import 'package:flutter/foundation.dart';
import 'package:latlong2/latlong.dart' show LatLng;

import 'waypoint_mission.dart';

/// What a tap on the map adds.
enum MapTool { waypoint, poi }

/// The point editor's tabs (GO 4's `gs_waypoint_2_point_editor_view`).
enum PointField {
  altitude('Altitude'),
  speed('Speed'),
  heading('Heading'),
  gimbal('Gimbal'),
  action('Action'),
  poi('POI'),
  radius('Turn radius');

  const PointField(this.label);
  final String label;
}

/// A numeric field's range and step for the swipe readout and −/+.
@immutable
class FieldRange {
  const FieldRange(this.min, this.max, this.step, this.unit);

  final double min;
  final double max;
  final double step;
  final String unit;

  double clamp(double v) => ((v / step).round() * step).clamp(min, max).toDouble();
}

/// The Waypoints editor's state (plan P7): the mission being edited, what is
/// selected, the map tool, and an undo history. Pure — the map layers and the
/// HUD panels both listen to it, and the tests drive it directly.
class WaypointEditor extends ChangeNotifier {
  WaypointEditor({WaypointMissionSpec mission = const WaypointMissionSpec()}) : _mission = mission;

  WaypointMissionSpec _mission;
  WaypointMissionSpec get mission => _mission;

  /// The selected waypoint, or null.
  int? selected;

  /// The selected POI's id, or null. A waypoint and a POI are never both selected.
  String? selectedPoi;

  MapTool tool = MapTool.waypoint;
  PointField field = PointField.altitude;

  /// Edited since it was last loaded or saved.
  bool dirty = false;

  final List<WaypointMissionSpec> _undo = <WaypointMissionSpec>[];
  static const int _undoDepth = 40;
  bool get canUndo => _undo.isNotEmpty;

  /// Altitude for the first waypoint of a new route.
  static const double defaultAltitude = 50;

  /// Ranges of the numeric fields (MSDK 4.18 limits, narrowed to what GO 4 offers).
  static const FieldRange altitudeRange = FieldRange(-200, WaypointMissionSpec.maxAltitudeSdk, 1, 'm');
  static const FieldRange speedRange = FieldRange(WaypointMissionSpec.minSpeed, WaypointMissionSpec.maxSpeed, 0.5, 'm/s');
  static const FieldRange headingRange = FieldRange(-180, 180, 1, '°');
  static const FieldRange radiusRange = FieldRange(WaypointMissionSpec.minTurnRadius, 200, 0.5, 'm');
  static const FieldRange hoverRange = FieldRange(0, 32, 1, 's');
  static const FieldRange poiHeightRange = FieldRange(-200, 500, 1, 'm');

  static FieldRange gimbalRange({double min = -90, double max = 30}) => FieldRange(min, max, 1, '°');

  WaypointSpec? get selectedPoint => selected == null || selected! >= _mission.points.length ? null : _mission.points[selected!];
  MissionPoi? get selectedPoiSpec => _mission.poi(selectedPoi);

  // ── History ───────────────────────────────────────────────────────────────

  void _set(WaypointMissionSpec next, {bool record = true}) {
    if (record) {
      _undo.add(_mission);
      if (_undo.length > _undoDepth) _undo.removeAt(0);
    }
    _mission = next;
    dirty = true;
    _fixSelection();
    notifyListeners();
  }

  void undo() {
    if (_undo.isEmpty) return;
    _mission = _undo.removeLast();
    dirty = true;
    _fixSelection();
    notifyListeners();
  }

  /// A drag moves a marker many times; only its start goes into the history.
  void beginDrag() {
    _undo.add(_mission);
    if (_undo.length > _undoDepth) _undo.removeAt(0);
  }

  void _fixSelection() {
    if (selected != null && selected! >= _mission.points.length) selected = _mission.points.isEmpty ? null : _mission.points.length - 1;
    if (selectedPoi != null && _mission.poi(selectedPoi) == null) selectedPoi = null;
  }

  // ── Whole mission ─────────────────────────────────────────────────────────

  void load(WaypointMissionSpec m) {
    _mission = m;
    _undo.clear();
    selected = m.points.isEmpty ? null : 0;
    selectedPoi = null;
    dirty = false;
    notifyListeners();
  }

  void markSaved(WaypointMissionSpec stored) {
    _mission = stored;
    dirty = false;
    notifyListeners();
  }

  void clear() {
    if (_mission.points.isEmpty && _mission.pois.isEmpty) return;
    _set(_mission.copyWith(points: const <WaypointSpec>[], pois: const <MissionPoi>[]));
    selected = null;
    selectedPoi = null;
  }

  void updateRoute(WaypointMissionSpec Function(WaypointMissionSpec m) change) => _set(change(_mission));

  void setTool(MapTool t) {
    if (tool == t) return;
    tool = t;
    notifyListeners();
  }

  void setField(PointField f) {
    if (field == f) return;
    field = f;
    notifyListeners();
  }

  // ── Map gestures ──────────────────────────────────────────────────────────

  /// A tap on empty map adds what the tool says.
  void tapMap(LatLng at) => tool == MapTool.poi ? addPoi(at) : addPoint(at);

  // ── Waypoints ─────────────────────────────────────────────────────────────

  /// Appends a waypoint (or inserts it at [index]); it takes the altitude,
  /// speed and gimbal of the point before it, as GO 4 does, and is selected.
  void addPoint(LatLng at, {int? index}) {
    if (_mission.points.length >= WaypointMissionSpec.maxPoints) return;
    final List<WaypointSpec> pts = List<WaypointSpec>.of(_mission.points);
    final int i = (index ?? pts.length).clamp(0, pts.length);
    final WaypointSpec? like = pts.isEmpty ? null : pts[(i - 1).clamp(0, pts.length - 1)];
    pts.insert(
      i,
      WaypointSpec(
        at: at,
        altitude: like?.altitude ?? defaultAltitude,
        speed: like?.speed,
        gimbalPitch: like?.gimbalPitch,
        turnRadius: like?.turnRadius ?? WaypointMissionSpec.minTurnRadius,
      ),
    );
    _set(_mission.copyWith(points: pts));
    selected = i;
    selectedPoi = null;
    notifyListeners();
  }

  /// Adds a waypoint halfway along leg [leg] (between points leg and leg+1).
  void insertMidpoint(int leg) {
    final List<WaypointSpec> pts = _mission.points;
    if (leg < 0 || leg + 1 >= pts.length) return;
    final LatLng a = pts[leg].at, b = pts[leg + 1].at;
    addPoint(LatLng((a.latitude + b.latitude) / 2, (a.longitude + b.longitude) / 2), index: leg + 1);
    final WaypointSpec mid = _mission.points[leg + 1];
    _replace(leg + 1, mid.copyWith(altitude: (pts[leg].altitude + pts[leg + 1].altitude) / 2), record: false);
  }

  void movePoint(int i, LatLng at, {bool record = false}) => _replace(i, _mission.points[i].copyWith(at: at), record: record);

  void removePoint(int i) {
    if (i < 0 || i >= _mission.points.length) return;
    final List<WaypointSpec> pts = List<WaypointSpec>.of(_mission.points)..removeAt(i);
    _set(_mission.copyWith(points: pts));
    if (pts.isEmpty) {
      selected = null;
    } else if (selected != null && selected! >= i) {
      selected = (selected! - 1).clamp(0, pts.length - 1);
    }
    notifyListeners();
  }

  void select(int? i) {
    selected = i;
    if (i != null) selectedPoi = null;
    notifyListeners();
  }

  void selectNext(int delta) {
    if (_mission.points.isEmpty) return;
    select(((selected ?? 0) + delta).clamp(0, _mission.points.length - 1));
  }

  /// [record] false for the steps of a swipe that [beginDrag] already saved.
  void updatePoint(int i, WaypointSpec Function(WaypointSpec p) change, {bool record = true}) =>
      _replace(i, change(_mission.points[i]), record: record);

  void _replace(int i, WaypointSpec p, {bool record = true}) {
    if (i < 0 || i >= _mission.points.length) return;
    final List<WaypointSpec> pts = List<WaypointSpec>.of(_mission.points);
    pts[i] = p;
    _set(_mission.copyWith(points: pts), record: record);
  }

  /// A per-point heading other than Route only works with per-waypoint
  /// headings, so choosing one switches the route over.
  void setHeading(int i, WaypointHeading h, {int? custom}) {
    final WaypointSpec p = _mission.points[i];
    final List<WaypointSpec> pts = List<WaypointSpec>.of(_mission.points);
    pts[i] = p.copyWith(heading: h, customHeading: custom ?? p.customHeading);
    final bool needsPerPoint = h != WaypointHeading.route && _mission.headingMode != RouteHeadingMode.perPoint;
    _set(_mission.copyWith(points: pts, headingMode: needsPerPoint ? RouteHeadingMode.perPoint : null));
  }

  /// Copies the selected waypoint's [f] to every waypoint.
  void applyToAll(PointField f) {
    final WaypointSpec? src = selectedPoint;
    if (src == null) return;
    final List<WaypointSpec> pts = <WaypointSpec>[
      for (final WaypointSpec p in _mission.points)
        switch (f) {
          PointField.altitude => p.copyWith(altitude: src.altitude),
          PointField.speed => p.copyWith(speed: src.speed),
          PointField.heading => p.copyWith(heading: src.heading, customHeading: src.customHeading),
          PointField.gimbal => p.copyWith(gimbalPitch: src.gimbalPitch, gimbalAimPoi: src.gimbalAimPoi),
          PointField.action => p.copyWith(action: src.action, hoverSeconds: src.hoverSeconds),
          PointField.poi => p.copyWith(poiId: src.poiId),
          PointField.radius => p.copyWith(turnRadius: src.turnRadius),
        },
    ];
    _set(_mission.copyWith(points: pts));
  }

  // ── Points of interest ────────────────────────────────────────────────────

  int _poiSeq = 0;

  void addPoi(LatLng at) {
    String id;
    do {
      id = 'poi${++_poiSeq}';
    } while (_mission.poi(id) != null);
    _set(_mission.copyWith(pois: <MissionPoi>[..._mission.pois, MissionPoi(id: id, at: at)]));
    selectedPoi = id;
    selected = null;
    notifyListeners();
  }

  void movePoi(String id, LatLng at) => _replacePoi(id, (MissionPoi p) => p.copyWith(at: at), record: false);

  void updatePoi(String id, MissionPoi Function(MissionPoi p) change, {bool record = true}) =>
      _replacePoi(id, change, record: record);

  void _replacePoi(String id, MissionPoi Function(MissionPoi p) change, {bool record = true}) {
    _set(
      _mission.copyWith(pois: <MissionPoi>[for (final MissionPoi p in _mission.pois) p.id == id ? change(p) : p]),
      record: record,
    );
  }

  /// Removes the POI and unlinks every waypoint that faced it.
  void removePoi(String id) {
    _set(_mission.copyWith(
      pois: <MissionPoi>[for (final MissionPoi p in _mission.pois) if (p.id != id) p],
      points: <WaypointSpec>[
        for (final WaypointSpec w in _mission.points)
          w.poiId == id ? w.copyWith(poiId: null, gimbalAimPoi: false, heading: w.heading == WaypointHeading.poi ? WaypointHeading.route : null) : w,
      ],
    ));
  }

  void selectPoi(String? id) {
    selectedPoi = id;
    if (id != null) selected = null;
    notifyListeners();
  }

  /// Links waypoint [i] to [poiId] (null unlinks). Linking turns the point to
  /// face it, as GO 4 does; unlinking turns a POI-facing point back to Route.
  void linkPoi(int i, String? poiId) {
    final WaypointSpec p = _mission.points[i];
    if (poiId == null) {
      _replace(i, p.copyWith(poiId: null, gimbalAimPoi: false, heading: p.heading == WaypointHeading.poi ? WaypointHeading.route : null));
      return;
    }
    final List<WaypointSpec> pts = List<WaypointSpec>.of(_mission.points);
    pts[i] = p.copyWith(poiId: poiId, heading: WaypointHeading.poi);
    final bool needsPerPoint = _mission.headingMode != RouteHeadingMode.perPoint;
    _set(_mission.copyWith(points: pts, headingMode: needsPerPoint ? RouteHeadingMode.perPoint : null));
  }
}