import 'dart:ui' show Offset, Rect, Size;

import 'package:flutter/foundation.dart';

/// What the pilot has chosen in an ActiveTrack or TapFly session, before and
/// while the operator runs: shared by the video overlay and the mode panel.
class VisionSession extends ChangeNotifier {
  TrackMode trackMode = TrackMode.trace;
  TapFlyDirection direction = TapFlyDirection.forward;
  double speed = 5;

  /// A box drawn (or tapped) on the video, 0..1, waiting for GO.
  Rect? pendingBox;

  /// When [pendingBox] is a subject the aircraft found itself: its index.
  int? pendingSubject;

  /// A TapFly target, 0..1, waiting for GO.
  Offset? pendingPoint;

  /// Trace may fly backwards ahead of a subject coming towards it; null until read.
  bool? retreat;

  void setRetreat(bool? on) {
    retreat = on;
    notifyListeners();
  }

  /// Picks an auto-sensed subject: its box with its index.
  void pickSubject(int index, Rect box) {
    pendingBox = box;
    pendingSubject = index;
    notifyListeners();
  }

  void setTrackMode(TrackMode m) {
    trackMode = m;
    notifyListeners();
  }

  void setDirection(TapFlyDirection d) {
    direction = d;
    notifyListeners();
  }

  void setSpeed(double v) {
    speed = v;
    notifyListeners();
  }

  void setPendingBox(Rect? r) {
    pendingBox = r;
    pendingSubject = null;
    notifyListeners();
  }

  void setPendingPoint(Offset? p) {
    pendingPoint = p;
    notifyListeners();
  }

  void clearPending() {
    if (pendingBox == null && pendingPoint == null) return;
    pendingBox = null;
    pendingSubject = null;
    pendingPoint = null;
    notifyListeners();
  }
}

/// ActiveTrack's follow styles (plan P7b, GO 4's Trace / Profile / Spotlight).
enum TrackMode {
  /// Follows behind (or ahead of) the subject.
  trace('Trace', 'TRACE'),

  /// Flies alongside it.
  profile('Profile', 'PROFILE'),

  /// Stays put and keeps the camera on it; the pilot flies.
  spotlight('Spotlight', 'SPOTLIGHT');

  const TrackMode(this.label, this.sdk);
  final String label;
  final String sdk;

  static TrackMode? fromSdk(String? s) {
    for (final TrackMode m in values) {
      if (m.sdk == s) return m;
    }
    return null;
  }
}

/// TapFly's directions (GO 4's Forward / Backward / Free).
enum TapFlyDirection {
  forward('Forward', 'FORWARD'),
  backward('Backward', 'BACKWARD'),

  /// Flies towards the point while the pilot turns the aircraft freely.
  free('Free', 'FREE');

  const TapFlyDirection(this.label, this.sdk);
  final String label;
  final String sdk;
}

/// The live-view geometry the touch layers share: screen points to the
/// operators' 0..1 picture coordinates.
///
/// The native view letterboxes the feed to its own aspect ratio, so the
/// picture is [contentRect] — centred in the view, with black bars on two
/// sides. Every mapping goes through that rect; a touch on a bar is no touch.
abstract final class VisionGeometry {
  /// A drawn box smaller than this (px, either side) is taken as a tap.
  static const double minDrag = 24;

  /// The box a tap makes, as a fraction of the picture: a person-sized window.
  static const Size tapBox = Size(0.12, 0.22);

  /// Where the picture of size [video] sits inside [view] (aspect fit,
  /// centred); the whole view while the feed size is unknown.
  static Rect contentRect(Size view, Size? video) {
    if (video == null || video.isEmpty || view.isEmpty) return Offset.zero & view;
    final double aspect = video.width / video.height;
    final double w, h;
    if (view.width / view.height > aspect) {
      h = view.height;
      w = h * aspect;
    } else {
      w = view.width;
      h = w / aspect;
    }
    return Rect.fromLTWH((view.width - w) / 2, (view.height - h) / 2, w, h);
  }

  /// The 0..1 box between two corners of a drag, clipped to the picture; null
  /// when it is too small to be a deliberate box, or misses the picture.
  static Rect? dragBox(Offset a, Offset b, Rect content) {
    if ((a.dx - b.dx).abs() < minDrag || (a.dy - b.dy).abs() < minDrag) return null;
    final Rect r = Rect.fromPoints(a, b).intersect(content);
    if (r.width < minDrag || r.height < minDrag) return null;
    return Rect.fromLTRB(
      (r.left - content.left) / content.width,
      (r.top - content.top) / content.height,
      (r.right - content.left) / content.width,
      (r.bottom - content.top) / content.height,
    );
  }

  /// A [tapBox] centred on a tap, kept inside the picture; null on a bar.
  static Rect? tapBoxAt(Offset p, Rect content) {
    final Offset? n = normalise(p, content);
    if (n == null) return null;
    final double cx = n.dx.clamp(tapBox.width / 2, 1 - tapBox.width / 2);
    final double cy = n.dy.clamp(tapBox.height / 2, 1 - tapBox.height / 2);
    return Rect.fromCenter(center: Offset(cx, cy), width: tapBox.width, height: tapBox.height);
  }

  /// [p] as 0..1 of the picture; null when it falls on a bar.
  static Offset? normalise(Offset p, Rect content) {
    if (!content.contains(p)) return null;
    return Offset((p.dx - content.left) / content.width, (p.dy - content.top) / content.height);
  }

  static Rect toScreen(Rect r, Rect content) => Rect.fromLTRB(
        content.left + r.left * content.width,
        content.top + r.top * content.height,
        content.left + r.right * content.width,
        content.top + r.bottom * content.height,
      );

  static Offset pointToScreen(Offset p, Rect content) => Offset(content.left + p.dx * content.width, content.top + p.dy * content.height);
}