ente/lib/ui/gallery.dart

import 'dart:async';

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:logging/logging.dart';
import 'package:photos/core/event_bus.dart';
import 'package:photos/events/files_updated_event.dart';
import 'package:photos/models/file.dart';
import 'package:photos/models/selected_files.dart';
import 'package:photos/ui/common_elements.dart';
import 'package:photos/ui/huge_listview/huge_listview.dart';
import 'package:photos/ui/huge_listview/lazy_loading_gallery.dart';
import 'package:photos/ui/loading_widget.dart';
import 'package:photos/utils/date_time_util.dart';
import 'package:scrollable_positioned_list/scrollable_positioned_list.dart';

class Gallery extends StatefulWidget {
  final Future<List<File>> Function(int creationStartTime, int creationEndTime,
      {int limit}) asyncLoader;
  final Stream<FilesUpdatedEvent> reloadEvent;
  final SelectedFiles selectedFiles;
  final String tagPrefix;
  final Widget headerWidget;

  Gallery({
    @required this.asyncLoader,
    @required this.selectedFiles,
    @required this.tagPrefix,
    this.reloadEvent,
    this.headerWidget,
  });

  @override
  _GalleryState createState() {
    return _GalleryState();
  }
}

class _GalleryState extends State<Gallery> {
  static const int kInitialLoadLimit = 100;

  final _hugeListViewKey = GlobalKey<HugeListViewState>();

  Logger _logger;
  int _index = 0;
  List<File> _files = [];
  List<List<File>> _collatedFiles = [];
  bool _hasLoadedFiles = false;
  StreamSubscription<FilesUpdatedEvent> _reloadEventSubscription;

  @override
  void initState() {
    _logger = Logger("Gallery_" + widget.tagPrefix);
    _logger.info("initState");
    if (widget.reloadEvent != null) {
      _reloadEventSubscription = widget.reloadEvent.listen((event) {
        _logger.info("Building gallery because reload event fired");
        _loadFiles();
      });
    }
    _loadFiles(limit: kInitialLoadLimit).then((value) => _loadFiles());
    super.initState();
  }

  Future<bool> _loadFiles({int limit}) async {
    _logger.info("Loading files");
    final startTime = DateTime.now().microsecondsSinceEpoch;
    final files = await widget
        .asyncLoader(0, DateTime.now().microsecondsSinceEpoch, limit: limit);
    final endTime = DateTime.now().microsecondsSinceEpoch;
    final duration = Duration(microseconds: endTime - startTime);
    _logger.info(
        "Time taken to load: " + duration.inMilliseconds.toString() + "ms");
    final collatedFiles = _collateFiles(files);
    if (_collatedFiles.length != collatedFiles.length) {
      if (mounted) {
        _logger.info("Days updated");
        setState(() {
          _hasLoadedFiles = true;
          _files = files;
          _collatedFiles = collatedFiles;
        });
      }
    } else {
      _files = files;
      _collatedFiles = collatedFiles;
    }
    return true;
  }

  @override
  void dispose() {
    _reloadEventSubscription.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    _logger.info("Building " + widget.tagPrefix);
    if (!_hasLoadedFiles) {
      return loadWidget;
    }
    return _getListView();
  }

  Widget _getListView() {
    return HugeListView<List<File>>(
      key: _hugeListViewKey,
      controller: ItemScrollController(),
      startIndex: _index,
      totalCount: _collatedFiles.length,
      isDraggableScrollbarEnabled: _collatedFiles.length > 30,
      waitBuilder: (_) {
        return loadWidget;
      },
      emptyResultBuilder: (_) {
        return nothingToSeeHere;
      },
      itemBuilder: (context, index) {
        var gallery;
        gallery = LazyLoadingGallery(
          _files,
          _collatedFiles[index],
          index,
          widget.reloadEvent,
          widget.asyncLoader,
          widget.selectedFiles,
          widget.tagPrefix,
          Bus.instance
              .on<GalleryIndexUpdatedEvent>()
              .where((event) => event.tag == widget.tagPrefix)
              .map((event) => event.index),
        );
        if (widget.headerWidget != null && index == 0) {
          gallery = Column(children: [widget.headerWidget, gallery]);
        }
        return gallery;
      },
      labelTextBuilder: (int index) {
        return getMonthAndYear(DateTime.fromMicrosecondsSinceEpoch(
            _collatedFiles[index][0].creationTime));
      },
      thumbBackgroundColor: Color(0xFF151515),
      thumbDrawColor: Colors.white.withOpacity(0.5),
      firstShown: (int firstIndex) {
        Bus.instance
            .fire(GalleryIndexUpdatedEvent(widget.tagPrefix, firstIndex));
      },
    );
  }

  List<List<File>> _collateFiles(List<File> files) {
    final List<File> dailyFiles = [];
    final List<List<File>> collatedFiles = [];
    for (int index = 0; index < files.length; index++) {
      if (index > 0 &&
          !_areFromSameDay(
              files[index - 1].creationTime, files[index].creationTime)) {
        final List<File> collatedDailyFiles = [];
        collatedDailyFiles.addAll(dailyFiles);
        collatedFiles.add(collatedDailyFiles);
        dailyFiles.clear();
      }
      dailyFiles.add(files[index]);
    }
    if (dailyFiles.isNotEmpty) {
      collatedFiles.add(dailyFiles);
    }
    collatedFiles
        .sort((a, b) => b[0].creationTime.compareTo(a[0].creationTime));
    return collatedFiles;
  }

  bool _areFromSameDay(int firstCreationTime, int secondCreationTime) {
    var firstDate = DateTime.fromMicrosecondsSinceEpoch(firstCreationTime);
    var secondDate = DateTime.fromMicrosecondsSinceEpoch(secondCreationTime);
    return firstDate.year == secondDate.year &&
        firstDate.month == secondDate.month &&
        firstDate.day == secondDate.day;
  }
}

class GalleryIndexUpdatedEvent {
  final String tag;
  final int index;

  GalleryIndexUpdatedEvent(this.tag, this.index);
}