aves/lib/widgets/viewer/controller.dart

import 'dart:async';
import 'dart:math';

import 'package:aves/model/entry.dart';
import 'package:aves/model/settings/enums/enums.dart';
import 'package:aves/theme/durations.dart';
import 'package:aves_magnifier/aves_magnifier.dart';
import 'package:flutter/widgets.dart';

class ViewerController {
  final ValueNotifier<AvesEntry?> entryNotifier = ValueNotifier(null);
  final ViewerTransition transition;
  final Duration? autopilotInterval;
  final bool autopilotAnimatedZoom;
  final bool repeat;

  late final ScaleLevel _initialScale;
  late final ValueNotifier<bool> _autopilotNotifier;
  Timer? _playTimer;
  final StreamController _streamController = StreamController.broadcast();
  final Map<TickerProvider, AnimationController> _autopilotAnimationControllers = {};
  ScaleLevel? _autopilotInitialScale;

  Stream<dynamic> get _events => _streamController.stream;

  Stream<ViewerShowNextEvent> get showNextCommands => _events.where((event) => event is ViewerShowNextEvent).cast<ViewerShowNextEvent>();

  Stream<ViewerOverlayToggleEvent> get overlayCommands => _events.where((event) => event is ViewerOverlayToggleEvent).cast<ViewerOverlayToggleEvent>();

  bool get autopilot => _autopilotNotifier.value;

  set autopilot(bool enabled) => _autopilotNotifier.value = enabled;

  ScaleLevel get initialScale => _autopilotInitialScale ?? _initialScale;

  static final _autopilotScaleTweens = [
    Tween<double>(begin: 1, end: 1.2),
    Tween<double>(begin: 1.2, end: 1),
  ];

  ViewerController({
    ScaleLevel initialScale = const ScaleLevel(ref: ScaleReference.contained),
    this.transition = ViewerTransition.parallax,
    this.repeat = false,
    bool autopilot = false,
    this.autopilotInterval,
    this.autopilotAnimatedZoom = false,
  }) {
    _initialScale = initialScale;
    _autopilotNotifier = ValueNotifier(autopilot);
    _autopilotNotifier.addListener(_onAutopilotChanged);
    _onAutopilotChanged();
  }

  void dispose() {
    _autopilotNotifier.removeListener(_onAutopilotChanged);
    _clearAutopilotAnimations();
    _stopPlayTimer();
    _streamController.close();
  }

  void _onAutopilotChanged() {
    _clearAutopilotAnimations();
    _stopPlayTimer();
    if (autopilot && autopilotInterval != null) {
      _playTimer = Timer.periodic(autopilotInterval!, (_) => _streamController.add(ViewerShowNextEvent()));
      _streamController.add(const ViewerOverlayToggleEvent(visible: false));
    }
  }

  void _stopPlayTimer() => _playTimer?.cancel();

  void _clearAutopilotAnimations() => _autopilotAnimationControllers.keys.toSet().forEach((v) => stopAutopilotAnimation(vsync: v));

  void stopAutopilotAnimation({required TickerProvider vsync}) => _autopilotAnimationControllers.remove(vsync)?.dispose();

  void startAutopilotAnimation({
    required TickerProvider vsync,
    required void Function({required ScaleLevel scaleLevel}) onUpdate,
  }) {
    stopAutopilotAnimation(vsync: vsync);
    if (!autopilot || !autopilotAnimatedZoom) return;

    final scaleLevelRef = _initialScale.ref;
    final scaleFactorTween = _autopilotScaleTweens[Random().nextInt(_autopilotScaleTweens.length)];
    _autopilotInitialScale = ScaleLevel(ref: scaleLevelRef, factor: scaleFactorTween.begin!);

    final animationController = AnimationController(
      duration: autopilotInterval,
      vsync: vsync,
    );
    animationController.addListener(() => onUpdate.call(
          scaleLevel: ScaleLevel(
            ref: scaleLevelRef,
            factor: scaleFactorTween.evaluate(CurvedAnimation(
              parent: animationController,
              curve: Curves.linear,
            )),
          ),
        ));
    _autopilotAnimationControllers[vsync] = animationController;
    Future.delayed(Durations.viewerHorizontalPageAnimation).then((_) => _autopilotAnimationControllers[vsync]?.forward());
  }
}

@immutable
class ViewerShowNextEvent {}

@immutable
class ViewerOverlayToggleEvent {
  final bool? visible;

  const ViewerOverlayToggleEvent({required this.visible});
}

class PageTransitionEffects {
  static TransitionBuilder fade(
    PageController pageController,
    int index, {
    required bool zoomIn,
  }) =>
      (context, child) {
        double opacity = 0;
        double dx = 0;
        double scale = 1;
        if (pageController.hasClients && pageController.position.haveDimensions) {
          final position = (pageController.page! - index).clamp(-1.0, 1.0);
          final width = pageController.position.viewportDimension;
          opacity = (1 - position.abs()).clamp(0, 1);
          dx = position * width;
          if (zoomIn) {
            scale = 1 + position;
          }
        }
        return Opacity(
          opacity: opacity,
          child: Transform.translate(
            offset: Offset(dx, 0),
            child: Transform.scale(
              scale: scale,
              child: child,
            ),
          ),
        );
      };

  static TransitionBuilder slide(
    PageController pageController,
    int index, {
    required bool parallax,
  }) =>
      (context, child) {
        double dx = 0;
        if (pageController.hasClients && pageController.position.haveDimensions) {
          final position = (pageController.page! - index).clamp(-1.0, 1.0);
          final width = pageController.position.viewportDimension;
          if (parallax) {
            dx = position * width / 2;
          }
        }
        return ClipRect(
          child: Transform.translate(
            offset: Offset(dx, 0),
            child: child,
          ),
        );
      };

  static TransitionBuilder none(
    PageController pageController,
    int index,
  ) =>
      (context, child) {
        double opacity = 0;
        double dx = 0;
        if (pageController.hasClients && pageController.position.haveDimensions) {
          final position = (pageController.page! - index).clamp(-1.0, 1.0);
          final width = pageController.position.viewportDimension;
          opacity = (1 - position.abs()).roundToDouble().clamp(0, 1);
          dx = position * width;
        }
        return Opacity(
          opacity: opacity,
          child: Transform.translate(
            offset: Offset(dx, 0),
            child: child,
          ),
        );
      };
}