to t('.delete'), 'account-remove-outline', user_registration_path,
+    form_class: 'tools-area', method: :delete, data: {turbo: false},
+    onclick: {confirm: t('.confirm_delete')} %>
+</div>
+
+<%= labeled_form_for resource, url: registration_path(resource),
+  html: {method: :patch, class: 'main-area'} do |f| %>
+
+  <%= f.email_field :email, size: 30, autofocus: true, autocomplete: 'off' %>
+  <% if resource.pending_reconfirmation? %>
+    <%= f.text_field :unconfirmed_email, readonly: true,
+      confirmation_sent_at: l(resource.confirmation_sent_at) %>
+  <% end %>
+
+  <%= f.select :status, User.statuses, readonly: true %>
+
+  <%= f.password_field :password, size: 30, autocomplete: 'new-password',
+    minlength: @minimum_password_length %>
+  <%= f.password_field :password_confirmation, size: 30, autocomplete: 'off',
+    minlength: @minimum_password_length %>
+
+  <%= f.submit %>
+<% end %>

app/views/users/profiles/new.html.erb

@@ -0,0 +1,16 @@
+<%= labeled_form_for resource, url: user_registration_path,
+  html: {class: 'main-area', onsubmit: 'formValidate(event)'} do |f| %>
+
+  <%= f.email_field :email, required: true, size: 30, autofocus: true,
+    autocomplete: 'email' %>
+  <%= f.password_field :password, required: true, size: 30,
+    minlength: @minimum_password_length, autocomplete: 'new-password' %>
+  <%= f.password_field :password_confirmation, required: true, size: 30,
+    minlength: @minimum_password_length, autocomplete: 'off' %>
+
+  <%= f.submit t(:register), data: {turbo: false} %>
+
+  <%= image_button_tag t(:resend_confirmation), 'email-sync-outline',
+    class: 'auxiliary', formaction: user_confirmation_path, formnovalidate: true,
+    data: {validate: f.field_id(:email)} %>
+<% end %>