/* Provii Protocol Specification, main.css
 *
 * Constraints this stylesheet lives within:
 *   - CSP: default-src 'none'; style-src 'unsafe-inline' 'self'; img-src 'self' data:
 *     (no font-src, no script-src). Fonts must be local or system stack.
 *   - Zero JavaScript on the spec page.
 *   - WCAG 2.2 AA contrast on every token pair, light and dark.
 *   - Reading measure capped at ~68ch on the main column.
 *
 * Brand tokens mirror provii-website/src/styles/global.css where sensible.
 */

/* ------------------------------------------------------------------ *
 * Brand tokens, light mode defaults
 * ------------------------------------------------------------------ */
:root {
  color-scheme: light dark;

  /* Primary palette, mirrored from provii-website. */
  --color-primary-50:  #e6f6fb;
  --color-primary-100: #b3e3f3;
  --color-primary-200: #80d0eb;
  --color-primary-300: #4dbde3;
  --color-primary-400: #1aabdb;
  --color-primary-500: #0091c7;
  --color-primary-600: #00749f;
  --color-primary-700: #005777;
  --color-primary-800: #003a4f;
  --color-primary-900: #001d28;

  --color-secondary-500: #b664f8;
  --color-secondary-700: #6d3c95;

  /* Neutral ramp, tuned for AA against both white and near-black. */
  --color-ink:       #1a1d21; /* body text */
  --color-ink-soft:  #4a5058; /* muted text, captions */
  --color-ink-mute:  #6b7280; /* dates, page-footer meta */
  --color-line:      #e4e7eb; /* hairlines, table borders */
  --color-line-soft: #eef0f3;
  --color-surface:       #ffffff;
  --color-surface-sunken: #f7f8fa;
  --color-surface-raised: #ffffff;
  --color-code-bg:   #f3f4f6;
  --color-code-ink:  #1a1d21;

  /* Semantic */
  --color-link:         var(--color-primary-600);
  --color-link-visited: var(--color-secondary-700);
  --color-accent:       var(--color-primary-500);
  --color-accent-soft:  var(--color-primary-50);

  /* Typography scale, 1.25 ratio from 1rem base */
  --font-size-body: 1rem;
  --font-size-h1:   2.25rem;
  --font-size-h2:   1.75rem;
  --font-size-h3:   1.375rem;
  --font-size-h4:   1.125rem;
  --font-size-small: 0.875rem;

  /* Font stack, system only. CSP currently forbids font-src entirely so
   * loading Inter from a CDN is off the table without relaxing the policy. */
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen,
               Ubuntu, Cantarell, "Helvetica Neue", sans-serif;
  --font-mono: "SF Mono", "JetBrains Mono", "Fira Code", Menlo, Consolas,
               "Liberation Mono", monospace;

  /* Layout */
  --sidebar-width: 280px;
  --measure:       68ch;
  --content-max:   48rem;
  --layout-gap:    2.5rem;
  --content-padding-x: 1.5rem;

  /* Radius, shadow */
  --radius-sm: 4px;
  --radius-md: 6px;
  --radius-lg: 10px;

  /* Focus ring, thick, high contrast, visible in both themes */
  --focus-ring: 0 0 0 3px rgba(0, 145, 199, 0.45);
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-ink:       #e6e8eb;
    --color-ink-soft:  #b1b7bf;
    --color-ink-mute:  #8a929c;
    --color-line:      #2a3038;
    --color-line-soft: #1d2229;
    --color-surface:       #0d1117;
    --color-surface-sunken: #11161d;
    --color-surface-raised: #161c24;
    --color-code-bg:   #1a2029;
    --color-code-ink:  #e6e8eb;

    --color-link:         var(--color-primary-300);
    --color-link-visited: #d09cf8; /* secondary-300 */
    --color-accent:       var(--color-primary-400);
    --color-accent-soft:  rgba(0, 145, 199, 0.14);

    --focus-ring: 0 0 0 3px rgba(77, 189, 227, 0.55);
  }
}

/* ------------------------------------------------------------------ *
 * Reset + base
 * ------------------------------------------------------------------ */
*, *::before, *::after { box-sizing: border-box; }

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: var(--font-size-body);
  line-height: 1.65;
  color: var(--color-ink);
  background: var(--color-surface);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* Selection colour, brand primary, tuned for AA on both themes. */
::selection {
  background: rgba(0, 145, 199, 0.30);
  color: inherit;
}

/* Focus ring, applies only when keyboard-focused. */
:focus-visible {
  outline: none;
  box-shadow: var(--focus-ring);
  border-radius: 2px;
}

/* ------------------------------------------------------------------ *
 * Skip link (keyboard accessibility)
 * ------------------------------------------------------------------ */
.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  padding: 0.5rem 1rem;
  background: var(--color-primary-600);
  color: #ffffff;
  z-index: 100;
  text-decoration: none;
  border-radius: 0 0 var(--radius-md) 0;
}
.skip-link:focus {
  top: 0;
}

/* ------------------------------------------------------------------ *
 * Site header strip
 * ------------------------------------------------------------------ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-line);
}
.site-header-inner {
  max-width: calc(var(--sidebar-width) + var(--content-max) + var(--layout-gap) + (var(--content-padding-x) * 2));
  margin: 0 auto;
  padding: 0.75rem var(--content-padding-x);
  display: flex;
  align-items: baseline;
  gap: 1rem;
}
.site-title {
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--color-ink);
  text-decoration: none;
  letter-spacing: -0.01em;
}
.site-title:hover { color: var(--color-link); }
.site-version {
  font-family: var(--font-mono);
  font-size: var(--font-size-small);
  padding: 0.1rem 0.5rem;
  background: var(--color-accent-soft);
  color: var(--color-link);
  border-radius: var(--radius-sm);
  border: 1px solid var(--color-line);
}

/* ------------------------------------------------------------------ *
 * Two-column layout: sticky sidebar + main content
 * ------------------------------------------------------------------ */
.layout {
  max-width: calc(var(--sidebar-width) + var(--content-max) + var(--layout-gap) + (var(--content-padding-x) * 2));
  margin: 0 auto;
  padding: 0 var(--content-padding-x);
  display: grid;
  grid-template-columns: var(--sidebar-width) minmax(0, 1fr);
  gap: var(--layout-gap);
  align-items: start;
}

.sidebar {
  position: sticky;
  /* site-header is ~52px tall; small buffer keeps the ToC from touching it */
  top: 3.5rem;
  max-height: calc(100vh - 3.5rem);
  overflow-y: auto;
  overflow-x: hidden;
  padding: 1.5rem 0.5rem 1.5rem 0;
  font-size: 0.9rem;
  line-height: 1.5;
  /* thin scrollbar in browsers that honour it */
  scrollbar-width: thin;
  scrollbar-color: var(--color-line) transparent;
}
.sidebar::-webkit-scrollbar { width: 8px; }
.sidebar::-webkit-scrollbar-thumb {
  background: var(--color-line);
  border-radius: 4px;
}

.sidebar-title {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-ink-mute);
  margin: 0 0 0.75rem 0;
  padding: 0 0.5rem;
  border-bottom: none;         /* override generic h2 */
  padding-bottom: 0;
  scroll-margin-top: 0;
}

.sidebar nav ul {
  list-style: none;
  padding-left: 0.75rem;
  margin: 0;
  border-left: 1px solid var(--color-line);
}
.sidebar nav > ul {
  border-left: none;
  padding-left: 0;
}
.sidebar nav ul ul {
  margin-top: 0.15rem;
  margin-bottom: 0.15rem;
  font-size: 0.95em;
}
.sidebar nav li {
  margin: 0.15rem 0;
}
.sidebar nav a {
  display: block;
  padding: 0.2rem 0.5rem;
  color: var(--color-ink-soft);
  text-decoration: none;
  border-radius: var(--radius-sm);
  border-left: 2px solid transparent;
  margin-left: -0.5rem;
  padding-left: 0.5rem;
}
.sidebar nav a:hover {
  color: var(--color-ink);
  background: var(--color-surface-sunken);
}
.sidebar nav a:focus-visible {
  color: var(--color-link);
}
/* :target gives a cheap "current" indicator when the user clicks a ToC link */
.sidebar nav a[href^="#"]:active {
  color: var(--color-link);
  border-left-color: var(--color-accent);
}

.content {
  min-width: 0; /* allow children with overflow to actually overflow */
  padding: 1.5rem 0 4rem 0;
  max-width: var(--measure);
}

/* ------------------------------------------------------------------ *
 * Document header (title, metadata block)
 * ------------------------------------------------------------------ */
.doc-header {
  margin-bottom: 2rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--color-line);
}
.doc-header .title {
  font-size: var(--font-size-h1);
  line-height: 1.2;
  margin: 0 0 0.5rem 0;
  letter-spacing: -0.02em;
}
.doc-header .subtitle {
  font-size: 1.125rem;
  color: var(--color-ink-soft);
  margin: 0.25rem 0;
}
.doc-header .author,
.doc-header .date {
  color: var(--color-ink-mute);
  font-size: var(--font-size-small);
  margin: 0.1rem 0;
}

/* ------------------------------------------------------------------ *
 * Prose
 * ------------------------------------------------------------------ */
h1, h2, h3, h4, h5, h6 {
  line-height: 1.25;
  color: var(--color-ink);
  letter-spacing: -0.01em;
  margin-top: 2rem;
  margin-bottom: 0.75rem;
  position: relative;
  scroll-margin-top: 4rem; /* offset for sticky site header */
}
/* Section divs from --section-divs are the actual targets of ToC links
 * (pandoc puts the id on the section, not the heading), so they need the
 * same scroll offset. */
.content section[id] { scroll-margin-top: 4rem; }
h1 { font-size: var(--font-size-h1); }
h2 {
  font-size: var(--font-size-h2);
  padding-bottom: 0.3rem;
  border-bottom: 1px solid var(--color-line);
  margin-top: 2.75rem;
}
h3 { font-size: var(--font-size-h3); margin-top: 2rem; }
h4 { font-size: var(--font-size-h4); }

/* Permalink anchor on headings.
 * The Lua filter emits the anchor as a SIBLING of the heading, not a child,
 * so that pandoc's ToC writer (which copies heading inline content verbatim)
 * doesn't pick up the "#" character. We position the anchor absolutely
 * against its containing section/div; each section block already has a
 * positioning context via the rules below. */
section, div.doc-section {
  position: relative;
}
a.anchor {
  /* Use adjacent-sibling positioning: the anchor always follows its heading
   * immediately. We pull it up to sit next to the heading text with a
   * negative margin so it overlays the heading's left gutter. */
  display: block;
  position: absolute;
  margin-top: -2.1rem;        /* lift to heading row (h2 line-height) */
  margin-left: -1.3rem;       /* sit in the left gutter */
  font-weight: 400;
  font-size: 1rem;
  color: var(--color-ink-mute);
  text-decoration: none;
  opacity: 0;
  transition: opacity 0.12s ease-in;
  padding: 0 0.25rem;
  line-height: 1;
}
/* Reveal on section hover or when the anchor gets keyboard focus. */
h1:hover + a.anchor,
h2:hover + a.anchor,
h3:hover + a.anchor,
h4:hover + a.anchor,
h5:hover + a.anchor,
h6:hover + a.anchor,
a.anchor:hover,
a.anchor:focus-visible {
  opacity: 1;
}
a.anchor:hover { color: var(--color-link); text-decoration: none; }

p {
  margin: 0 0 1rem 0;
}

a {
  color: var(--color-link);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 2px;
}
a:hover {
  color: var(--color-primary-700);
  text-decoration-thickness: 2px;
}
@media (prefers-color-scheme: dark) {
  a:hover { color: var(--color-primary-200); }
}
a:visited {
  color: var(--color-link-visited);
}

strong { font-weight: 600; }

ul, ol {
  margin: 0 0 1rem 0;
  padding-left: 1.5rem;
}
li { margin: 0.25rem 0; }
li > ul, li > ol { margin: 0.25rem 0; }

blockquote {
  margin: 1.25rem 0;
  padding: 0.25rem 0 0.25rem 1rem;
  border-left: 3px solid var(--color-accent);
  color: var(--color-ink-soft);
  background: var(--color-surface-sunken);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
}
blockquote p:last-child { margin-bottom: 0; }

hr {
  border: none;
  border-top: 1px solid var(--color-line);
  margin: 2.5rem 0;
}

/* ------------------------------------------------------------------ *
 * Tables
 * ------------------------------------------------------------------ */
table {
  border-collapse: collapse;
  width: 100%;
  margin: 1.25rem 0;
  font-size: 0.95rem;
  /* let wide tables scroll rather than break the layout */
  display: block;
  overflow-x: auto;
}
thead {
  background: var(--color-surface-sunken);
}
th, td {
  border: 1px solid var(--color-line);
  padding: 0.5rem 0.75rem;
  text-align: left;
  vertical-align: top;
}
th {
  font-weight: 600;
  color: var(--color-ink);
  background: var(--color-surface-sunken);
}
tbody tr:nth-child(even) {
  background: var(--color-line-soft);
}

/* ------------------------------------------------------------------ *
 * Code
 * ------------------------------------------------------------------ */
code, kbd, pre, samp {
  font-family: var(--font-mono);
  font-size: 0.9em;
}
code {
  background: var(--color-code-bg);
  color: var(--color-code-ink);
  padding: 0.1em 0.35em;
  border-radius: var(--radius-sm);
  border: 1px solid var(--color-line);
}
pre {
  background: var(--color-code-bg);
  color: var(--color-code-ink);
  padding: 0.9rem 1rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--color-line);
  overflow-x: auto;
  line-height: 1.5;
  margin: 1.25rem 0;
}
pre code {
  background: transparent;
  padding: 0;
  border: none;
  border-radius: 0;
  font-size: inherit;
}

kbd {
  display: inline-block;
  padding: 0.15rem 0.4rem;
  background: var(--color-surface-raised);
  border: 1px solid var(--color-line);
  border-bottom-width: 2px;
  border-radius: var(--radius-sm);
  font-size: 0.85em;
  line-height: 1;
  color: var(--color-ink);
}

/* ------------------------------------------------------------------ *
 * Skylighting (pandoc --highlight-style=tango) token classes
 * We restyle tango's colours so they fit the brand and pass AA on both
 * themes. Pandoc emits classes like .kw .dt .st .co etc. inside
 * <pre class="sourceCode"><code class="sourceCode language-xxx">.
 * ------------------------------------------------------------------ */
pre.sourceCode { padding: 0.9rem 1rem; }
code.sourceCode { display: block; }
/* Pandoc inserts invisible line-anchor links inside each code line for line
 * numbering. Strip all decoration so they don't flash into existence. */
pre.sourceCode a[aria-hidden="true"] {
  color: inherit;
  text-decoration: none;
  border: none;
}
.sourceCode span.al { color: #c0392b; font-weight: 600; }   /* alert */
.sourceCode span.an { color: #5a6270; font-style: italic; } /* annotation */
.sourceCode span.at { color: var(--color-primary-700); }    /* attribute */
.sourceCode span.bn { color: var(--color-secondary-700); }  /* base number */
.sourceCode span.cf { color: var(--color-primary-700); font-weight: 600; } /* control flow */
.sourceCode span.ch { color: #2e8555; }                     /* char */
.sourceCode span.cn { color: var(--color-secondary-700); }  /* constant */
.sourceCode span.co { color: #5a6270; font-style: italic; }  /* comment, AA on code-bg */
.sourceCode span.do { color: #5a6270; font-style: italic; }  /* doc comment */
.sourceCode span.dt { color: var(--color-primary-700); }    /* data type */
.sourceCode span.dv { color: var(--color-secondary-700); }  /* decimal value */
.sourceCode span.er { color: #c0392b; font-weight: 600; }   /* error */
.sourceCode span.fl { color: var(--color-secondary-700); }  /* float */
.sourceCode span.fu { color: var(--color-primary-700); }    /* function */
.sourceCode span.im { color: var(--color-primary-700); font-weight: 600; } /* import */
.sourceCode span.kw { color: var(--color-primary-700); font-weight: 600; } /* keyword */
.sourceCode span.op { color: var(--color-ink); }            /* operator */
.sourceCode span.ot { color: var(--color-primary-700); }    /* other */
.sourceCode span.pp { color: var(--color-secondary-700); }  /* preprocessor */
.sourceCode span.sc { color: #2e8555; }                     /* special char */
.sourceCode span.ss { color: #2e8555; }                     /* special string */
.sourceCode span.st { color: #2e8555; }                     /* string */
.sourceCode span.va { color: var(--color-ink); }            /* variable */
.sourceCode span.vs { color: #2e8555; }                     /* verbatim string */
.sourceCode span.wa { color: #b35900; font-style: italic; } /* warning */

@media (prefers-color-scheme: dark) {
  .sourceCode span.at,
  .sourceCode span.cf,
  .sourceCode span.dt,
  .sourceCode span.fu,
  .sourceCode span.im,
  .sourceCode span.kw,
  .sourceCode span.ot { color: #4dbde3; }
  .sourceCode span.bn,
  .sourceCode span.cn,
  .sourceCode span.dv,
  .sourceCode span.fl,
  .sourceCode span.pp { color: #c39bff; }
  .sourceCode span.ch,
  .sourceCode span.sc,
  .sourceCode span.ss,
  .sourceCode span.st,
  .sourceCode span.vs { color: #7ee2a8; }
  .sourceCode span.co,
  .sourceCode span.do,
  .sourceCode span.an { color: #8a929c; }
  .sourceCode span.wa { color: #f0b060; }
}

/* Figures */
figure { margin: 1.5rem 0; text-align: center; }
figcaption {
  font-size: var(--font-size-small);
  color: var(--color-ink-soft);
  margin-top: 0.5rem;
}

/* Inline section-number badge, when the Lua filter has set data-section. */
h2[data-section]::before,
h3[data-section]::before,
h4[data-section]::before {
  /* The heading text already starts with the number; we don't want to
   * double-print it. Keep the attribute available for citation tools but
   * render nothing here. Exposed via [data-section] attribute selector so
   * future tooling or print CSS can style it. */
  content: none;
}

/* ------------------------------------------------------------------ *
 * Responsive: collapse sidebar below 820px
 * ------------------------------------------------------------------ */
@media (max-width: 820px) {
  .layout {
    grid-template-columns: 1fr;
    gap: 1rem;
  }
  .sidebar {
    position: static;
    max-height: none;
    overflow: visible;
    padding: 1rem 0;
    border-bottom: 1px solid var(--color-line);
    margin-bottom: 1rem;
  }
  .site-header { position: static; }
  .content { padding-top: 0.5rem; }
  .content { max-width: 100%; }
  h2 { margin-top: 2rem; }
  h1 > a.anchor,
  h2 > a.anchor,
  h3 > a.anchor,
  h4 > a.anchor {
    /* on narrow screens an off-canvas anchor would clip; inline it */
    position: static;
    opacity: 1;
    margin-right: 0.25rem;
    color: var(--color-ink-mute);
  }
}

/* ------------------------------------------------------------------ *
 * Print styles moved to print.css (loaded with media="print").
 * ------------------------------------------------------------------ */