refactor(web): extract PhotostreamManager base class

web/src/lib/components/timeline/Timeline.svelte

@@ -33,7 +33,7 @@
   import { deleteAssets, updateStackedAssetInTimeline, updateUnstackedAssetInTimeline } from '$lib/utils/actions';
   import { archiveAssets, cancelMultiselect, selectAllAssets, stackAssets } from '$lib/utils/asset-utils';
   import { navigate } from '$lib/utils/navigation';
-  import { getTimes, toTimelineAsset, type ScrubberListener, type TimelineYearMonth } from '$lib/utils/timeline-util';
+  import { getSegmentIdentifier, getTimes, toTimelineAsset, type ScrubberListener, type TimelineYearMonth } from '$lib/utils/timeline-util';
   import { AssetVisibility, getAssetInfo, type AlbumResponseDto, type PersonResponseDto } from '@immich/sdk';
   import { modalManager } from '@immich/ui';
   import { DateTime } from 'luxon';
@@ -670,7 +670,7 @@
           break;
         }
         if (started) {
-          await timelineManager.loadMonthGroup(monthGroup.yearMonth);
+          await timelineManager.loadSegment(monthGroup.identifier);
           for (const asset of monthGroup.assetsIterator()) {
             if (deselect) {
               assetInteraction.removeAssetFromMultiselectGroup(asset.id);
@@ -811,7 +811,7 @@
   $effect(() => {
     if ($showAssetViewer) {
       const { localDateTime } = getTimes($viewingAsset.fileCreatedAt, DateTime.local().offset / 60);
-      void timelineManager.loadMonthGroup({ year: localDateTime.year, month: localDateTime.month });
+      void timelineManager.loadSegment(getSegmentIdentifier({ year: localDateTime.year, month: localDateTime.month }));
     }
   });
 </script>

web/src/lib/managers/timeline-manager/PhotostreamManager.svelte.ts

@@ -0,0 +1,293 @@
+import { updateIntersectionMonthGroup } from '$lib/managers/timeline-manager/internal/intersection-support.svelte';
+import { updateGeometry } from '$lib/managers/timeline-manager/internal/layout-support.svelte';
+import { CancellableTask } from '$lib/utils/cancellable-task';
+import { clamp, debounce } from 'lodash-es';
+
+import type { PhotostreamSegment, SegmentIdentifier } from '$lib/managers/timeline-manager/PhotostreamSegment.svelte';
+import type { MonthGroup } from '$lib/managers/timeline-manager/month-group.svelte';
+import type { TimelineManagerLayoutOptions, TimelineManagerOptions, Viewport } from './types';
+
+export abstract class PhotostreamManager {
+  isInitialized = $state(false);
+  topSectionHeight = $state(0);
+  bottomSectionHeight = $state(60);
+  abstract get months(): PhotostreamSegment[];
+  timelineHeight = $derived.by(
+    () => this.months.reduce((accumulator, b) => accumulator + b.height, 0) + this.topSectionHeight,
+  );
+  assetCount = $derived.by(() => this.months.reduce((accumulator, b) => accumulator + b.assetsCount, 0));
+
+  topIntersectingMonthGroup: PhotostreamSegment | undefined = $state();
+
+  visibleWindow = $derived.by(() => ({
+    top: this.#scrollTop,
+    bottom: this.#scrollTop + this.viewportHeight,
+  }));
+
+  protected initTask = new CancellableTask(
+    () => (this.isInitialized = true),
+    () => (this.isInitialized = false),
+    () => void 0,
+  );
+
+  protected options: TimelineManagerOptions = {};
+
+  #viewportHeight = $state(0);
+  #viewportWidth = $state(0);
+  #scrollTop = $state(0);
+
+  #rowHeight = $state(235);
+  #headerHeight = $state(48);
+  #gap = $state(12);
+
+  #scrolling = $state(false);
+  #suspendTransitions = $state(false);
+  #resetScrolling = debounce(() => (this.#scrolling = false), 1000);
+  #resetSuspendTransitions = debounce(() => (this.suspendTransitions = false), 1000);
+  scrollCompensation: {
+    heightDelta: number | undefined;
+    scrollTop: number | undefined;
+    monthGroup: PhotostreamSegment | undefined;
+  } = $state({
+    heightDelta: 0,
+    scrollTop: 0,
+    monthGroup: undefined,
+  });
+
+  constructor() {}
+
+  setLayoutOptions({ headerHeight = 48, rowHeight = 235, gap = 12 }: TimelineManagerLayoutOptions) {
+    let changed = false;
+    changed ||= this.#setHeaderHeight(headerHeight);
+    changed ||= this.#setGap(gap);
+    changed ||= this.#setRowHeight(rowHeight);
+    if (changed) {
+      this.refreshLayout();
+    }
+  }
+
+  #setHeaderHeight(value: number) {
+    if (this.#headerHeight == value) {
+      return false;
+    }
+    this.#headerHeight = value;
+    return true;
+  }
+
+  get headerHeight() {
+    return this.#headerHeight;
+  }
+
+  #setGap(value: number) {
+    if (this.#gap == value) {
+      return false;
+    }
+    this.#gap = value;
+    return true;
+  }
+
+  get gap() {
+    return this.#gap;
+  }
+
+  #setRowHeight(value: number) {
+    if (this.#rowHeight == value) {
+      return false;
+    }
+    this.#rowHeight = value;
+    return true;
+  }
+
+  get rowHeight() {
+    return this.#rowHeight;
+  }
+
+  set scrolling(value: boolean) {
+    this.#scrolling = value;
+    if (value) {
+      this.suspendTransitions = true;
+      this.#resetScrolling();
+    }
+  }
+
+  get scrolling() {
+    return this.#scrolling;
+  }
+
+  set suspendTransitions(value: boolean) {
+    this.#suspendTransitions = value;
+    if (value) {
+      this.#resetSuspendTransitions();
+    }
+  }
+
+  get suspendTransitions() {
+    return this.#suspendTransitions;
+  }
+
+  set viewportWidth(value: number) {
+    const changed = value !== this.#viewportWidth;
+    this.#viewportWidth = value;
+    this.suspendTransitions = true;
+    void this.updateViewportGeometry(changed);
+  }
+
+  get viewportWidth() {
+    return this.#viewportWidth;
+  }
+
+  set viewportHeight(value: number) {
+    this.#viewportHeight = value;
+    this.#suspendTransitions = true;
+    void this.updateViewportGeometry(false);
+  }
+
+  get viewportHeight() {
+    return this.#viewportHeight;
+  }
+
+  updateSlidingWindow(scrollTop: number) {
+    if (this.#scrollTop !== scrollTop) {
+      this.#scrollTop = scrollTop;
+      this.updateIntersections();
+    }
+  }
+
+  clearScrollCompensation() {
+    this.scrollCompensation = {
+      heightDelta: undefined,
+      scrollTop: undefined,
+      monthGroup: undefined,
+    };
+  }
+
+  updateIntersections() {
+    if (!this.isInitialized || this.visibleWindow.bottom === this.visibleWindow.top) {
+      return;
+    }
+    let topIntersectingMonthGroup = undefined;
+    for (const month of this.months) {
+      updateIntersectionMonthGroup(this, month);
+      if (!topIntersectingMonthGroup && month.actuallyIntersecting) {
+        topIntersectingMonthGroup = month;
+      }
+    }
+    if (topIntersectingMonthGroup !== undefined && this.topIntersectingMonthGroup !== topIntersectingMonthGroup) {
+      this.topIntersectingMonthGroup = topIntersectingMonthGroup;
+    }
+    for (const month of this.months) {
+      if (month === this.topIntersectingMonthGroup) {
+        this.topIntersectingMonthGroup.percent = clamp(
+          (this.visibleWindow.top - this.topIntersectingMonthGroup.top) / this.topIntersectingMonthGroup.height,
+          0,
+          1,
+        );
+      } else {
+        month.percent = 0;
+      }
+    }
+  }
+
+  protected async init(options: TimelineManagerOptions) {
+    this.isInitialized = true;
+    // this.months = [];
+
+    await this.initTask.execute(async () => undefined, true);
+  }
+
+  public destroy() {
+    this.isInitialized = false;
+  }
+
+  async updateViewport(viewport: Viewport) {
+    if (viewport.height === 0 && viewport.width === 0) {
+      return;
+    }
+
+    if (this.viewportHeight === viewport.height && this.viewportWidth === viewport.width) {
+      return;
+    }
+
+    if (!this.initTask.executed) {
+      await (this.initTask.loading ? this.initTask.waitUntilCompletion() : this.init(this.options));
+    }
+
+    const changedWidth = viewport.width !== this.viewportWidth;
+    this.viewportHeight = viewport.height;
+    this.viewportWidth = viewport.width;
+    this.updateViewportGeometry(changedWidth);
+  }
+
+  protected updateViewportGeometry(changedWidth: boolean) {
+    if (!this.isInitialized) {
+      return;
+    }
+    if (this.viewportWidth === 0 || this.viewportHeight === 0) {
+      return;
+    }
+    for (const month of this.months) {
+      updateGeometry(this, month, { invalidateHeight: changedWidth });
+    }
+    this.updateIntersections();
+  }
+
+  createLayoutOptions() {
+    const viewportWidth = this.viewportWidth;
+
+    return {
+      spacing: 2,
+      heightTolerance: 0.15,
+      rowHeight: this.#rowHeight,
+      rowWidth: Math.floor(viewportWidth),
+    };
+  }
+
+  async loadSegment(identifier: SegmentIdentifier, options?: { cancelable: boolean }): Promise<void> {
+    let cancelable = true;
+    if (options) {
+      cancelable = options.cancelable;
+    }
+    const segment = this.getSegmentByIdentifier(identifier);
+    if (!segment) {
+      return;
+    }
+
+    if (segment.loader?.executed) {
+      return;
+    }
+
+    const result = await segment.loader?.execute(async (signal: AbortSignal) => {
+      await this.fetchSegment(segment, signal);
+    }, cancelable);
+    if (result === 'LOADED') {
+      updateIntersectionMonthGroup(this, segment);
+    }
+  }
+
+  getSegmentMatcher(identifier: SegmentIdentifier) {
+    return (segment: MonthGroup) => {
+      return identifier;
+    };
+  }
+  getSegmentByIdentifier(identifier: SegmentIdentifier) {
+    return this.months.find((segment) => identifier.matches(segment));
+  }
+
+  protected abstract fetchSegment(segment: PhotostreamSegment, signal: AbortSignal): Promise<void>;
+
+  refreshLayout() {
+    for (const month of this.months) {
+      updateGeometry(this, month, { invalidateHeight: true });
+    }
+    this.updateIntersections();
+  }
+
+  getMaxScrollPercent() {
+    const totalHeight = this.timelineHeight + this.bottomSectionHeight + this.topSectionHeight;
+    return (totalHeight - this.viewportHeight) / totalHeight;
+  }
+
+  getMaxScroll() {
+    return this.topSectionHeight + this.bottomSectionHeight + (this.timelineHeight - this.viewportHeight);
+  }
+}

web/src/lib/managers/timeline-manager/PhotostreamSegment.svelte.ts

@@ -0,0 +1,133 @@
+import { CancellableTask } from '$lib/utils/cancellable-task';
+import { handleError } from '$lib/utils/handle-error';
+import { t } from 'svelte-i18n';
+import { get } from 'svelte/store';
+
+import type { PhotostreamManager } from '$lib/managers/timeline-manager/PhotostreamManager.svelte';
+import type { TimelineAsset } from '$lib/managers/timeline-manager/types';
+
+export type SegmentIdentifier = {
+  matches(segment: PhotostreamSegment): boolean;
+};
+export abstract class PhotostreamSegment {
+  #intersecting = $state(false);
+  actuallyIntersecting = $state(false);
+  #isLoaded = $state(false);
+
+  #height = $state(0);
+  #top = $state(0);
+
+  initialCount = $state(0);
+  percent = $state(0);
+  assetsCount = $derived(this.isLoaded ? this.getAssets().length : this.initialCount);
+  loader = new CancellableTask(
+    () => this.markLoaded(),
+    () => this.markCanceled,
+    () => this.handleLoadError,
+  );
+  isHeightActual = $state(false);
+
+  abstract get timelineManager(): PhotostreamManager;
+
+  abstract get identifier(): SegmentIdentifier;
+
+  get isLoaded() {
+    return this.#isLoaded;
+  }
+
+  protected markLoaded() {
+    this.#isLoaded = true;
+  }
+
+  protected markCanceled() {
+    this.#isLoaded = false;
+  }
+
+  set intersecting(newValue: boolean) {
+    const old = this.#intersecting;
+    if (old === newValue) {
+      return;
+    }
+    this.#intersecting = newValue;
+    if (newValue) {
+      this.load();
+    } else {
+      this.cancel();
+    }
+  }
+
+  get intersecting() {
+    return this.#intersecting;
+  }
+
+  abstract load(): Promise<void>;
+
+  abstract getAssets(): TimelineAsset[];
+
+  set height(height: number) {
+    if (this.#height === height) {
+      return;
+    }
+    const { timelineManager: store, percent } = this;
+    const index = store.months.indexOf(this);
+    const heightDelta = height - this.#height;
+    this.#height = height;
+    const prevMonthGroup = store.months[index - 1];
+    if (prevMonthGroup) {
+      const newTop = prevMonthGroup.#top + prevMonthGroup.#height;
+      if (this.#top !== newTop) {
+        this.#top = newTop;
+      }
+    }
+    for (let cursor = index + 1; cursor < store.months.length; cursor++) {
+      const monthGroup = this.timelineManager.months[cursor];
+      const newTop = monthGroup.#top + heightDelta;
+      if (monthGroup.#top !== newTop) {
+        monthGroup.#top = newTop;
+      }
+    }
+    if (store.topIntersectingMonthGroup) {
+      const currentIndex = store.months.indexOf(store.topIntersectingMonthGroup);
+      if (currentIndex > 0) {
+        if (index < currentIndex) {
+          store.scrollCompensation = {
+            heightDelta,
+            scrollTop: undefined,
+            monthGroup: this,
+          };
+        } else if (percent > 0) {
+          const top = this.top + height * percent;
+          store.scrollCompensation = {
+            heightDelta: undefined,
+            scrollTop: top,
+            monthGroup: this,
+          };
+        }
+      }
+    }
+  }
+
+  get height() {
+    return this.#height;
+  }
+
+  get top(): number {
+    return this.#top + this.timelineManager.topSectionHeight;
+  }
+
+  protected handleLoadError(error: unknown) {
+    const _$t = get(t);
+    handleError(error, _$t('errors.failed_to_load_assets'));
+  }
+
+  cancel() {
+    this.loader?.cancel();
+  }
+
+  layout(_noDefer: boolean) {}
+
+  updateIntersection({ intersecting, actuallyIntersecting }: { intersecting: boolean; actuallyIntersecting: boolean }) {
+    this.intersecting = intersecting;
+    this.actuallyIntersecting = actuallyIntersecting;
+  }
+}

web/src/lib/managers/timeline-manager/internal/intersection-support.svelte.ts

@@ -1,27 +1,24 @@
+import type { PhotostreamManager } from '$lib/managers/timeline-manager/PhotostreamManager.svelte';
+import type { PhotostreamSegment } from '$lib/managers/timeline-manager/PhotostreamSegment.svelte';
 import { TUNABLES } from '$lib/utils/tunables';
-import type { MonthGroup } from '../month-group.svelte';
 import type { TimelineManager } from '../timeline-manager.svelte';
 
 const {
   TIMELINE: { INTERSECTION_EXPAND_TOP, INTERSECTION_EXPAND_BOTTOM },
 } = TUNABLES;
 
-export function updateIntersectionMonthGroup(timelineManager: TimelineManager, month: MonthGroup) {
+export function updateIntersectionMonthGroup(timelineManager: PhotostreamManager, month: PhotostreamSegment) {
-  const actuallyIntersecting = calculateMonthGroupIntersecting(timelineManager, month, 0, 0);
+  const actuallyIntersecting = calculateSegmentIntersecting(timelineManager, month, 0, 0);
   let preIntersecting = false;
   if (!actuallyIntersecting) {
-    preIntersecting = calculateMonthGroupIntersecting(
+    preIntersecting = calculateSegmentIntersecting(
       timelineManager,
       month,
       INTERSECTION_EXPAND_TOP,
       INTERSECTION_EXPAND_BOTTOM,
     );
   }
-  month.intersecting = actuallyIntersecting || preIntersecting;
+  month.updateIntersection({ intersecting: actuallyIntersecting || preIntersecting, actuallyIntersecting });
-  month.actuallyIntersecting = actuallyIntersecting;
-  if (preIntersecting || actuallyIntersecting) {
-    timelineManager.clearDeferredLayout(month);
-  }
 }
 
 /**
@@ -40,9 +37,9 @@ export function isIntersecting(regionTop: number, regionBottom: number, windowTo
   );
 }
 
-export function calculateMonthGroupIntersecting(
+export function calculateSegmentIntersecting(
-  timelineManager: TimelineManager,
+  timelineManager: PhotostreamManager,
-  monthGroup: MonthGroup,
+  monthGroup: PhotostreamSegment,
   expandTop: number,
   expandBottom: number,
 ) {

web/src/lib/managers/timeline-manager/internal/layout-support.svelte.ts

@@ -1,8 +1,13 @@
+import type { PhotostreamManager } from '$lib/managers/timeline-manager/PhotostreamManager.svelte';
+import type { PhotostreamSegment } from '$lib/managers/timeline-manager/PhotostreamSegment.svelte';
 import type { MonthGroup } from '../month-group.svelte';
-import type { TimelineManager } from '../timeline-manager.svelte';
 import type { UpdateGeometryOptions } from '../types';
 
-export function updateGeometry(timelineManager: TimelineManager, month: MonthGroup, options: UpdateGeometryOptions) {
+export function updateGeometry(
+  timelineManager: PhotostreamManager,
+  month: PhotostreamSegment,
+  options: UpdateGeometryOptions,
+) {
   const { invalidateHeight, noDefer = false } = options;
   if (invalidateHeight) {
     month.isHeightActual = false;
@@ -17,10 +22,10 @@ export function updateGeometry(timelineManager: TimelineManager, month: MonthGro
     }
     return;
   }
-  layoutMonthGroup(timelineManager, month, noDefer);
+  month.layout(noDefer);
 }
 
-export function layoutMonthGroup(timelineManager: TimelineManager, month: MonthGroup, noDefer: boolean = false) {
+export function layoutMonthGroup(timelineManager: PhotostreamManager, month: MonthGroup, noDefer: boolean = false) {
   let cumulativeHeight = 0;
   let cumulativeWidth = 0;
   let currentRowHeight = 0;

web/src/lib/managers/timeline-manager/internal/operations-support.svelte.ts

@@ -25,8 +25,7 @@ export function addAssetsToMonthGroups(
     let month = getMonthGroupByDate(timelineManager, asset.localDateTime);
 
     if (!month) {
-      month = new MonthGroup(timelineManager, asset.localDateTime, 1, options.order);
+      month = new MonthGroup(timelineManager, asset.localDateTime, 1, true, options.order);
-      month.isLoaded = true;
       timelineManager.months.push(month);
     }
 

web/src/lib/managers/timeline-manager/month-group.svelte.ts

@@ -1,22 +1,20 @@
 import { AssetOrder, type TimeBucketAssetResponseDto } from '@immich/sdk';
 
-import { CancellableTask } from '$lib/utils/cancellable-task';
-import { handleError } from '$lib/utils/handle-error';
 import {
   formatGroupTitle,
   formatMonthGroupTitle,
   fromTimelinePlainDate,
   fromTimelinePlainDateTime,
   fromTimelinePlainYearMonth,
+  getSegmentIdentifier,
   getTimes,
   setDifference,
   type TimelineDateTime,
   type TimelineYearMonth,
 } from '$lib/utils/timeline-util';
 
-import { t } from 'svelte-i18n';
+import { layoutMonthGroup, updateGeometry } from '$lib/managers/timeline-manager/internal/layout-support.svelte';
-import { get } from 'svelte/store';
+import { PhotostreamSegment, type SegmentIdentifier } from '$lib/managers/timeline-manager/PhotostreamSegment.svelte';
-
 import { SvelteSet } from 'svelte/reactivity';
 import { DayGroup } from './day-group.svelte';
 import { GroupInsertionCache } from './group-insertion-cache.svelte';
@@ -24,73 +22,52 @@ import type { TimelineManager } from './timeline-manager.svelte';
 import type { AssetDescriptor, AssetOperation, Direction, MoveAsset, TimelineAsset } from './types';
 import { ViewerAsset } from './viewer-asset.svelte';
 
-export class MonthGroup {
+export class MonthGroup extends PhotostreamSegment {
-  #intersecting: boolean = $state(false);
-  actuallyIntersecting: boolean = $state(false);
-  isLoaded: boolean = $state(false);
   dayGroups: DayGroup[] = $state([]);
-  readonly timelineManager: TimelineManager;
 
-  #height: number = $state(0);
-  #top: number = $state(0);
-
-  #initialCount: number = 0;
   #sortOrder: AssetOrder = AssetOrder.Desc;
-  percent: number = $state(0);
+  #yearMonth: TimelineYearMonth;
-
+  #identifier: SegmentIdentifier;
-  assetsCount: number = $derived(
+  #timelineManager: TimelineManager;
-    this.isLoaded
-      ? this.dayGroups.reduce((accumulator, g) => accumulator + g.viewerAssets.length, 0)
-      : this.#initialCount,
-  );
-  loader: CancellableTask | undefined;
-  isHeightActual: boolean = $state(false);
 
   readonly monthGroupTitle: string;
-  readonly yearMonth: TimelineYearMonth;
 
   constructor(
-    store: TimelineManager,
+    timelineManager: TimelineManager,
     yearMonth: TimelineYearMonth,
     initialCount: number,
+    loaded: boolean,
     order: AssetOrder = AssetOrder.Desc,
   ) {
-    this.timelineManager = store;
+    super();
-    this.#initialCount = initialCount;
+    this.initialCount = initialCount;
+    this.#yearMonth = yearMonth;
+    this.#identifier = getSegmentIdentifier(yearMonth);
+    this.#timelineManager = timelineManager;
     this.#sortOrder = order;
-
-    this.yearMonth = yearMonth;
     this.monthGroupTitle = formatMonthGroupTitle(fromTimelinePlainYearMonth(yearMonth));
-
+    if (loaded) {
-    this.loader = new CancellableTask(
+      this.markLoaded();
-      () => {
-        this.isLoaded = true;
-      },
-      () => {
-        this.dayGroups = [];
-        this.isLoaded = false;
-      },
-      this.#handleLoadError,
-    );
-  }
-
-  set intersecting(newValue: boolean) {
-    const old = this.#intersecting;
-    if (old === newValue) {
-      return;
-    }
-    this.#intersecting = newValue;
-    if (newValue) {
-      void this.timelineManager.loadMonthGroup(this.yearMonth);
-    } else {
-      this.cancel();
     }
   }
 
-  get intersecting() {
+  get identifier() {
-    return this.#intersecting;
+    return this.#identifier;
   }
 
+  get timelineManager() {
+    return this.#timelineManager;
+  }
+
+  get yearMonth() {
+    return this.#yearMonth;
+  }
+
+  load(): Promise<void> {
+    return this.timelineManager.loadSegment(this.#identifier);
+  }
+
+
   get lastDayGroup() {
     return this.dayGroups.at(-1);
   }
@@ -247,61 +224,6 @@ export class MonthGroup {
     return year + '-' + month;
   }
 
-  set height(height: number) {
-    if (this.#height === height) {
-      return;
-    }
-    const { timelineManager: store, percent } = this;
-    const index = store.months.indexOf(this);
-    const heightDelta = height - this.#height;
-    this.#height = height;
-    const prevMonthGroup = store.months[index - 1];
-    if (prevMonthGroup) {
-      const newTop = prevMonthGroup.#top + prevMonthGroup.#height;
-      if (this.#top !== newTop) {
-        this.#top = newTop;
-      }
-    }
-    for (let cursor = index + 1; cursor < store.months.length; cursor++) {
-      const monthGroup = this.timelineManager.months[cursor];
-      const newTop = monthGroup.#top + heightDelta;
-      if (monthGroup.#top !== newTop) {
-        monthGroup.#top = newTop;
-      }
-    }
-    if (store.topIntersectingMonthGroup) {
-      const currentIndex = store.months.indexOf(store.topIntersectingMonthGroup);
-      if (currentIndex > 0) {
-        if (index < currentIndex) {
-          store.scrollCompensation = {
-            heightDelta,
-            scrollTop: undefined,
-            monthGroup: this,
-          };
-        } else if (percent > 0) {
-          const top = this.top + height * percent;
-          store.scrollCompensation = {
-            heightDelta: undefined,
-            scrollTop: top,
-            monthGroup: this,
-          };
-        }
-      }
-    }
-  }
-
-  get height() {
-    return this.#height;
-  }
-
-  get top(): number {
-    return this.#top + this.timelineManager.topSectionHeight;
-  }
-
-  #handleLoadError(error: unknown) {
-    const _$t = get(t);
-    handleError(error, _$t('errors.failed_to_load_assets'));
-  }
 
   findDayGroupForAsset(asset: TimelineAsset) {
     for (const group of this.dayGroups) {
@@ -316,7 +238,7 @@ export class MonthGroup {
   }
 
   findAssetAbsolutePosition(assetId: string) {
-    this.timelineManager.clearDeferredLayout(this);
+    this.#clearDeferredLayout();
     for (const group of this.dayGroups) {
       const viewerAsset = group.viewerAssets.find((viewAsset) => viewAsset.id === assetId);
       if (viewerAsset) {
@@ -374,4 +296,26 @@ export class MonthGroup {
   cancel() {
     this.loader?.cancel();
   }
+
+  layout(noDefer: boolean) {
+    layoutMonthGroup(this.timelineManager, this, noDefer);
+  }
+
+  #clearDeferredLayout() {
+    const hasDeferred = this.dayGroups.some((group) => group.deferredLayout);
+    if (hasDeferred) {
+      updateGeometry(this.timelineManager, this, { invalidateHeight: true, noDefer: true });
+      for (const group of this.dayGroups) {
+        group.deferredLayout = false;
+      }
+    }
+  }
+
+  updateIntersection({ intersecting, actuallyIntersecting }: { intersecting: boolean; actuallyIntersecting: boolean }) {
+    this.intersecting = intersecting;
+    this.actuallyIntersecting = actuallyIntersecting;
+    if (intersecting) {
+      this.#clearDeferredLayout();
+    }
+  }
 }

web/src/lib/managers/timeline-manager/timeline-manager.svelte.spec.ts

@@ -1,7 +1,7 @@
 import { sdkMock } from '$lib/__mocks__/sdk.mock';
 import { getMonthGroupByDate } from '$lib/managers/timeline-manager/internal/search-support.svelte';
 import { AbortError } from '$lib/utils';
-import { fromISODateTimeUTCToObject } from '$lib/utils/timeline-util';
+import { fromISODateTimeUTCToObject, getSegmentIdentifier } from '$lib/utils/timeline-util';
 import { type AssetResponseDto, type TimeBucketAssetResponseDto } from '@immich/sdk';
 import { timelineAssetFactory, toResponseDto } from '@test-data/factories/asset-factory';
 import { TimelineManager } from './timeline-manager.svelte';
@@ -92,7 +92,7 @@ describe('TimelineManager', () => {
     });
   });
 
-  describe('loadMonthGroup', () => {
+  describe('loadSegment', () => {
     let timelineManager: TimelineManager;
     const bucketAssets: Record<string, TimelineAsset[]> = {
       '2024-01-03T00:00:00.000Z': timelineAssetFactory.buildList(1).map((asset) =>
@@ -129,46 +129,46 @@ describe('TimelineManager', () => {
 
     it('loads a month', async () => {
       expect(getMonthGroupByDate(timelineManager, { year: 2024, month: 1 })?.getAssets().length).toEqual(0);
-      await timelineManager.loadMonthGroup({ year: 2024, month: 1 });
+      await timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 1 }));
       expect(sdkMock.getTimeBucket).toBeCalledTimes(1);
       expect(getMonthGroupByDate(timelineManager, { year: 2024, month: 1 })?.getAssets().length).toEqual(3);
     });
 
     it('ignores invalid months', async () => {
-      await timelineManager.loadMonthGroup({ year: 2023, month: 1 });
+      await timelineManager.loadSegment(getSegmentIdentifier({ year: 2023, month: 1 }));
       expect(sdkMock.getTimeBucket).toBeCalledTimes(0);
     });
 
     it('cancels month loading', async () => {
       const month = getMonthGroupByDate(timelineManager, { year: 2024, month: 1 })!;
-      void timelineManager.loadMonthGroup({ year: 2024, month: 1 });
+      void timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 1 }));
       const abortSpy = vi.spyOn(month!.loader!.cancelToken!, 'abort');
       month?.cancel();
       expect(abortSpy).toBeCalledTimes(1);
-      await timelineManager.loadMonthGroup({ year: 2024, month: 1 });
+      await timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 1 }));
       expect(getMonthGroupByDate(timelineManager, { year: 2024, month: 1 })?.getAssets().length).toEqual(3);
     });
 
     it('prevents loading months multiple times', async () => {
       await Promise.all([
-        timelineManager.loadMonthGroup({ year: 2024, month: 1 }),
+        timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 1 })),
-        timelineManager.loadMonthGroup({ year: 2024, month: 1 }),
+        timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 1 })),
       ]);
       expect(sdkMock.getTimeBucket).toBeCalledTimes(1);
 
-      await timelineManager.loadMonthGroup({ year: 2024, month: 1 });
+      await timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 1 }));
       expect(sdkMock.getTimeBucket).toBeCalledTimes(1);
     });
 
     it('allows loading a canceled month', async () => {
       const month = getMonthGroupByDate(timelineManager, { year: 2024, month: 1 })!;
-      const loadPromise = timelineManager.loadMonthGroup({ year: 2024, month: 1 });
+      const loadPromise = timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 1 }));
 
       month.cancel();
       await loadPromise;
       expect(month?.getAssets().length).toEqual(0);
 
-      await timelineManager.loadMonthGroup({ year: 2024, month: 1 });
+      await timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 1 }));
       expect(month!.getAssets().length).toEqual(3);
     });
   });
@@ -477,7 +477,7 @@ describe('TimelineManager', () => {
     });
 
     it('returns previous assetId', async () => {
-      await timelineManager.loadMonthGroup({ year: 2024, month: 1 });
+      await timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 1 }));
       const month = getMonthGroupByDate(timelineManager, { year: 2024, month: 1 });
 
       const a = month!.getAssets()[0];
@@ -487,8 +487,8 @@ describe('TimelineManager', () => {
     });
 
     it('returns previous assetId spanning multiple months', async () => {
-      await timelineManager.loadMonthGroup({ year: 2024, month: 2 });
+      await timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 2 }));
-      await timelineManager.loadMonthGroup({ year: 2024, month: 3 });
+      await timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 3 }));
 
       const month = getMonthGroupByDate(timelineManager, { year: 2024, month: 2 });
       const previousMonth = getMonthGroupByDate(timelineManager, { year: 2024, month: 3 });
@@ -499,23 +499,23 @@ describe('TimelineManager', () => {
     });
 
     it('loads previous month', async () => {
-      await timelineManager.loadMonthGroup({ year: 2024, month: 2 });
+      await timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 2 }));
       const month = getMonthGroupByDate(timelineManager, { year: 2024, month: 2 });
       const previousMonth = getMonthGroupByDate(timelineManager, { year: 2024, month: 3 });
       const a = month!.getFirstAsset();
       const b = previousMonth!.getFirstAsset();
-      const loadMonthGroupSpy = vi.spyOn(month!.loader!, 'execute');
+      const loadSegmentSpy = vi.spyOn(month!.loader!, 'execute');
       const previousMonthSpy = vi.spyOn(previousMonth!.loader!, 'execute');
       const previous = await timelineManager.getLaterAsset(a);
       expect(previous).toEqual(b);
-      expect(loadMonthGroupSpy).toBeCalledTimes(0);
+      expect(loadSegmentSpy).toBeCalledTimes(0);
       expect(previousMonthSpy).toBeCalledTimes(0);
     });
 
     it('skips removed assets', async () => {
-      await timelineManager.loadMonthGroup({ year: 2024, month: 1 });
+      await timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 1 }));
-      await timelineManager.loadMonthGroup({ year: 2024, month: 2 });
+      await timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 2 }));
-      await timelineManager.loadMonthGroup({ year: 2024, month: 3 });
+      await timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 3 }));
 
       const [assetOne, assetTwo, assetThree] = await getAssets(timelineManager);
       timelineManager.removeAssets([assetTwo.id]);
@@ -523,7 +523,7 @@ describe('TimelineManager', () => {
     });
 
     it('returns null when no more assets', async () => {
-      await timelineManager.loadMonthGroup({ year: 2024, month: 3 });
+      await timelineManager.loadSegment(getSegmentIdentifier({ year: 2024, month: 3 }));
       expect(await timelineManager.getLaterAsset(timelineManager.months[0].getFirstAsset())).toBeUndefined();
     });
   });

web/src/lib/managers/timeline-manager/timeline-manager.svelte.ts

@@ -3,12 +3,16 @@ import { AssetOrder, getAssetInfo, getTimeBuckets } from '@immich/sdk';
 import { authManager } from '$lib/managers/auth-manager.svelte';
 
 import { CancellableTask } from '$lib/utils/cancellable-task';
-import { toTimelineAsset, type TimelineDateTime, type TimelineYearMonth } from '$lib/utils/timeline-util';
+import {
+  getSegmentIdentifier,
+  toTimelineAsset,
+  type TimelineDateTime,
+  type TimelineYearMonth,
+} from '$lib/utils/timeline-util';
 
-import { clamp, debounce, isEqual } from 'lodash-es';
+import { isEqual } from 'lodash-es';
 import { SvelteDate, SvelteMap, SvelteSet } from 'svelte/reactivity';
 
-import { updateIntersectionMonthGroup } from '$lib/managers/timeline-manager/internal/intersection-support.svelte';
 import { updateGeometry } from '$lib/managers/timeline-manager/internal/layout-support.svelte';
 import { loadFromTimeBuckets } from '$lib/managers/timeline-manager/internal/load-support.svelte';
 import {
@@ -23,6 +27,8 @@ import {
   retrieveRange as retrieveRangeUtil,
 } from '$lib/managers/timeline-manager/internal/search-support.svelte';
 import { WebsocketSupport } from '$lib/managers/timeline-manager/internal/websocket-support.svelte';
+import { PhotostreamManager } from '$lib/managers/timeline-manager/PhotostreamManager.svelte';
+import { PhotostreamSegment } from '$lib/managers/timeline-manager/PhotostreamSegment.svelte';
 import { DayGroup } from './day-group.svelte';
 import { isMismatched, updateObject } from './internal/utils.svelte';
 import { MonthGroup } from './month-group.svelte';
@@ -32,29 +38,14 @@ import type {
   Direction,
   ScrubberMonth,
   TimelineAsset,
-  TimelineManagerLayoutOptions,
   TimelineManagerOptions,
-  Viewport,
 } from './types';
 
-export class TimelineManager {
+export class TimelineManager extends PhotostreamManager {
-  isInitialized = $state(false);
-  months: MonthGroup[] = $state([]);
-  topSectionHeight = $state(0);
-  timelineHeight = $derived(this.months.reduce((accumulator, b) => accumulator + b.height, 0) + this.topSectionHeight);
-  assetCount = $derived(this.months.reduce((accumulator, b) => accumulator + b.assetsCount, 0));
-
   albumAssets: Set<string> = new SvelteSet();
-
   scrubberMonths: ScrubberMonth[] = $state([]);
   scrubberTimelineHeight: number = $state(0);
-
+  #months: MonthGroup[] = $state([]);
-  topIntersectingMonthGroup: MonthGroup | undefined = $state();
-
-  visibleWindow = $derived.by(() => ({
-    top: this.#scrollTop,
-    bottom: this.#scrollTop + this.viewportHeight,
-  }));
 
   initTask = new CancellableTask(
     () => {
@@ -72,121 +63,12 @@ export class TimelineManager {
   );
 
   static #INIT_OPTIONS = {};
-  #viewportHeight = $state(0);
+
-  #viewportWidth = $state(0);
-  #scrollTop = $state(0);
   #websocketSupport: WebsocketSupport | undefined;
-
-  #rowHeight = $state(235);
-  #headerHeight = $state(48);
-  #gap = $state(12);
-
   #options: TimelineManagerOptions = TimelineManager.#INIT_OPTIONS;
 
-  #scrolling = $state(false);
+  get months() {
-  #suspendTransitions = $state(false);
+    return this.#months;
-  #resetScrolling = debounce(() => (this.#scrolling = false), 1000);
-  #resetSuspendTransitions = debounce(() => (this.suspendTransitions = false), 1000);
-  scrollCompensation: {
-    heightDelta: number | undefined;
-    scrollTop: number | undefined;
-    monthGroup: MonthGroup | undefined;
-  } = $state({
-    heightDelta: 0,
-    scrollTop: 0,
-    monthGroup: undefined,
-  });
-
-  constructor() {}
-
-  setLayoutOptions({ headerHeight = 48, rowHeight = 235, gap = 12 }: TimelineManagerLayoutOptions) {
-    let changed = false;
-    changed ||= this.#setHeaderHeight(headerHeight);
-    changed ||= this.#setGap(gap);
-    changed ||= this.#setRowHeight(rowHeight);
-    if (changed) {
-      this.refreshLayout();
-    }
-  }
-
-  #setHeaderHeight(value: number) {
-    if (this.#headerHeight == value) {
-      return false;
-    }
-    this.#headerHeight = value;
-    return true;
-  }
-
-  get headerHeight() {
-    return this.#headerHeight;
-  }
-
-  #setGap(value: number) {
-    if (this.#gap == value) {
-      return false;
-    }
-    this.#gap = value;
-    return true;
-  }
-
-  get gap() {
-    return this.#gap;
-  }
-
-  #setRowHeight(value: number) {
-    if (this.#rowHeight == value) {
-      return false;
-    }
-    this.#rowHeight = value;
-    return true;
-  }
-
-  get rowHeight() {
-    return this.#rowHeight;
-  }
-
-  set scrolling(value: boolean) {
-    this.#scrolling = value;
-    if (value) {
-      this.suspendTransitions = true;
-      this.#resetScrolling();
-    }
-  }
-
-  get scrolling() {
-    return this.#scrolling;
-  }
-
-  set suspendTransitions(value: boolean) {
-    this.#suspendTransitions = value;
-    if (value) {
-      this.#resetSuspendTransitions();
-    }
-  }
-
-  get suspendTransitions() {
-    return this.#suspendTransitions;
-  }
-
-  set viewportWidth(value: number) {
-    const changed = value !== this.#viewportWidth;
-    this.#viewportWidth = value;
-    this.suspendTransitions = true;
-    void this.#updateViewportGeometry(changed);
-  }
-
-  get viewportWidth() {
-    return this.#viewportWidth;
-  }
-
-  set viewportHeight(value: number) {
-    this.#viewportHeight = value;
-    this.#suspendTransitions = true;
-    void this.#updateViewportGeometry(false);
-  }
-
-  get viewportHeight() {
-    return this.#viewportHeight;
   }
 
   async *assetsIterator(options?: {
@@ -198,7 +80,7 @@ export class TimelineManager {
     const direction = options?.direction ?? 'earlier';
     let { startDayGroup, startAsset } = options ?? {};
     for (const monthGroup of this.monthGroupIterator({ direction, startMonthGroup: options?.startMonthGroup })) {
-      await this.loadMonthGroup(monthGroup.yearMonth, { cancelable: false });
+      await this.loadSegment(monthGroup.identifier, { cancelable: false });
       yield* monthGroup.assetsIterator({ startDayGroup, startAsset, direction });
       startDayGroup = startAsset = undefined;
     }
@@ -234,75 +116,24 @@ export class TimelineManager {
     this.#websocketSupport = undefined;
   }
 
-  updateSlidingWindow(scrollTop: number) {
-    if (this.#scrollTop !== scrollTop) {
-      this.#scrollTop = scrollTop;
-      this.updateIntersections();
-    }
-  }
-
-  clearScrollCompensation() {
-    this.scrollCompensation = {
-      heightDelta: undefined,
-      scrollTop: undefined,
-      monthGroup: undefined,
-    };
-  }
-
-  updateIntersections() {
-    if (!this.isInitialized || this.visibleWindow.bottom === this.visibleWindow.top) {
-      return;
-    }
-    let topIntersectingMonthGroup = undefined;
-    for (const month of this.months) {
-      updateIntersectionMonthGroup(this, month);
-      if (!topIntersectingMonthGroup && month.actuallyIntersecting) {
-        topIntersectingMonthGroup = month;
-      }
-    }
-    if (topIntersectingMonthGroup !== undefined && this.topIntersectingMonthGroup !== topIntersectingMonthGroup) {
-      this.topIntersectingMonthGroup = topIntersectingMonthGroup;
-    }
-    for (const month of this.months) {
-      if (month === this.topIntersectingMonthGroup) {
-        this.topIntersectingMonthGroup.percent = clamp(
-          (this.visibleWindow.top - this.topIntersectingMonthGroup.top) / this.topIntersectingMonthGroup.height,
-          0,
-          1,
-        );
-      } else {
-        month.percent = 0;
-      }
-    }
-  }
-
-  clearDeferredLayout(month: MonthGroup) {
-    const hasDeferred = month.dayGroups.some((group) => group.deferredLayout);
-    if (hasDeferred) {
-      updateGeometry(this, month, { invalidateHeight: true, noDefer: true });
-      for (const group of month.dayGroups) {
-        group.deferredLayout = false;
-      }
-    }
-  }
-
   async #initializeMonthGroups() {
     const timebuckets = await getTimeBuckets({
       ...authManager.params,
       ...this.#options,
     });
 
-    this.months = timebuckets.map((timeBucket) => {
+    this.#months = timebuckets.map((timeBucket) => {
       const date = new SvelteDate(timeBucket.timeBucket);
       return new MonthGroup(
         this,
         { year: date.getUTCFullYear(), month: date.getUTCMonth() + 1 },
         timeBucket.count,
+        false,
         this.#options.order,
       );
     });
     this.albumAssets.clear();
-    this.#updateViewportGeometry(false);
+    this.updateViewportGeometry(false);
   }
 
   async updateOptions(options: TimelineManagerOptions) {
@@ -313,13 +144,13 @@ export class TimelineManager {
       return;
     }
     await this.initTask.reset();
-    await this.#init(options);
+    await this.init(options);
-    this.#updateViewportGeometry(false);
+    this.updateViewportGeometry(false);
   }
 
-  async #init(options: TimelineManagerOptions) {
+  async init(options: TimelineManagerOptions) {
     this.isInitialized = false;
-    this.months = [];
+    this.#months = [];
     this.albumAssets.clear();
     await this.initTask.execute(async () => {
       this.#options = options;
@@ -332,36 +163,8 @@ export class TimelineManager {
     this.isInitialized = false;
   }
 
-  async updateViewport(viewport: Viewport) {
+  updateViewportGeometry(changedWidth: boolean) {
-    if (viewport.height === 0 && viewport.width === 0) {
+    super.updateViewportGeometry(changedWidth);
-      return;
-    }
-
-    if (this.viewportHeight === viewport.height && this.viewportWidth === viewport.width) {
-      return;
-    }
-
-    if (!this.initTask.executed) {
-      await (this.initTask.loading ? this.initTask.waitUntilCompletion() : this.#init(this.#options));
-    }
-
-    const changedWidth = viewport.width !== this.viewportWidth;
-    this.viewportHeight = viewport.height;
-    this.viewportWidth = viewport.width;
-    this.#updateViewportGeometry(changedWidth);
-  }
-
-  #updateViewportGeometry(changedWidth: boolean) {
-    if (!this.isInitialized) {
-      return;
-    }
-    if (this.viewportWidth === 0 || this.viewportHeight === 0) {
-      return;
-    }
-    for (const month of this.months) {
-      updateGeometry(this, month, { invalidateHeight: changedWidth });
-    }
-    this.updateIntersections();
     this.#createScrubberMonths();
   }
 
@@ -376,37 +179,8 @@ export class TimelineManager {
     this.scrubberTimelineHeight = this.timelineHeight;
   }
 
-  createLayoutOptions() {
+  protected fetchSegment(segment: PhotostreamSegment, signal: AbortSignal): Promise<void> {
-    const viewportWidth = this.viewportWidth;
+    return loadFromTimeBuckets(this, segment as MonthGroup, this.#options, signal);
-
-    return {
-      spacing: 2,
-      heightTolerance: 0.15,
-      rowHeight: this.#rowHeight,
-      rowWidth: Math.floor(viewportWidth),
-    };
-  }
-
-  async loadMonthGroup(yearMonth: TimelineYearMonth, options?: { cancelable: boolean }): Promise<void> {
-    let cancelable = true;
-    if (options) {
-      cancelable = options.cancelable;
-    }
-    const monthGroup = getMonthGroupByDate(this, yearMonth);
-    if (!monthGroup) {
-      return;
-    }
-
-    if (monthGroup.loader?.executed) {
-      return;
-    }
-
-    const result = await monthGroup.loader?.execute(async (signal: AbortSignal) => {
-      await loadFromTimeBuckets(this, monthGroup, this.#options, signal);
-    }, cancelable);
-    if (result === 'LOADED') {
-      updateIntersectionMonthGroup(this, monthGroup);
-    }
   }
 
   addAssets(assets: TimelineAsset[]) {
@@ -442,7 +216,7 @@ export class TimelineManager {
   }
 
   async #loadMonthGroupAtTime(yearMonth: TimelineYearMonth, options?: { cancelable: boolean }) {
-    await this.loadMonthGroup(yearMonth, options);
+    await this.loadSegment(getSegmentIdentifier(yearMonth), options);
     return getMonthGroupByDate(this, yearMonth);
   }
 
@@ -454,7 +228,7 @@ export class TimelineManager {
   async getRandomMonthGroup() {
     const random = Math.floor(Math.random() * this.months.length);
     const month = this.months[random];
-    await this.loadMonthGroup(month.yearMonth, { cancelable: false });
+    await this.loadSegment(getSegmentIdentifier(month.yearMonth), { cancelable: false });
     return month;
   }
 
@@ -527,7 +301,7 @@ export class TimelineManager {
     if (!monthGroup) {
       return;
     }
-    await this.loadMonthGroup(dateTime, { cancelable: false });
+    await this.loadSegment(getSegmentIdentifier(dateTime), { cancelable: false });
     const asset = monthGroup.findClosest(dateTime);
     if (asset) {
       return asset;

web/src/lib/utils/asset-utils.ts

@@ -513,7 +513,7 @@ export const selectAllAssets = async (timelineManager: TimelineManager, assetInt
 
   try {
     for (const monthGroup of timelineManager.months) {
-      await timelineManager.loadMonthGroup(monthGroup.yearMonth);
+      await timelineManager.loadSegment(monthGroup.identifier);
 
       if (!get(isSelectingAllAssets)) {
         assetInteraction.clearMultiselect();

web/src/lib/utils/timeline-util.ts

@@ -29,6 +29,12 @@ export type ScrubberListener = (
   scrubberMonthScrollPercent: number,
 ) => void | Promise<void>;
 
+export const getSegmentIdentifier = (yearMonth: TimelineYearMonth | TimelineDateTime) => ({
+  matches(segment: any) {
+    return segment.yearMonth && segment.yearMonth.year === yearMonth.year && segment.yearMonth.month === yearMonth.month;
+  },
+});
+
 // used for AssetResponseDto.dateTimeOriginal, amongst others
 export const fromISODateTime = (isoDateTime: string, timeZone: string): DateTime<true> =>
   DateTime.fromISO(isoDateTime, { zone: timeZone, locale: get(locale) }) as DateTime<true>;