import 'dart:async';

import 'package:flutter/foundation.dart';
import 'package:flutter/services.dart';
import 'package:watch_bridge_contract/watch_bridge_contract.dart';

import '../infrastructure/watch_bridge/native_watch_bridge_client.dart';

final class WatchSessionUiState {
  const WatchSessionUiState({
    required this.projection,
    this.commandPending = false,
    this.waitingForPhone = false,
    this.connectionLost = false,
    this.staleProjection = false,
    this.lastAck,
  });

  final WatchSessionProjection projection;
  final bool commandPending;
  final bool waitingForPhone;
  final bool connectionLost;
  final bool staleProjection;
  final WatchCommandAckEvent? lastAck;

  bool get actionsEnabled => !commandPending && !connectionLost;

  WatchSessionUiState copyWith({
    WatchSessionProjection? projection,
    bool? commandPending,
    bool? waitingForPhone,
    bool? connectionLost,
    bool? staleProjection,
    WatchCommandAckEvent? lastAck,
  }) {
    return WatchSessionUiState(
      projection: projection ?? this.projection,
      commandPending: commandPending ?? this.commandPending,
      waitingForPhone: waitingForPhone ?? this.waitingForPhone,
      connectionLost: connectionLost ?? this.connectionLost,
      staleProjection: staleProjection ?? this.staleProjection,
      lastAck: lastAck ?? this.lastAck,
    );
  }
}

final class WatchSessionViewModel extends ValueNotifier<WatchSessionUiState> {
  WatchSessionViewModel({
    NativeWatchBridgeClient nativeClient =
        const MethodChannelNativeWatchBridgeClient(),
    Duration waitingThreshold = const Duration(milliseconds: 500),
    Duration commandTimeout = const Duration(seconds: 2),
    Duration staleProjectionThreshold = const Duration(seconds: 6),
    Duration connectionLostThreshold = const Duration(seconds: 10),
  }) : _nativeClient = nativeClient,
       _waitingThreshold = waitingThreshold,
       _commandTimeout = commandTimeout,
       _staleProjectionThreshold = staleProjectionThreshold,
       _connectionLostThreshold = connectionLostThreshold,
       super(WatchSessionUiState(projection: _initialProjection())) {
    _subscriptions.add(_nativeClient.projections.listen(_handleProjection));
    _subscriptions.add(_nativeClient.acks.listen(_handleAck));
    _subscriptions.add(
      _nativeClient.connectionEvents.listen(_handleConnectionEvent),
    );
    unawaited(_nativeClient.requestCapabilityRefresh());
    unawaited(_nativeClient.requestResync());
    _freshnessTimer = Timer.periodic(const Duration(seconds: 1), (_) {
      _syncFreshnessState();
    });
  }

  final NativeWatchBridgeClient _nativeClient;
  final Duration _waitingThreshold;
  final Duration _commandTimeout;
  final Duration _staleProjectionThreshold;
  final Duration _connectionLostThreshold;
  final _subscriptions = <StreamSubscription<dynamic>>[];

  Timer? _waitingTimer;
  Timer? _commandTimeoutTimer;
  Timer? _freshnessTimer;
  WatchCommandEnvelope? _pendingCommand;
  DateTime? _lastProjectionReceivedAt;
  var _commandCounter = 0;

  Future<void> refresh() async {
    value = value.copyWith(connectionLost: false);
    try {
      await _nativeClient.requestCapabilityRefresh();
      await _nativeClient.requestResync();
    } on PlatformException {
      value = value.copyWith(connectionLost: true);
      unawaited(HapticFeedback.heavyImpact());
    }
  }

  Future<void> sendPrimaryAction() async {
    final action = value.projection.primaryAction;
    final command = switch (action) {
      WatchPrimaryAction.none => null,
      WatchPrimaryAction.startCurrentExercise =>
        WatchCommandType.startCurrentExercise,
      WatchPrimaryAction.pauseSession => WatchCommandType.pauseSession,
      WatchPrimaryAction.resumeSession => WatchCommandType.resumeSession,
      WatchPrimaryAction.startPreparedTimedStep =>
        WatchCommandType.startPreparedTimedStep,
      WatchPrimaryAction.skipCurrentRest => WatchCommandType.skipCurrentRest,
    };
    if (command == null) {
      await refresh();
      return;
    }
    await _sendCommand(command);
  }

  Future<void> sendSecondaryAction(WatchSecondaryAction action) {
    final command = switch (action) {
      WatchSecondaryAction.skipCurrentStep => WatchCommandType.skipCurrentStep,
      WatchSecondaryAction.skipCurrentPassage =>
        WatchCommandType.skipCurrentPassage,
      WatchSecondaryAction.finishCurrentSet => WatchCommandType.finishCurrentSet,
      WatchSecondaryAction.skipCurrentSet => WatchCommandType.skipCurrentSet,
      WatchSecondaryAction.skipCurrentRest => WatchCommandType.skipCurrentRest,
    };
    return _sendCommand(command);
  }

  @override
  void dispose() {
    _waitingTimer?.cancel();
    _commandTimeoutTimer?.cancel();
    _freshnessTimer?.cancel();
    for (final subscription in _subscriptions) {
      unawaited(subscription.cancel());
    }
    super.dispose();
  }

  Future<void> _sendCommand(WatchCommandType type) async {
    if (!value.actionsEnabled || value.projection.deviceSessionId.isEmpty) {
      return;
    }
    final nowMs = DateTime.now().toUtc().millisecondsSinceEpoch;
    final command = WatchCommandEnvelope(
      commandId: 'watch-$nowMs-${_commandCounter++}',
      type: type,
      sessionId: value.projection.deviceSessionId,
      expectedRevision: value.projection.revision,
      sentAtEpochMs: nowMs,
    );
    _pendingCommand = command;
    value = value.copyWith(
      commandPending: true,
      waitingForPhone: false,
      connectionLost: false,
    );
    _waitingTimer?.cancel();
    _commandTimeoutTimer?.cancel();
    _waitingTimer = Timer(_waitingThreshold, () {
      value = value.copyWith(waitingForPhone: true);
    });
    _commandTimeoutTimer = Timer(_commandTimeout, () {
      _pendingCommand = null;
      value = value.copyWith(
        commandPending: false,
        waitingForPhone: false,
        connectionLost: true,
      );
      unawaited(HapticFeedback.heavyImpact());
    });
    try {
      await _nativeClient.sendCommand(command);
    } on PlatformException {
      _pendingCommand = null;
      _clearCommandTimers();
      value = value.copyWith(
        commandPending: false,
        waitingForPhone: false,
        connectionLost: true,
      );
      unawaited(HapticFeedback.heavyImpact());
    }
  }

  void _handleProjection(WatchSessionProjection projection) {
    final previousProjection = value.projection;
    _lastProjectionReceivedAt = DateTime.now();
    _pendingCommand = null;
    _clearCommandTimers();
    value = WatchSessionUiState(
      projection: projection,
      lastAck: value.lastAck,
    );
    _triggerProjectionHaptic(previousProjection, projection);
  }

  void _handleAck(WatchCommandAckEvent ack) {
    if (_pendingCommand?.commandId != ack.commandId) {
      value = value.copyWith(lastAck: ack);
      return;
    }
    _waitingTimer?.cancel();
    value = value.copyWith(
      waitingForPhone: false,
      connectionLost: false,
      lastAck: ack,
    );
    unawaited(HapticFeedback.lightImpact());
    if (_isRejected(ack.status)) {
      _pendingCommand = null;
      _clearCommandTimers();
      value = value.copyWith(commandPending: false);
      unawaited(_nativeClient.requestResync());
    }
  }

  void _handleConnectionEvent(WatchBridgeConnectionEvent event) {
    value = value.copyWith(connectionLost: !event.isReachable);
    if (event.isReachable || event.requestsResync) {
      unawaited(_nativeClient.requestResync());
    }
  }

  void _syncFreshnessState() {
    final receivedAt = _lastProjectionReceivedAt;
    if (receivedAt == null) {
      return;
    }
    final age = DateTime.now().difference(receivedAt);
    final stale = age >= _staleProjectionThreshold;
    final lost = age >= _connectionLostThreshold;
    if (stale != value.staleProjection || lost != value.connectionLost) {
      value = value.copyWith(staleProjection: stale, connectionLost: lost);
    }
  }

  void _clearCommandTimers() {
    _waitingTimer?.cancel();
    _waitingTimer = null;
    _commandTimeoutTimer?.cancel();
    _commandTimeoutTimer = null;
  }

  void _triggerProjectionHaptic(
    WatchSessionProjection previous,
    WatchSessionProjection current,
  ) {
    final phaseChanged = previous.phase != current.phase;
    final enteredReadyTimer = current.phase == WatchSessionPhase.nextTimerReady &&
        previous.phase != WatchSessionPhase.nextTimerReady;
    final enteredRestEnd =
        previous.phase == WatchSessionPhase.restRunning &&
        current.phase != WatchSessionPhase.restRunning &&
        current.phase != WatchSessionPhase.restPaused;
    if (phaseChanged && (enteredReadyTimer || enteredRestEnd)) {
      unawaited(HapticFeedback.mediumImpact());
      unawaited(Future<void>.delayed(const Duration(milliseconds: 120), () {
        return HapticFeedback.mediumImpact();
      }));
    }
  }
}

bool _isRejected(WatchCommandAck ack) {
  return switch (ack) {
    WatchCommandAck.accepted || WatchCommandAck.acceptedNoOp => false,
    _ => true,
  };
}

WatchSessionProjection _initialProjection() {
  return WatchSessionProjection(
    deviceSessionId: '',
    revision: 0,
    projectedAtEpochMs: DateTime.now().toUtc().millisecondsSinceEpoch,
    phase: WatchSessionPhase.noActiveSession,
    phoneReachable: false,
    seriesIndex: 0,
    seriesTotal: 0,
    exerciseName: '',
    primaryAction: WatchPrimaryAction.none,
    statusLabel: 'Téléphone indisponible',
  );
}