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

import 'package:flutter/foundation.dart';
import 'package:path_provider/path_provider.dart';

import 'flight_record.dart';
import 'flight_record_sync.dart';
import 'fly_prefs.dart';

/// Where recorded flights live on the phone.
abstract class FlightRecordStore {
  Future<List<FlightRecord>> loadAll();
  Future<void> save(FlightRecord r);
  Future<void> delete(String id);
}

/// One JSON file per flight under the app's documents directory
/// (`flight_records/<id>.json`); an unreadable file is skipped, not fatal.
class FileFlightRecordStore implements FlightRecordStore {
  FileFlightRecordStore({Future<Directory> Function()? root}) : _root = root ?? getApplicationDocumentsDirectory;

  final Future<Directory> Function() _root;
  Directory? _dir;

  Future<Directory> _folder() async {
    if (_dir != null) return _dir!;
    final Directory d = Directory('${(await _root()).path}${Platform.pathSeparator}flight_records');
    if (!await d.exists()) await d.create(recursive: true);
    return _dir = d;
  }

  File _file(Directory d, String id) => File('${d.path}${Platform.pathSeparator}$id.json');

  @override
  Future<List<FlightRecord>> loadAll() async {
    final Directory d = await _folder();
    final List<FlightRecord> out = <FlightRecord>[];
    await for (final FileSystemEntity f in d.list()) {
      if (f is! File || !f.path.endsWith('.json')) continue;
      try {
        final Object? j = jsonDecode(await f.readAsString());
        if (j is Map) out.add(FlightRecord.fromJson(Map<String, dynamic>.from(j)));
      } catch (_) {
        // A half-written file from a crash: skip it.
      }
    }
    return out;
  }

  @override
  Future<void> save(FlightRecord r) async {
    final File f = _file(await _folder(), r.id);
    // Write then rename, so a crash never leaves a truncated record.
    final File tmp = File('${f.path}.tmp');
    await tmp.writeAsString(jsonEncode(r.toJson()), flush: true);
    await tmp.rename(f.path);
  }

  @override
  Future<void> delete(String id) async {
    final File f = _file(await _folder(), id);
    if (await f.exists()) await f.delete();
  }
}

/// The phone's flight records (plan P9): every flight the [FlightRecorder]
/// finishes is saved here and, while signed in and
/// [FlyPrefs.autoUploadFlights] is on, uploaded to the API Server's logbook.
/// Flights that could not be uploaded stay pending and retry on [uploadPending].
class FlightLog extends ChangeNotifier {
  FlightLog({required this.store, required this.remote});

  final FlightRecordStore store;
  final LogbookRemote remote;

  List<FlightRecord> _records = <FlightRecord>[];
  bool _loaded = false;
  final Set<String> _uploading = <String>{};

  /// Newest first.
  List<FlightRecord> get records => List<FlightRecord>.unmodifiable(_records);
  bool get loaded => _loaded;
  bool isUploading(FlightRecord r) => _uploading.contains(r.id);

  /// Real flights not in the logbook yet.
  List<FlightRecord> get pending => <FlightRecord>[for (final FlightRecord r in _records) if (!r.uploaded && !r.simulated) r];

  /// The latest flight, which is where Find My Drone looks first.
  FlightRecord? get latest => _records.isEmpty ? null : _records.first;

  Future<void> load() async {
    try {
      _records = await store.loadAll();
    } catch (_) {
      _records = <FlightRecord>[];
    }
    _sort();
    _loaded = true;
    notifyListeners();
  }

  void _sort() => _records.sort((FlightRecord a, FlightRecord b) => b.start.compareTo(a.start));

  /// A flight the recorder just finished.
  Future<void> add(FlightRecord r) async {
    _records.removeWhere((FlightRecord x) => x.id == r.id);
    _records.add(r);
    _sort();
    notifyListeners();
    await _save(r);
    if (FlyPrefs.autoUploadFlights.value && remote.available && !r.simulated) await upload(r);
  }

  Future<void> _save(FlightRecord r) async {
    try {
      await store.save(r);
    } catch (_) {
      // Storage full or gone: the record lives in memory until the app closes.
    }
  }

  Future<FlightRecord> upload(FlightRecord r) async {
    if (r.uploaded || !_uploading.add(r.id)) return r;
    notifyListeners();
    try {
      await uploadFlightRecord(r, remote);
      await _save(r);
    } finally {
      _uploading.remove(r.id);
      notifyListeners();
    }
    return r;
  }

  /// Retries every pending flight; answers how many made it.
  Future<int> uploadPending() async {
    if (!remote.available) return 0;
    int ok = 0;
    for (final FlightRecord r in pending) {
      if ((await upload(r)).uploaded) ok++;
    }
    return ok;
  }

  Future<void> delete(FlightRecord r) async {
    _records.removeWhere((FlightRecord x) => x.id == r.id);
    notifyListeners();
    try {
      await store.delete(r.id);
    } catch (_) {}
  }
}