aves/lib/widgets/common/magnifier/controller/controller.dart

import 'dart:async';
import 'dart:ui';

import 'package:aves/widgets/common/magnifier/controller/state.dart';
import 'package:aves/widgets/common/magnifier/scale/scale_boundaries.dart';
import 'package:aves/widgets/common/magnifier/scale/scale_level.dart';
import 'package:aves/widgets/common/magnifier/scale/state.dart';
import 'package:flutter/widgets.dart';

class MagnifierController {
  final StreamController<MagnifierState> _stateStreamController = StreamController.broadcast();
  final StreamController<ScaleBoundaries> _scaleBoundariesStreamController = StreamController.broadcast();
  final StreamController<ScaleStateChange> _scaleStateChangeStreamController = StreamController.broadcast();

  bool _disposed = false;
  late MagnifierState _currentState, initial, previousState;
  ScaleBoundaries? _scaleBoundaries;
  late ScaleStateChange _currentScaleState, previousScaleState;

  MagnifierController({
    MagnifierState? initialState,
  }) : super() {
    initial = initialState ??
        const MagnifierState(
          position: Offset.zero,
          scale: null,
          source: ChangeSource.internal,
        );
    previousState = initial;
    _currentState = initial;
    _setState(initial);

    const _initialScaleState = ScaleStateChange(state: ScaleState.initial, source: ChangeSource.internal);
    previousScaleState = _initialScaleState;
    _currentScaleState = _initialScaleState;
    _setScaleState(_initialScaleState);
  }

  Stream<MagnifierState> get stateStream => _stateStreamController.stream;

  Stream<ScaleBoundaries> get scaleBoundariesStream => _scaleBoundariesStreamController.stream;

  Stream<ScaleStateChange> get scaleStateChangeStream => _scaleStateChangeStreamController.stream;

  MagnifierState get currentState => _currentState;

  Offset get position => currentState.position;

  double? get scale => currentState.scale;

  ScaleBoundaries get scaleBoundaries => _scaleBoundaries!;

  ScaleStateChange get scaleState => _currentScaleState;

  bool get hasScaleSateChanged => previousScaleState != scaleState;

  bool get isZooming => scaleState.state == ScaleState.zoomedIn || scaleState.state == ScaleState.zoomedOut;

  void dispose() {
    _disposed = true;
    _stateStreamController.close();
    _scaleBoundariesStreamController.close();
    _scaleStateChangeStreamController.close();
  }

  void update({
    Offset? position,
    double? scale,
    required ChangeSource source,
  }) {
    position = position ?? this.position;
    scale = scale ?? this.scale;
    if (this.position == position && this.scale == scale) return;
    assert((scale ?? 0) >= 0);

    previousState = currentState;
    _setState(MagnifierState(
      position: position,
      scale: scale,
      source: source,
    ));
  }

  void setScaleState(ScaleState newValue, ChangeSource source, {Offset? childFocalPoint}) {
    if (_disposed || _currentScaleState.state == newValue) return;

    previousScaleState = _currentScaleState;
    _currentScaleState = ScaleStateChange(state: newValue, source: source, childFocalPoint: childFocalPoint);
    _scaleStateChangeStreamController.add(scaleState);
  }

  void _setState(MagnifierState state) {
    if (_disposed || _currentState == state) return;

    _currentState = state;
    _stateStreamController.add(state);
  }

  void setScaleBoundaries(ScaleBoundaries scaleBoundaries) {
    if (_disposed || _scaleBoundaries == scaleBoundaries) return;

    _scaleBoundaries = scaleBoundaries;
    _scaleBoundariesStreamController.add(scaleBoundaries);

    if (!isZooming) {
      update(
        scale: getScaleForScaleState(_currentScaleState.state),
        source: ChangeSource.internal,
      );
    }
  }

  void _setScaleState(ScaleStateChange scaleState) {
    if (_disposed || _currentScaleState == scaleState) return;

    _currentScaleState = scaleState;
    _scaleStateChangeStreamController.add(_currentScaleState);
  }

  double? getScaleForScaleState(ScaleState scaleState) {
    double _clamp(double scale) => scale.clamp(scaleBoundaries.minScale, scaleBoundaries.maxScale);

    switch (scaleState) {
      case ScaleState.initial:
      case ScaleState.zoomedIn:
      case ScaleState.zoomedOut:
        return _clamp(scaleBoundaries.initialScale);
      case ScaleState.covering:
        return _clamp(ScaleLevel.scaleForCovering(scaleBoundaries.viewportSize, scaleBoundaries.childSize));
      case ScaleState.originalSize:
        return _clamp(scaleBoundaries.originalScale);
      default:
        return null;
    }
  }
}