// Designer moon pack → `src/moon-art.generated.ts` (#661, variant A).
//
// The pack is one full-moon SVG; the card applies the phase as a mask (C5).
// The generator is the gate for what the designer's file may contain: a square
// 512 viewBox with the documented disc, vector shapes and gradients only — no
// filters, raster, fonts, scripts or external references — and at most 30 KB.
// Ids are prefixed so the art can live in the card's shadow root next to
// everything else. `--check` fails when the committed module has drifted.
import { createHash } from 'node:crypto';
import fs from 'node:fs';
import path from 'node:path';
import process from 'node:process';
import { fileURLToPath } from 'node:url';

const ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..');
export const MOON_PACK_DIR = path.join(ROOT, 'assets', 'moon', 'houseplan-1.0.0');
const OUT = path.join(ROOT, 'src', 'moon-art.generated.ts');
/** Brief to the designer: ≤ 30 KB before compression. */
export const MOON_SVG_MAX_BYTES = 30 * 1024;
const ALLOWED_TAGS = new Set([
  'svg', 'title', 'defs', 'g', 'path', 'circle', 'ellipse', 'mask', 'radialGradient', 'linearGradient', 'stop',
]);
const ID_PREFIX = 'hp-moon-';

const fail = (message) => { throw new Error(`Moon pack: ${message}`); };

/** pack.json: identity, licence and the disc geometry the mask is built for. */
export function validateMoonPack(pack) {
  if (!pack || typeof pack !== 'object' || Array.isArray(pack)) fail('pack.json must be an object');
  if (pack.schema_version !== 1) fail('schema_version must be 1');
  if (pack.pack_id !== 'houseplan') fail('pack_id must be "houseplan"');
  if (typeof pack.pack_version !== 'string' || !/^\d+\.\d+\.\d+$/.test(pack.pack_version)) fail('pack_version must be semver');
  if (pack.license !== 'MIT') fail('license must be MIT');
  if (typeof pack.source_url !== 'string' || !pack.source_url.startsWith('https://')) fail('source_url must be https');
  if (pack.file !== 'moon.svg') fail('file must be moon.svg');
  if (JSON.stringify(pack.view_box) !== '[0,0,512,512]') fail('view_box must be [0, 0, 512, 512]');
  if (JSON.stringify(pack.disc) !== '{"cx":256,"cy":256,"r":240}') fail('disc must be centred at 256 with r 240');
  if (pack.mirror !== false) fail('mirror must be false (owner 2026-09-29)');
  if (pack.lit_side !== 'left') fail('lit_side must be "left" (owner 2026-09-29)');
  return pack;
}

/** The SVG body the card inlines: validated, title dropped, ids prefixed. */
export function moonArtFromSvg(source) {
  const text = String(source).replace(/^/, '').trim();
  if (Buffer.byteLength(text, 'utf8') > MOON_SVG_MAX_BYTES) fail(`moon.svg is larger than ${MOON_SVG_MAX_BYTES} bytes`);
  if (/<!DOCTYPE|<!ENTITY|<\?|<!--|<!\[CDATA/i.test(text)) fail('moon.svg contains active XML');
  if (/href\s*=|url\((?!#)|@import|base64|font-family|style\s*=/i.test(text)) fail('moon.svg references outside itself or carries styles');
  for (const [, name] of text.matchAll(/<\/?([A-Za-z][\w:-]*)/g)) {
    if (!ALLOWED_TAGS.has(name)) fail(`moon.svg contains <${name}>`);
  }
  const root = text.match(/^<svg\b([^>]*)>([\s\S]*)<\/svg>$/);
  if (!root) fail('moon.svg is not one SVG root');
  if (!/\bviewBox="0 0 512 512"/.test(root[1])) fail('moon.svg must have viewBox="0 0 512 512"');
  let body = root[2].replace(/<title>[\s\S]*?<\/title>/g, '');
  const ids = [...body.matchAll(/\bid="([^"]+)"/g)].map((match) => match[1]);
  if (new Set(ids).size !== ids.length) fail('moon.svg repeats an id');
  for (const [, ref] of body.matchAll(/url\(#([^)]+)\)/g)) {
    if (!ids.includes(ref)) fail(`moon.svg references a missing id: ${ref}`);
  }
  if (/[`\\]|\$\{/.test(body)) fail('moon.svg contains template-literal syntax');
  body = body
    .replace(/\bid="([^"]+)"/g, (_, id) => `id="${ID_PREFIX}${id}"`)
    .replace(/url\(#([^)]+)\)/g, (_, id) => `url(#${ID_PREFIX}${id})`);
  return body;
}

export function generateMoonModule(packDir = MOON_PACK_DIR) {
  const pack = validateMoonPack(JSON.parse(fs.readFileSync(path.join(packDir, 'pack.json'), 'utf8')));
  const svg = fs.readFileSync(path.join(packDir, pack.file), 'utf8');
  const art = moonArtFromSvg(svg);
  const sha = createHash('sha256').update(svg).digest('hex');
  return [
    '/* Generated by scripts/generate-moon-assets.mjs. DO NOT EDIT. */',
    `// Designer pack assets/moon/${pack.pack_id}-${pack.pack_version} (#661). Lazy: imported only by`,
    '// moon-runtime.ts, never by the initial View graph (C7).',
    '// A static Lit template: no directive, no binding, nothing parsed at runtime but the art.',
    "import { svg } from 'lit';",
    `export const MOON_PACK = ${JSON.stringify(`${pack.pack_id}-${pack.pack_version}`)};`,
    `export const MOON_ART_SHA256 = ${JSON.stringify(sha)};`,
    `export const MOON_ART = svg\`${art}\`;`,
    '',
  ].join('\n');
}

if (fileURLToPath(import.meta.url) === path.resolve(process.argv[1] || '')) {
  const next = generateMoonModule();
  if (process.argv.includes('--check')) {
    const current = fs.existsSync(OUT) ? fs.readFileSync(OUT, 'utf8') : '';
    if (current !== next) {
      console.error('src/moon-art.generated.ts is stale: run node scripts/generate-moon-assets.mjs');
      process.exit(1);
    }
    console.log('moon art is up to date');
  } else {
    fs.writeFileSync(OUT, next);
    console.log(`wrote ${path.relative(ROOT, OUT)}`);
  }
}