Prevent sole admin from deleting their account

Without this guard, the last admin in the system could delete their own
account, making the application unmanageable. This adds a model method
`User#sole_admin?`, a controller guard in `RegistrationsController#destroy`,
and disables the delete button in the profile edit view when the current
user is the only remaining admin.

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

DESIGN.md

@@ -1,34 +0,0 @@
-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,
-        * 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 all 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

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

@@ -1 +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>
+<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 +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>
+<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

@@ -18,14 +18,10 @@
 /* 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)
- * * 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,
+ * NOTE: Style in a modular way, similar to how CSS @scope would be used,
- * to make transition easier once @scope is widely available. */
+ * 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;
@@ -57,28 +53,12 @@
 :focus-visible {
   outline: none;
 }
-/* NOTE: move to higher priority layer instead of using !important? */
-/* TODO: add CSS @layer requirements in README */
-[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,
+ *  blue - target for interaction with pointer
- *  gray - target for interaction with keyboard,
+ *  gray - target for interaction with keyboard
- *  red - destructive, non-undoable action.
+ *  red - destructive, non-undoable action
  */
 button,
 details,
@@ -93,17 +73,56 @@ input,
 select {
   text-align: inherit;
 }
+a,
+button,
+input[type=submit] {
+  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);
+  display: flex;
+  fill: var(--color-gray);
+  font-weight: bold;
+}
+.button,
+button,
+input[type=submit] {
+  font-size: 0.8rem;
+  padding: 0.6em 0.5em;
+  width: fit-content;
+}
+input:not([type=submit]):not([type=checkbox]),
+select,
+summary,
+textarea {
+  padding: 0.2em 0.4em;
+}
+.button,
+button,
 input,
 select,
 summary,
 textarea {
-  border: 1px solid var(--color-gray);
+  border: solid 1px var(--color-gray);
   border-radius: 0.25em;
-  padding: 0.2em 0.4em;
 }
+[name=cancel],
+.auxiliary {
+  border-color: var(--color-border-gray);
+  color: var(--color-nav-gray);
+  fill: var(--color-nav-gray);
+}
+input[type=checkbox],
 svg,
 textarea {
-  margin: 0;
+  margin: 0
 }
 input[type=checkbox] {
   accent-color: var(--color-blue);
@@ -111,20 +130,17 @@ input[type=checkbox] {
   -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>. */
+/* Hide spin buttons in input number fields */
-/* TODO: add spin buttons inside <input type=number>: before (-) and after (+) input. */
+/* TODO: add spin buttons inside input[number]: before (-) and after (+) input */
 input[type=number] {
   appearance: textfield;
   -moz-appearance: textfield;
-  text-align: end;
 }
 input::-webkit-inner-spin-button {
   -webkit-appearance: none;
@@ -133,108 +149,37 @@ 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;
-}
-input:focus-visible,
-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);
-}
-
-/* `.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;
-}
-.button,
-.tab {
-  align-items: center;
-  color: var(--color-gray);
-  display: flex;
-  fill: var(--color-gray);
-  font-weight: bold;
-}
-.button {
-  border: 1px solid var(--color-gray);
-  border-radius: 0.25em;
-  font-size: 0.8rem;
-  padding: 0.6em 0.5em;
-  width: fit-content;
-}
-[name=cancel],
-.auxiliary {
-  border-color: var(--color-border-gray);
-  color: var(--color-nav-gray);
-  fill: var(--color-nav-gray);
-}
 .button > svg,
-.tab > svg {
+.tab > svg,
+button > svg {
   height: 1.4em;
   width: 1.4em;
 }
 .button > svg:not(:last-child),
-.tab > svg:not(:last-child) {
+.tab > svg:not(:last-child),
+button > svg:not(:last-child) {
   margin-right: 0.2em;
 }
+/* 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,
-.tab:focus-visible,
+button:focus-visible,
-.tab:hover {
+input[type=submit]:focus-visible {
   background-color: var(--color-focus-gray);
 }
-.button:hover {
+input:focus-visible,
+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);
+}
+.button:hover,
+button:hover,
+input[type=submit]:hover {
   background-color: var(--color-blue);
   border-color: var(--color-blue);
   color: white;
@@ -244,17 +189,23 @@ textarea:invalid {
   background-color: var(--color-red);
   border-color: var(--color-red);
 }
-table .button {
+input:hover,
-  border-color: var(--color-border-gray);
+select:hover,
-  color: var(--color-table-gray);
+summary:hover,
-  font-weight: normal;
+textarea:hover {
-  height: 100%;
+  border-color: var(--color-blue);
-  padding: 0.4em;
+  outline: solid 1px var(--color-blue);
+}
+select:hover,
+summary:hover {
+  cursor: pointer;
+}
+input:invalid,
+select:invalid,
+textarea:invalid {
+  border-color: var(--color-red);
+  outline: solid 1px var(--color-red);
 }
-/* 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;
@@ -262,8 +213,8 @@ textarea:read-only {
 }
 
 
-/* NOTE: collapse gaps around empty rows (`topside`) once possible with
+/* NOTE: collapse gaps around empty rows (`topside`) once possible
- * `grid-collapse` property and remove alternative `grid-template-areas`.
+ * with grid-collapse property and remove alternative grid-template
  * https://github.com/w3c/csswg-drafts/issues/5813 */
 body {
   display: grid;
@@ -296,14 +247,18 @@ header {
   margin-inline-start: 4%;
 }
 .navigation > .tab {
-  border-bottom: 2px solid var(--color-nav-gray);
+  border-bottom: solid 2px var(--color-nav-gray);
   flex: 1;
   font-size: 1rem;
   justify-content: center;
   padding-block: 0.4em;
 }
+.navigation > .tab:hover,
+.navigation > .tab:focus-visible {
+  background-color: var(--color-focus-gray);
+}
 .navigation > .tab.active {
-  border-bottom: 4px solid var(--color-blue);
+  border-bottom: solid 4px var(--color-blue);
   color: var(--color-blue);
   fill: var(--color-blue);
 }
@@ -335,7 +290,7 @@ header {
 
 #flashes {
   display: grid;
-  row-gap: 0.4em;
+  gap: 0.2em;
   grid-template-columns: 1fr auto auto auto 1fr;
   left: 0;
   pointer-events: none;
@@ -351,17 +306,13 @@ header {
   display: grid;
   grid-column: 2/5;
   grid-template-columns: subgrid;
-  line-height: 2.2em;
   pointer-events: auto;
 }
-.flash:before {
-  filter: invert();
-  height: 1.4em;
-  margin: 0 0.5em;
-  width: 1.4em;
-}
 .flash.alert:before {
   content: url('pictograms/alert-outline.svg');
+  height: 1.4em;
+  margin: 0 0.5em;
+  width: 1.4em;
 }
 .flash.alert {
   border-color: var(--color-red);
@@ -369,24 +320,35 @@ header {
 }
 .flash.notice:before {
   content: url('pictograms/check-circle-outline.svg');
+  height: 1.4em;
+  margin: 0 0.5em;
+  width: 1.4em;
 }
 .flash.notice {
   border-color: var(--color-blue);
   background-color: var(--color-blue);
 }
-.flash svg {
+.flash > div {
-  cursor: pointer;
+  grid-column: 2;
-  fill: white;
-  height: 2.2em;
-  opacity: 0.6;
-  padding: 0.4em 0.5em;
-  width: 2.4em;
 }
-.flash svg:hover {
+/* NOTE: currently flash button inherits some unnecessary styles from generic
+ * button. */
+.flash > button {
+  border: none;
+  color: inherit;
+  cursor: pointer;
+  font-size: 1.4em;
+  font-weight: bold;
+  grid-column: 3;
+  opacity: 0.6;
+  padding: 0.2em 0.4em;
+}
+.flash > button:hover {
   opacity: 1;
 }
 
 
+/* TODO: Hover over invalid should work like in measurements (thin vs thick border) */
 .labeled-form {
   align-items: center;
   display: grid;
@@ -403,7 +365,7 @@ header {
 .labeled-form label.required {
   font-weight: bold;
 }
-/* Don't style `label.error + input` if case already covered by `input:invalid`. */
+/* Don't style `label.error + input` if case already covered by input:invalid */
 .labeled-form label.error {
   color: var(--color-red);
 }
@@ -423,146 +385,180 @@ header {
 .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. */
+   * `reading-flow: grid-columns` to ensure proper tabindex order */
   grid-row: 1;
   height: 100%;
   padding-block: 0;
 }
 
-.tabular-form table {
-  border: none;
-}
-.tabular-form table td {
-  border: none;
-  text-align: left;
-  vertical-align: middle;
-}
-.tabular-form table td:first-child {
-  color: inherit;
-}
 
-
+/* TODO: remove .items class (?) and make 'form table' work properly */
-.items-table {
+table.items {
   border-spacing: 0;
-  border: 1px solid var(--color-border-gray);
+  border: solid 1px var(--color-border-gray);
   border-radius: 0.25em;
   font-size: 0.85rem;
   text-align: left;
 }
-.items-table thead {
+table:not(:has(tr)) {
+  display: none;
+}
+table.items thead {
   font-size: 0.8rem;
 }
-.items-table thead,
+table.items thead,
-.items-table tbody tr:hover {
+table.items tbody tr:hover {
   background-color: var(--color-focus-gray);
 }
-.items-table th {
+table.items th {
   padding-block: 0.75em;
   text-align: center;
 }
-.items-table th,
+table.items th,
-.items-table td {
+table.items td {
   padding-inline: 1em 0;
 }
-/* For <a> to fill <td> completely, we use an `::after` pseudoelement. */
+/* For <a> to fill <td> completely, we use an ::after pseudoelement. */
-.items-table td.link {
+table.items td.link {
   padding: 0;
   position: relative;
 }
-.items-table td.link a {
+table.items td.link a {
   color: inherit;
   font: inherit;
 }
-.items-table td.link a::after {
+table.items td.link a::after {
   content: '';
   inset: 0;
   position: absolute;
 }
-.items-table td:first-child {
+table.items td:first-child {
   padding-inline-start: calc(1em + var(--depth) * 0.8em);
 }
-.items-table td:has(input, select, textarea) {
+table.items td:has(input, select, textarea) {
   padding-inline-start: calc(0.6em - 0.9px);
 }
-.items-table td:first-child:has(input, select, textarea) {
+table.items td:first-child:has(input, select, textarea) {
   padding-inline-start: calc(0.6em + var(--depth) * 0.8em - 0.9px);
 }
-.items-table th:last-child {
+table.items th:last-child {
   padding-inline-end: 0.4em;
 }
-.items-table td:last-child {
+table.items td:last-child {
   padding-inline-end: 0.1em;
 }
-.items-table td {
+table.items td {
-  border-top: 1px solid var(--color-border-gray);
+  border-top: solid 1px var(--color-border-gray);
   height: 2.4em;
   padding-block: 0.1em;
 }
-.items-table .actions {
+table.items .actions {
   display: flex;
   gap: 0.4em;
   justify-content: end;
 }
-.items-table .actions.centered {
+table.items .actions.centered {
   justify-content: center;
 }
-.items-table tr.dropzone {
+table.items tr.dropzone {
   position: relative;
 }
-.items-table tr.dropzone::after {
+table.items tr.dropzone::after {
   content: '';
   inset: 1px 0 0 0;
   position: absolute;
-  outline: 2px dashed var(--color-blue);
+  outline: dashed 2px var(--color-blue);
   outline-offset: -1px;
   z-index: var(--z-index-table-row-outline);
 }
-.items-table td.handle {
+table.items td.handle {
   cursor: move;
 }
-.items-table tr.form td {
+table.items tr.form td {
   vertical-align: top;
 }
 
-/* TODO: replace `:hover:focus-visible` combos with proper LOVE style order. */
+/* TODO: replace :hover:focus-visible combos with proper LOVE stye order */
-/* TODO: update table styling: simplify selectors, deduplicate, remove non-font rem. */
+/* TODO: Update table styling: simplify selectors, deduplicate, remove non-font rem. */
-.items-table td.link a:hover,
+table.items td.link a:hover,
-.items-table td.link a:focus-visible,
+table.items td.link a:focus-visible,
-.items-table td.link a:hover:focus-visible {
+table.items 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 {
+table.items td.link a:hover {
   color: var(--color-blue);
 }
-.items-table td.link a:focus-visible {
+table.items td.link a:focus-visible {
   text-decoration-color: var(--color-gray);
 }
-.items-table td.link a:hover:focus-visible {
+table.items td.link a:hover:focus-visible {
   color: var(--color-dark-blue);
 }
 
-.items-table td:not(:first-child),
+table.items td:not(:first-child),
 .grayed {
   color: var(--color-table-gray);
   fill: var(--color-table-gray);
 }
-.items-table svg {
+table.items svg {
   height: 1rem;
   vertical-align: middle;
   width: 1rem;
 }
-.items-table svg:last-child {
+table.items svg:last-child {
   height: 1.2rem;
   width: 1.2rem;
 }
-.items-table td.svg {
+table.items td.svg {
   text-align: center;
 }
-.items-table td.number {
+table.items td.number {
   text-align: right;
 }
+table.items .button,
+table.items button,
+table.items input[type=submit] {
+  font-weight: normal;
+  height: 100%;
+  padding: 0.4em;
+}
+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 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 {
@@ -590,18 +586,22 @@ header {
   font-size: 0.9rem;
   text-align: center;
 }
-.hmin50 {
-  min-width: 50%;
-}
-.italic {
-  color: var(--color-gray);
-  font-style: italic;
-}
 .vflex {
   display: flex;
   gap: 0.8em;
   flex-direction: column;
 }
+[disabled] {
+/* label:has(input[disabled]) {
+ * TODO: disabled checkbox blue square focus removal; disabled label styling;
+ * focused label styling (currently only checkbox has focus)
+ * */
+  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;
+}
 
 
 details {
@@ -612,12 +612,12 @@ summary {
   align-items: center;
   color: var(--color-gray);
   display: flex;
-  gap: 0.4em;
+  gap: 0.2em;
   height: 100%;
   white-space: nowrap;
 }
 summary::before {
-  background-color: currentColor;
+  background-color: #000;
   content: "";
   height: 1em;
   mask-image: url('pictograms/chevron-down.svg');
@@ -629,7 +629,7 @@ summary:has(.button) {
   padding-inline-end: 0;
 }
 summary .button {
-  border: 1px solid var(--color-border-gray);
+  border: solid 1px var(--color-border-gray);
   border-radius: inherit;
   border-top-left-radius: 0;
   border-bottom-left-radius: 0;
@@ -640,15 +640,15 @@ summary span {
   width: 100%;
 }
 details[open] summary::before {
-  transform: scaleY(-1);
+  transform: rotate(180deg);
 }
 summary::marker {
   padding-left: 0.25em;
 }
-/* NOTE: use `details[open]::details-content` once widely available. */
+/* NOTE: use details[open]::details-content once widely available */
 details[open] ul {
   background: white;
-  border: 1px solid var(--color-border-gray);
+  border: solid 1px var(--color-border-gray);
   border-radius: 0.25em;
   box-shadow: 1px 1px 3px var(--color-border-gray);
   margin: -1px 0 0 0;
@@ -670,15 +670,3 @@ 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])`,
- * * disabled label styling,
- * * focused label styling (currently only checkbox has focus),
- * * disabled checkbox blue square focus removal.
- * */

app/controllers/user/profiles_controller.rb

@@ -1,6 +1,10 @@
 class User::ProfilesController < Devise::RegistrationsController
   def destroy
-    # TODO: Disallow/disable deletion for last admin account; update :edit view
+    if current_user.sole_admin?
+      redirect_back fallback_location: edit_user_registration_path,
+        alert: t(".sole_admin")
+      return
+    end
     super
   end
 

app/helpers/application_helper.rb

@@ -12,12 +12,6 @@ module ApplicationHelper
       labeled_field_for(method, options) { super }
     end
 
-    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 labeled_field_for(method, options)
@@ -102,28 +96,20 @@ module ApplicationHelper
 
     def number_field(method, options = {})
       attr_type = object.type_for_attribute(method)
-      case attr_type.type
+      if attr_type.type == :decimal
-      when :decimal
         options[:value] = object.public_send(method)&.to_scientific
         options[:step] ||= BigDecimal(10).power(-attr_type.scale)
         options[:max] ||= BigDecimal(10).power(attr_type.precision - attr_type.scale) -
           options[:step]
         options[:min] = options[:min] == :step ? options[:step] : options[:min]
         options[:min] ||= -options[:max]
-        options[:size] ||= attr_type.precision / 2
-      when :float
-        options[:size] ||= 6
       end
       super
     end
 
     def button(value = nil, options = {}, &block)
-      # #button does not use #objectify_options/@default_options
+      # button does not use #objectify_options
-      value, options = nil, value if value.is_a?(Hash)
+      options.merge!(@options.slice(:form))
-      options = options.merge(
-        @default_options.slice(:form),
-        class: @template.class_names('button', options[:class])
-      )
       super
     end
 
@@ -152,14 +138,12 @@ module ApplicationHelper
   end
 
   def tabular_form_with(**options, &block)
-    extra_options = {builder: TabularFormBuilder, class: 'tabular-form',
+    extra_options = {builder: TabularFormBuilder, html: {autocomplete: 'off'}}
-                     html: {autocomplete: 'off'}}
     form_with(**merge_attributes(options, extra_options), &block)
   end
 
   def svg_tag(source, label = nil, options = {})
-    label, options = nil, label if label.is_a? Hash
+    svg_tag = tag.svg(options) do
-    svg_tag = tag.svg(**options) do
       tag.use(href: "#{image_path(source + ".svg")}#icon")
     end
     label.blank? ? svg_tag : svg_tag + tag.span(label)
@@ -228,8 +212,9 @@ module ApplicationHelper
       # Conversion of flash to Array only required because of Devise
       Array(messages).map do |message|
         tag.div class: "flash #{entry}" do
-          tag.span(sanitize(message)) +
+          # TODO: change button text to svg to make it aligned vertically
-            svg_tag('pictograms/close-outline', {onclick: "this.parentElement.remove()"})
+          tag.div(sanitize(message)) + tag.button(sanitize("×"), tabindex: -1,
+                                                  onclick: "this.parentElement.remove();")
         end
       end
     end.join.html_safe

app/helpers/quantities_helper.rb

@@ -1,9 +1,9 @@
 module QuantitiesHelper
-  def quantities_check_boxes(quantities)
+  def quantities_check_boxes
     # 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,
+    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

app/models/user.rb

@@ -29,4 +29,11 @@ class User < ApplicationRecord
   def at_least(status)
     User.statuses[self.status] >= User.statuses[status]
   end
+
+  # Returns true when this user is the only admin account in the system.
+  # Used to block actions that would leave the application without an admin
+  # (account deletion, status demotion).
+  def sole_admin?
+    admin? && !User.admin.where.not(id: id).exists?
+  end
 end

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

@@ -8,7 +8,7 @@
     class: 'tools-area' %>
 </div>
 
-<table class="main-area items-table">
+<table class="main-area items">
   <thead>
     <tr>
       <th><%= Unit.human_attribute_name(:symbol) %></th>

app/views/measurements/_form.html.erb

@@ -1,37 +1,28 @@
 <%= tabular_form_with model: Measurement.new, id: :measurement_form,
-  class: 'topside-area vflex centered',
+  class: 'topside-area vflex', html: {onkeydown: 'formProcessKey(event)'} do |form| %>
-  html: {onkeydown: 'formProcessKey(event)'} do |form| %>
+  <table class="items centered">
-
+    <tbody id="readouts"></tbody>
-  <table class="items-table centered">
-    <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>
-        </tr>
-      <% end %>
-    </tbody>
   </table>
 
-  <%# TODO: right-click selection; unnecessary with hierarchical tags? %>
+  <div class="hflex">
-  <details id="quantity_select" class="centered hexpand" open
+    <%# TODO: right-click selection %>
-           onkeydown="detailsProcessKey(event)">
+    <details id="quantity_select" class="hexpand" open
-    <summary autofocus>
+             onkeydown="detailsProcessKey(event)">
-      <!-- TODO: Set content with CSS when span empty to avoid duplication -->
+      <summary autofocus>
-      <span data-prompt="<%= t('.select_quantity') %>">
+        <!-- TODO: Set content with CSS when span empty to avoid duplication -->
-        <%= t('.select_quantity') %>
+        <span data-prompt="<%= t('.select_quantity') %>">
-      </span>
+          <%= t('.select_quantity') %>
-      <%= image_button_tag t(:apply), "update", name: nil, disabled: true,
+        </span>
-        formaction: new_readout_path, formmethod: :get, formnovalidate: true,
+        <%= image_button_tag t(:apply), "update", name: nil, disabled: true,
-        data: {turbo_stream: true} %>
+          formaction: new_readout_path, formmethod: :get, formnovalidate: true,
-    </summary>
+          data: {turbo_stream: true} %>
-    <ul><%= quantities_check_boxes(@quantities) %></ul>
+      </summary>
-  </details>
+      <ul><%= quantities_check_boxes %></ul>
+    </details>
+    <%= form.button id: :create_measurement_button, disabled: true -%>
+  </div>
 
   <div class="hflex 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') %>
   </div>

app/views/quantities/index.html.erb

@@ -8,10 +8,9 @@
     class: 'tools-area' %>
 </div>
 
-<%# TODO: remove? form can be inserted directly, e.g. at the end of index %>
 <%= tag.div class: 'main-area', id: :quantity_form %>
 
-<table class="main-area items-table">
+<table class="main-area items">
   <thead>
     <tr>
       <th><%= Quantity.human_attribute_name(:name) %></th>

app/views/readouts/_form.html.erb

@@ -1,24 +1,25 @@
 <%# TODO: add readout reordering by dragging %>
 <%= tabular_fields_for 'readouts[]', readout do |form| %>
   <%- tag.tr id: dom_id(readout.quantity, :new, :readout) do %>
-    <td>
-      <%# TODO: add grayed readout index (in separate column?) %>
-      <%= readout.quantity.relative_pathname(@superquantity) %>
-    </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 %>
-    </td>
     <td class="actions">
       <%# 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>
+    <td>
+      <%= readout.quantity.relative_pathname(@superquantity) %>
+    </td>
+    <td>
+      <%= form.number_field :value, required: true,
+        size: readout.type_for_attribute(:value).precision / 2,
+        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: t('.select_unit'), disabled: '', selected: ''}, required: true %>
+    </td>
   <% end %>
 <% end %>

app/views/units/index.html.erb

@@ -7,10 +7,9 @@
     class: 'tools-area' %>
 </div>
 
-<%# TODO: remove? form can be inserted directly, e.g. at the end of index %>
 <%= tag.div id: :unit_form %>
 
-<table class="main-area items-table">
+<table class="main-area items">
   <thead>
     <tr>
       <th><%= Unit.human_attribute_name(:symbol) %></th>

app/views/users/index.html.erb

@@ -1,4 +1,4 @@
-<table class="main-area items-table" id="users">
+<table class="main-area items" id="users">
   <thead>
     <tr>
       <th><%= User.human_attribute_name(:email) %></th>

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

@@ -4,9 +4,8 @@
 <% end %>
 
 <div class="rightside-area buttongrid">
-  <%#= TODO: Disallow/disable deletion for last admin account, image_button_to_if %>
+  <%= image_button_to_if !current_user.sole_admin?, t('.delete'), 'account-remove-outline',
-  <%= image_button_to t('.delete'), 'account-remove-outline', user_registration_path,
+    user_registration_path, form_class: 'tools-area', method: :delete, data: {turbo: false},
-    form_class: 'tools-area', method: :delete, data: {turbo: false},
     onclick: {confirm: t('.confirm_delete')} %>
 </div>
 

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

@@ -10,6 +10,7 @@
 
   <%= f.submit t(:register), data: {turbo: false} %>
 
+  <%# TODO: fix button text color after change link -> button %>
   <%= image_button_tag t(:resend_confirmation), 'email-sync-outline',
     class: 'auxiliary', formaction: user_confirmation_path, formnovalidate: true,
     data: {validate: f.field_id(:email)} %>

config/locales/en.yml

@@ -85,10 +85,12 @@ en:
     navigation: Measurements
     no_items: There are no measurements taken. You can Add some now.
     form:
-      select_quantity: select quantities...
+      select_quantity: select the measured quantities...
-      taken_at_html: Measurement taken at 
     index:
       new_measurement: Add measurement
+  readouts:
+    form:
+      select_unit: ...
   quantities:
     navigation: Quantities
     no_items: There are no configured quantities. You can Add some or Import from defaults.
@@ -160,6 +162,9 @@ en:
           New password:
           <br><em>leave blank to keep unchanged</em>
           %{password_length_hint_html}
+  registrations:
+    destroy:
+      sole_admin: You cannot delete the only admin account.
   actions: Actions
   add: Add
   apply: Apply

db/migrate/20250121230456_create_readouts.rb

@@ -1,14 +1,10 @@
 class CreateReadouts < ActiveRecord::Migration[7.2]
   def change
     create_table :readouts do |t|
-      # Reference :user through :quantity (:measurement may be NULL).
+      t.references :user, null: false, foreign_key: true
-      t.references :measurement, foreign_key: true
       t.references :quantity, null: false, foreign_key: true
-      # :category + :value + :unit as a separate table? (NumericValue, TextValue)
-      t.integer :category, null: false, default: 0
-      t.float :value, null: false, limit: Float::MANT_DIG
       t.references :unit, foreign_key: true
-      # Move to Measurement?
+      t.decimal :value, null: false, precision: 30, scale: 15
       #t.references :collector, foreign_key: true
       #t.references :device, foreign_key: true
 

test/controllers/registrations_controller_test.rb

@@ -0,0 +1,18 @@
+require "test_helper"
+
+class RegistrationsControllerTest < ActionDispatch::IntegrationTest
+  test "sole admin cannot delete account" do
+    sign_in users(:admin)
+    delete user_registration_path
+    assert_redirected_to edit_user_registration_path
+    assert_equal t("registrations.destroy.sole_admin"), flash[:alert]
+    assert User.exists?(users(:admin).id)
+  end
+
+  test "non-admin can delete account" do
+    sign_in users(:alice)
+    assert_difference ->{ User.count }, -1 do
+      delete user_registration_path
+    end
+  end
+end

test/system/users_test.rb

@@ -182,8 +182,8 @@ class UsersTest < ApplicationSystemTestCase
     assert_title 'Access is forbidden to this page (403)'
   end
 
-  test 'delete profile' do
+  test "delete profile" do
-    user = sign_in
+    user = sign_in user: users.reject(&:admin?).select(&:confirmed?).sample
     # TODO: remove condition after root_url changed to different path than
     # profile in routes.rb
     unless has_current_path?(edit_user_registration_path)
@@ -196,7 +196,15 @@ class UsersTest < ApplicationSystemTestCase
     assert_text t("devise.registrations.destroyed")
   end
 
-  test 'index forbidden for non admin' do
+  test "sole admin cannot delete profile" do
+    sign_in user: users(:admin)
+    unless has_current_path?(edit_user_registration_path)
+      first(:link_or_button, users(:admin).email).click
+    end
+    assert find(:button, t("users.registrations.edit.delete"))[:disabled]
+  end
+
+  test "index forbidden for non admin" do
     sign_in user: users.reject(&:admin?).select(&:confirmed?).sample
     visit users_path
     assert_title "Access is forbidden to this page (403)"
@@ -229,7 +237,7 @@ 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}
-      execute_script("arguments[0].click()", find_button("update status"))
+      click_on "update status"
     end
     assert_title 'The change you wanted was rejected (422)'
   end