import 'dart:convert';

import 'package:flutter/services.dart';

/// Embedded Tailscale tsnet client for Flutter.
///
/// Provides a WireGuard tunnel to Constellation heaters via Tailscale,
/// without requiring the user to install the Tailscale app.
///
/// Architecture: Go xcframework (tsnet) ↔ Swift bridge ↔ MethodChannel ↔ Dart
///
/// Usage:
/// ```dart
/// final ts = TailscaleKit();
/// await ts.start(authKey: 'tskey-auth-...');
/// final port = await ts.startProxy('100.64.0.5');
/// grpcService.connect('127.0.0.1', port: port);
/// ```
class TailscaleKit {
  static const _channel = MethodChannel('tailscale_kit');

  /// Join the Tailnet with the given auth key.
  ///
  /// [authKey] is a Tailscale auth key (reusable, tag-scoped).
  /// [hostname] is the name this device will appear as in the Tailnet.
  ///
  /// The auth key is typically received from the heater during BLE provisioning.
  /// State is persisted to the app's documents directory so the device
  /// identity survives app restarts.
  Future<void> start({
    required String authKey,
    String hostname = 'constellation-phone',
  }) async {
    await _channel.invokeMethod('start', {
      'authKey': authKey,
      'hostname': hostname,
    });
  }

  /// Create a localhost TCP proxy to a heater's Tailscale IP.
  ///
  /// Returns the local port number. Connect gRPC to `127.0.0.1:<port>`.
  /// Traffic is forwarded through the Tailscale WireGuard tunnel to
  /// [heaterTailscaleIP]:[port] on the heater.
  ///
  /// Uses userspace netstack — no VPN entitlement needed on iOS.
  Future<int> startProxy(String heaterTailscaleIP, {int port = 5050}) async {
    final localPort = await _channel.invokeMethod<int>('startProxy', {
      'ip': heaterTailscaleIP,
      'port': port,
    });
    return localPort!;
  }

  /// Stop the local TCP proxy.
  Future<void> stopProxy() async {
    await _channel.invokeMethod('stopProxy');
  }

  /// Disconnect from the Tailnet and clean up.
  Future<void> stop() async {
    await _channel.invokeMethod('stop');
  }

  /// Get the current Tailscale connection status.
  Future<TailscaleStatus> status() async {
    final json = await _channel.invokeMethod<String>('status');
    if (json == null) {
      return TailscaleStatus(state: TailscaleState.stopped);
    }
    return TailscaleStatus.fromJson(jsonDecode(json) as Map<String, dynamic>);
  }

  /// Get this device's Tailscale IPv4 address (100.x.x.x).
  Future<String> tailscaleIP() async {
    final ip = await _channel.invokeMethod<String>('tailscaleIP');
    return ip!;
  }
}

enum TailscaleState {
  stopped,
  starting,
  running,
  needsLogin,
}

class TailscaleStatus {
  final TailscaleState state;
  final String? selfIP;
  final String? backendState;
  final List<TailscalePeer> peers;

  TailscaleStatus({
    required this.state,
    this.selfIP,
    this.backendState,
    this.peers = const [],
  });

  factory TailscaleStatus.fromJson(Map<String, dynamic> json) {
    final backendState = json['BackendState'] as String? ?? '';
    final state = switch (backendState) {
      'Running' => TailscaleState.running,
      'Starting' => TailscaleState.starting,
      'NeedsLogin' || 'NeedsMachineAuth' => TailscaleState.needsLogin,
      _ => TailscaleState.stopped,
    };

    final selfNode = json['Self'] as Map<String, dynamic>?;
    final selfIP = selfNode?['TailscaleIPs'] is List
        ? (selfNode!['TailscaleIPs'] as List).firstOrNull as String?
        : null;

    final peerMap = json['Peer'] as Map<String, dynamic>? ?? {};
    final peers = peerMap.values
        .map((p) => TailscalePeer.fromJson(p as Map<String, dynamic>))
        .toList();

    return TailscaleStatus(
      state: state,
      selfIP: selfIP,
      backendState: backendState,
      peers: peers,
    );
  }

  bool get isRunning => state == TailscaleState.running;
}

class TailscalePeer {
  final String hostname;
  final List<String> tailscaleIPs;
  final bool online;

  TailscalePeer({
    required this.hostname,
    required this.tailscaleIPs,
    required this.online,
  });

  factory TailscalePeer.fromJson(Map<String, dynamic> json) {
    final ips = json['TailscaleIPs'] as List? ?? [];
    return TailscalePeer(
      hostname: json['HostName'] as String? ?? '',
      tailscaleIPs: ips.map((ip) => ip as String).toList(),
      online: json['Online'] as bool? ?? false,
    );
  }
}