immich/mobile/lib/modules/asset_viewer/ui/remote_photo_view.dart

import 'package:cached_network_image/cached_network_image.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:photo_view/photo_view.dart';

enum _RemoteImageStatus { empty, thumbnail, preview, full }

class _RemotePhotoViewState extends State<RemotePhotoView> {
  late CachedNetworkImageProvider _imageProvider;
  _RemoteImageStatus _status = _RemoteImageStatus.empty;
  bool _zoomedIn = false;

  static const int swipeThreshold = 100;

  @override
  Widget build(BuildContext context) {
    bool allowMoving = _status == _RemoteImageStatus.full;

    return IgnorePointer(
      ignoring: !allowMoving,
      child: PhotoView(
        imageProvider: _imageProvider,
        minScale: PhotoViewComputedScale.contained,
        enablePanAlways: true,
        scaleStateChangedCallback: _scaleStateChanged,
        onScaleEnd: _onScaleListener,
      ),
    );
  }

  void _onScaleListener(
    BuildContext context,
    ScaleEndDetails details,
    PhotoViewControllerValue controllerValue,
  ) {
    // Disable swipe events when zoomed in
    if (_zoomedIn) {
      return;
    }
    if (controllerValue.position.dy > swipeThreshold) {
      widget.onSwipeDown();
    } else if (controllerValue.position.dy < -swipeThreshold) {
      widget.onSwipeUp();
    }
  }

  void _scaleStateChanged(PhotoViewScaleState state) {
    // _onScaleListener;
    _zoomedIn = state != PhotoViewScaleState.initial;
    if (_zoomedIn) {
      widget.isZoomedListener.value = true;
    } else {
      widget.isZoomedListener.value = false;
    }
    widget.isZoomedFunction();
  }

  void _fireStartLoadingEvent() {
    if (widget.onLoadingStart != null) widget.onLoadingStart!();
  }

  void _fireFinishedLoadingEvent() {
    if (widget.onLoadingCompleted != null) widget.onLoadingCompleted!();
  }

  CachedNetworkImageProvider _authorizedImageProvider(String url) {
    return CachedNetworkImageProvider(
      url,
      headers: {"Authorization": widget.authToken},
      cacheKey: url,
    );
  }

  void _performStateTransition(
    _RemoteImageStatus newStatus,
    CachedNetworkImageProvider provider,
  ) {
    if (_status == newStatus) return;

    if (_status == _RemoteImageStatus.full &&
        newStatus == _RemoteImageStatus.thumbnail) return;

    if (_status == _RemoteImageStatus.preview &&
        newStatus == _RemoteImageStatus.thumbnail) return;

    if (_status == _RemoteImageStatus.full &&
        newStatus == _RemoteImageStatus.preview) return;

    if (!mounted) return;

    if (newStatus != _RemoteImageStatus.full) {
      _fireStartLoadingEvent();
    } else {
      _fireFinishedLoadingEvent();
    }

    setState(() {
      _status = newStatus;
      _imageProvider = provider;
    });
  }

  void _loadImages() {
    CachedNetworkImageProvider thumbnailProvider =
        _authorizedImageProvider(widget.thumbnailUrl);
    _imageProvider = thumbnailProvider;

    thumbnailProvider.resolve(const ImageConfiguration()).addListener(
      ImageStreamListener((ImageInfo imageInfo, _) {
        _performStateTransition(
          _RemoteImageStatus.thumbnail,
          thumbnailProvider,
        );
      }),
    );

    if (widget.previewUrl != null) {
      CachedNetworkImageProvider previewProvider =
          _authorizedImageProvider(widget.previewUrl!);
      previewProvider.resolve(const ImageConfiguration()).addListener(
        ImageStreamListener((ImageInfo imageInfo, _) {
          _performStateTransition(_RemoteImageStatus.preview, previewProvider);
        }),
      );
    }

    CachedNetworkImageProvider fullProvider =
        _authorizedImageProvider(widget.imageUrl);
    fullProvider.resolve(const ImageConfiguration()).addListener(
      ImageStreamListener((ImageInfo imageInfo, _) {
        _performStateTransition(_RemoteImageStatus.full, fullProvider);
      }),
    );
  }

  @override
  void initState() {
    _loadImages();
    super.initState();
  }
}

class RemotePhotoView extends StatefulWidget {
  const RemotePhotoView(
      {Key? key,
      required this.thumbnailUrl,
      required this.imageUrl,
      required this.authToken,
      required this.isZoomedFunction,
      required this.isZoomedListener,
      required this.onSwipeDown,
      required this.onSwipeUp,
      this.previewUrl,
      this.onLoadingCompleted,
      this.onLoadingStart})
      : super(key: key);

  final String thumbnailUrl;
  final String imageUrl;
  final String authToken;
  final String? previewUrl;
  final Function? onLoadingCompleted;
  final Function? onLoadingStart;

  final void Function() onSwipeDown;
  final void Function() onSwipeUp;
  final void Function() isZoomedFunction;

  final ValueNotifier<bool> isZoomedListener;

  @override
  State<StatefulWidget> createState() {
    return _RemotePhotoViewState();
  }
}