/// One headless CLI run: a local note log, its node id, and a Firebase client.
///
/// Built only from Flutter-free pieces of the app (the [NoteRepository], the
/// [SyncService] every device runs, and [kProject]) so `dart run` works with
/// no Flutter engine — the same constraint `tool/sync_smoke.dart` lives under.
/// The writes are therefore ordinary CRDT changes from one more device, never
/// records hand-written into RTDB.
library;

import 'dart:convert';
import 'dart:io';

import 'package:crdt_sync/crdt_sync.dart';
import 'package:crdt_sync/crdt_sync_io.dart';
import 'package:http/http.dart' as http;
import 'package:path/path.dart' as p;
import 'package:todo/cli/file_credential_store.dart';
import 'package:todo/cli/pull_only_store.dart';
import 'package:todo/data/note_repository.dart';
import 'package:todo/sync/firebase_project.dart';
import 'package:todo/sync/sync_service.dart';
import 'package:uuid/uuid.dart';

/// Default data dir: `$XDG_DATA_HOME/todo-cli`, else `~/.local/share/todo-cli`.
String defaultDataDir(Map<String, String> env) {
  final xdg = env['XDG_DATA_HOME'] ?? '';
  final base = xdg.isNotEmpty
      ? xdg
      : p.join(env['HOME'] ?? '', '.local', 'share');
  return p.join(base, 'todo-cli');
}

/// Node ids of the installs Claude files notes through: the MCP server and
/// the CLI under the same data root as [defaultDataDir]. Missing ones are
/// skipped.
Set<String> claudeNodeIds(Map<String, String> env) {
  final cli = defaultDataDir(env);
  return {
    for (final dir in [cli, p.join(p.dirname(cli), 'todo-mcp')])
      if (File(p.join(dir, CliSession.nodeIdFileName)) case final f
          when f.existsSync())
        f.readAsStringSync().trim(),
  }..remove('');
}

/// The open state of one CLI invocation. Call [close] when done.
class CliSession {
  /// Wraps already-open parts; [open] is the normal way in. Public so a test
  /// can subclass the session and script [sync]'s outcome.
  CliSession(
    this.dataDir,
    this.repository,
    this._firebase, {
    this.passphraseFile,
    this.sharedPasswordFile,
  });

  /// The fleet-wide crdt-sync password the Python daemons read too
  /// (`~/.config/crdt-sync/password`), found from the seed's config root.
  final File? sharedPasswordFile;

  /// Where the passphrase is read from besides the environment: next to the
  /// seeded Firebase session, e.g. `~/.config/todo/e2e_passphrase`.
  final File? passphraseFile;

  /// File holding this install's persisted CRDT node id.
  static const nodeIdFileName = 'node_id';

  /// File holding the per-peer revision cache (see [SyncService.stateStore]).
  static const syncStateFileName = 'sync_state.json';

  /// The CLI's private copy of the Firebase session.
  static const credentialsFileName = 'firebase_auth.json';

  /// Where the local log, node id and session copy live.
  final String dataDir;

  /// The note store, exactly the class the app uses.
  final NoteRepository repository;

  final FirebaseRestClient _firebase;

  /// Opens (creating on first use) the session rooted at [dataDir].
  ///
  /// [seedCredentials] is todo's desktop session, read once and never written.
  /// [httpClient] replaces the real network client (tests only).
  static Future<CliSession> open(
    String dataDir, {
    required String seedCredentials,
    String seedApp = 'todo',
    http.Client? httpClient,
  }) async {
    final dir = Directory(dataDir);
    await dir.create(recursive: true);
    // Holds a database-write credential: owner-only, like ~/.config/todo.
    await Process.run('chmod', ['700', dir.path]);
    final repository = await NoteRepository.openWith(
      persistence: FileLogPersistence(
        File(p.join(dataDir, NoteRepository.logFileName)),
      ),
      nodeId: await _nodeId(dataDir),
    );
    final auth = FirebaseTokenProvider(
      apiKey: kProject.apiKey,
      httpClient: httpClient,
      store: FileCredentialStore(
        file: File(p.join(dataDir, credentialsFileName)),
        seedFile: File(seedCredentials),
      ),
    );
    if (!await auth.hasSession()) {
      await repository.close();
      throw FirebaseAuthError(
        'no Firebase session: $seedCredentials is missing; re-seed it with '
        '`python3 ~/src/utils/crdt-sync/tool/seed_session.py --app $seedApp`',
      );
    }
    final firebase = FirebaseRestClient(
      databaseUrl: kProject.databaseUrl,
      auth: auth,
      httpClient: httpClient,
    );
    return CliSession(
      dataDir,
      repository,
      firebase,
      passphraseFile: File(
        p.join(p.dirname(seedCredentials), e2ePassphraseFileName),
      ),
      sharedPasswordFile: File(
        p.join(p.dirname(p.dirname(seedCredentials)), 'crdt-sync', 'password'),
      ),
    );
  }

  /// Pull every peer's log and merge it; with [push], also publish this
  /// node's merged log and its revision, exactly as a device's sync tick does.
  ///
  /// Without [push] nothing is written anywhere remote, and the revision cache
  /// is bypassed so a read always sees every peer's current log.
  Future<SyncResult> sync({required bool push}) async {
    final plainService = SyncService(
      stateStore: push
          ? PersistedSyncStateStore(
              FileLogPersistence(File(p.join(dataDir, syncStateFileName))),
            )
          : null,
    );
    final e2e = await openEncryptedStore(
      store: _remote(push: push),
      oldPrefix: plainService.notesDir,
      readPassphrase: _readPassphrase,
      // Argon2id once per install, not on every CLI/MCP call.
      keyCache: E2eKeyCache(read: _readCachedKey, write: _writeCachedKey),
    );
    if (!push) {
      // Read-only during the migration: old builds still write the plaintext
      // prefix, so merge it, then the encrypted one when this host has a key.
      final plain = await const SyncService().sync(
        repository,
        _remote(push: false),
      );
      if (e2e is! E2eReady) return plain;
      final layout = E2eLayout.of(plainService.notesDir);
      return await SyncService(
        notesDir: layout.prefix,
        revsPath: layout.revsPath,
      ).sync(repository, e2e.store);
    }
    if (e2e is! E2eReady) {
      throw StateError(
        'sync is locked: put the crdt-sync passphrase in '
        '$e2ePassphraseEnv or ${passphraseFile?.path ?? e2ePassphraseFileName}',
      );
    }
    final layout = E2eLayout.of(plainService.notesDir);
    return await SyncService(
      notesDir: layout.prefix,
      revsPath: layout.revsPath,
      stateStore: plainService.stateStore,
    ).sync(repository, e2e.store);
  }

  RemoteStore _remote({required bool push}) =>
      push ? _firebase : PullOnlyStore(_firebase);

  /// Owner-only file in the data dir caching the derived E2E key.
  static const e2eKeyFileName = 'e2e_key';

  File get _keyFile => File(p.join(dataDir, e2eKeyFileName));

  Future<List<int>?> _readCachedKey() async {
    final file = _keyFile;
    if (!file.existsSync()) return null;
    try {
      return base64.decode((await file.readAsString()).trim());
    } on FormatException {
      return null;
    }
  }

  Future<void> _writeCachedKey(List<int> bytes) async {
    final file = _keyFile;
    // Restrict before the key is written, never after.
    await file.writeAsString('');
    await Process.run('chmod', ['600', file.path]);
    await file.writeAsString(base64.encode(bytes), flush: true);
  }

  /// Environment variable holding the shared crdt-sync passphrase.
  static const e2ePassphraseEnv = 'TODO_E2E_PASSPHRASE';

  /// File name of the passphrase, beside the seeded Firebase session.
  static const e2ePassphraseFileName = 'e2e_passphrase';

  Future<String?> _readPassphrase() async {
    final fromEnv = Platform.environment[e2ePassphraseEnv];
    if (fromEnv != null && fromEnv.isNotEmpty) return fromEnv;
    for (final file in [passphraseFile, sharedPasswordFile]) {
      if (file != null && file.existsSync()) {
        final text = (await file.readAsString()).trim();
        if (text.isNotEmpty) return text;
      }
    }
    return null;
  }

  /// Releases the log and the HTTP client.
  Future<void> close() async {
    _firebase.close();
    await repository.close();
  }

  /// Reads this install's node id, minting and persisting a uuid on first run.
  ///
  /// Never a fixed name: two installs sharing an id would overwrite each
  /// other's file under `todo-sync/notes/` and lose writes.
  static Future<String> _nodeId(String dataDir) async {
    final file = File(p.join(dataDir, nodeIdFileName));
    if (file.existsSync()) {
      final stored = (await file.readAsString()).trim();
      if (stored.isNotEmpty) return stored;
    }
    final minted = const Uuid().v4();
    await file.writeAsString('$minted\n');
    return minted;
  }
}