Source Code added

mobile/lib/presentation/widgets/timeline/segment.model.dart

@@ -0,0 +1,95 @@
+import 'package:collection/collection.dart';
+import 'package:flutter/widgets.dart';
+import 'package:immich_mobile/domain/models/timeline.model.dart';
+
+// Segments are the time groups buckets in the timeline view.
+// Each segment contains a header and a list of asset rows.
+abstract class Segment {
+  // The index of the first row of the segment, usually the header, but if not, it can be any asset.
+  final int firstIndex;
+  // The index of the last asset of the segment.
+  final int lastIndex;
+  // The offset of the first row from beginning of the timeline.
+  final double startOffset;
+  // The offset of the last row from beginning of the timeline.
+  final double endOffset;
+  // The spacing between the header and the first row of the segment.
+  final double spacing;
+  final double headerExtent;
+  // the start index of the asset of this segment from the beginning of the timeline.
+  final int firstAssetIndex;
+  final Bucket bucket;
+
+  // The index of the row after the header
+  final int gridIndex;
+  // The offset of the row after the header
+  final double gridOffset;
+  // The type of the header
+  final HeaderType header;
+
+  const Segment({
+    required this.firstIndex,
+    required this.lastIndex,
+    required this.startOffset,
+    required this.endOffset,
+    required this.firstAssetIndex,
+    required this.bucket,
+    required this.headerExtent,
+    required this.spacing,
+    required this.header,
+  }) : gridIndex = firstIndex + 1,
+       gridOffset = startOffset + headerExtent + spacing;
+
+  bool containsIndex(int index) => firstIndex <= index && index <= lastIndex;
+
+  bool isWithinOffset(double offset) => startOffset <= offset && offset <= endOffset;
+
+  int getMinChildIndexForScrollOffset(double scrollOffset);
+  int getMaxChildIndexForScrollOffset(double scrollOffset);
+  double indexToLayoutOffset(int index);
+
+  Widget builder(BuildContext context, int index);
+
+  @override
+  bool operator ==(Object other) {
+    if (identical(this, other)) return true;
+
+    return other is Segment &&
+        other.firstIndex == firstIndex &&
+        other.lastIndex == lastIndex &&
+        other.startOffset == startOffset &&
+        other.endOffset == endOffset &&
+        other.spacing == spacing &&
+        other.firstAssetIndex == firstAssetIndex &&
+        other.headerExtent == headerExtent &&
+        other.gridIndex == gridIndex &&
+        other.gridOffset == gridOffset &&
+        other.header == header;
+  }
+
+  @override
+  int get hashCode =>
+      firstIndex.hashCode ^
+      lastIndex.hashCode ^
+      startOffset.hashCode ^
+      endOffset.hashCode ^
+      spacing.hashCode ^
+      headerExtent.hashCode ^
+      firstAssetIndex.hashCode ^
+      gridIndex.hashCode ^
+      gridOffset.hashCode ^
+      header.hashCode;
+
+  @override
+  String toString() {
+    return 'Segment(firstIndex: $firstIndex, lastIndex: $lastIndex)';
+  }
+}
+
+extension SegmentListExtension on List<Segment> {
+  bool equals(List<Segment> other) => length == other.length && lastOrNull?.endOffset == other.lastOrNull?.endOffset;
+
+  Segment? findByIndex(int index) => firstWhereOrNull((s) => s.containsIndex(index));
+
+  Segment? findByOffset(double offset) => firstWhereOrNull((s) => s.isWithinOffset(offset)) ?? lastOrNull;
+}