relatica/lib/models/timeline.dart

import 'dart:collection';

import 'package:flutter/foundation.dart';

import 'timeline_identifiers.dart';

const defaultLowestId = 9223372036854775807;
const defaultHighestId = 0;

enum InsertionType {
  beginning,
  end,
}

class Timeline {
  final TimelineIdentifiers timelineId;
  final List<String> _postIds = [];
  int _lowestStatusId = defaultLowestId;
  int _highestStatusId = defaultHighestId;

  int get highestStatusId => _highestStatusId;

  int get lowestStatusId => _lowestStatusId;

  Timeline(this.timelineId, {List<String>? initialPostIds}) {
    if (initialPostIds != null) {
      _postIds.addAll(initialPostIds);
    }
  }

  List<String> get posts => UnmodifiableListView(_postIds);

  Timeline addOrUpdate(
    List<String> newIds, {
    required InsertionType insertionType,
  }) {
    final newIdsSet = Set.from(newIds);
    final updatedIds = _postIds.where((i) => !newIdsSet.contains(i)).toList();

    for (final idString in newIds) {
      final id = int.parse(idString);
      if (_lowestStatusId > id) {
        _lowestStatusId = id;
      }

      if (_highestStatusId < id) {
        _highestStatusId = id;
      }
    }

    switch (insertionType) {
      case InsertionType.beginning:
        updatedIds.insertAll(0, newIds);
        break;
      case InsertionType.end:
        updatedIds.addAll(newIds);
        break;
    }

    final existingIds = <String>{};
    for (int i = 0; i < updatedIds.length; i++) {
      final id = updatedIds[i];
      if (existingIds.contains(id)) {
        updatedIds.removeAt(i);
      } else {
        existingIds.add(id);
      }
    }

    updatedIds.sort((p1, p2) {
      final id1 = num.parse(p1);
      final id2 = num.parse(p2);
      return id2.compareTo(id1);
    });

    return Timeline(timelineId, initialPostIds: updatedIds)
      .._lowestStatusId = lowestStatusId
      .._highestStatusId = highestStatusId;
  }

  bool removeTimelineEntry(String id) {
    return _postIds.remove(id);
  }

  void clear() {
    _postIds.clear();
    _lowestStatusId = defaultLowestId;
    _highestStatusId = defaultHighestId;
  }

  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
      other is Timeline &&
          runtimeType == other.runtimeType &&
          timelineId == other.timelineId &&
          listEquals(_postIds, other._postIds);

  @override
  int get hashCode => timelineId.hashCode ^ Object.hashAll(_postIds);
}