library panorama;

import 'dart:async';
import 'dart:ui' as ui;
import 'dart:math' as math;
import 'package:flutter/material.dart';
import 'package:flutter_cube/flutter_cube.dart';
import 'package:motion_sensors/motion_sensors.dart';

enum SensorControl {
  /// No sensor used.
  None,

  /// Use gyroscope and accelerometer.
  Orientation,

  /// Use magnetometer and accelerometer. The logitude 0 points to north.
  AbsoluteOrientation,
}

class Panorama extends StatefulWidget {
  Panorama({
    Key key,
    this.latitude = 0,
    this.longitude = 0,
    this.zoom = 1.0,
    this.minLatitude = -90.0,
    this.maxLatitude = 90.0,
    this.minLongitude = -180.0,
    this.maxLongitude = 180.0,
    this.minZoom = 1.0,
    this.maxZoom = 5.0,
    this.sensitivity = 1.0,
    this.animSpeed = 0.0,
    this.animReverse = true,
    this.latSegments = 32,
    this.lonSegments = 64,
    this.interactive = true,
    this.sensorControl = SensorControl.None,
    this.onViewChanged,
    this.child,
  }) : super(key: key);

  /// The initial latitude, in degrees, between -90 and 90. default to 0 (the vertical center of the image).
  final double latitude;

  /// The initial longitude, in degrees, between -180 and 180. default to 0 (the horizontal center of the image).
  final double longitude;

  /// The initial zoom, default to 1.0.
  final double zoom;

  /// The minimal latitude to show. default to -90.0
  final double minLatitude;

  /// The maximal latitude to show. default to 90.0
  final double maxLatitude;

  /// The minimal longitude to show. default to -180.0
  final double minLongitude;

  /// The maximal longitude to show. default to 180.0
  final double maxLongitude;

  /// The minimal zomm. default to 1.0
  final double minZoom;

  /// The maximal zomm. default to 5.0
  final double maxZoom;

  /// The sensitivity of the gesture. default to 1.0
  final double sensitivity;

  /// The Speed of rotation by animation. default to 0.0
  final double animSpeed;

  /// Reverse rotation when the current longitude reaches the minimal or maximum. default to true
  final bool animReverse;

  /// The number of vertical divisions of the sphere.
  final int latSegments;

  /// The number of horizontal divisions of the sphere.
  final int lonSegments;

  /// Interact with the panorama. default to true
  final bool interactive;

  /// Control the panorama with motion sensors.
  final SensorControl sensorControl;

  /// It is called when the view direction has changed, sending the new longitude and latitude values back.
  final Function(double longitude, double latitude, double tilt) onViewChanged;

  /// Specify an Image(equirectangular image) widget to the panorama.
  final Image child;

  @override
  _PanoramaState createState() => _PanoramaState();
}

class _PanoramaState extends State<Panorama> with SingleTickerProviderStateMixin {
  Scene scene;
  double latitude;
  double longitude;
  double latitudeDelta = 0;
  double longitudeDelta = 0;
  double zoomDelta = 0;
  Offset _lastFocalPoint;
  double _lastZoom;
  double _radius = 500;
  double _dampingFactor = 0.05;
  double _animateDirection = 1.0;
  AnimationController _controller;
  double screenOrientation = 0.0;
  Vector3 orientation = Vector3(0, radians(90), 0);
  StreamSubscription _orientationSubscription;
  StreamSubscription _screenOrientSubscription;

  void _handleScaleStart(ScaleStartDetails details) {
    _lastFocalPoint = details.localFocalPoint;
    _lastZoom = null;
  }

  void _handleScaleUpdate(ScaleUpdateDetails details) {
    final offset = details.localFocalPoint - _lastFocalPoint;
    _lastFocalPoint = details.localFocalPoint;
    latitudeDelta += widget.sensitivity * 0.5 * math.pi * offset.dy / scene.camera.viewportHeight;
    longitudeDelta -= widget.sensitivity * _animateDirection * 0.5 * math.pi * offset.dx / scene.camera.viewportHeight;
    if (_lastZoom == null) {
      _lastZoom = scene.camera.zoom;
    }
    zoomDelta += _lastZoom * details.scale - (scene.camera.zoom + zoomDelta);
    if (widget.sensorControl == SensorControl.None && !_controller.isAnimating) {
      _controller.reset();
      if (widget.animSpeed != 0) {
        _controller.repeat();
      } else
        _controller.forward();
    }
  }

  void _updateView() {
    if (scene == null) return;
    // auto rotate
    longitudeDelta += 0.001 * widget.animSpeed;
    // animate vertical rotating
    latitude += latitudeDelta * _dampingFactor * widget.sensitivity;
    latitudeDelta *= 1 - _dampingFactor * widget.sensitivity;
    // animate horizontal rotating
    longitude += _animateDirection * longitudeDelta * _dampingFactor * widget.sensitivity;
    longitudeDelta *= 1 - _dampingFactor * widget.sensitivity;
    // animate zomming
    final double zoom = scene.camera.zoom + zoomDelta * _dampingFactor;
    zoomDelta *= 1 - _dampingFactor;
    scene.camera.zoom = zoom.clamp(widget.minZoom, widget.maxZoom);
    // stop animation if not needed
    if (latitudeDelta.abs() < 0.001 && longitudeDelta.abs() < 0.001 && zoomDelta.abs() < 0.001) {
      if (widget.animSpeed == 0 && _controller.isAnimating) _controller.stop();
    }

    // rotate for screen orientation
    Quaternion q = Quaternion.axisAngle(Vector3(0, 0, 1), screenOrientation);
    // rotate for device orientation
    q *= Quaternion.euler(-orientation.z, -orientation.y, -orientation.x);
    // rotate to latitude zero
    q *= Quaternion.axisAngle(Vector3(1, 0, 0), math.pi * 0.5);

    // check and limit the rotation range
    Vector3 o = quaternionToOrientation(q);
    final double minLat = radians(math.max(-89.9, widget.minLatitude));
    final double maxLat = radians(math.min(89.9, widget.maxLatitude));
    final double minLon = radians(widget.minLongitude);
    final double maxLon = radians(widget.maxLongitude);
    final double lat = (-o.y).clamp(minLat, maxLat);
    final double lon = o.x.clamp(minLon, maxLon);
    if (lat + latitude < minLat) latitude = minLat - lat;
    if (lat + latitude > maxLat) latitude = maxLat - lat;
    if (maxLon - minLon < math.pi * 2) {
      if (lon + longitude < minLon || lon + longitude > maxLon) {
        longitude = (lon + longitude < minLon ? minLon : maxLon) - lon;
        // reverse rotation when reaching the boundary
        if (widget.animSpeed != 0) {
          if (widget.animReverse)
            _animateDirection *= -1.0;
          else
            _controller.stop();
        }
      }
    }
    o.x = lon;
    o.y = -lat;
    q = orientationToQuaternion(o);

    // rotate to longitude zero
    q *= Quaternion.axisAngle(Vector3(0, 1, 0), -math.pi * 0.5);
    // rotate around the global Y axis
    q *= Quaternion.axisAngle(Vector3(0, 1, 0), longitude);
    // rotate around the local X axis
    q = Quaternion.axisAngle(Vector3(1, 0, 0), -latitude) * q;

    o = quaternionToOrientation(q * Quaternion.axisAngle(Vector3(0, 1, 0), math.pi * 0.5));
    widget.onViewChanged?.call(degrees(o.x), degrees(-o.y), degrees(o.z));

    q.rotate(scene.camera.target..setFrom(Vector3(0, 0, -_radius)));
    q.rotate(scene.camera.up..setFrom(Vector3(0, 1, 0)));
    scene.update();
  }

  void _onSceneCreated(Scene scene) {
    this.scene = scene;
    if (widget.child != null) {
      loadImageFromProvider(widget.child.image).then((ui.Image image) {
        final Mesh mesh = generateSphereMesh(radius: _radius, latSegments: widget.latSegments, lonSegments: widget.lonSegments, texture: image);
        scene.world.add(Object(name: 'surface', mesh: mesh, backfaceCulling: false));
        scene.updateTexture();
        scene.camera.near = 1.0;
        scene.camera.far = _radius + 1.0;
        scene.camera.fov = 75;
        scene.camera.zoom = widget.zoom;
        scene.camera.position.setFrom(Vector3(0, 0, 0.1));
        _updateView();
      });
    }
  }

  @override
  void initState() {
    super.initState();
    latitude = degrees(widget.latitude);
    longitude = degrees(widget.longitude);

    switch (widget.sensorControl) {
      case SensorControl.Orientation:
        motionSensors.orientationUpdateInterval = Duration.microsecondsPerSecond ~/ 60;
        _orientationSubscription = motionSensors.orientation.listen((OrientationEvent event) {
          orientation.setFrom(Vector3(event.yaw, event.pitch, event.roll));
          _updateView();
        });
        break;
      case SensorControl.AbsoluteOrientation:
        motionSensors.absoluteOrientationUpdateInterval = Duration.microsecondsPerSecond ~/ 60;
        _orientationSubscription = motionSensors.absoluteOrientation.listen((AbsoluteOrientationEvent event) {
          orientation.setFrom(Vector3(event.yaw, event.pitch, event.roll));
          _updateView();
        });
        break;
      default:
    }

    motionSensors.screenOrientation.listen((ScreenOrientationEvent event) {
      screenOrientation = radians(event.angle);
    });

    _controller = AnimationController(duration: Duration(milliseconds: 60000), vsync: this)..addListener(_updateView);
    if (widget.sensorControl == SensorControl.None && widget.animSpeed != 0) _controller.repeat();
  }

  @override
  void dispose() {
    _orientationSubscription?.cancel();
    _screenOrientSubscription?.cancel();
    _controller.dispose();
    super.dispose();
  }

  @override
  void didUpdateWidget(Panorama oldWidget) {
    super.didUpdateWidget(oldWidget);
    final Object surface = scene.world.find(RegExp('surface'));
    if (surface == null) return;
    if (widget.latSegments != oldWidget.latSegments || widget.lonSegments != oldWidget.lonSegments) {
      surface.mesh = generateSphereMesh(radius: _radius, latSegments: widget.latSegments, lonSegments: widget.lonSegments, texture: surface.mesh.texture);
    }
    if (widget.child?.image != oldWidget.child?.image) {
      loadImageFromProvider(widget.child.image).then((ui.Image image) {
        surface.mesh.texture = image;
        surface.mesh.textureRect = Rect.fromLTWH(0, 0, image.width.toDouble(), image.height.toDouble());
        scene.updateTexture();
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return widget.interactive
        ? GestureDetector(
            onScaleStart: _handleScaleStart,
            onScaleUpdate: _handleScaleUpdate,
            child: Cube(interactive: false, onSceneCreated: _onSceneCreated),
          )
        : Cube(interactive: false, onSceneCreated: _onSceneCreated);
  }
}

Mesh generateSphereMesh({num radius = 1.0, int latSegments = 16, int lonSegments = 16, ui.Image texture}) {
  int count = (latSegments + 1) * (lonSegments + 1);
  List<Vector3> vertices = List<Vector3>(count);
  List<Offset> texcoords = List<Offset>(count);
  List<Polygon> indices = List<Polygon>(latSegments * lonSegments * 2);

  int i = 0;
  for (int y = 0; y <= latSegments; ++y) {
    final double v = y / latSegments;
    final double sv = math.sin(v * math.pi);
    final double cv = math.cos(v * math.pi);
    for (int x = 0; x <= lonSegments; ++x) {
      final double u = x / lonSegments;
      vertices[i] = Vector3(radius * math.cos(u * math.pi * 2.0) * sv, radius * cv, radius * math.sin(u * math.pi * 2.0) * sv);
      texcoords[i] = Offset(u, 1.0 - v);
      i++;
    }
  }

  i = 0;
  for (int y = 0; y < latSegments; ++y) {
    final int base1 = (lonSegments + 1) * y;
    final int base2 = (lonSegments + 1) * (y + 1);
    for (int x = 0; x < lonSegments; ++x) {
      indices[i++] = Polygon(base1 + x, base1 + x + 1, base2 + x);
      indices[i++] = Polygon(base1 + x + 1, base2 + x + 1, base2 + x);
    }
  }

  final Mesh mesh = Mesh(vertices: vertices, texcoords: texcoords, indices: indices, texture: texture);
  return mesh;
}

/// Get ui.Image from ImageProvider
Future<ui.Image> loadImageFromProvider(ImageProvider provider) async {
  final Completer<ui.Image> completer = Completer<ui.Image>();
  final ImageStream imageStream = provider.resolve(ImageConfiguration());
  ImageStreamListener listener;
  listener = ImageStreamListener((ImageInfo imageInfo, bool synchronousCall) {
    completer.complete(imageInfo.image);
    imageStream.removeListener(listener);
  });
  imageStream.addListener(listener);
  return completer.future;
}

Vector3 quaternionToOrientation(Quaternion q) {
  // final Matrix4 m = Matrix4.compose(Vector3.zero(), q, Vector3.all(1.0));
  // final Vector v = motionSensors.getOrientation(m);
  // return Vector3(v.z, v.y, v.x);
  final storage = q.storage;
  final double x = storage[0];
  final double y = storage[1];
  final double z = storage[2];
  final double w = storage[3];
  final double roll = math.atan2(-2 * (x * y - w * z), 1.0 - 2 * (x * x + z * z));
  final double pitch = math.asin(2 * (y * z + w * x));
  final double yaw = math.atan2(-2 * (x * z - w * y), 1.0 - 2 * (x * x + y * y));
  return Vector3(yaw, pitch, roll);
}

Quaternion orientationToQuaternion(Vector3 v) {
  final Matrix4 m = Matrix4.identity();
  m.rotateZ(v.z);
  m.rotateX(v.y);
  m.rotateY(v.x);
  return Quaternion.fromRotation(m.getRotation());
}