import { createHash } from 'node:crypto';
import { readFileSync } from 'node:fs';
import { gunzipSync } from 'node:zlib';
import path from 'node:path';
import { fileURLToPath } from 'node:url';

export const gameDbRoot = fileURLToPath(new URL('../data/game-db/', import.meta.url));
export const sha256 = bytes => createHash('sha256').update(bytes).digest('hex');

export function openGameDb(pointer, root = gameDbRoot) {
  if (!/^snapshots\/[a-zA-Z0-9]{64}$/.test(pointer.snapshot ?? '')) throw new Error('Invalid game DB snapshot path');
  const directory = path.join(root, pointer.snapshot);
  const bytes = readFileSync(path.join(directory, 'manifest.json'));
  if (sha256(bytes) !== pointer.manifestSha256) throw new Error('Game DB manifest hash mismatch');
  const manifest = JSON.parse(bytes);
  if (manifest.schemaVersion !== 1 || manifest.kind !== 'android-master-db' || manifest.locale !== 'kor' ||
      pointer.snapshot !== `snapshots/${manifest.masterDataVersion}` || !Object.keys(manifest.tables ?? {}).length) {
    throw new Error('Invalid game DB manifest');
  }
  return { ...manifest, ...pointer, directory };
}

export function sourceMetadata(source) {
  return { kind: source.kind, masterDataVersion: source.masterDataVersion, locale: source.locale,
    capturedAt: source.capturedAt, manifestSha256: source.manifestSha256 };
}

export function prepareGameDbSource(locale = 'kor', { review = false } = {}) {
  if (locale !== 'kor') throw new Error(`Current game DB contains Korean only; no external fallback for ${locale}`);
  const pointer = JSON.parse(readFileSync(path.join(gameDbRoot, 'current.json'), 'utf8'));
  const source = openGameDb(pointer);
  if (!review) {
    let report;
    try { report = JSON.parse(readFileSync(path.join(gameDbRoot, 'review/latest.json'), 'utf8')); }
    catch { throw new Error('Run npm run data:sync and report its changes before data:apply.'); }
    if (report.target.manifestSha256 !== source.manifestSha256) throw new Error('Game DB changed after review; run data:sync again.');
  }
  return source;
}

export function readGameDbText(source, filename) {
  const name = filename.replace(/\.json$/, '');
  const table = source.tables[name];
  if (!table || table.file !== `${name}.json.gz` || !/^[A-Za-z0-9_]+$/.test(name)) throw new Error(`Missing game DB table: ${filename}`);
  const packed = readFileSync(path.join(source.directory, table.file));
  if (sha256(packed) !== table.gzipSha256) throw new Error(`Game DB archive hash mismatch: ${name}`);
  const raw = gunzipSync(packed);
  if (sha256(raw) !== table.sha256) throw new Error(`Game DB table hash mismatch: ${name}`);
  const rows = JSON.parse(raw);
  if (!Array.isArray(rows) || rows.length !== table.rows) throw new Error(`Game DB row count mismatch: ${name}`);
  return raw.toString('utf8');
}

export function readGameDbTable(locale, filename) {
  return JSON.parse(readGameDbText(prepareGameDbSource(locale), filename));
}