Refactor charts: dedicated nav tab, JSON data transport, tests

Replace the toggle-view approach and hidden DOM data carrier with a
proper dedicated Charts page:

- Move Charts out of Measurements view toggles into its own nav tab
  and route (GET /charts)
- ChartsController serializes readout data as JSON (ordered by
  taken_at); the view embeds it in a <script type="application/json">
  element instead of rendering a hidden copy of the measurements
  partial just to ferry data attributes to JS
- buildCharts() reads from the JSON element directly — no DOM parsing,
  no sorting in JS (server already orders the data)
- Turbo load handler detects the charts page via #charts-data presence
- Add controller tests (authentication, data shape, ordering,
  data isolation between users) and system tests

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -0,0 +1,84 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Fixin.me is a "quantified self" Rails 7.2.3 application for personal data tracking. Users define hierarchical **quantities** (metrics to track), **units** (with optional conversion hierarchies), and **readouts** (individual measurements). There is also a non-persistent **measurement** model used as a form wrapper.
+
+## Setup
+
+Configuration files are distributed as `.dist` templates — copy and customize before use:
+
+```bash
+cp config/application.rb.dist config/application.rb
+cp config/database.yml.dist config/database.yml
+cp config/puma.rb.dist config/puma.rb
+```
+
+```bash
+bundle config --local frozen true
+bundle config --local path .gem
+bundle config --local with mysql development test   # or: pg, sqlite
+bundle install
+RAILS_ENV=development bundle exec rails db:create db:migrate db:seed
+```
+
+## Common Commands
+
+```bash
+bundle exec rails s                                          # start server
+bundle exec rails test                                       # all unit/model/controller tests
+bundle exec rails test:system                                # all system tests (Capybara + Selenium)
+bundle exec rails test test/system/units_test.rb            # single test file
+bundle exec rails test --seed 64690 --name test_add_unit    # single test by name
+bundle exec rails db:seed:export                             # export default settings as seed file
+```
+
+## Architecture
+
+### Data Model
+
+- **Quantity** — hierarchical tree (self-referential `parent_id`). Cached `depth` and `pathname` fields are recomputed via recursive CTEs on write. Direct assignment to cached fields is blocked.
+- **Unit** — optional hierarchy via `base_id` and `multiplier` for unit conversion. Multiplier precision/scale is validated by a custom validator.
+- **Readout** — single measurement: `value` (IEEE 754 float), `quantity`, `unit`, `category`.
+- **Measurement** — `ActiveModel::Model` form wrapper (not database-backed); bridges the readout creation form.
+- **User** — Devise-managed with a status enum: `admin`, `active`, `restricted`, `locked`, `disabled`. Admins can disguise as other users.
+
+### Hierarchical Queries
+
+Both `Quantity` and `Unit` use recursive CTEs for tree traversal (ordered traversal, ancestors, progenies, common ancestors). `lib/core_ext/arel/` patches Arel to support CTE with `UPDATE`/`DELETE` statements, working around Rails issue #54658.
+
+### Custom Extensions (`lib/core_ext/`)
+
+- **arel/** — CTE support for UPDATE/DELETE
+- **active_model/** — precision/scale validator used by `Unit#multiplier`
+- **active_record/** — `attr_cached` mechanism (see `ApplicationRecord`)
+- **action_view/** — record identifier suffixes
+- Miscellaneous: `Array#delete_bang`, `BigDecimal` scientific notation
+
+### Response Handling
+
+Controllers respond to both HTML and Turbo Stream formats. Errors during Turbo Stream requests trigger a redirect with flash rather than rendering inline, handled in `ApplicationController`.
+
+### Numeric Precision
+
+Readout values are stored as IEEE 754 double-precision floats (not fixed-point decimals). Rationale in `DESIGN.md`: biological values span many orders of magnitude; 15-digit float precision is sufficient and avoids conversion overhead.
+
+### Routes
+
+```
+measurements   GET/POST /measurements
+readouts       GET/POST /readouts, DELETE /readouts/:id/discard
+quantities     CRUD + POST /quantities/:id/reparent
+units          CRUD + POST /units/:id/rebase
+users          CRUD + POST /users/:id/disguise, POST /users/revert
+default/       namespace for default units import/export and admin panel
+root           → /units (authenticated), /sign_in (unauthenticated)
+```
+
+## Database Requirements
+
+The database must support:
+- Recursive CTEs with `UPDATE`/`DELETE` (MySQL ≥ 8.0, PostgreSQL, or SQLite3)
+- Decimal precision of 30+ digits

app/assets/images/pictograms/view-columns.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" id="icon" viewBox="0 0 24 24"><path d="M4,4H8V20H4V4M10,4H14V20H10V4M16,4H21V20H16V4Z"/></svg>

app/assets/images/pictograms/view-rows.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" id="icon" viewBox="0 0 24 24"><path d="M3,5H21V7H3V5M3,11H21V13H3V11M3,17H21V19H3V17Z"/></svg>

app/assets/stylesheets/application.css

@@ -18,14 +18,12 @@
 /* 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>; <a> as link/button),
+ * 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: review styles with multiple selectors and try to convert them to the same
- * specificity. */
 :root {
   --color-focus-gray: #f3f3f3;
   --color-border-gray: #dddddd;
@@ -38,6 +36,7 @@
   --color-blue: #009ade;
   --color-dark-red: #b21237;
   --color-red: #ff1f5b;
+  --color-purple: #8b2be2;
 
   --depth: 0;
 
@@ -57,8 +56,8 @@
 :focus-visible {
   outline: none;
 }
-/* NOTE: move to higher priority layer instead of using !important? */
-/* TODO: add CSS @layer requirements in README */
+/* NOTE: move to higher priority layer instead of using !important?; add CSS
+ * @layer requirements in README */
 [disabled] {
   border-color: var(--color-border-gray) !important;
   color: var(--color-border-gray) !important;
@@ -80,10 +79,13 @@
  *  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;
@@ -101,7 +103,19 @@ textarea {
   border-radius: 0.25em;
   padding: 0.2em 0.4em;
 }
-svg,
+svg {
+  height: 1.4em;
+  margin: 0 0.2em 0 0;
+  width: 1.4em;
+}
+svg:last-child {
+  margin-right: 0;
+}
+.chart-panel svg {
+  height: auto;
+  margin: 0;
+  width: auto;
+}
 textarea {
   margin: 0;
 }
@@ -153,6 +167,10 @@ table form summary,
 table form textarea {
   color: inherit;
 }
+table svg:not(:only-child) {
+  height: 1.25em;
+  width: 1.25em;
+}
 input:focus-visible,
 select:focus-visible,
 select:focus-within,
@@ -214,21 +232,21 @@ textarea:invalid {
   padding: 0.6em 0.5em;
   width: fit-content;
 }
+.link {
+  color: inherit;
+  text-decoration: underline 1px var(--color-border-gray);
+  text-underline-offset: 0.25em;
+}
+button.link {
+  border: none;
+  padding: 0;
+}
 [name=cancel],
 .auxiliary {
   border-color: var(--color-border-gray);
   color: var(--color-nav-gray);
   fill: var(--color-nav-gray);
 }
-.button > svg,
-.tab > svg {
-  height: 1.4em;
-  width: 1.4em;
-}
-.button > svg:not(:last-child),
-.tab > svg:not(:last-child) {
-  margin-right: 0.2em;
-}
 .button:focus-visible,
 .tab:focus-visible,
 .tab:hover {
@@ -244,6 +262,20 @@ textarea:invalid {
   background-color: var(--color-red);
   border-color: var(--color-red);
 }
+tr:has(select[data-changed]) button[name="button"],
+.set-default-unit:not([disabled]) {
+  background-color: var(--color-purple);
+  border-color: var(--color-purple);
+  color: white;
+  fill: white;
+}
+.link:focus-visible {
+  text-decoration-color: var(--color-gray);
+}
+.link:hover {
+  color: var(--color-blue);
+  text-decoration-color: var(--color-blue);
+}
 table .button {
   border-color: var(--color-border-gray);
   color: var(--color-table-gray);
@@ -251,15 +283,6 @@ table .button {
   height: 100%;
   padding: 0.4em;
 }
-/* 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. */
-/* TODO: apply link class to non-button/-tab links. Add light underscore for links? */
-input[type=text]:read-only,
-textarea:read-only {
-  border: none;
-  padding-inline: 0;
-}
 
 
 /* NOTE: collapse gaps around empty rows (`topside`) once possible with
@@ -271,16 +294,16 @@ body {
   grid-template-areas:
     "header    header  header"
     "nav       nav     nav"
-    "leftside  topside rightside"
     "leftside  main    rightside";
   grid-template-columns: 1fr minmax(max-content, 2fr) 1fr;
   font-family: system-ui;
   margin: 0.4em;
 }
-body:not(:has(.topside-area)) {
+body:has(> .topside-area) {
   grid-template-areas:
     "header    header  header"
     "nav       nav     nav"
+    "leftside  topside rightside"
     "leftside  main    rightside";
 }
 
@@ -355,7 +378,7 @@ header {
   pointer-events: auto;
 }
 .flash:before {
-  filter: invert();
+  filter: invert(100%);
   height: 1.4em;
   margin: 0 0.5em;
   width: 1.4em;
@@ -431,14 +454,18 @@ header {
 
 .tabular-form table {
   border: none;
+  border-spacing: 0.4em 0;
+  margin-inline: -0.4em;
 }
 .tabular-form table td {
   border: none;
-  text-align: left;
   vertical-align: middle;
 }
-.tabular-form table td:first-child {
-  color: inherit;
+.tabular-form table td {
+  padding-inline: 0;
+}
+.tabular-form table :is(form, input, select, textarea):only-child {
+  margin-inline-start: 0;
 }
 
 
@@ -457,59 +484,41 @@ header {
   background-color: var(--color-focus-gray);
 }
 .items-table th {
-  padding-block: 0.75em;
+  padding: 0.75em 0 0.75em 1em;
   text-align: center;
 }
-.items-table th,
-.items-table td {
-  padding-inline: 1em 0;
-}
-/* For <a> to fill <td> completely, we use an `::after` pseudoelement. */
-.items-table td.link {
-  padding: 0;
-  position: relative;
-}
-.items-table td.link a {
-  color: inherit;
-  font: inherit;
-}
-.items-table td.link a::after {
-  content: '';
-  inset: 0;
-  position: absolute;
-}
-.items-table td:first-child {
-  padding-inline-start: calc(1em + var(--depth) * 0.8em);
-}
-.items-table td:has(input, select, textarea) {
-  padding-inline-start: calc(0.6em - 0.9px);
-}
-.items-table td:first-child:has(input, select, textarea) {
-  padding-inline-start: calc(0.6em + var(--depth) * 0.8em - 0.9px);
-}
 .items-table th:last-child {
   padding-inline-end: 0.4em;
 }
-.items-table td:last-child {
-  padding-inline-end: 0.1em;
-}
 .items-table td {
   border-top: 1px solid var(--color-border-gray);
   height: 2.4em;
-  padding-block: 0.1em;
+  padding: 0.1em 0 0.1em calc(1em + var(--depth) * 0.8em);
 }
-.items-table .actions {
-  display: flex;
+.items-table td:last-child {
+  padding-inline-end: 0.1em;
+}
+.items-table :is(form, input, select, textarea):only-child {
+  margin-inline-start: calc(-0.4em - 0.9px);
+}
+/* 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;
 }
-.items-table .actions.centered {
-  justify-content: center;
-}
-.items-table tr.dropzone {
+.items-table .dropzone {
   position: relative;
 }
-.items-table tr.dropzone::after {
+.items-table .dropzone::after {
   content: '';
   inset: 1px 0 0 0;
   position: absolute;
@@ -517,72 +526,37 @@ header {
   outline-offset: -1px;
   z-index: var(--z-index-table-row-outline);
 }
-.items-table td.handle {
-  cursor: move;
+.items-table .handle {
+  cursor: grab;
 }
-.items-table tr.form td {
-  vertical-align: top;
+.items-table .form td {
+  vertical-align: middle;
 }
-
-/* TODO: replace `:hover:focus-visible` combos with proper LOVE style order. */
-/* TODO: update table styling: simplify selectors, deduplicate, remove non-font rem. */
-.items-table td.link a:hover,
-.items-table td.link a:focus-visible,
-.items-table td.link a:hover:focus-visible {
-  text-decoration: underline;
-  text-decoration-thickness: 0.05rem;
-  text-underline-offset: 0.2rem;
-}
-.items-table td.link a:hover {
-  color: var(--color-blue);
-}
-.items-table td.link a:focus-visible {
-  text-decoration-color: var(--color-gray);
-}
-.items-table td.link a:hover:focus-visible {
-  color: var(--color-dark-blue);
-}
-
 .items-table td:not(:first-child),
 .grayed {
   color: var(--color-table-gray);
-  fill: var(--color-table-gray);
+  fill: var(--color-gray);
 }
-.items-table svg {
-  height: 1rem;
-  vertical-align: middle;
-  width: 1rem;
-}
-.items-table svg:last-child {
-  height: 1.2rem;
-  width: 1.2rem;
-}
-.items-table td.svg {
+.items-table td:has(> svg:only-child) {
   text-align: center;
 }
-.items-table td.number {
-  text-align: right;
-}
 
 
-.centered {
+.center {
   margin: 0 auto;
 }
-.extendedright {
-  margin-right: auto;
-}
 .hexpand {
   width: 100%;
 }
-.hflex {
+.flex {
   display: flex;
   gap: 0.8em;
 }
-.hflex.reverse {
+.flex.reverse {
   flex-direction: row-reverse;
 }
-.hflex.centered {
-  justify-content: center;
+.flex.vertical {
+  flex-direction: column;
 }
 .hint {
   color: var(--color-table-gray);
@@ -597,10 +571,11 @@ header {
   color: var(--color-gray);
   font-style: italic;
 }
-.vflex {
-  display: flex;
-  gap: 0.8em;
-  flex-direction: column;
+.ralign {
+  text-align: right;
+}
+.rextend {
+  margin-right: auto;
 }
 
 
@@ -647,7 +622,7 @@ summary::marker {
 }
 /* NOTE: use `details[open]::details-content` once widely available. */
 details[open] ul {
-  background: white;
+  background-color: white;
   border: 1px solid var(--color-border-gray);
   border-radius: 0.25em;
   box-shadow: 1px 1px 3px var(--color-border-gray);
@@ -670,11 +645,6 @@ li input[type=checkbox] {
 li::marker {
   content: '';
 }
-
-#measurement_form {
-  min-width: 66%;
-  width: max-content;
-}
 /*
  * TODO:
  * * disable <label> containing disabled checkbox: `label:has(input[disabled])`,
@@ -682,3 +652,50 @@ li::marker {
  * * focused label styling (currently only checkbox has focus),
  * * disabled checkbox blue square focus removal.
  * */
+
+#measurement_form {
+  min-width: 66%;
+  width: max-content;
+}
+.measurements-section {
+  overflow-x: auto;
+}
+body[data-measurements-view=wide] .measurements-compact,
+body[data-measurements-view=compact] .measurements-wide {
+  display: none;
+}
+body[data-measurements-view=compact] .view-toggle[data-view=compact],
+body[data-measurements-view=wide] .view-toggle[data-view=wide] {
+  background-color: var(--color-blue);
+  border-color: var(--color-blue);
+  color: white;
+  fill: white;
+}
+.chart-panel {
+  width: 100%;
+}
+#measurements tr.grouped td {
+  border-top: none;
+}
+#measurements tr.grouped .taken-at,
+#measurements tr.grouped .created-at {
+  visibility: hidden;
+}
+.measurements-wide td {
+  vertical-align: middle;
+  white-space: nowrap;
+}
+.wide-cell {
+  align-items: center;
+  display: inline-flex;
+  gap: 0.25em;
+}
+.wide-cell .button {
+  border: none;
+  font-size: inherit;
+  height: auto;
+  padding: 0;
+}
+.wide-cell button.link::after {
+  content: none;
+}

app/controllers/charts_controller.rb

@@ -0,0 +1,12 @@
+class ChartsController < ApplicationController
+  def index
+    readouts = current_user.readouts.includes(:quantity, :unit).order(:taken_at, :id)
+    @readouts_json = readouts.map { |r|
+      { takenAt: r.taken_at&.iso8601,
+        quantityId: r.quantity_id,
+        quantityName: r.quantity.name,
+        value: r.value.to_f,
+        unit: r.unit.symbol }
+    }.to_json
+  end
+end

app/controllers/measurements_controller.rb

@@ -1,7 +1,12 @@
 class MeasurementsController < ApplicationController
+  before_action :find_readout, only: [:destroy, :edit, :update]
+
+  before_action except: :index do
+    raise AccessForbidden unless current_user.at_least(:active)
+  end
+
   def index
-    @measurements = []
-    #@measurements = current_user.units.ordered.includes(:base, :subunits)
+    @measurements = current_user.readouts.includes(:quantity, :unit).order(taken_at: :desc, id: :desc)
   end
 
   def new
@@ -9,8 +14,40 @@ class MeasurementsController < ApplicationController
   end
 
   def create
+    taken_at = params.permit(:taken_at)[:taken_at]
+    readout_params = params.permit(readouts: Readout::ATTRIBUTES).fetch(:readouts, [])
+    @readouts = readout_params.map { |rp| current_user.readouts.build(rp.merge(taken_at: taken_at)) }
+
+    if @readouts.present? && @readouts.all?(&:valid?)
+      ActiveRecord::Base.transaction { @readouts.each(&:save!) }
+      flash.now[:notice] = t('.success', count: @readouts.size)
+    else
+      errors = @readouts.flat_map { |r| r.errors.full_messages }
+      flash.now[:alert] = errors.present? ? errors.first : t('.no_readouts')
+    end
+  end
+
+  def edit
+    @user_units = current_user.units.ordered
+  end
+
+  def update
+    if @readout.update(params.require(:readout).permit(:value, :unit_id, :taken_at))
+      flash.now[:notice] = t('.success')
+    else
+      @user_units = current_user.units.ordered
+      render :edit
+    end
   end
 
   def destroy
+    @readout.destroy!
+    flash.now[:notice] = t('.success')
+  end
+
+  private
+
+  def find_readout
+    @readout = current_user.readouts.find(params[:id])
   end
 end

app/controllers/quantities_controller.rb

@@ -8,6 +8,10 @@ class QuantitiesController < ApplicationController
     raise AccessForbidden unless current_user.at_least(:active)
   end
 
+  before_action only: [:new, :edit, :create, :update] do
+    @user_units = current_user.units.ordered
+  end
+
   def index
     @quantities = current_user.quantities.ordered.includes(:parent, :subquantities)
   end

app/helpers/application_helper.rb

@@ -86,6 +86,7 @@ module ApplicationHelper
     def initialize(...)
       super(...)
       @default_options.merge!(@options.slice(:form))
+      @default_html_options.merge!(@options.slice(:form))
     end
 
     [:text_field, :password_field, :text_area].each do |selector|
@@ -170,6 +171,7 @@ module ApplicationHelper
       ['measurements', 'scale-bathroom', :restricted],
       ['quantities', 'axis-arrow', :restricted, 'right'],
       ['units', 'weight-gram', :restricted],
+      ['charts', 'chart-line', :restricted],
       # TODO: display users tab only if >1 user present; sole_user?/sole_admin?
       ['users', 'account-multiple-outline', :admin],
     ]

app/javascript/application.js

@@ -9,6 +9,196 @@ function showPage(event) {
 }
 document.addEventListener('turbo:load', showPage)
 
+function groupMeasurements() {
+  var tbody = document.getElementById('measurements');
+  if (!tbody) return;
+  var prevTakenAt = null;
+  Array.from(tbody.querySelectorAll('tr[data-taken-at]'))
+    .filter(function(row) { return row.style.display !== 'none' })
+    .forEach(function(row) {
+      var takenAt = row.dataset.takenAt;
+      row.classList.toggle('grouped', takenAt !== null && takenAt === prevTakenAt);
+      prevTakenAt = takenAt;
+    });
+}
+
+function buildWideTable() {
+  var tbody = document.getElementById('measurements');
+  var wideContainer = document.getElementById('measurements-wide');
+  if (!tbody || !wideContainer) return;
+
+  var rows = Array.from(tbody.querySelectorAll('tr[data-taken-at]'));
+
+  if (rows.length === 0) { wideContainer.innerHTML = ''; return; }
+
+  // Unique quantities in alphabetical order
+  var qOrder = [], qSeen = new Set();
+  rows.forEach(function(r) {
+    var id = r.dataset.quantityId;
+    if (id && !qSeen.has(id)) { qSeen.add(id); qOrder.push({id: id, name: r.dataset.quantityName}); }
+  });
+  qOrder.sort(function(a, b) { return a.name.localeCompare(b.name); });
+
+  // Group rows by taken_at, preserving order
+  var groups = [], groupMap = new Map();
+  rows.forEach(function(r) {
+    var key = r.dataset.takenAt || '';
+    if (!groupMap.has(key)) { var g = {rows: []}; groups.push(g); groupMap.set(key, g); }
+    groupMap.get(key).rows.push(r);
+  });
+
+  // Read column headers from compact thead
+  var ths = document.querySelectorAll('.measurements-compact thead th');
+  var takenAtHeader = ths[3] ? ths[3].textContent : '';
+  var createdAtHeader = ths[4] ? ths[4].textContent : '';
+
+  var table = document.createElement('table');
+  table.className = 'items-table';
+
+  // Header
+  var thead = table.createTHead();
+  var hrow = thead.insertRow();
+  [takenAtHeader].concat(qOrder.map(function(q) { return q.name; })).concat([createdAtHeader]).forEach(function(text) {
+    var th = document.createElement('th');
+    th.textContent = text;
+    hrow.appendChild(th);
+  });
+
+  // Body
+  var tbodyEl = table.createTBody();
+  groups.forEach(function(group) {
+    var tr = tbodyEl.insertRow();
+
+    // Taken at
+    var tdTime = tr.insertCell();
+    var takenAtEl = group.rows[0].querySelector('.taken-at');
+    tdTime.textContent = takenAtEl ? takenAtEl.textContent : '';
+
+    // One cell per quantity
+    qOrder.forEach(function(q) {
+      var td = tr.insertCell();
+      var readoutRow = group.rows.find(function(r) { return r.dataset.quantityId === q.id; });
+      if (readoutRow) {
+        td.className = 'ralign';
+        var wrap = document.createElement('span');
+        wrap.className = 'wide-cell';
+        var editLink = readoutRow.querySelector('a.link');
+        if (editLink) {
+          var editUrl = editLink.href + (editLink.href.includes('?') ? '&' : '?') + 'view=wide';
+          var btn = document.createElement('button');
+          btn.className = 'link';
+          btn.type = 'button';
+          btn.dataset.editUrl = editUrl;
+          btn.addEventListener('click', function() { editMeasurementWide(this.dataset.editUrl); this.blur(); });
+          btn.textContent = readoutRow.dataset.value;
+          wrap.appendChild(btn);
+          wrap.appendChild(document.createTextNode('\u00a0' + readoutRow.dataset.unit));
+        } else {
+          wrap.appendChild(document.createTextNode(readoutRow.dataset.value + '\u00a0' + readoutRow.dataset.unit));
+        }
+        var srcActions = readoutRow.querySelector('td.flex');
+        if (srcActions) srcActions.querySelectorAll('form').forEach(function(f) {
+          var cloned = f.cloneNode(true);
+          var span = cloned.querySelector('button span');
+          if (span) span.remove();
+          wrap.appendChild(cloned);
+        });
+        td.appendChild(wrap);
+      }
+    });
+
+    // Created at (from first row of group)
+    var tdCreated = tr.insertCell();
+    var createdAtEl = group.rows[0].querySelector('.created-at');
+    tdCreated.textContent = createdAtEl ? createdAtEl.textContent : '';
+  });
+
+  wideContainer.innerHTML = '';
+  wideContainer.appendChild(table);
+}
+
+function buildCharts() {
+  var container = document.getElementById('measurements-charts');
+  var dataEl = document.getElementById('charts-data');
+  if (!container || !dataEl) return;
+
+  var readouts = JSON.parse(dataEl.textContent);
+  container.innerHTML = '';
+  if (readouts.length === 0) return;
+
+  // Data arrives sorted by taken_at from the server; group into per-quantity traces
+  var quantities = new Map();
+  readouts.forEach(function(r) {
+    if (!r.takenAt) return;
+    if (!quantities.has(r.quantityId)) {
+      quantities.set(r.quantityId, { name: r.quantityName, unit: r.unit, x: [], y: [] });
+    }
+    var q = quantities.get(r.quantityId);
+    q.x.push(r.takenAt);
+    q.y.push(r.value);
+  });
+
+  var traces = [];
+  quantities.forEach(function(q) {
+    traces.push({
+      x: q.x,
+      y: q.y,
+      mode: 'lines+markers',
+      type: 'scatter',
+      name: q.name + ' (' + q.unit + ')',
+      marker: { size: 5 }
+    });
+  });
+
+  var div = document.createElement('div');
+  div.className = 'chart-panel';
+  container.appendChild(div);
+
+  Plotly.newPlot(div, traces, {
+    xaxis: { type: 'date', tickformat: '%Y-%m-%d %H:%M' },
+    yaxis: {},
+    margin: { t: 20, r: 20, b: 80, l: 60 },
+    paper_bgcolor: 'transparent',
+    plot_bgcolor: 'transparent',
+    font: { family: 'system-ui' },
+    legend: { orientation: 'h', y: -0.25 }
+  }, { responsive: true, displayModeBar: false });
+}
+
+function getMeasurementsView() {
+  return localStorage.getItem('measurements-view') || 'compact';
+}
+
+function applyMeasurementsView(view) {
+  document.body.dataset.measurementsView = view;
+  if (view === 'wide') buildWideTable();
+}
+
+function setMeasurementsView(view) {
+  localStorage.setItem('measurements-view', view);
+  applyMeasurementsView(view);
+}
+window.setMeasurementsView = setMeasurementsView
+
+document.addEventListener('turbo:load', function() {
+  if (document.getElementById('charts-data')) {
+    buildCharts();
+    return;
+  }
+  var tbody = document.getElementById('measurements');
+  if (!tbody) return;
+  groupMeasurements();
+  applyMeasurementsView(getMeasurementsView());
+  new MutationObserver(function() {
+    groupMeasurements();
+    var view = getMeasurementsView();
+    if (view === 'wide') buildWideTable();
+  }).observe(tbody, {
+    childList: true, subtree: true,
+    attributes: true, attributeFilter: ['style']
+  });
+})
+
 function detailsChange(event) {
   var target = event.currentTarget
   var count = target.querySelectorAll('input:checked:not([disabled])').length
@@ -37,6 +227,65 @@ window.detailsObserver = new MutationObserver((mutations) => {
   mutations[0].target.dispatchEvent(new Event('change', {bubbles: true}))
 });
 
+function editMeasurementWide(url) {
+  fetch(url, {
+    headers: {
+      'Accept': 'text/vnd.turbo-stream.html',
+      'X-Requested-With': 'XMLHttpRequest'
+    }
+  })
+  .then(response => response.text())
+  .then(html => {
+    Turbo.renderStreamMessage(html);
+    requestAnimationFrame(() => {
+      var panel = document.getElementById('measurement_edit_form');
+      if (panel && panel.firstElementChild) {
+        panel.scrollIntoView({behavior: 'smooth', block: 'nearest'});
+      }
+    });
+  });
+}
+window.editMeasurementWide = editMeasurementWide
+
+function readoutUnitChanged(select) {
+  var button = select.closest('tr').querySelector('.set-default-unit');
+  if (select.value && select.value !== select.dataset.defaultUnitId) {
+    button.removeAttribute('disabled');
+    button.removeAttribute('aria-disabled');
+    button.removeAttribute('tabindex');
+  } else {
+    button.setAttribute('disabled', 'disabled');
+    button.setAttribute('aria-disabled', 'true');
+    button.setAttribute('tabindex', '-1');
+  }
+}
+window.readoutUnitChanged = readoutUnitChanged
+
+function setDefaultUnit(button) {
+  var select = button.closest('tr').querySelector('select[data-default-unit-id]');
+  var params = new URLSearchParams();
+  params.append('quantity[default_unit_id]', select.value);
+
+  fetch(button.dataset.path, {
+    body: params,
+    headers: {
+      'Accept': 'text/vnd.turbo-stream.html',
+      'X-CSRF-Token': document.head.querySelector('meta[name=csrf-token]').content,
+      'X-Requested-With': 'XMLHttpRequest'
+    },
+    method: 'PATCH'
+  })
+  .then(response => {
+    if (response.ok) {
+      select.dataset.defaultUnitId = select.value;
+      readoutUnitChanged(select);
+    }
+    return response.text();
+  })
+  .then(html => Turbo.renderStreamMessage(html));
+}
+window.setDefaultUnit = setDefaultUnit
+
 function formValidate(event) {
   var id = event.submitter.getAttribute("data-validate")
   if (!id) return;

app/models/quantity.rb

@@ -1,9 +1,10 @@
 class Quantity < ApplicationRecord
-  ATTRIBUTES = [:name, :description, :parent_id]
+  ATTRIBUTES = [:name, :description, :parent_id, :default_unit_id]
   attr_cached :depth, :pathname
 
   belongs_to :user, optional: true
   belongs_to :parent, optional: true, class_name: "Quantity"
+  belongs_to :default_unit, optional: true, class_name: "Unit"
   has_many :subquantities, ->{ order(:name) }, class_name: "Quantity",
     inverse_of: :parent, dependent: :restrict_with_error
 

app/models/readout.rb

@@ -1,5 +1,5 @@
 class Readout < ApplicationRecord
-  ATTRIBUTES = [:quantity_id, :value, :unit_id]
+  ATTRIBUTES = [:quantity_id, :value, :unit_id, :taken_at]
 
   belongs_to :user
   belongs_to :quantity

app/views/charts/index.html.erb

@@ -0,0 +1,2 @@
+<div class="main-area" id="measurements-charts"></div>
+<script id="charts-data" type="application/json"><%= raw @readouts_json %></script>

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/layouts/application.html.erb

@@ -14,6 +14,7 @@
     <%= csp_meta_tag %>
 
     <%= stylesheet_link_tag "spreadsheet" %>
+    <script src="https://cdn.plot.ly/plotly-basic-2.35.2.min.js"></script>
     <%= javascript_importmap_tags %>
 
     <%#= turbo_page_requires_reload_tag %>
@@ -23,10 +24,10 @@
   </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) %>

app/views/measurements/_edit_form.html.erb

@@ -0,0 +1,24 @@
+<%= tabular_fields_for @readout, form: form_tag do |form| %>
+  <%- tag.tr id: row, class: "form", onkeydown: "formProcessKey(event)",
+    data: {form: form_tag, hidden_row: hidden_row, link: link} do %>
+    <td><%= @readout.quantity %></td>
+    <td class="ralign">
+      <%= form.number_field :value, required: true, autofocus: true %>
+    </td>
+    <td>
+      <%= form.collection_select :unit_id, @user_units, :id,
+        ->(u){ sanitize('&emsp;' * (u.base_id? ? 1 : 0) + u.symbol) },
+        {}, required: true %>
+    </td>
+    <td>
+      <%= form.datetime_field :taken_at %>
+    </td>
+    <td></td>
+    <td class="flex">
+      <%= form.button %>
+      <%= image_link_to t(:cancel), "close-outline", measurements_path,
+        class: 'dangerous', name: :cancel,
+        onclick: render_turbo_stream('edit_form_close', {row: row}) %>
+    </td>
+  <% end %>
+<% end %>

app/views/measurements/_edit_form_close.html.erb

@@ -0,0 +1,2 @@
+<%= turbo_stream.close_form row %>
+<%= turbo_stream.update :flashes %>

app/views/measurements/_edit_panel.html.erb

@@ -0,0 +1,33 @@
+<% form_tag = dom_id(@readout, :edit, :form) %>
+<% row = dom_id(@readout, :edit) %>
+<% hidden_row = dom_id(@readout) %>
+
+<%= tabular_form_with model: @readout, url: measurement_path(@readout),
+  id: form_tag do |form| %>
+  <table class="items-table">
+    <tbody>
+      <%= tag.tr id: row, class: "form", onkeydown: "formProcessKey(event)",
+        data: {form: form_tag, hidden_row: hidden_row} do %>
+        <td><%= @readout.quantity %></td>
+        <td class="ralign">
+          <%= form.number_field :value, required: true, autofocus: true %>
+        </td>
+        <td>
+          <%= form.collection_select :unit_id, @user_units, :id,
+            ->(u){ sanitize('&emsp;' * (u.base_id? ? 1 : 0) + u.symbol) },
+            {}, required: true %>
+        </td>
+        <td>
+          <%= form.datetime_field :taken_at %>
+        </td>
+        <td></td>
+        <td class="flex">
+          <%= form.button %>
+          <%= image_link_to t(:cancel), "close-outline", measurements_path,
+            class: 'dangerous', name: :cancel,
+            onclick: render_turbo_stream('edit_form_close', {row: row}) %>
+        </td>
+      <% end %>
+    </tbody>
+  </table>
+<% end %>

app/views/measurements/_form.html.erb

@@ -1,14 +1,14 @@
 <%= tabular_form_with model: Measurement.new, id: :measurement_form,
-  class: 'topside-area vflex centered',
+  class: 'topside-area flex vertical center',
   html: {onkeydown: 'formProcessKey(event)'} do |form| %>
 
-  <table class="items-table centered">
+  <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="number">
-            <%= form.datetime_field :taken_at, required: true %>
+          <td colspan="3" class="ralign">
+            <%= form.datetime_field :taken_at, required: true, value: Time.current.strftime('%Y-%m-%dT%H:%M') %>
           </td>
         </tr>
       <% end %>
@@ -16,7 +16,7 @@
   </table>
 
   <%# TODO: right-click selection; unnecessary with hierarchical tags? %>
-  <details id="quantity_select" class="centered hexpand" open
+  <details id="quantity_select" class="center hexpand" open
            onkeydown="detailsProcessKey(event)">
     <summary autofocus>
       <!-- TODO: Set content with CSS when span empty to avoid duplication -->
@@ -30,7 +30,7 @@
     <ul><%= quantities_check_boxes(@quantities) %></ul>
   </details>
 
-  <div class="hflex reverse">
+  <div class="flex reverse">
     <%= form.button id: :create_measurement_button, disabled: true -%>
     <%= image_link_to t(:cancel), "close-outline", measurements_path, name: :cancel,
       class: 'dangerous', onclick: render_turbo_stream('form_close') %>

app/views/measurements/_readout.html.erb

@@ -0,0 +1,22 @@
+<%= tag.tr id: dom_id(readout), data: {taken_at: readout.taken_at&.iso8601,
+  quantity_id: readout.quantity_id, quantity_name: readout.quantity.name,
+  value: format("%.10g", readout.value), unit: readout.unit.symbol} do %>
+  <td>
+    <% if current_user.at_least(:active) %>
+      <%= link_to readout.quantity, edit_measurement_path(readout),
+        class: 'link', onclick: 'this.blur();', data: {turbo_stream: true} %>
+    <% else %>
+      <%= readout.quantity %>
+    <% end %>
+  </td>
+  <td class="ralign"><%= format("%.10g", readout.value) %></td>
+  <td><%= readout.unit %></td>
+  <td class="taken-at"><%= l(readout.taken_at) if readout.taken_at %></td>
+  <td class="created-at"><%= l(readout.created_at) %></td>
+  <% if current_user.at_least(:active) %>
+    <td class="flex">
+      <%= image_button_to t('.destroy'), 'delete-outline', measurement_path(readout),
+        method: :delete, data: {turbo_stream: true} %>
+    </td>
+  <% end %>
+<% end %>

app/views/measurements/edit.turbo_stream.erb

@@ -0,0 +1,18 @@
+<% ids = {row: dom_id(@readout, :edit),
+          hidden_row: dom_id(@readout),
+          link: nil,
+          form_tag: dom_id(@readout, :edit, :form)} %>
+
+<% if params[:view] == 'wide' %>
+  <%= turbo_stream.update :measurement_edit_form, partial: 'edit_panel' %>
+  <%= turbo_stream.hide ids[:hidden_row] %>
+<% else %>
+  <%= turbo_stream.append :measurement_edit_form do %>
+    <%- tabular_form_with model: @readout, url: measurement_path(@readout),
+      html: {id: ids[:form_tag]} do %>
+    <% end %>
+  <% end %>
+  <%= turbo_stream.hide ids[:hidden_row] %>
+  <%= turbo_stream.remove ids[:row] %>
+  <%= turbo_stream.after @readout, partial: 'edit_form', locals: ids -%>
+<% end %>

app/views/measurements/index.html.erb

@@ -5,10 +5,36 @@
       id: :new_measurement_link, onclick: 'this.blur();',
       data: {turbo_stream: true} %>
   <% end %>
+  <%= image_button_tag '', 'view-rows', name: nil, type: 'button',
+    class: 'view-toggle', title: t('.view_compact'),
+    data: {view: 'compact'}, onclick: "setMeasurementsView('compact')" %>
+  <%= image_button_tag '', 'view-columns', name: nil, type: 'button',
+    class: 'view-toggle', title: t('.view_wide'),
+    data: {view: 'wide'}, onclick: "setMeasurementsView('wide')" %>
+
+</div>
+
+<div class="main-area measurements-section">
+  <%= tag.div id: :measurement_edit_form %>
+  <table class="items-table measurements-compact">
+    <thead>
+      <tr>
+        <th><%= Quantity.model_name.human %></th>
+        <th><%= Readout.human_attribute_name(:value) %></th>
+        <th><%= Unit.model_name.human %></th>
+        <th><%= Readout.human_attribute_name(:taken_at) %></th>
+        <th><%= Readout.human_attribute_name(:created_at) %></th>
+        <% if current_user.at_least(:active) %>
+          <th></th>
+        <% end %>
+      </tr>
+    </thead>
+    <tbody id="measurements">
+      <%= render(partial: 'readout', collection: @measurements, as: :readout) || render_no_items %>
+    </tbody>
+  </table>
+
+  <div id="measurements-wide" class="measurements-wide"></div>
+
 </div>
 
-<table class="main-area">
-  <tbody id="measurements">
-    <%= render(@measurements) || render_no_items %>
-  </tbody>
-</table>

app/views/measurements/update.turbo_stream.erb

@@ -0,0 +1,2 @@
+<%= turbo_stream.close_form dom_id(@readout, :edit) %>
+<%= turbo_stream.replace @readout, partial: 'measurements/readout', locals: {readout: @readout} %>

app/views/quantities/_form.html.erb

@@ -8,8 +8,13 @@
     <td>
       <%= form.text_area :description, cols: 30, rows: 1, escape: false %>
     </td>
+    <td>
+      <%= form.collection_select :default_unit_id, @user_units, :id,
+        ->(u){ sanitize('&emsp;' * (u.base_id? ? 1 : 0) + u.symbol) },
+        {include_blank: true}, onchange: "this.dataset.changed = ''" %>
+    </td>
 
-    <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}) %>

app/views/quantities/_quantity.html.erb

@@ -5,14 +5,15 @@
            data: {drag_path: reparent_quantity_path(quantity), drop_id: dom_id(quantity),
                   drop_id_param: "quantity[parent_id]"} do %>
 
-  <td class="link" style="--depth:<%= quantity.depth %>">
-    <%= link_to quantity, edit_quantity_path(quantity), onclick: 'this.blur();',
-      data: {turbo_stream: true} %>
+  <td style="--depth:<%= quantity.depth %>">
+    <%= link_to quantity, edit_quantity_path(quantity), class: 'link',
+      onclick: 'this.blur();', data: {turbo_stream: true} %>
   </td>
   <td><%= quantity.description %></td>
+  <td><%= quantity.default_unit&.symbol %></td>
 
   <% if current_user.at_least(:active) %>
-    <td class="actions">
+    <td class="flex">
       <%= 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} %>
 

app/views/quantities/index.html.erb

@@ -15,7 +15,8 @@
   <thead>
     <tr>
       <th><%= Quantity.human_attribute_name(:name) %></th>
-      <th><%= Quantity.human_attribute_name(:description) %></th>
+      <th class="hexpand"><%= Quantity.human_attribute_name(:description) %></th>
+      <th><%= Quantity.human_attribute_name(:default_unit) %></th>
       <% if current_user.at_least(:active) %>
         <th><%= t :actions %></th>
         <th></th>
@@ -25,7 +26,7 @@
                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 colspan="5"><%= t '.top_level_drop' %></th>
     <% end %>
   </thead>
   <tbody id="quantities">

app/views/readouts/_form.html.erb

@@ -4,18 +4,25 @@
     <td>
       <%# 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: readout_counter == 0 %>
     </td>
     <td>
-      <%= form.hidden_field :quantity_id %>
       <%= form.collection_select :unit_id, @user_units, :id,
         ->(u){ sanitize('&emsp;' * (u.base_id ? 1 : 0) + u.symbol) },
-        {prompt: '', disabled: '', selected: ''}, required: true %>
+        {prompt: '', disabled: '', selected: readout.quantity.default_unit_id || ''}, required: true,
+        data: {default_unit_id: readout.quantity.default_unit_id || ''},
+        onchange: "readoutUnitChanged(this)" %>
     </td>
-    <td class="actions">
+    <td class="flex">
       <%# TODO: change to _link_ after giving up displaying relative paths %>
+      <%= image_button_tag '', 'check-circle-outline',
+        class: 'set-default-unit', name: nil, type: 'button', disabled: true,
+        title: t('readouts.form.set_default_unit'),
+        data: {path: quantity_path(readout.quantity)},
+        onclick: 'setDefaultUnit(this)' %>
       <%= image_button_tag '', 'delete-outline', class: 'dangerous', name: nil,
         formaction: discard_readouts_path(readout.quantity),
         formmethod: :get, formnovalidate: true, data: {turbo_stream: true} %>

app/views/units/_form.html.erb

@@ -8,11 +8,11 @@
     <td>
       <%= form.text_area :description, cols: 30, rows: 1, escape: false %>
     </td>
-    <td class="number">
+    <td>
       <%= form.number_field :multiplier, required: true, size: 10, min: :step if @unit.base_id? %>
     </td>
 
-    <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}) %>

app/views/units/_unit.html.erb

@@ -6,14 +6,15 @@
                   drop_id: dom_id(unit.base || unit),
                   drop_id_param: "unit[base_id]"} do %>
 
-  <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 style="--depth:<%= unit.base_id? ? 1 : 0 %>">
+    <%= link_to unit, edit_unit_path(unit), class: 'link', onclick: 'this.blur();',
+      data: {turbo_stream: true} %>
   </td>
   <td><%= unit.description %></td>
-  <td class="number"><%= unit.multiplier.to_html %></td>
+  <td class="ralign"><%= unit.multiplier.to_html %></td>
 
   <% 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} %>

app/views/units/index.html.erb

@@ -14,7 +14,7 @@
   <thead>
     <tr>
       <th><%= Unit.human_attribute_name(:symbol) %></th>
-      <th><%= Unit.human_attribute_name(:description) %></th>
+      <th class="hexpand"><%= Unit.human_attribute_name(:description) %></th>
       <th><%= Unit.human_attribute_name(:multiplier) %></th>
       <% if current_user.at_least(:active) %>
         <th><%= t :actions %></th>

app/views/users/index.html.erb

@@ -11,7 +11,7 @@
   <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 %>
@@ -22,11 +22,11 @@
             <% end %>
           <% end %>
         </td>
-        <td class="svg">
+        <td>
           <%= svg_tag 'pictograms/checkbox-marked-outline' if user.confirmed_at.present? %>
         </td>
         <td><%= l user.created_at, format: :without_tz %></td>
-        <td class="actions">
+        <td class="flex">
           <% if allow_disguise?(user) %>
             <%= image_link_to t('.disguise'), 'incognito', disguise_user_path(user) %>
           <% end %>

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

@@ -8,7 +8,7 @@
     <%= f.email_field :email, autofocus: true, autocomplete: "email" %>
   </div>
 
-  <div class="actions">
+  <div class="flex">
     <%= f.submit "Resend unlock instructions" %>
   </div>
 <% end %>

config/environments/test.rb

@@ -58,4 +58,7 @@ Rails.application.configure do
   # config.action_view.annotate_rendered_view_with_filenames = true
 
   config.log_level = :info
+
+  # Allow Capybara's dynamic test server host (127.0.0.1:<random_port>)
+  config.hosts << '127.0.0.1'
 end

config/locales/en.yml

@@ -11,8 +11,13 @@ en:
   activerecord:
     attributes:
       quantity:
+        default_unit: Default unit
         description: Description
         name: Name
+      readout:
+        created_at: Recorded at
+        taken_at: Taken at
+        value: Value
       unit:
         base: Base unit
         description: Description
@@ -81,6 +86,11 @@ en:
       revert: Revert
       sign_out: Sign out
       source_code: Get code
+  readouts:
+    form:
+      set_default_unit: Set as default unit
+  charts:
+    navigation: Charts
   measurements:
     navigation: Measurements
     no_items: There are no measurements taken. You can Add some now.
@@ -89,6 +99,21 @@ en:
       taken_at_html: Measurement taken at 
     index:
       new_measurement: Add measurement
+      view_compact: Compact view
+      view_wide: Wide view
+      view_charts: Charts
+    readout:
+      edit: Edit
+      destroy: Delete
+    create:
+      success:
+        one: Recorded 1 measurement.
+        other: Recorded %{count} measurements.
+      no_readouts: No readouts selected.
+    update:
+      success: Measurement updated.
+    destroy:
+      success: Measurement deleted.
   quantities:
     navigation: Quantities
     no_items: There are no configured quantities. You can Add some or Import from defaults.

config/routes.rb

@@ -1,5 +1,6 @@
 Rails.application.routes.draw do
   resources :measurements
+  resources :charts, only: [:index]
 
   resources :readouts, only: [:new] do
     collection {get 'new/:id/discard', action: :discard, as: :discard}

db/migrate/20260402000000_add_taken_at_to_readouts.rb

@@ -0,0 +1,5 @@
+class AddTakenAtToReadouts < ActiveRecord::Migration[7.2]
+  def change
+    add_column :readouts, :taken_at, :datetime
+  end
+end

db/migrate/20260403000000_add_default_unit_to_quantities.rb

@@ -0,0 +1,5 @@
+class AddDefaultUnitToQuantities < ActiveRecord::Migration[7.2]
+  def change
+    add_reference :quantities, :default_unit, foreign_key: {to_table: :units}, null: true
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.2].define(version: 2025_01_21_230456) do
+ActiveRecord::Schema[7.2].define(version: 2026_04_03_000000) do
   create_table "quantities", charset: "utf8mb4", collation: "utf8mb4_0900_as_ci", force: :cascade do |t|
     t.bigint "user_id"
     t.string "name", limit: 31, null: false
@@ -20,6 +20,8 @@ ActiveRecord::Schema[7.2].define(version: 2025_01_21_230456) do
     t.datetime "updated_at", null: false
     t.integer "depth", default: 0, null: false
     t.string "pathname", limit: 511, null: false
+    t.bigint "default_unit_id"
+    t.index ["default_unit_id"], name: "index_quantities_on_default_unit_id"
     t.index ["parent_id"], name: "index_quantities_on_parent_id"
     t.index ["user_id", "parent_id", "name"], name: "index_quantities_on_user_id_and_parent_id_and_name", unique: true
     t.index ["user_id"], name: "index_quantities_on_user_id"
@@ -32,6 +34,7 @@ ActiveRecord::Schema[7.2].define(version: 2025_01_21_230456) do
     t.decimal "value", precision: 30, scale: 15, null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.datetime "taken_at"
     t.index ["quantity_id", "created_at"], name: "index_readouts_on_quantity_id_and_created_at", unique: true
     t.index ["quantity_id"], name: "index_readouts_on_quantity_id"
     t.index ["unit_id"], name: "index_readouts_on_unit_id"
@@ -70,6 +73,7 @@ ActiveRecord::Schema[7.2].define(version: 2025_01_21_230456) do
   end
 
   add_foreign_key "quantities", "quantities", column: "parent_id", on_delete: :cascade
+  add_foreign_key "quantities", "units", column: "default_unit_id"
   add_foreign_key "quantities", "users"
   add_foreign_key "readouts", "quantities"
   add_foreign_key "readouts", "units"

test/controllers/charts_controller_test.rb

@@ -0,0 +1,63 @@
+require "test_helper"
+
+class ChartsControllerTest < ActionDispatch::IntegrationTest
+  setup do
+    host! '127.0.0.1'
+    @user = users(:alice)
+    post new_user_session_path, params: { user: { email: @user.email, password: 'alice' } }
+    @quantity = @user.quantities.create!(name: 'Weight')
+    @unit = @user.units.create!(symbol: 'kg')
+  end
+
+  test "requires authentication" do
+    delete destroy_user_session_path
+    get charts_path
+    assert_response :redirect
+  end
+
+  test "index returns ok" do
+    get charts_path
+    assert_response :success
+  end
+
+  test "embeds readout data as JSON in script tag" do
+    users(:alice).readouts.create!(quantity: @quantity, unit: @unit, value: 82.5, taken_at: 1.day.ago)
+
+    get charts_path
+
+    assert_select 'script#charts-data[type="application/json"]' do |elements|
+      data = JSON.parse(elements.first.children.first.to_s)
+      assert_equal 1, data.size
+      assert_equal 'Weight', data.first['quantityName']
+      assert_in_delta 82.5, data.first['value']
+      assert_equal 'kg', data.first['unit']
+      assert_not_nil data.first['takenAt']
+    end
+  end
+
+  test "orders readouts by taken_at ascending" do
+    older = users(:alice).readouts.create!(quantity: @quantity, unit: @unit, value: 80.0, taken_at: 2.days.ago)
+    newer = users(:alice).readouts.create!(quantity: @quantity, unit: @unit, value: 82.5, taken_at: 1.day.ago)
+
+    get charts_path
+
+    assert_select 'script#charts-data[type="application/json"]' do |elements|
+      data = JSON.parse(elements.first.children.first.to_s)
+      assert_equal older.taken_at.iso8601, data.first['takenAt']
+      assert_equal newer.taken_at.iso8601, data.last['takenAt']
+    end
+  end
+
+  test "does not expose other users readouts" do
+    bob_quantity = users(:bob).quantities.create!(name: 'Steps')
+    bob_unit = users(:bob).units.create!(symbol: 'steps')
+    users(:bob).readouts.create!(quantity: bob_quantity, unit: bob_unit, value: 5000, taken_at: 1.day.ago)
+
+    get charts_path
+
+    assert_select 'script#charts-data[type="application/json"]' do |elements|
+      data = JSON.parse(elements.first.children.first.to_s)
+      assert data.none? { |r| r['quantityName'] == 'Steps' }, "Bob's data must not appear"
+    end
+  end
+end

test/controllers/measurements_controller_test.rb

@@ -1,8 +1,7 @@
 require "test_helper"
 
 class MeasurementsControllerTest < ActionDispatch::IntegrationTest
-  #test "should get index" do
-  #  get measurements_index_url
-  #  assert_response :success
-  #end
+  # test "the truth" do
+  #   assert true
+  # end
 end

test/system/charts_test.rb

@@ -0,0 +1,26 @@
+require "application_system_test_case"
+
+class ChartsTest < ApplicationSystemTestCase
+  setup do
+    @user = sign_in(user: users(:alice))
+    @quantity = @user.quantities.create!(name: 'Weight')
+    @unit = @user.units.create!(symbol: 'kg')
+    @user.readouts.create!(quantity: @quantity, unit: @unit, value: 82.5, taken_at: 1.day.ago)
+    @user.readouts.create!(quantity: @quantity, unit: @unit, value: 83.1, taken_at: Time.now)
+    visit charts_path
+  end
+
+  test "charts page is reachable from navigation" do
+    visit root_path
+    click_on t('charts.navigation')
+    assert_current_path charts_path
+  end
+
+  test "renders Plotly chart panel" do
+    assert_selector '#measurements-charts .chart-panel', wait: 5
+  end
+
+  test "chart legend shows quantity name with unit" do
+    assert_text 'Weight (kg)', wait: 5
+  end
+end

test/system/measurements_test.rb

@@ -0,0 +1,64 @@
+require "application_system_test_case"
+
+class MeasurementsTest < ApplicationSystemTestCase
+  setup do
+    @user = sign_in(user: users(:alice))
+
+    @quantity = @user.quantities.create!(name: 'Weight')
+    @unit = @user.units.create!(symbol: 'kg')
+    @readout = @user.readouts.create!(quantity: @quantity, unit: @unit, value: 82.5)
+
+    visit measurements_path
+  end
+
+  test "index shows quantity name as edit link for active user" do
+    within 'tbody' do
+      assert_selector :link, exact_text: @quantity.name
+    end
+  end
+
+  test "edit opens inline form on quantity link click" do
+    within 'tbody' do
+      click_on @quantity.name
+      assert_selector ':focus'
+      assert_selector 'input[name="readout[value]"]'
+    end
+  end
+
+  test "edit and update measurement value" do
+    within 'tbody' do
+      click_on @quantity.name
+      fill_in 'readout[value]', with: '83.1'
+      assert_difference ->{ @readout.reload.value }, 83.1 - @readout.value do
+        click_on t('helpers.submit.update')
+      end
+      assert_no_selector :fillable_field
+      assert_selector :link, exact_text: @quantity.name
+    end
+    assert_selector '.flash.notice', text: t('measurements.update.success')
+  end
+
+  test "cancel edit restores original row" do
+    within 'tbody' do
+      click_on @quantity.name
+      assert_selector 'input[name="readout[value]"]'
+      click_on t(:cancel)
+      assert_no_selector :fillable_field
+      assert_selector :link, exact_text: @quantity.name
+    end
+  end
+
+  test "wide view edit opens panel form" do
+    @readout.update!(taken_at: Time.now)
+    visit measurements_path
+    execute_script("localStorage.removeItem('measurements-view')")
+    visit measurements_path
+
+    find('button[data-view="wide"]').click
+    within '#measurements-wide' do
+      assert_text format("%.10g", 82.5), wait: 3
+      find('button.link').click
+    end
+    assert_selector '#measurement_edit_form input[name="readout[value]"]', wait: 5
+  end
+end

test/system/quantities_test.rb

@@ -0,0 +1,45 @@
+require "application_system_test_case"
+
+class QuantitiesTest < ApplicationSystemTestCase
+  setup do
+    @user = sign_in(user: users(:alice))
+    @unit = @user.units.create!(symbol: 'kg')
+    @quantity = @user.quantities.create!(name: 'Weight')
+    visit quantities_path
+  end
+
+  test "update button turns red when default unit changes" do
+    click_on 'Weight'
+
+    button = find('button[name=button]')
+    initial_color = evaluate_script("getComputedStyle(arguments[0]).backgroundColor", button)
+
+    select 'kg', from: 'quantity[default_unit_id]'
+
+    changed_color = evaluate_script("getComputedStyle(arguments[0]).backgroundColor", button)
+    refute_equal initial_color, changed_color, "Button color should change when default unit is altered"
+  end
+
+  test "saving default unit pre-selects it in measurements form" do
+    click_on 'Weight'
+    select 'kg', from: 'quantity[default_unit_id]'
+    click_on t('helpers.submit.update')
+    assert_selector '.flash.notice'
+
+    @quantity.reload
+    assert_equal @unit.id, @quantity.default_unit_id
+
+    visit measurements_path
+    find(:link_or_button, t('measurements.index.new_measurement')).click
+    assert_selector '#measurement_form'
+
+    within '#quantity_select' do
+      check 'Weight'
+    end
+    find('button[formaction]').click
+
+    within 'tbody#readouts' do
+      assert_selector "option[value='#{@unit.id}'][selected]"
+    end
+  end
+end

test/system/users_test.rb

@@ -229,7 +229,7 @@ class UsersTest < ApplicationSystemTestCase
       user = User.find_by_email!(first(:link).text)
       inject_button_to first('td:not(.link)'), "update status", user_path(user), method: :patch,
         params: {user: {status: User.statuses.keys.sample}}, data: {turbo: false}
-      click_on "update status"
+      execute_script("arguments[0].click()", find_button("update status"))
     end
     assert_title 'The change you wanted was rejected (422)'
   end