import 'package:flutter/foundation.dart';

import 'state/parse.dart';

/// The three directions MSDK's FlightAssistant sets distances for.
enum SensingDirection {
  horizontal('Horizontal', 'Horizontal'),
  up('Upward', 'Upward'),
  down('Downward', 'Downward');

  const SensingDirection(this.sdk, this.label);

  /// `DJIFlightAssistantObstacleSensingDirection` name.
  final String sdk;
  final String label;
}

/// Which of the two distances.
enum SensingKind {
  /// `setVisualObstaclesAvoidanceDistance`: where the aircraft brakes.
  avoidance,

  /// `setMaxPerceptionDistance`: how far it looks (the warning distance).
  perception,
}

/// The aircraft's obstacle braking and perception distances (plan P8, GO 4 /
/// Pilot's Vision "obstacle distance" rows). A null value is a direction the
/// aircraft refused to report, and its row hides.
@immutable
class SensingDistances {
  const SensingDistances({this.avoidance = const <SensingDirection, double?>{}, this.perception = const <SensingDirection, double?>{}});

  factory SensingDistances.fromBridge(Map<String, dynamic> m) {
    Map<SensingDirection, double?> read(Object? v) {
      final Map<String, dynamic>? g = asMap(v);
      return <SensingDirection, double?>{for (final SensingDirection d in SensingDirection.values) d: finite(g?[d.sdk])};
    }

    return SensingDistances(avoidance: read(m['avoidance']), perception: read(m['perception']));
  }

  final Map<SensingDirection, double?> avoidance;
  final Map<SensingDirection, double?> perception;

  double? value(SensingKind k, SensingDirection d) => (k == SensingKind.avoidance ? avoidance : perception)[d];

  bool get isEmpty => avoidance.values.every((double? v) => v == null) && perception.values.every((double? v) => v == null);

  SensingDistances withValue(SensingKind k, SensingDirection d, double v) => SensingDistances(
        avoidance: k == SensingKind.avoidance ? <SensingDirection, double?>{...avoidance, d: v} : avoidance,
        perception: k == SensingKind.perception ? <SensingDirection, double?>{...perception, d: v} : perception,
      );

  /// Range and step a row offers. MSDK 4.18 documents no limits; these follow
  /// DJI Pilot's sliders and the flight controller refuses anything it does not
  /// accept (the row then rolls back). Unverified on hardware.
  static ({double min, double max, double step}) range(SensingKind k, SensingDirection d) => switch ((k, d)) {
        (SensingKind.avoidance, SensingDirection.down) => (min: 0.5, max: 3, step: 0.1),
        (SensingKind.avoidance, _) => (min: 1, max: 10, step: 0.5),
        (SensingKind.perception, SensingDirection.down) => (min: 1, max: 10, step: 0.5),
        (SensingKind.perception, _) => (min: 5, max: 40, step: 1),
      };

  /// [v] moved [steps] steps within the range, snapped to the step.
  static double stepped(SensingKind k, SensingDirection d, double v, int steps) {
    final ({double min, double max, double step}) r = range(k, d);
    final double next = ((v / r.step).round() + steps) * r.step;
    return double.parse(next.clamp(r.min, r.max).toStringAsFixed(2));
  }
}