// Linux descriptor-anchored metadata reader. Never opens credential.json.
// Directory FDs keep traversal inside the checked tree even during rename races.
import { open, readdir, lstat } from 'node:fs/promises';
import { constants } from 'node:fs';
import { resolve } from 'node:path';
import { ValidationError, validId, validateProvider, validateAccount,
  validateSettingsProfile, validateHarnessManifest } from './records.mjs';
const fail = code => { throw new ValidationError('registry', code); };
const fdPath = handle => `/proc/self/fd/${handle.fd}`;
const ioCode = e => e instanceof ValidationError ? e : new ValidationError('registry',
  ({ ENOENT: 'missing-path', EACCES: 'inaccessible-path', EPERM: 'inaccessible-path',
    ENOTDIR: 'not-a-directory', ELOOP: 'symlink-forbidden' })[e.code] ?? 'read-failed');
function privateMode(s, directory) {
  if (s.uid !== process.getuid() || (s.mode & 0o777) !== (directory ? 0o700 : 0o600))
    fail('insecure-permissions');
}
async function directory(path, privateRequired = true) {
  const before = await lstat(path);
  if (before.isSymbolicLink()) fail('symlink-forbidden');
  if (!before.isDirectory()) fail('not-a-directory');
  if (privateRequired) privateMode(before, true);
  const h = await open(path, constants.O_RDONLY | constants.O_DIRECTORY | constants.O_NOFOLLOW);
  try {
    const after = await h.stat();
    if (before.dev !== after.dev || before.ino !== after.ino) fail('path-changed');
    if (privateRequired) privateMode(after, true);
    return h;
  } catch (e) { await h.close(); throw e; }
}
async function rootDirectory(root) {
  if (process.platform !== 'linux' || typeof process.getuid !== 'function') fail('unsupported-platform');
  if (typeof root !== 'string' || !root.length || root.split('/').includes('..')) fail('invalid-root');
  const parts = resolve(root).split('/').filter(Boolean);
  if (!parts.length) fail('invalid-root');
  let h = await directory('/', false);
  try {
    for (let i = 0; i < parts.length; i++) {
      const next = await directory(`${fdPath(h)}/${parts[i]}`, i === parts.length - 1);
      await h.close(); h = next;
    }
    return h;
  } catch (e) { await h.close(); throw e; }
}
async function withDirectory(parent, name, fn) {
  const h = await directory(`${fdPath(parent)}/${name}`);
  try { return await fn(h); } finally { await h.close(); }
}
async function jsonFile(parent, name) {
  const path = `${fdPath(parent)}/${name}`;
  const before = await lstat(path);
  if (before.isSymbolicLink()) fail('symlink-forbidden');
  if (!before.isFile()) fail('not-a-regular-file');
  privateMode(before, false);
  if (before.size > 1024 * 1024) fail('record-too-large');
  const h = await open(path, constants.O_RDONLY | constants.O_NOFOLLOW | constants.O_NONBLOCK);
  try {
    const after = await h.stat();
    if (!after.isFile() || before.dev !== after.dev || before.ino !== after.ino) fail('path-changed');
    privateMode(after, false);
    // Bounded read even if the writer grows the file after stat.
    const buffer = Buffer.alloc(1024 * 1024 + 1);
    let length = 0;
    while (length < buffer.length) {
      const { bytesRead } = await h.read(buffer, length, buffer.length - length, null);
      if (!bytesRead) break;
      length += bytesRead;
    }
    if (length > 1024 * 1024) fail('record-too-large');
    try { return JSON.parse(buffer.toString('utf8', 0, length)); }
    catch { fail('invalid-json'); }
  } finally { await h.close(); }
}
async function records(dir, validator, target) {
  for (const name of (await readdir(fdPath(dir))).sort()) {
    if (!name.endsWith('.json') || !validId(name.slice(0, -5))) fail('invalid-record-name');
    const id = name.slice(0, -5), record = await jsonFile(dir, name);
    const errors = validator(record);
    if (errors.length) throw errors[0];
    if (record.id !== id) fail('id-path-mismatch');
    if (Object.hasOwn(target, id)) fail('duplicate-id');
    target[id] = record;
  }
}
function emptyEntries() {
  return Object.fromEntries(['providers', 'accounts', 'profiles', 'selections', 'harnesses']
    .map(k => [k, Object.create(null)]));
}
export async function loadRegistry(root) {
  const entries = emptyEntries();
  let handle;
  try {
    handle = await rootDirectory(root);
    await withDirectory(handle, 'auth', async auth => {
      await withDirectory(auth, 'providers', d => records(d, validateProvider, entries.providers));
      await withDirectory(auth, 'accounts', async accounts => {
        for (const provider of (await readdir(fdPath(accounts))).sort()) {
          if (!validId(provider)) fail('invalid-provider-directory');
          await withDirectory(accounts, provider, async pd => {
            for (const id of (await readdir(fdPath(pd))).sort()) {
              if (!validId(id)) fail('invalid-account-directory');
              await withDirectory(pd, id, async ad => {
                // Do not stat, open or parse the credential sibling.
                const account = await jsonFile(ad, 'account.json');
                const errors = validateAccount(account, provider);
                if (errors.length) throw errors[0];
                if (account.id !== id) fail('id-path-mismatch');
                entries.accounts[`${provider}/${id}`] = account;
              });
            }
          });
        }
      });
      await withDirectory(auth, 'settings', d => records(d, validateSettingsProfile, entries.profiles));
    });
    await withDirectory(handle, 'harnesses', d => records(d, validateHarnessManifest, entries.harnesses));
    for (const provider of Object.values(entries.providers))
      for (const id of Object.keys(provider.harnesses))
        if (!Object.hasOwn(entries.harnesses, id)) fail('missing-harness');
    for (const account of Object.values(entries.accounts)) {
      const provider = entries.providers[account.provider];
      if (!provider) fail('missing-provider');
      if (!provider.credentialTypes.includes(account.type)) fail('credential-type-not-supported');
    }
    for (const profile of Object.values(entries.profiles)) {
      for (const ref of profile.allowedAccounts) if (!entries.accounts[ref]) fail('missing-account');
      for (const id of [...(profile.providers ?? []), ...Object.keys(profile.models ?? {})])
        if (!entries.providers[id]) fail('missing-provider');
      for (const ref of Object.values(profile.defaultAccounts ?? {}))
        if (!entries.accounts[ref]) fail('missing-default-account');
    }
    if (!Object.keys(entries.providers).length || !Object.keys(entries.profiles).length ||
        !Object.keys(entries.harnesses).length) fail('empty-registry');
    return { entries, errors: [] };
  } catch (e) {
    // Never return partially trusted data after a refusal.
    return { entries: emptyEntries(), errors: [ioCode(e)] };
  } finally { if (handle) await handle.close(); }
}