Checkbox draft v0.1.0

/*
 * Checkbox — vanilla CSS reference implementation.
 * Spec:   packages/components/specs/components/checkbox.spec.json
 * Tokens: packages/tokens/dist/css/components/checkbox.css (generated from packages/tokens/src/components/checkbox.tokens.json)
 *
 * Rules:
 *  - Only --checkbox-* custom properties may appear here. No raw values, no semantic tokens.
 *  - The root is a wrapper (grid: control, label, description); the native input is the control,
 *    drawn by the component (appearance: none). The mark is a pseudo-element of the input.
 *  - Size is a data attribute on the root; states are native pseudo-classes of the input, and the
 *    root's [data-state="<state>"] forces them for review. Precedence follows the spec order:
 *    default < hover < focus-visible < checked < indeterminate < invalid < disabled, so hover does not
 *    repaint a checked box and disabled wins over everything (packages/tokens/AGENTS.md "Which token applies").
 *  - Private properties (--_*) are the single place an option or a state writes to.
 */

.ds-checkbox {
  /* Defaults = size "medium", state "default". */
  --_control-size: var(--checkbox-control-size-medium);
  --_control-radius: var(--checkbox-control-border-radius-medium);
  --_control-background: var(--checkbox-control-background-default);
  --_control-border-color: var(--checkbox-control-border-color-default);
  --_control-color: var(--checkbox-control-color-checked);
  --_label-color: var(--checkbox-label-color-default);
  --_description-color: var(--checkbox-description-color-default);
  --_label-font-family: var(--checkbox-label-typography-medium-font-family);
  --_label-font-size: var(--checkbox-label-typography-medium-font-size);
  --_label-font-weight: var(--checkbox-label-typography-medium-font-weight);
  --_label-line-height: var(--checkbox-label-typography-medium-line-height);
  --_label-letter-spacing: var(--checkbox-label-typography-medium-letter-spacing);
  --_description-font-family: var(--checkbox-description-typography-medium-font-family);
  --_description-font-size: var(--checkbox-description-typography-medium-font-size);
  --_description-font-weight: var(--checkbox-description-typography-medium-font-weight);
  --_description-line-height: var(--checkbox-description-typography-medium-line-height);
  --_description-letter-spacing: var(--checkbox-description-typography-medium-letter-spacing);

  box-sizing: border-box;
  display: inline-grid;
  grid-template-columns: auto 1fr;
  column-gap: var(--checkbox-container-column-gap);
  row-gap: var(--checkbox-container-row-gap);
  align-items: start;
  vertical-align: middle;
}

/* ---- Size ---------------------------------------------------------------- */

.ds-checkbox[data-size="small"] {
  --_control-size: var(--checkbox-control-size-small);
  --_control-radius: var(--checkbox-control-border-radius-small);
  --_label-font-family: var(--checkbox-label-typography-small-font-family);
  --_label-font-size: var(--checkbox-label-typography-small-font-size);
  --_label-font-weight: var(--checkbox-label-typography-small-font-weight);
  --_label-line-height: var(--checkbox-label-typography-small-line-height);
  --_label-letter-spacing: var(--checkbox-label-typography-small-letter-spacing);
  --_description-font-family: var(--checkbox-description-typography-small-font-family);
  --_description-font-size: var(--checkbox-description-typography-small-font-size);
  --_description-font-weight: var(--checkbox-description-typography-small-font-weight);
  --_description-line-height: var(--checkbox-description-typography-small-line-height);
  --_description-letter-spacing: var(--checkbox-description-typography-small-letter-spacing);
}

/* ---- Parts --------------------------------------------------------------- */

.ds-checkbox__control {
  box-sizing: border-box;
  display: inline-grid;
  place-content: center;
  inline-size: var(--_control-size);
  block-size: var(--_control-size);
  flex: none;
  margin: 0;
  /* Centers the box on the first line of the label. */
  margin-block-start: calc((var(--_label-line-height) * var(--_label-font-size) - var(--_control-size)) / 2);
  border: var(--checkbox-control-border-width) solid var(--_control-border-color);
  border-radius: var(--_control-radius);
  background-color: var(--_control-background);
  color: var(--_control-color);
  cursor: pointer;
  appearance: none;
  -webkit-appearance: none;
  transition:
    background-color var(--checkbox-control-transition-duration) var(--checkbox-control-transition-easing),
    border-color var(--checkbox-control-transition-duration) var(--checkbox-control-transition-easing);
}

/* The mark: a check (two borders rotated) when checked, a bar when indeterminate. Drawn in currentColor
   from the control's color token; its geometry is a fraction of the control size, never a literal length. */
.ds-checkbox__control::after {
  content: "";
  display: block;
  box-sizing: border-box;
  inline-size: calc(var(--_control-size) * 0.3);
  block-size: calc(var(--_control-size) * 0.55);
  margin-block-end: calc(var(--_control-size) * 0.12);
  border: solid currentColor;
  border-width: 0 calc(var(--_control-size) * 0.12) calc(var(--_control-size) * 0.12) 0;
  transform: rotate(45deg);
  opacity: 0;
}

.ds-checkbox__label {
  grid-column: 2;
  color: var(--_label-color);
  font-family: var(--_label-font-family);
  font-size: var(--_label-font-size);
  font-weight: var(--_label-font-weight);
  line-height: var(--_label-line-height);
  letter-spacing: var(--_label-letter-spacing);
  cursor: pointer;
}

.ds-checkbox__description {
  grid-column: 2;
  margin: 0;
  color: var(--_description-color);
  font-family: var(--_description-font-family);
  font-size: var(--_description-font-size);
  font-weight: var(--_description-font-weight);
  line-height: var(--_description-line-height);
  letter-spacing: var(--_description-letter-spacing);
}

/* ---- States -------------------------------------------------------------- */
/* Order matters: hover < checked < indeterminate < invalid < disabled. Hover never repaints a checked,
   indeterminate or disabled box (the checked token wins over hover, as in the token rule). */

.ds-checkbox:where([data-state="hover"]) .ds-checkbox__control:not(:checked, :indeterminate, :disabled),
.ds-checkbox:not([data-state]) .ds-checkbox__control:hover:not(:checked, :indeterminate, :disabled) {
  --_control-background: var(--checkbox-control-background-hover);
  --_control-border-color: var(--checkbox-control-border-color-hover);
}

.ds-checkbox:where([data-state="checked"]) .ds-checkbox__control,
.ds-checkbox__control:checked {
  --_control-background: var(--checkbox-control-background-checked);
  --_control-border-color: var(--checkbox-control-border-color-checked);
  --_control-color: var(--checkbox-control-color-checked);
}
.ds-checkbox:where([data-state="checked"]) .ds-checkbox__control::after,
.ds-checkbox__control:checked::after {
  opacity: 1;
}

.ds-checkbox:where([data-state="indeterminate"]) .ds-checkbox__control,
.ds-checkbox__control:indeterminate {
  --_control-background: var(--checkbox-control-background-indeterminate);
  --_control-border-color: var(--checkbox-control-border-color-indeterminate);
  --_control-color: var(--checkbox-control-color-indeterminate);
}
.ds-checkbox:where([data-state="indeterminate"]) .ds-checkbox__control::after,
.ds-checkbox__control:indeterminate::after {
  inline-size: calc(var(--_control-size) * 0.5);
  block-size: 0;
  margin: 0;
  border-width: 0 0 calc(var(--_control-size) * 0.12) 0;
  transform: none;
  opacity: 1;
}

.ds-checkbox:where([data-state="invalid"]) .ds-checkbox__control,
.ds-checkbox__control[aria-invalid="true"] {
  --_control-border-color: var(--checkbox-control-border-color-invalid);
}

.ds-checkbox:where([data-state="disabled"]),
.ds-checkbox:has(.ds-checkbox__control:disabled) {
  --_label-color: var(--checkbox-label-color-disabled);
  --_description-color: var(--checkbox-description-color-disabled);
}
.ds-checkbox:where([data-state="disabled"]) .ds-checkbox__control,
.ds-checkbox__control:disabled {
  --_control-background: var(--checkbox-control-background-disabled);
  --_control-border-color: var(--checkbox-control-border-color-disabled);
  --_control-color: var(--checkbox-control-color-disabled);
  cursor: not-allowed;
}
.ds-checkbox:where([data-state="disabled"]) .ds-checkbox__label,
.ds-checkbox:has(.ds-checkbox__control:disabled) .ds-checkbox__label {
  cursor: not-allowed;
}

.ds-checkbox__control:focus {
  outline: none;
}

.ds-checkbox:where([data-state="focus-visible"]) .ds-checkbox__control,
.ds-checkbox__control:focus-visible {
  outline: var(--checkbox-control-outline-width-focus-visible) solid var(--checkbox-control-outline-color-focus-visible);
  outline-offset: var(--checkbox-control-outline-offset-focus-visible);
}

@media (prefers-reduced-motion: reduce) {
  .ds-checkbox__control {
    transition: none;
  }
}

/**
 * Checkbox — HTML template for the web implementation.
 * Pure function of the spec properties (packages/components/specs/components/checkbox.spec.json) -> HTML string.
 * Used by the docs site (server and client side). No DOM, no framework, no script: the native
 * checkbox holds the state, the label activates it, the browser announces it.
 *
 * Extra props: `id` names the input (the label points at it; unique in the page; without it
 * instances are numbered in render order); `name` and `value` are the form field's; `attrs` adds
 * HTML attributes to the input (so the docs site can wire its own forms).
 * Extra sandbox-only prop: `state` forces a visual state through data-state on the root.
 */
import { escapeHtml, escapeAttr } from '../../lib/template-utils.mjs';

export const meta = { id: 'checkbox', selector: '.ds-checkbox' };

let count = 0;

export function render(props = {}) {
  const {
    label = 'Label',
    description = null,
    size = 'medium',
    checked = false,
    disabled = false,
    invalid = false,
    required = false,
    state = null,
    id = null,
    name = null,
    value = null,
    attrs: extra = {},
  } = props;

  const inputId = id ?? `ds-checkbox-${++count}`;
  const descriptionId = `${inputId}-description`;
  const rootAttrs = ['class="ds-checkbox"', `data-size="${escapeAttr(size)}"`];
  if (disabled) rootAttrs.push('data-disabled');
  if (invalid) rootAttrs.push('data-invalid');
  if (state && state !== 'default') rootAttrs.push(`data-state="${escapeAttr(state)}"`);

  const inputAttrs = ['type="checkbox"', 'class="ds-checkbox__control"', 'data-part="control"', `id="${escapeAttr(inputId)}"`];
  if (name) inputAttrs.push(`name="${escapeAttr(name)}"`);
  if (value != null) inputAttrs.push(`value="${escapeAttr(value)}"`);
  if (checked) inputAttrs.push('checked');
  if (disabled) inputAttrs.push('disabled');
  if (required) inputAttrs.push('required');
  if (invalid) inputAttrs.push('aria-invalid="true"');
  if (description) inputAttrs.push(`aria-describedby="${escapeAttr(descriptionId)}"`);
  for (const [k, v] of Object.entries(extra)) {
    if (v === false || v == null) continue;
    inputAttrs.push(v === true ? escapeAttr(k) : `${escapeAttr(k)}="${escapeAttr(v)}"`);
  }

  const parts = [
    `<input ${inputAttrs.join(' ')}>`,
    `<label class="ds-checkbox__label" data-part="label" for="${escapeAttr(inputId)}">${escapeHtml(label)}</label>`,
  ];
  if (description) parts.push(`<p class="ds-checkbox__description" data-part="description" id="${escapeAttr(descriptionId)}">${escapeHtml(description)}</p>`);
  return `<div ${rootAttrs.join(' ')}>${parts.join('')}</div>`;
}