// v0.3 Phase 4k — Lumotia quietware colour-contrast check.
//
// Parses the v0.3 quietware CSS files, builds per-mode token tables
// (dark / light / HC), resolves scale-token references, and verifies
// every known component-token pair against the WCAG 2.2 minima:
//
//   Normal text:     4.5:1
//   Large text / UI: 3:1
//
// Exits 0 on full pass, 1 on any failure. Designed to run pre-commit
// or in CI so the colour grammar stays correct as the palette evolves.
//
// Invocation:  node scripts/check-colour-contrast.mjs

import { readFileSync } from "node:fs";
import { resolve, dirname } from "node:path";
import { fileURLToPath } from "node:url";

const here = dirname(fileURLToPath(import.meta.url));
const SCALES_PATH = resolve(here, "../src/design-system/v0.3-quietware-scales.css");
const TOKENS_PATH = resolve(here, "../src/design-system/v0.3-quietware-tokens.css");

// Pairs to check. Each entry: [fg-token, bg-token, label, min].
// Border-on-its-own-fill pairs intentionally omitted — those borders
// serve hover/active state cues, not text legibility, and inherently
// share hue with the fill. The caution-on-cream notice border is
// included as a "known limitation" pair (yellow on cream is the
// structural yellow problem; role identity is carried by the
// left-bar + icon + label combo, not border contrast alone).
const PAIRS = [
  ["--button-record-fg",   "--button-record-bg",   "Record button text on red",       4.5],
  ["--button-primary-fg",  "--button-primary-bg",  "Primary button text on blue",     4.5],
  ["--button-danger-fg",   "--button-danger-bg",   "Danger button text on red",       4.5],
  ["--button-success-fg",  "--button-success-bg",  "Success button text on green",    4.5],
  ["--button-caution-fg",  "--button-caution-bg",  "Caution button text on yellow",   4.5],
  ["--button-neutral-fg",  "--button-neutral-bg",  "Neutral button text",             4.5],
  ["--progress-download-fill",     "--progress-track", "Download progress vs track",  3.0],
  ["--progress-success-fill",      "--progress-track", "Success progress vs track",   3.0],
  ["--progress-disk-danger-fill",  "--progress-track", "Disk-danger progress",        3.0],
  ["--notice-info-border",  "--color-bg-card", "Info notice border on card",      3.0],
  ["--color-text",          "--color-bg",        "Body text on background",        4.5],
  ["--color-text",          "--color-bg-card",   "Body text on card surface",      4.5],
];

// Pairs that fail but are KNOWN structural limitations. Report only,
// do not count toward exit code.
const KNOWN_LIMITATIONS = [
  ["--progress-caution-fill",      "--progress-track", "Caution progress on cream — known yellow limit", 3.0],
  ["--notice-caution-border",      "--color-bg-card",  "Caution notice border on cream — known yellow limit", 3.0],
];

// Each scope: name + selectors it represents.
const SCOPES = [
  { name: "Quietware DARK",   selectors: [':root[data-design="quietware"]'] },
  { name: "Quietware LIGHT",  selectors: [':root[data-design="quietware"]', ':root[data-design="quietware"][data-theme="light"]'] },
  { name: "Quietware HC light", selectors: [
    ':root[data-design="quietware"]',
    ':root[data-design="quietware"][data-contrast="high"]',
  ]},
  { name: "Quietware HC dark", selectors: [
    ':root[data-design="quietware"]',
    ':root[data-design="quietware"][data-contrast="high"]',
    ':root[data-design="quietware"][data-contrast="high"]:not([data-theme="light"])',
  ]},
];

// --- parser ---

function parseCSS(source) {
  // Strip comments and split blocks. Each block: { selector, decls: Map<key,value> }.
  const stripped = source.replace(/\/\*[\s\S]*?\*\//g, "");
  const blocks = [];
  const blockRe = /([^{}]+)\{([^{}]*)\}/g;
  let m;
  while ((m = blockRe.exec(stripped)) !== null) {
    const selector = m[1].trim();
    const body = m[2];
    const decls = new Map();
    for (const decl of body.split(";")) {
      const idx = decl.indexOf(":");
      if (idx < 0) continue;
      const key = decl.slice(0, idx).trim();
      const value = decl.slice(idx + 1).trim();
      if (key.startsWith("--")) decls.set(key, value);
    }
    blocks.push({ selector, decls });
  }
  return blocks;
}

const allBlocks = [
  ...parseCSS(readFileSync(SCALES_PATH, "utf8")),
  ...parseCSS(readFileSync(TOKENS_PATH, "utf8")),
];

// Build per-scope token tables.
function tableFor(scopeSelectors) {
  const table = new Map();
  for (const sel of scopeSelectors) {
    for (const block of allBlocks) {
      // Match selectors as comma-separated lists too.
      const sels = block.selector.split(",").map(s => s.trim());
      if (sels.includes(sel)) {
        for (const [k, v] of block.decls) table.set(k, v);
      }
    }
  }
  return table;
}

// Resolve a CSS value to a hex, following var() references through the table.
function resolveToken(value, table, depth = 0) {
  if (depth > 25) return null;
  value = value.trim();
  if (/^#[0-9a-fA-F]{3,8}$/.test(value)) return value;
  // var(--name, fallback)
  const varMatch = value.match(/^var\((--[a-zA-Z0-9-_]+)(?:,\s*(.+))?\)$/);
  if (varMatch) {
    const name = varMatch[1];
    const fallback = varMatch[2];
    if (table.has(name)) return resolveToken(table.get(name), table, depth + 1);
    if (fallback) return resolveToken(fallback, table, depth + 1);
    return null;
  }
  // color-mix(...) — handle the simple `color-mix(in <space>, X N%, Y)` form.
  const mixMatch = value.match(/^color-mix\(\s*in\s+\w+\s*,\s*(.+)\s+(\d+(?:\.\d+)?)%\s*,\s*(.+)\)$/);
  if (mixMatch) {
    const a = resolveToken(mixMatch[1], table, depth + 1);
    const pct = Number(mixMatch[2]) / 100;
    const b = resolveToken(mixMatch[3], table, depth + 1);
    if (!a) return null;
    if (mixMatch[3].trim() === "transparent") return a; // contrast against the visible part
    if (!b) return a;
    return mixHex(a, b, pct);
  }
  // rgb(...) — rare, ignore for now.
  return null;
}

function hexToRgb(hex) {
  hex = hex.replace("#", "");
  if (hex.length === 3) hex = hex.split("").map(c => c + c).join("");
  if (hex.length === 8) hex = hex.slice(0, 6);
  return [parseInt(hex.slice(0, 2), 16), parseInt(hex.slice(2, 4), 16), parseInt(hex.slice(4, 6), 16)];
}

function rgbToHex([r, g, b]) {
  return "#" + [r, g, b].map(c => Math.max(0, Math.min(255, Math.round(c))).toString(16).padStart(2, "0").toUpperCase()).join("");
}

function mixHex(aHex, bHex, ratio) {
  const a = hexToRgb(aHex);
  const b = hexToRgb(bHex);
  return rgbToHex(a.map((v, i) => v * ratio + b[i] * (1 - ratio)));
}

function srgbLin(c) {
  c /= 255;
  return c <= 0.03928 ? c / 12.92 : Math.pow((c + 0.055) / 1.055, 2.4);
}

function luminance([r, g, b]) {
  return 0.2126 * srgbLin(r) + 0.7152 * srgbLin(g) + 0.0722 * srgbLin(b);
}

function contrast(a, b) {
  const la = luminance(hexToRgb(a));
  const lb = luminance(hexToRgb(b));
  const [hi, lo] = la > lb ? [la, lb] : [lb, la];
  return (hi + 0.05) / (lo + 0.05);
}

// --- run checks ---

let totalFails = 0;
const out = [];

for (const scope of SCOPES) {
  const table = tableFor(scope.selectors);
  out.push(`\n=== ${scope.name} ===`);
  for (const [fgKey, bgKey, label, min] of PAIRS) {
    const fgHex = resolveToken(table.get(fgKey) ?? "", table);
    const bgHex = resolveToken(table.get(bgKey) ?? "", table);
    if (!fgHex || !bgHex) {
      out.push(`  ?? ${label}: ${fgKey}=${fgHex ?? "unresolved"} / ${bgKey}=${bgHex ?? "unresolved"}`);
      continue;
    }
    const ratio = contrast(fgHex, bgHex);
    const ok = ratio >= min;
    const marker = ok ? " ok" : "FAIL";
    out.push(`  ${marker}  ${label}  fg=${fgHex} on bg=${bgHex}  ${ratio.toFixed(2)}:1 (min ${min}:1)`);
    if (!ok) totalFails += 1;
  }
  // Known limitations — report only.
  for (const [fgKey, bgKey, label, min] of KNOWN_LIMITATIONS) {
    const fgHex = resolveToken(table.get(fgKey) ?? "", table);
    const bgHex = resolveToken(table.get(bgKey) ?? "", table);
    if (!fgHex || !bgHex) continue;
    const ratio = contrast(fgHex, bgHex);
    const ok = ratio >= min;
    out.push(`  ${ok ? " ok" : "warn"}  ${label}  fg=${fgHex} on bg=${bgHex}  ${ratio.toFixed(2)}:1 (target ${min}:1)`);
  }
}

console.log(out.join("\n"));
console.log(`\nTotal failures: ${totalFails}`);
process.exit(totalFails ? 1 : 0);