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| 1 | +import 'dart:math' as math; |
| 2 | + |
| 3 | +import '../api/model/model.dart'; |
| 4 | + |
| 5 | +extension Max<T extends num> on Iterable<T> { |
| 6 | + /// Finds the maximum number in an [Iterable]. |
| 7 | + /// |
| 8 | + /// Returns null if the [Iterable] is empty. |
| 9 | + T? max() => isNotEmpty ? reduce(math.max) : null; |
| 10 | +} |
| 11 | + |
| 12 | +extension PossibleIndex<T extends num> on List<T> { |
| 13 | + /// The index of [element] in this sorted list. |
| 14 | + /// |
| 15 | + /// Uses binary search to find the index, so the list must be sorted, |
| 16 | + /// otherwise the result is unpredictable. |
| 17 | + /// |
| 18 | + /// If [element] is found, returns its index (0-based). |
| 19 | + /// |
| 20 | + /// ```dart |
| 21 | + /// final somePrimes = [11, 13, 17, 23, 27, 29]; |
| 22 | + /// final index = somePrimes.possibleIndexOf(17); // 2 |
| 23 | + /// ``` |
| 24 | + /// If [element] is not found, returns the possible index (1-based) |
| 25 | + /// with a negative sign, where if the [element] is inserted, |
| 26 | + /// the order of the list is maintained. |
| 27 | + /// |
| 28 | + /// ```dart |
| 29 | + /// final somePrimes = [11, 13, 17, 23, 27, 29]; |
| 30 | + /// int index = somePrimes.possibleIndexOf(7); // -1 |
| 31 | + /// index = somePrimes.possibleIndexOf(19); // -4 |
| 32 | + /// ``` |
| 33 | + int possibleIndexOf(T element) { |
| 34 | + int low = 0; |
| 35 | + int high = length - 1; |
| 36 | + |
| 37 | + while (high >= low) { |
| 38 | + int mid = (low + high) ~/ 2; |
| 39 | + if (element == this[mid]) { |
| 40 | + return mid; |
| 41 | + } else if (element < this[mid]) { |
| 42 | + high = mid - 1; |
| 43 | + } else { |
| 44 | + low = mid + 1; |
| 45 | + } |
| 46 | + } |
| 47 | + return -low - 1; |
| 48 | + } |
| 49 | +} |
| 50 | + |
| 51 | +/// A data structure to keep track of message ids. |
| 52 | +class IdTracker { |
| 53 | + final List<int> _ids = []; |
| 54 | + |
| 55 | + void add(int id) { |
| 56 | + if (_ids.isEmpty) { |
| 57 | + _ids.add(id); |
| 58 | + } else { |
| 59 | + int i = _ids.possibleIndexOf(id); |
| 60 | + if (i >= 0) { // the [id] already exists, so do not add it. |
| 61 | + return; |
| 62 | + } |
| 63 | + i = -i - 1; // change the index back to 0-based for readability. |
| 64 | + if (i == _ids.length) { // the [id] should be added to the end of the list. |
| 65 | + _ids.add(id); |
| 66 | + } else { |
| 67 | + _ids.insert(i, id); |
| 68 | + } |
| 69 | + } |
| 70 | + } |
| 71 | + |
| 72 | + // TODO: remove |
| 73 | + |
| 74 | + /// The maximum id in the tracker list. |
| 75 | + /// |
| 76 | + /// Returns -1 if the tracker list is empty. |
| 77 | + int get maxId => _ids.isNotEmpty ? _ids.last : -1; |
| 78 | + |
| 79 | + @override |
| 80 | + String toString() { |
| 81 | + return _ids.toString(); |
| 82 | + } |
| 83 | +} |
| 84 | + |
| 85 | +/// A data structure to keep track of stream and topic messages. |
| 86 | +/// |
| 87 | +/// The owner should call [clear] in order to free resources. |
| 88 | +class RecentSenders { |
| 89 | + // streamSenders[streamId][senderId] = IdTracker |
| 90 | + final Map<int, Map<int, IdTracker>> _streamSenders = {}; |
| 91 | + |
| 92 | + // topicSenders[streamId][topic][senderId] = IdTracker |
| 93 | + final Map<int, Map<String, Map<int, IdTracker>>> _topicSenders = {}; |
| 94 | + |
| 95 | + void clear() { |
| 96 | + _streamSenders.clear(); |
| 97 | + _topicSenders.clear(); |
| 98 | + } |
| 99 | + |
| 100 | + int maxIdForStreamSender({required int streamId, required int senderId}) { |
| 101 | + return _streamSenders[streamId]?[senderId]?.maxId ?? -1; |
| 102 | + } |
| 103 | + |
| 104 | + int maxIdForStreamTopicSender({ |
| 105 | + required int streamId, |
| 106 | + required String topic, |
| 107 | + required int senderId, |
| 108 | + }) { |
| 109 | + topic = topic.toLowerCase(); |
| 110 | + return _topicSenders[streamId]?[topic]?[senderId]?.maxId ?? -1; |
| 111 | + } |
| 112 | + |
| 113 | + void addStreamMessage({ |
| 114 | + required int streamId, |
| 115 | + required int senderId, |
| 116 | + required messageId, |
| 117 | + }) { |
| 118 | + final senderMap = _streamSenders[streamId] ?? {}; |
| 119 | + final idTracker = senderMap[senderId] ?? IdTracker(); |
| 120 | + _streamSenders[streamId] = senderMap; |
| 121 | + senderMap[senderId] = idTracker; |
| 122 | + idTracker.add(messageId); |
| 123 | + } |
| 124 | + |
| 125 | + void addTopicMessage({ |
| 126 | + required int streamId, |
| 127 | + required String topic, |
| 128 | + required int senderId, |
| 129 | + required messageId, |
| 130 | + }) { |
| 131 | + topic = topic.toLowerCase(); |
| 132 | + final topicMap = _topicSenders[streamId] ?? {}; |
| 133 | + final senderMap = topicMap[topic] ?? {}; |
| 134 | + final idTracker = senderMap[senderId] ?? IdTracker(); |
| 135 | + _topicSenders[streamId] = topicMap; |
| 136 | + topicMap[topic] = senderMap; |
| 137 | + senderMap[senderId] = idTracker; |
| 138 | + idTracker.add(messageId); |
| 139 | + } |
| 140 | + |
| 141 | + void processStreamMessage(Message message) { |
| 142 | + if (message is! StreamMessage) { |
| 143 | + return; |
| 144 | + } |
| 145 | + |
| 146 | + final streamId = message.streamId; |
| 147 | + final topic = message.subject; |
| 148 | + final senderId = message.senderId; |
| 149 | + final messageId = message.id; |
| 150 | + |
| 151 | + addStreamMessage( |
| 152 | + streamId: streamId, senderId: senderId, messageId: messageId); |
| 153 | + addTopicMessage( |
| 154 | + streamId: streamId, |
| 155 | + topic: topic, |
| 156 | + senderId: senderId, |
| 157 | + messageId: messageId); |
| 158 | + } |
| 159 | + |
| 160 | + // TODO: removeTopicMessage |
| 161 | + |
| 162 | + int compareByRecency({ |
| 163 | + required User userA, |
| 164 | + required User userB, |
| 165 | + required int streamId, |
| 166 | + // TODO(#493): may turn this into a non-nullable string. |
| 167 | + required String? topic, |
| 168 | + }) { |
| 169 | + int aMessageId, bMessageId; |
| 170 | + |
| 171 | + if (topic != null) { |
| 172 | + aMessageId = maxIdForStreamTopicSender( |
| 173 | + streamId: streamId, topic: topic, senderId: userA.userId); |
| 174 | + bMessageId = maxIdForStreamTopicSender( |
| 175 | + streamId: streamId, topic: topic, senderId: userB.userId); |
| 176 | + |
| 177 | + if (aMessageId != bMessageId) { |
| 178 | + return bMessageId - aMessageId; |
| 179 | + } |
| 180 | + } |
| 181 | + |
| 182 | + aMessageId = |
| 183 | + maxIdForStreamSender(streamId: streamId, senderId: userA.userId); |
| 184 | + bMessageId = |
| 185 | + maxIdForStreamSender(streamId: streamId, senderId: userB.userId); |
| 186 | + |
| 187 | + return bMessageId - aMessageId; |
| 188 | + } |
| 189 | +} |
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