import 'dart:async';
import 'dart:math' as math;

import 'package:flutter/material.dart';
import 'package:flutter_map/flutter_map.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:latlong2/latlong.dart';

import '../../../domain/mission/route_geometry.dart';
import '../../../domain/waypoint/flat_waypoint_list.dart';
import '../../providers/current_mission_provider.dart';
import '../../widgets/bottom_stats_bar.dart';
import '../../widgets/halo_menu.dart';
import '../../widgets/mission_map.dart';
import '../../widgets/reticle_button.dart';
import '../../widgets/value_wheel.dart';
import '../../widgets/waypoint_list_panel.dart';

/// Reticle-Zustand (HTML-Demonstrator: Variable `mode`).
/// idle: kein Wegpunkt in der Naehe, Tap legt einen neuen an.
/// snapped: Kartenmitte ist auf einen bestehenden Wegpunkt eingerastet.
/// editing: Wegpunkt wird bearbeitet - Kartenverschieben repositioniert ihn
/// live, das Halo-Menue (Loiter/Landing/Entfernen) ist sichtbar.
enum _ReticleMode { idle, snapped, editing }

/// Missionsplanung: Karte + Wegpunktliste (Architektur-Doku 3.6/3.7).
/// Kein eigenes Scaffold - die Kopfleiste (Plan/Fly-Umschalter) und der
/// gemeinsame Scaffold-Rahmen liegen im AppShell darueber.
class PlanScreen extends ConsumerStatefulWidget {
  const PlanScreen({super.key});

  @override
  ConsumerState<PlanScreen> createState() => _PlanScreenState();
}

class _PlanScreenState extends ConsumerState<PlanScreen> {
  final _mapController = MapController();
  StreamSubscription<MapEvent>? _mapEventSub;

  _ReticleMode _mode = _ReticleMode.idle;
  int _targetIndex = -1;
  bool _mapReady = false;
  bool _listOpen = false;

  // TODO: aus dem aktiven Drohnen-Profil (Doku 3.5) uebernehmen, sobald die
  // Profilverwaltung existiert. Werte entsprechen dem Default-Profil
  // T1 Ranger im HTML-Demonstrator (DEFAULT_DRONE).
  static const _altMin = -500.0;
  static const _altMax = 2000.0;
  static const _altStep = 10.0;
  static const _altPxPerStep = 14.0;
  static const _altMajorEvery = 5;

  static const _speedMin = 13.0;
  static const _speedMax = 25.0;
  static const _speedStep = 1.0;
  static const _speedPxPerStep = 14.0;
  static const _speedMajorEvery = 5;

  static const _defaultCatchRadiusM = 60.0;
  static const _minTurnRadius = 35.0;
  static const _maxClimbRate = 5.0;
  static const _maxDescentRate = 6.0;

  double _curAlt = 60;
  double _curSpeed = 15;

  // Radius des Reticle-Buttons (siehe ReticleButton: 55px Durchmesser).
  static const _reticleRadiusPx = 55 / 2;

  static const _distance = Distance(roundResult: false);

  @override
  void initState() {
    super.initState();
    _mapEventSub = _mapController.mapEventStream.listen(_onMapEvent);
  }

  @override
  void dispose() {
    _mapEventSub?.cancel();
    _mapController.dispose();
    super.dispose();
  }

  void _onMapEvent(MapEvent event) {
    if (event is MapEventMoveEnd) {
      _handleMoveEnd();
    } else if (event is MapEventMove) {
      if (_mode == _ReticleMode.editing && _targetIndex >= 0) {
        final waypoints = ref.read(currentMissionProvider);
        if (_targetIndex < waypoints.length) {
          final center = _mapController.camera.center;
          ref.read(currentMissionProvider.notifier).moveWaypoint(
                _targetIndex,
                center.latitude,
                center.longitude,
              );
        }
      } else if (_mode == _ReticleMode.idle) {
        // Nur fuer die gestrichelte Vorschaulinie neu zeichnen.
        setState(() {});
      }
    }
  }

  /// Metergenauer Fangradius des Reticle bei aktuellem Zoom/Breitengrad
  /// (HTML-Demonstrator: currentSnapMeters()).
  double _currentSnapMeters() {
    final camera = _mapController.camera;
    final metersPerPixel = 156543.03392 *
        math.cos(camera.center.latitude * math.pi / 180) /
        math.pow(2, camera.zoom);
    return _reticleRadiusPx * metersPerPixel;
  }

  void _handleMoveEnd() {
    if (_mode == _ReticleMode.editing) return;

    final waypoints = ref.read(currentMissionProvider);
    final center = _mapController.camera.center;
    final snapMeters = _currentSnapMeters();

    var bestIndex = -1;
    var bestDist = snapMeters;
    for (var i = 0; i < waypoints.length; i++) {
      final d = _distance(center, LatLng(waypoints[i].lat, waypoints[i].lon));
      if (d < bestDist) {
        bestDist = d;
        bestIndex = i;
      }
    }

    setState(() {
      if (bestIndex >= 0) {
        _mode = _ReticleMode.snapped;
        _targetIndex = bestIndex;
        final target = waypoints[bestIndex];
        final targetLatLng = LatLng(target.lat, target.lon);
        if (_distance(center, targetLatLng) > 0.5) {
          // flutter_map's MapController.move() emits MapEventMove, nicht
          // MoveEnd - anders als Leaflets panTo() droht hier also keine
          // Rekursion in _handleMoveEnd, ein Guard ist nicht noetig.
          _mapController.move(targetLatLng, _mapController.camera.zoom);
        }
      } else {
        _mode = _ReticleMode.idle;
        _targetIndex = -1;
      }
    });
  }

  void _onReticleTap() {
    switch (_mode) {
      case _ReticleMode.idle:
        final center = _mapController.camera.center;
        final waypoints = ref.read(currentMissionProvider);
        ref.read(currentMissionProvider.notifier).addWaypoint(
              Waypoint(
                lat: center.latitude,
                lon: center.longitude,
                altitudeM: _curAlt,
                speedMs: _curSpeed,
                catchRadiusM: _defaultCatchRadiusM,
              ),
            );
        setState(() {
          _targetIndex = waypoints.length;
          _mode = _ReticleMode.snapped;
        });
      case _ReticleMode.snapped:
        final waypoints = ref.read(currentMissionProvider);
        if (_targetIndex >= 0 && _targetIndex < waypoints.length) {
          final target = waypoints[_targetIndex];
          setState(() {
            _mode = _ReticleMode.editing;
            _curAlt = target.altitudeM;
            _curSpeed = target.speedMs;
          });
        }
      case _ReticleMode.editing:
        setState(() => _mode = _ReticleMode.snapped);
    }
  }

  void _onHaloAction(HaloAction action) {
    if (_mode != _ReticleMode.editing || _targetIndex < 0) return;
    final notifier = ref.read(currentMissionProvider.notifier);

    switch (action) {
      case HaloAction.loiter:
        notifier.toggleAction(_targetIndex, WaypointAction.loiter);
        setState(() => _mode = _ReticleMode.snapped);
      case HaloAction.landing:
        notifier.toggleAction(_targetIndex, WaypointAction.landing);
        setState(() => _mode = _ReticleMode.snapped);
      case HaloAction.remove:
        notifier.removeAt(_targetIndex);
        setState(() {
          _mode = _ReticleMode.idle;
          _targetIndex = -1;
        });
    }
  }

  void _onAltChanged(double value) {
    setState(() => _curAlt = value);
    if (_mode == _ReticleMode.editing && _targetIndex >= 0) {
      ref.read(currentMissionProvider.notifier).setAltitude(_targetIndex, value);
    }
  }

  void _onSpeedChanged(double value) {
    setState(() => _curSpeed = value);
    if (_mode == _ReticleMode.editing && _targetIndex >= 0) {
      ref.read(currentMissionProvider.notifier).setSpeed(_targetIndex, value);
    }
  }

  // Wegpunktliste (Doku 3.6): Aenderungen wirken auf einen explizit
  // angegebenen Index, nicht zwingend den aktuellen Reticle-Zielpunkt.

  void _onRowAltitudeChanged(int index, double value) {
    ref.read(currentMissionProvider.notifier).setAltitude(index, value);
    if (_mode == _ReticleMode.editing && index == _targetIndex) {
      setState(() => _curAlt = value);
    }
  }

  void _onRowSpeedChanged(int index, double value) {
    ref.read(currentMissionProvider.notifier).setSpeed(index, value);
    if (_mode == _ReticleMode.editing && index == _targetIndex) {
      setState(() => _curSpeed = value);
    }
  }

  void _onRowCatchRadiusChanged(int index, double value) {
    ref.read(currentMissionProvider.notifier).setCatchRadius(index, value);
  }

  void _onRowActionChanged(int index, WaypointAction action) {
    ref.read(currentMissionProvider.notifier).setAction(index, action);
  }

  void _onRowDelete(int index) {
    ref.read(currentMissionProvider.notifier).removeAt(index);
    setState(() {
      if (_targetIndex == index) {
        _mode = _ReticleMode.idle;
        _targetIndex = -1;
      } else if (_targetIndex > index) {
        _targetIndex -= 1;
      }
    });
  }

  /// Zeile antippen zentriert die Karte auf diesen Wegpunkt und schliesst
  /// die Liste (Doku 3.6). Danach wird die Snap-Erkennung einmal manuell
  /// angestossen, da flutter_maps MapController.move() - anders als
  /// Leaflets panTo() - kein MoveEnd-Event feuert.
  void _onCenterOnWaypoint(int index) {
    final waypoints = ref.read(currentMissionProvider);
    if (index < 0 || index >= waypoints.length) return;
    final wp = waypoints[index];
    setState(() => _listOpen = false);
    _mapController.move(LatLng(wp.lat, wp.lon), _mapController.camera.zoom);
    _handleMoveEnd();
  }

  ({double distanceM, double durationSec}) _missionStats(
    List<Waypoint> waypoints,
  ) {
    var totalDist = 0.0;
    var totalDur = 0.0;
    for (var i = 0; i < waypoints.length - 1; i++) {
      final a = LatLng(waypoints[i].lat, waypoints[i].lon);
      final b = LatLng(waypoints[i + 1].lat, waypoints[i + 1].lon);
      final d = _distance(a, b);
      totalDist += d;
      totalDur += d / waypoints[i + 1].speedMs;
    }
    return (distanceM: totalDist, durationSec: totalDur);
  }

  @override
  Widget build(BuildContext context) {
    final waypoints = ref.watch(currentMissionProvider);

    final routeGeometry = buildRouteGeometry(
      waypoints,
      minTurnRadius: _minTurnRadius,
      maxClimbRate: _maxClimbRate,
      maxDescentRate: _maxDescentRate,
    );
    final missionStats = _missionStats(waypoints);

    List<LatLng>? rubberBand;
    if (_mapReady && _mode == _ReticleMode.idle && waypoints.isNotEmpty) {
      final last = waypoints.last;
      rubberBand = [
        LatLng(last.lat, last.lon),
        _mapController.camera.center,
      ];
    }

    final targetWaypoint =
        (_targetIndex >= 0 && _targetIndex < waypoints.length)
            ? waypoints[_targetIndex]
            : null;

    final wheelBottomInset = math.max(
      MediaQuery.of(context).size.height * 0.06,
      124.0,
    );

    return Stack(
      children: [
        MissionMap(
          mapController: _mapController,
          onMapReady: () => setState(() => _mapReady = true),
          routeSegments: routeGeometry.segments,
          rubberBandLine: rubberBand,
          waypointMarkers: [
            for (var i = 0; i < waypoints.length; i++)
              _markerFor(
                waypoints[i],
                isTarget: i == _targetIndex,
                isBad: i < routeGeometry.vertexBad.length &&
                    routeGeometry.vertexBad[i],
              ),
          ],
        ),
        if (_mode == _ReticleMode.editing && targetWaypoint != null)
          Align(
            alignment: Alignment.center,
            child: HaloMenu(
              loiterActive: targetWaypoint.action == WaypointAction.loiter,
              landingActive: targetWaypoint.action == WaypointAction.landing,
              onAction: _onHaloAction,
            ),
          ),
        Align(
          alignment: Alignment.center,
          child: ReticleButton(icon: _reticleIcon, onTap: _onReticleTap),
        ),
        Positioned(
          top: 56,
          bottom: wheelBottomInset,
          left: 14,
          child: ValueWheel(
            value: _curAlt,
            min: _altMin,
            max: _altMax,
            step: _altStep,
            pxPerStep: _altPxPerStep,
            majorEvery: _altMajorEvery,
            onChanged: _onAltChanged,
          ),
        ),
        Positioned(
          top: 56,
          bottom: wheelBottomInset,
          left: 70,
          child: Center(child: _readout('Alt', _curAlt, 'm')),
        ),
        Positioned(
          top: 56,
          bottom: wheelBottomInset,
          right: 14,
          child: ValueWheel(
            value: _curSpeed,
            min: _speedMin,
            max: _speedMax,
            step: _speedStep,
            pxPerStep: _speedPxPerStep,
            majorEvery: _speedMajorEvery,
            onChanged: _onSpeedChanged,
          ),
        ),
        Positioned(
          top: 56,
          bottom: wheelBottomInset,
          right: 70,
          child: Center(child: _readout('Speed', _curSpeed, 'm/s')),
        ),
        Positioned(
          left: 0,
          right: 0,
          bottom: 0,
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              if (routeGeometry.vertexBad.any((bad) => bad) ||
                  routeGeometry.segments.any((s) => s.bad))
                Container(
                  width: double.infinity,
                  color: const Color(0xFF7C2D12),
                  padding: const EdgeInsets.symmetric(vertical: 4, horizontal: 12),
                  child: const Text(
                    'Route exceeds drone capabilities at highlighted point',
                    textAlign: TextAlign.center,
                    style: TextStyle(color: Color(0xFFFDE3D0), fontSize: 12),
                  ),
                ),
              BottomStatsBar(
                waypointCount: waypoints.length,
                totalDistanceM: missionStats.distanceM,
                totalDurationSec: missionStats.durationSec,
                onTap: () => setState(() => _listOpen = true),
              ),
            ],
          ),
        ),
        if (_listOpen)
          Positioned.fill(
            child: WaypointListPanel(
              activeIndex: _mode == _ReticleMode.idle ? -1 : _targetIndex,
              vertexBad: routeGeometry.vertexBad,
              altMin: _altMin,
              altMax: _altMax,
              speedMin: _speedMin,
              speedMax: _speedMax,
              onClose: () => setState(() => _listOpen = false),
              onCenterOnWaypoint: _onCenterOnWaypoint,
              onDelete: _onRowDelete,
              onAltitudeChanged: _onRowAltitudeChanged,
              onSpeedChanged: _onRowSpeedChanged,
              onCatchRadiusChanged: _onRowCatchRadiusChanged,
              onActionChanged: _onRowActionChanged,
            ),
          ),
      ],
    );
  }

  Widget _readout(String label, double value, String unit) {
    return Container(
      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 4),
      decoration: BoxDecoration(
        color: Colors.black.withValues(alpha: 0.7),
        borderRadius: BorderRadius.circular(6),
      ),
      child: Text(
        '$label: ${value.round()} $unit',
        style: const TextStyle(
          color: Colors.white,
          fontSize: 15,
          fontWeight: FontWeight.w500,
        ),
      ),
    );
  }

  IconData get _reticleIcon => switch (_mode) {
        _ReticleMode.idle => Icons.add,
        _ReticleMode.snapped => Icons.edit,
        _ReticleMode.editing => Icons.check,
      };

  CircleMarker _markerFor(
    Waypoint wp, {
    required bool isTarget,
    required bool isBad,
  }) {
    final highlighted = isTarget && _mode != _ReticleMode.idle;
    return CircleMarker(
      point: LatLng(wp.lat, wp.lon),
      radius: highlighted ? 9 : 6,
      color: isBad ? const Color(0xFFE2574A) : const Color(0xFF2B2B28),
      borderStrokeWidth: highlighted ? 3 : 1.5,
      borderColor: Colors.white,
    );
  }
}