import { createHash } from 'node:crypto';
import { constants } from 'node:fs';
import { lstat, mkdir, open, readFile, readdir } from 'node:fs/promises';
import { dirname, join, resolve } from 'node:path';
import { fileURLToPath } from 'node:url';

const scriptPath = fileURLToPath(import.meta.url);
const defaultRepositoryRoot = resolve(dirname(scriptPath), '..');

const isErrno = (error, code) =>
  typeof error === 'object' && error !== null && 'code' in error && error.code === code;

const directoryIdentity = (stats) => ({ dev: stats.dev, ino: stats.ino });
const hasSameDirectoryIdentity = (left, right) => left.dev === right.dev && left.ino === right.ino;

const assertNonSymlinkDirectory = (stats) => {
  if (stats.isSymbolicLink() || !stats.isDirectory()) {
    throw new Error('Prepared asset path must be a non-symlink directory.');
  }
};

export const assertPreparedAssetDirectoryIdentity = async (preparedAssetsPath, expectedIdentity) => {
  const current = await lstat(preparedAssetsPath);
  assertNonSymlinkDirectory(current);
  if (!hasSameDirectoryIdentity(directoryIdentity(current), expectedIdentity)) {
    throw new Error('Prepared asset directory identity changed during validation.');
  }
};

const assertOpenedDirectoryIdentity = async (preparedAssetsPath, expectedIdentity) => {
  const noFollowDirectoryFlags = constants.O_RDONLY | (constants.O_DIRECTORY ?? 0) | (constants.O_NOFOLLOW ?? 0);
  let handle;
  try {
    handle = await open(preparedAssetsPath, noFollowDirectoryFlags);
  } catch (error) {
    if (isErrno(error, 'ELOOP')) {
      throw new Error('Prepared asset path must be a non-symlink directory.');
    }
    if (isErrno(error, 'EINVAL') || isErrno(error, 'ENOTSUP') || isErrno(error, 'ENOSYS')) return;
    throw error;
  }

  try {
    const opened = await handle.stat();
    assertNonSymlinkDirectory(opened);
    if (!hasSameDirectoryIdentity(directoryIdentity(opened), expectedIdentity)) {
      throw new Error('Prepared asset directory identity changed during validation.');
    }
  } finally {
    await handle.close();
  }
};

const readJson = async (path, label) => {
  let value;
  try {
    value = JSON.parse(await readFile(path, 'utf8'));
  } catch (error) {
    throw new Error(`${label} must be valid JSON.`, { cause: error });
  }
  if (typeof value !== 'object' || value === null || Array.isArray(value)) {
    throw new Error(`${label} must be a JSON object.`);
  }
  return value;
};

const readManifest = async (repositoryRoot) => {
  const manifestPath = resolve(repositoryRoot, 'content/public/asset-manifest.json');
  const manifest = await readJson(manifestPath, 'Public asset manifest');
  if (Object.keys(manifest).length !== 1 || !Array.isArray(manifest.assets)) {
    throw new Error('Public asset manifest must contain exactly one assets array.');
  }
  const ids = new Set();
  const fileNames = new Set();
  const assets = manifest.assets.map((asset) => {
    if (typeof asset !== 'object' || asset === null || Array.isArray(asset)) {
      throw new Error('Every manifest asset must be an object.');
    }
    const { id, fileName, sha256 } = asset;
    if (typeof id !== 'string' || !/^[a-z][a-z0-9-]{0,63}$/u.test(id)) {
      throw new Error('Manifest asset ID must be a generated safe identifier.');
    }
    if (ids.has(id)) throw new Error(`Duplicate manifest asset ID: ${id}`);
    ids.add(id);
    if (typeof fileName !== 'string' || !/^[a-z0-9][a-z0-9-]*\.(avif|jpg|png|svg|webp|mp4|webm|opus|mp3)$/u.test(fileName)) {
      throw new Error(`Manifest filename must be a generated safe filename: ${id}`);
    }
    const foldedFileName = fileName.toLocaleLowerCase('en-US');
    if (fileNames.has(foldedFileName)) throw new Error(`Duplicate manifest filename: ${fileName}`);
    fileNames.add(foldedFileName);
    if (typeof sha256 !== 'string' || !/^[a-f0-9]{64}$/u.test(sha256)) {
      throw new Error(`Manifest asset must have a lowercase SHA-256 digest: ${id}`);
    }
    return { id, fileName, sha256 };
  });
  return assets;
};

const assetReferences = (content) => {
  const references = [];
  const projects = content.projects;
  if (typeof projects !== 'object' || projects === null || Array.isArray(projects)) {
    throw new Error('Portfolio content must contain project collections.');
  }
  for (const collectionName of ['selected', 'additional']) {
    const collection = projects[collectionName];
    if (!Array.isArray(collection)) throw new Error(`Portfolio ${collectionName} projects must be an array.`);
    for (const project of collection) {
      if (typeof project !== 'object' || project === null || Array.isArray(project) || !Array.isArray(project.assetIds)) {
        throw new Error('Every public project must contain an assetIds array.');
      }
      references.push(...project.assetIds);
    }
  }
  if (!Array.isArray(content.toolkit)) throw new Error('Portfolio toolkit must be an array.');
  for (const group of content.toolkit) {
    if (typeof group !== 'object' || group === null || Array.isArray(group) || !Array.isArray(group.technologies)) {
      throw new Error('Every toolkit group must contain a technologies array.');
    }
    for (const technology of group.technologies) {
      if (typeof technology !== 'object' || technology === null || Array.isArray(technology)) {
        throw new Error('Every toolkit technology must be an object.');
      }
      if (technology.assetId !== undefined) references.push(technology.assetId);
    }
  }
  if (typeof content.metadata !== 'object' || content.metadata === null || Array.isArray(content.metadata)) {
    throw new Error('Portfolio content must contain metadata.');
  }
  if (content.metadata.socialPreviewAssetId !== undefined) references.push(content.metadata.socialPreviewAssetId);
  if (content.soundtrack !== undefined) {
    if (typeof content.soundtrack !== 'object' || content.soundtrack === null || Array.isArray(content.soundtrack)) {
      throw new Error('Portfolio soundtrack must be an object.');
    }
    for (const regionName of ['intro', 'main', 'afterglow', 'driveLift']) {
      const region = content.soundtrack[regionName];
      if (typeof region !== 'object' || region === null || Array.isArray(region)) {
        throw new Error(`Portfolio soundtrack ${regionName} must be an object.`);
      }
      references.push(region.opusAssetId, region.mp3AssetId);
    }
  }
  return references;
};

const assertExactReferenceClosure = (assets, content) => {
  const manifestIds = new Set(assets.map((asset) => asset.id));
  const referencedIds = new Set();
  for (const assetId of assetReferences(content)) {
    if (typeof assetId !== 'string' || !/^[a-z][a-z0-9-]{0,63}$/u.test(assetId)) {
      throw new Error('Public asset reference must be a generated safe identifier.');
    }
    if (referencedIds.has(assetId)) throw new Error(`Duplicate public asset reference: ${assetId}`);
    referencedIds.add(assetId);
    if (!manifestIds.has(assetId)) throw new Error(`Unknown public asset reference: ${assetId}`);
  }
  for (const assetId of manifestIds) {
    if (!referencedIds.has(assetId)) throw new Error(`Unreferenced manifest asset: ${assetId}`);
  }
};

const ensurePreparedAssetDirectory = async (repositoryRoot) => {
  const preparedAssetsPath = resolve(repositoryRoot, 'inputs/prepared-assets');
  let initialStats;
  try {
    initialStats = await lstat(preparedAssetsPath);
  } catch (error) {
    if (!isErrno(error, 'ENOENT')) throw error;
    await mkdir(preparedAssetsPath, { recursive: true });
    initialStats = await lstat(preparedAssetsPath);
  }

  assertNonSymlinkDirectory(initialStats);
  const initialIdentity = directoryIdentity(initialStats);
  await assertOpenedDirectoryIdentity(preparedAssetsPath, initialIdentity);
  await assertPreparedAssetDirectoryIdentity(preparedAssetsPath, initialIdentity);
  return { preparedAssetsPath, initialIdentity };
};

const sha256 = (bytes) => createHash('sha256').update(bytes).digest('hex');

const readPreparedRegularFile = async (filePath, fileName) => {
  const noFollowFlags = constants.O_RDONLY | (constants.O_NOFOLLOW ?? 0);
  let handle;
  try {
    handle = await open(filePath, noFollowFlags);
  } catch (error) {
    if (isErrno(error, 'ELOOP')) {
      throw new Error(`Prepared asset must be a regular non-linked file: ${fileName}`);
    }
    throw error;
  }
  try {
    const stats = await handle.stat();
    if (!stats.isFile() || stats.nlink !== 1) {
      throw new Error(`Prepared asset must be a regular non-linked file: ${fileName}`);
    }
    return await handle.readFile();
  } finally {
    await handle.close();
  }
};

const verifyPreparedAssetFiles = async (repositoryRoot, assets) => {
  const { preparedAssetsPath, initialIdentity } = await ensurePreparedAssetDirectory(repositoryRoot);
  const expectedByName = new Map(assets.map((asset) => [asset.fileName, asset]));
  const foundNames = new Set();
  const members = await readdir(preparedAssetsPath, { withFileTypes: true });
  for (const member of members) {
    const asset = expectedByName.get(member.name);
    if (asset === undefined) throw new Error(`Extra prepared asset: ${member.name}`);
    if (member.isSymbolicLink() || !member.isFile()) {
      throw new Error(`Prepared asset must be a regular non-linked file: ${member.name}`);
    }
    const filePath = join(preparedAssetsPath, member.name);
    const stats = await lstat(filePath);
    if (stats.isSymbolicLink() || !stats.isFile() || stats.nlink !== 1) {
      throw new Error(`Prepared asset must be a regular non-linked file: ${member.name}`);
    }
    if (sha256(await readPreparedRegularFile(filePath, member.name)) !== asset.sha256) {
      throw new Error(`Prepared asset hash does not match manifest: ${member.name}`);
    }
    foundNames.add(member.name);
  }
  await assertPreparedAssetDirectoryIdentity(preparedAssetsPath, initialIdentity);
  for (const asset of assets) {
    if (!foundNames.has(asset.fileName)) throw new Error(`Missing prepared asset: ${asset.fileName}`);
  }
};

export const verifyApprovedAssetSet = async (repositoryRoot) => {
  const resolvedRepositoryRoot = resolve(repositoryRoot);
  const [assets, content] = await Promise.all([
    readManifest(resolvedRepositoryRoot),
    readJson(resolve(resolvedRepositoryRoot, 'content/public/portfolio-content.json'), 'Portfolio content'),
  ]);
  assertExactReferenceClosure(assets, content);
  await verifyPreparedAssetFiles(resolvedRepositoryRoot, assets);
};

export const materializeEmptyAssetSet = verifyApprovedAssetSet;

if (process.argv[1] !== undefined && resolve(process.argv[1]) === scriptPath) {
  await verifyApprovedAssetSet(defaultRepositoryRoot);
}