import { execFile } from 'node:child_process';
import fs from 'node:fs/promises';
import path from 'node:path';
import { promisify } from 'node:util';
import { inflateRawSync } from 'node:zlib';

const execFileAsync = promisify(execFile);

function extractDocumentContent(markdown) {
  const titleMatch = markdown.match(/^#\s+.+\n+/m);
  const body = markdown
    .slice((titleMatch?.index ?? 0) + (titleMatch?.[0].length ?? 0))
    .replace(/^<!--\s*footer:.*?-->\s*$/m, '')
    .replace(/<br\s*\/?>/gi, ' ')    // markup, not document text
    // A figure prints its caption; the image path is markup.
    .replace(/^!\[([^\]]*)\]\([^)]*\)\s*$/gm, '$1')
    // List markers are drawn by the renderer, not stored as text: the browser
    // paints them from <ol>/<ul> and Word from numbering.xml, so they are
    // markup here too and must not be expected in the extracted text.
    .replace(/^[-*]\s+/gm, '')
    .replace(/^\d+\.\s+/gm, '');
  return { body, fields: {} };
}

function compact(text) {
  return text.normalize('NFC').toLocaleLowerCase().replace(/[^\p{L}\p{N}]/gu, '');
}

async function markdownFiles(directory) {
  const entries = await fs.readdir(directory, { withFileTypes: true });
  const results = await Promise.all(entries.map(async (entry) => {
    const target = path.join(directory, entry.name);
    if (entry.isDirectory()) return markdownFiles(target);
    return entry.isFile() && entry.name.endsWith('.md') ? [target] : [];
  }));
  return results.flat();
}

async function pdfText(pdf) {
  const { stdout } = await execFileAsync('pdftotext', [pdf, '-'], { maxBuffer: 32 * 1024 * 1024 });
  return stdout;
}

// A .docx is a zip; only one member is needed, so it is read here rather than
// taking a dependency for it. Entries are located through the central
// directory, then inflated from their own local header.
function readZipEntry(buffer, name) {
  const endOfDirectory = buffer.lastIndexOf(Buffer.from([0x50, 0x4b, 0x05, 0x06]));
  if (endOfDirectory < 0) throw new Error('not a zip archive');
  const entries = buffer.readUInt16LE(endOfDirectory + 10);
  let cursor = buffer.readUInt32LE(endOfDirectory + 16);

  for (let index = 0; index < entries; index += 1) {
    if (buffer.readUInt32LE(cursor) !== 0x02014b50) throw new Error('damaged central directory');
    const method = buffer.readUInt16LE(cursor + 10);
    const compressedSize = buffer.readUInt32LE(cursor + 20);
    const nameLength = buffer.readUInt16LE(cursor + 28);
    const extraLength = buffer.readUInt16LE(cursor + 30);
    const commentLength = buffer.readUInt16LE(cursor + 32);
    const localOffset = buffer.readUInt32LE(cursor + 42);
    const entryName = buffer.toString('utf8', cursor + 46, cursor + 46 + nameLength);

    if (entryName === name) {
      const localName = buffer.readUInt16LE(localOffset + 26);
      const localExtra = buffer.readUInt16LE(localOffset + 28);
      const start = localOffset + 30 + localName + localExtra;
      const data = buffer.subarray(start, start + compressedSize);
      return method === 0 ? Buffer.from(data) : inflateRawSync(data);
    }
    cursor += 46 + nameLength + extraLength + commentLength;
  }
  throw new Error(`${name} not found in archive`);
}

async function docxText(docx) {
  const xml = readZipEntry(await fs.readFile(docx), 'word/document.xml').toString('utf8');
  // Paragraph and row ends are text boundaries; only <w:t> carries characters.
  return xml
    .replace(/<\/w:p>|<\/w:tr>|<w:br[^>]*\/>|<w:tab[^>]*\/>/g, '\n')
    .replace(/<w:t[^>]*>([^<]*)<\/w:t>/g, '$1')
    .replace(/<[^>]+>/g, '')
    .replaceAll('&amp;', '&').replaceAll('&lt;', '<').replaceAll('&gt;', '>')
    .replaceAll('&quot;', '"').replaceAll('&apos;', "'");
}

const READERS = { pdf: pdfText, docx: docxText };

function tally(text) {
  const counts = new Map();
  for (const character of compact(text)) counts.set(character, (counts.get(character) ?? 0) + 1);
  return counts;
}

async function main() {
  const [sourceRoot, deliveryRoot, ...requested] = process.argv.slice(2);
  if (!sourceRoot || !deliveryRoot) throw new Error('Usage: verify-content.mjs SOURCE_DIRECTORY DELIVERY_DIRECTORY [FORMAT…]');
  const formats = requested.length ? requested : Object.keys(READERS);
  const unknown = formats.filter((format) => !READERS[format]);
  if (unknown.length) throw new Error(`Unknown format(s): ${unknown.join(', ')}`);

  const sources = (await markdownFiles(sourceRoot)).sort();
  let failed = false;

  for (const format of formats) {
    const failures = [];
    for (const source of sources) {
      const relative = path.relative(sourceRoot, source);
      const rendered = path.join(deliveryRoot, relative.replace(/\.md$/, `.${format}`));
      const [markdown, extracted] = await Promise.all([
        fs.readFile(source, 'utf8'),
        READERS[format](rendered)
      ]);
      const { body } = extractDocumentContent(markdown);
      // Thai has no word spaces, so a run can wrap several times inside a narrow
      // table cell and reach the extracted text as separate fragments. Coverage is
      // therefore checked by character count: every character of the source must
      // appear in the rendering at least as many times. Clipped or dropped text
      // loses glyphs and still fails; re-wrapping does not.
      const counts = tally(extracted);
      const missing = [...tally(body)]
        .filter(([character, count]) => (counts.get(character) ?? 0) < count)
        .map(([character, count]) => `${character}×${count - (counts.get(character) ?? 0)}`);
      if (missing.length) failures.push(`${relative}: missing ${missing.slice(0, 12).join(', ')}${missing.length > 12 ? ', …' : ''}`);
    }

    if (failures.length) {
      failed = true;
      console.error(`Content coverage failed for ${failures.length}/${sources.length} ${format.toUpperCase()}s:`);
      failures.forEach((failure) => console.error(`- ${failure}`));
    } else {
      console.log(`Content coverage passed: ${sources.length}/${sources.length} ${format.toUpperCase()}s.`);
    }
  }

  if (failed) process.exit(1);
}

main().catch((error) => { console.error(error); process.exit(1); });