refactor(web): extract timeline selection logic into SelectableSegment and SelectableDay components

- Move asset selection, range selection, and keyboard interaction logic
  to SelectableSegment
  - Extract day group selection logic to SelectableDay component
  - Simplify Timeline component by removing selection-related state and
  handlers
  - Fix scroll compensation handling with dedicated while loop
  - Remove unused keyboard handlers from Scrubber component

web/src/lib/components/assets/thumbnail/thumbnail.svelte

@@ -121,6 +121,7 @@
 
   const onMouseLeave = () => {
     mouseOver = false;
+    onMouseEvent?.({ isMouseOver: false, selectedGroupIndex: groupIndex });
   };
 
   let timer: ReturnType<typeof setTimeout> | null = null;

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

@@ -0,0 +1,68 @@
+<script lang="ts">
+  import { uploadAssetsStore } from '$lib/stores/upload';
+
+  import { flip } from 'svelte/animate';
+  import { scale } from 'svelte/transition';
+
+  import type { TimelineAsset } from '$lib/managers/timeline-manager/types';
+  import type { ViewerAsset } from '$lib/managers/timeline-manager/viewer-asset.svelte';
+  import type { VirtualScrollManager } from '$lib/managers/VirtualScrollManager/VirtualScrollManager.svelte';
+  import type { CommonPosition } from '$lib/utils/layout-utils';
+  import type { Snippet } from 'svelte';
+
+  let { isUploading } = uploadAssetsStore;
+
+  interface Props {
+    viewerAssets: ViewerAsset[];
+    width: number;
+    height: number;
+    manager: VirtualScrollManager;
+    thumbnail: Snippet<
+      [
+        {
+          asset: TimelineAsset;
+          position: CommonPosition;
+        },
+      ]
+    >;
+    customThumbnailLayout?: Snippet<[asset: TimelineAsset]>;
+  }
+
+  let { viewerAssets, width, height, manager, thumbnail, customThumbnailLayout }: Props = $props();
+
+  const transitionDuration = $derived.by(() => (manager.suspendTransitions && !$isUploading ? 0 : 150));
+  const scaleDuration = $derived(transitionDuration === 0 ? 0 : transitionDuration + 100);
+
+  function filterIntersecting<R extends { intersecting: boolean }>(intersectables: R[]) {
+    return intersectables.filter((intersectable) => intersectable.intersecting);
+  }
+</script>
+
+<!-- Image grid -->
+<div data-image-grid class="relative overflow-clip" style:height={height + 'px'} style:width={width + 'px'}>
+  {#each filterIntersecting(viewerAssets) as viewerAsset (viewerAsset.id)}
+    {@const position = viewerAsset.position!}
+    {@const asset = viewerAsset.asset!}
+
+    <!-- note: don't remove data-asset-id - its used by web e2e tests -->
+    <div
+      data-asset-id={asset.id}
+      class="absolute"
+      style:top={position.top + 'px'}
+      style:left={position.left + 'px'}
+      style:width={position.width + 'px'}
+      style:height={position.height + 'px'}
+      out:scale|global={{ start: 0.1, duration: scaleDuration }}
+      animate:flip={{ duration: transitionDuration }}
+    >
+      {@render thumbnail({ asset, position })}
+      {@render customThumbnailLayout?.(asset)}
+    </div>
+  {/each}
+</div>
+
+<style>
+  [data-image-grid] {
+    user-select: none;
+  }
+</style>

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

@@ -0,0 +1,189 @@
+<script lang="ts">
+  import type { TimelineAsset } from '$lib/managers/timeline-manager/types';
+  import { AssetInteraction } from '$lib/stores/asset-interaction.svelte';
+  import { isSelectingAllAssets } from '$lib/stores/assets-store.svelte';
+  import { navigate } from '$lib/utils/navigation';
+
+  import { TimelineManager } from '$lib/managers/timeline-manager/timeline-manager.svelte';
+  import { assetsSnapshot } from '$lib/managers/timeline-manager/utils.svelte';
+  import { searchStore } from '$lib/stores/search.svelte';
+  import type { Snippet } from 'svelte';
+
+  interface Props {
+    content: Snippet<
+      [
+        {
+          onAssetOpen: (asset: TimelineAsset) => void;
+          onAssetSelect: (asset: TimelineAsset) => void;
+          onAssetHover: (asset: TimelineAsset | null) => void;
+        },
+      ]
+    >;
+
+    isSelectionMode: boolean;
+    singleSelect: boolean;
+    timelineManager: TimelineManager;
+    assetInteraction: AssetInteraction;
+    onAssetOpen?: (asset: TimelineAsset, defaultAssetOpen: () => void) => void;
+    onAssetSelect?: (asset: TimelineAsset) => void;
+  }
+
+  let { content, isSelectionMode, singleSelect, assetInteraction, timelineManager, onAssetOpen, onAssetSelect }: Props =
+    $props();
+
+  let shiftKeyIsDown = $state(false);
+  let isEmpty = $derived(timelineManager.isInitialized && timelineManager.months.length === 0);
+  let lastMouseHoverAsset: TimelineAsset | null = $state(null);
+
+  $effect(() => {
+    if (shiftKeyIsDown && lastMouseHoverAsset) {
+      void selectAssetCandidates(lastMouseHoverAsset);
+    }
+    if (isEmpty) {
+      assetInteraction.clearMultiselect();
+    }
+  });
+
+  const defaultAssetOpen = async (asset: TimelineAsset) => {
+    if (isSelectionMode || assetInteraction.selectionActive) {
+      await handleAssetSelect(asset);
+      return;
+    }
+    void navigate({ targetRoute: 'current', assetId: asset.id });
+  };
+
+  const handleOnAssetOpen = (asset: TimelineAsset) => {
+    if (onAssetOpen) {
+      onAssetOpen(asset, () => void defaultAssetOpen(asset));
+      return;
+    }
+    void defaultAssetOpen(asset);
+  };
+
+  // called when clicking asset with shift key pressed or with mouse
+  const handleAssetSelect = async (asset: TimelineAsset) => {
+    await handleSelectAssets(asset);
+
+    if (timelineManager.assetCount == assetInteraction.selectedAssets.length) {
+      isSelectingAllAssets.set(true);
+    } else {
+      isSelectingAllAssets.set(false);
+    }
+  };
+
+  const onKeyDown = (event: KeyboardEvent) => {
+    if (searchStore.isSearchEnabled) {
+      return;
+    }
+
+    if (event.key === 'Shift') {
+      event.preventDefault();
+      shiftKeyIsDown = true;
+      assetInteraction.clearAssetSelectionCandidates();
+      if (lastMouseHoverAsset) {
+        void selectAssetCandidates(lastMouseHoverAsset);
+        return;
+      }
+      if (!assetInteraction.assetSelectionStart) {
+        assetInteraction.setAssetSelectionStart(assetInteraction.selectedAssets.at(-1) ?? null);
+      }
+    }
+  };
+
+  const onKeyUp = (event: KeyboardEvent) => {
+    if (searchStore.isSearchEnabled) {
+      return;
+    }
+
+    if (event.key === 'Shift') {
+      event.preventDefault();
+      shiftKeyIsDown = false;
+      assetInteraction.clearAssetSelectionCandidates();
+    }
+  };
+
+  const handleOnHover = (asset: TimelineAsset | null) => {
+    if (asset) {
+      if (assetInteraction.selectionActive) {
+        void selectAssetCandidates(asset);
+      }
+      lastMouseHoverAsset = asset;
+    }
+  };
+
+  const handleSelectAssets = async (asset: TimelineAsset) => {
+    if (!asset) {
+      return;
+    }
+    onAssetSelect?.(asset);
+
+    if (singleSelect) {
+      return;
+    }
+
+    const rangeSelection = assetInteraction.assetSelectionCandidates.length > 0;
+    const deselect = assetInteraction.hasSelectedAsset(asset.id);
+
+    // Select/deselect already loaded assets
+    if (deselect) {
+      for (const candidate of assetInteraction.assetSelectionCandidates) {
+        assetInteraction.removeAssetFromMultiselectGroup(candidate.id);
+      }
+      assetInteraction.removeAssetFromMultiselectGroup(asset.id);
+    } else {
+      for (const candidate of assetInteraction.assetSelectionCandidates) {
+        handleSelectAsset(candidate);
+      }
+      handleSelectAsset(asset);
+    }
+
+    assetInteraction.clearAssetSelectionCandidates();
+
+    if (assetInteraction.assetSelectionStart && rangeSelection) {
+      const assets = await timelineManager.retrieveRange(assetInteraction.assetSelectionStart, asset);
+      for (const asset of assets) {
+        if (deselect) {
+          assetInteraction.removeAssetFromMultiselectGroup(asset.id);
+        } else {
+          handleSelectAsset(asset);
+        }
+      }
+    }
+    assetInteraction.setAssetSelectionStart(deselect ? null : asset);
+    return null;
+  };
+
+  const handleSelectAsset = (asset: TimelineAsset) => {
+    if ('albumAssets' in timelineManager) {
+      const tm = timelineManager as TimelineManager;
+      if (tm.albumAssets.has(asset.id)) {
+        return;
+      }
+    }
+
+    assetInteraction.selectAsset(asset);
+  };
+
+  const selectAssetCandidates = async (endAsset: TimelineAsset) => {
+    if (!shiftKeyIsDown) {
+      return;
+    }
+
+    const startAsset = assetInteraction.assetSelectionStart;
+    if (!startAsset) {
+      return;
+    }
+    const assets = assetsSnapshot(await timelineManager.retrieveRange(startAsset, endAsset));
+    assetInteraction.setAssetSelectionCandidates(assets);
+  };
+</script>
+
+<svelte:document onkeydown={onKeyDown} onkeyup={onKeyUp} />
+
+{@render content({
+  onAssetOpen: handleOnAssetOpen,
+  onAssetSelect: (asset) => {
+    void handleSelectAssets(asset);
+  },
+  onAssetHover: handleOnHover,
+})}

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

@@ -0,0 +1,62 @@
+<script lang="ts">
+  import type { TimelineAsset } from '$lib/managers/timeline-manager/types';
+  import { AssetInteraction } from '$lib/stores/asset-interaction.svelte';
+
+  import { DayGroup } from '$lib/managers/timeline-manager/day-group.svelte';
+
+  import type { Snippet } from 'svelte';
+
+  interface Props {
+    content: Snippet<
+      [
+        {
+          onDayGroupSelect: (dayGroup: DayGroup, asset: TimelineAsset[]) => void;
+          onDayGroupAssetSelect: (dayGroup: DayGroup, asset: TimelineAsset) => void;
+        },
+      ]
+    >;
+    onAssetSelect: (asset: TimelineAsset) => void;
+    assetInteraction: AssetInteraction;
+  }
+
+  let { content, assetInteraction, onAssetSelect }: Props = $props();
+
+  // called when clicking asset with shift key pressed or with mouse
+  const onDayGroupAssetSelect = (dayGroup: DayGroup, asset: TimelineAsset) => {
+    onAssetSelect(asset);
+
+    const assetsInDayGroup = dayGroup.getAssets();
+    const groupTitle = dayGroup.groupTitle;
+
+    // Check if all assets are selected in a group to toggle the group selection's icon
+    const selectedAssetsInGroupCount = assetsInDayGroup.filter((asset) =>
+      assetInteraction.hasSelectedAsset(asset.id),
+    ).length;
+    // if all assets are selected in a group, add the group to selected group
+    if (selectedAssetsInGroupCount == assetsInDayGroup.length) {
+      assetInteraction.addGroupToMultiselectGroup(groupTitle);
+    } else {
+      assetInteraction.removeGroupFromMultiselectGroup(groupTitle);
+    }
+  };
+
+  const onDayGroupSelect = (dayGroup: DayGroup, assets: TimelineAsset[]) => {
+    const group = dayGroup.groupTitle;
+    if (assetInteraction.selectedGroup.has(group)) {
+      assetInteraction.removeGroupFromMultiselectGroup(group);
+      for (const asset of assets) {
+        assetInteraction.removeAssetFromMultiselectGroup(asset.id);
+      }
+    } else {
+      assetInteraction.addGroupToMultiselectGroup(group);
+      for (const asset of assets) {
+        onAssetSelect(asset);
+      }
+    }
+  };
+</script>
+
+{@render content({
+  onDayGroupSelect,
+  onDayGroupAssetSelect,
+})}

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

@@ -0,0 +1,120 @@
+<script lang="ts">
+  import AssetLayout from '$lib/components/timeline/AssetLayout.svelte';
+  import { DayGroup } from '$lib/managers/timeline-manager/day-group.svelte';
+  import type { MonthGroup } from '$lib/managers/timeline-manager/month-group.svelte';
+  import type { TimelineAsset } from '$lib/managers/timeline-manager/types';
+  import { assetsSnapshot } from '$lib/managers/timeline-manager/utils.svelte';
+  import type { VirtualScrollManager } from '$lib/managers/VirtualScrollManager/VirtualScrollManager.svelte';
+  import type { AssetInteraction } from '$lib/stores/asset-interaction.svelte';
+  import { uploadAssetsStore } from '$lib/stores/upload';
+  import type { CommonPosition } from '$lib/utils/layout-utils';
+  import { fromTimelinePlainDate, getDateLocaleString } from '$lib/utils/timeline-util';
+  import { Icon } from '@immich/ui';
+  import { mdiCheckCircle, mdiCircleOutline } from '@mdi/js';
+  import type { Snippet } from 'svelte';
+
+  interface Props {
+    thumbnail: Snippet<[{ asset: TimelineAsset; position: CommonPosition; dayGroup: DayGroup; groupIndex: number }]>;
+    customThumbnailLayout?: Snippet<[TimelineAsset]>;
+    singleSelect: boolean;
+    assetInteraction: AssetInteraction;
+    monthGroup: MonthGroup;
+    manager: VirtualScrollManager;
+    onDayGroupSelect: (daygroup: DayGroup, assets: TimelineAsset[]) => void;
+  }
+  let {
+    thumbnail: thumbnailWithGroup,
+    customThumbnailLayout,
+    singleSelect,
+    assetInteraction,
+    monthGroup,
+    manager,
+    onDayGroupSelect,
+  }: Props = $props();
+
+  let { isUploading } = uploadAssetsStore;
+  let isMouseOverGroup = $state(false);
+  let hoveredDayGroup = $state();
+  const transitionDuration = $derived.by(() =>
+    monthGroup.timelineManager.suspendTransitions && !$isUploading ? 0 : 150,
+  );
+  function filterIntersecting<R extends { intersecting: boolean }>(intersectables: R[]) {
+    return intersectables.filter((intersectable) => intersectable.intersecting);
+  }
+  const getDayGroupFullDate = (dayGroup: DayGroup): string => {
+    const { month, year } = dayGroup.monthGroup.yearMonth;
+    const date = fromTimelinePlainDate({
+      year,
+      month,
+      day: dayGroup.day,
+    });
+    return getDateLocaleString(date);
+  };
+</script>
+
+{#each filterIntersecting(monthGroup.dayGroups) as dayGroup, groupIndex (dayGroup.day)}
+  {@const absoluteWidth = dayGroup.left}
+  {@const isDayGroupSelected = assetInteraction.selectedGroup.has(dayGroup.groupTitle)}
+  <!-- svelte-ignore a11y_no_static_element_interactions -->
+  <section
+    class={[
+      { 'transition-all': !monthGroup.timelineManager.suspendTransitions },
+      !monthGroup.timelineManager.suspendTransitions && `delay-${transitionDuration}`,
+    ]}
+    data-group
+    style:position="absolute"
+    style:transform={`translate3d(${absoluteWidth}px,${dayGroup.top}px,0)`}
+    onmouseenter={() => {
+      isMouseOverGroup = true;
+      hoveredDayGroup = dayGroup.groupTitle;
+    }}
+    onmouseleave={() => {
+      isMouseOverGroup = false;
+      hoveredDayGroup = null;
+    }}
+  >
+    <!-- Month title -->
+    <div
+      class="flex pt-7 pb-5 max-md:pt-5 max-md:pb-3 h-6 place-items-center text-xs font-medium text-immich-fg dark:text-immich-dark-fg md:text-sm"
+      style:width={dayGroup.width + 'px'}
+    >
+      {#if !singleSelect}
+        <div
+          class="hover:cursor-pointer transition-all duration-200 ease-out overflow-hidden w-0"
+          class:w-8={(hoveredDayGroup === dayGroup.groupTitle && isMouseOverGroup) ||
+            assetInteraction.selectedGroup.has(dayGroup.groupTitle)}
+          onclick={() => onDayGroupSelect(dayGroup, assetsSnapshot(dayGroup.getAssets()))}
+          onkeydown={() => onDayGroupSelect(dayGroup, assetsSnapshot(dayGroup.getAssets()))}
+        >
+          {#if isDayGroupSelected}
+            <Icon icon={mdiCheckCircle} size="24" class="text-primary" />
+          {:else}
+            <Icon icon={mdiCircleOutline} size="24" color="#757575" />
+          {/if}
+        </div>
+      {/if}
+
+      <span class="w-full truncate first-letter:capitalize" title={getDayGroupFullDate(dayGroup)}>
+        {dayGroup.groupTitle}
+      </span>
+    </div>
+
+    <AssetLayout
+      {manager}
+      viewerAssets={dayGroup.viewerAssets}
+      height={dayGroup.height}
+      width={dayGroup.width}
+      {customThumbnailLayout}
+    >
+      {#snippet thumbnail({ asset, position })}
+        {@render thumbnailWithGroup({ asset, position, dayGroup, groupIndex })}
+      {/snippet}
+    </AssetLayout>
+  </section>
+{/each}
+
+<style>
+  section {
+    contain: layout paint style;
+  }
+</style>

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

@@ -2,6 +2,10 @@
   import { afterNavigate, beforeNavigate } from '$app/navigation';
   import { page } from '$app/state';
   import { resizeObserver, type OnResizeCallback } from '$lib/actions/resize-observer';
+  import Thumbnail from '$lib/components/assets/thumbnail/thumbnail.svelte';
+  import AssetSelectionController from '$lib/components/timeline/AssetSelectionController.svelte';
+  import DaySelectionController from '$lib/components/timeline/DaySelectionController.svelte';
+  import Month from '$lib/components/timeline/Month.svelte';
   import Scrubber from '$lib/components/timeline/Scrubber.svelte';
   import TimelineAssetViewer from '$lib/components/timeline/TimelineAssetViewer.svelte';
   import TimelineKeyboardActions from '$lib/components/timeline/actions/TimelineKeyboardActions.svelte';
@@ -9,15 +13,12 @@
   import HotModuleReload from '$lib/elements/HotModuleReload.svelte';
   import Portal from '$lib/elements/Portal.svelte';
   import Skeleton from '$lib/elements/Skeleton.svelte';
-  import type { DayGroup } from '$lib/managers/timeline-manager/day-group.svelte';
   import { isIntersecting } from '$lib/managers/timeline-manager/internal/intersection-support.svelte';
   import type { MonthGroup } from '$lib/managers/timeline-manager/month-group.svelte';
   import { TimelineManager } from '$lib/managers/timeline-manager/timeline-manager.svelte';
   import type { TimelineAsset, TimelineManagerOptions, ViewportTopMonth } from '$lib/managers/timeline-manager/types';
-  import { assetsSnapshot } from '$lib/managers/timeline-manager/utils.svelte';
   import type { AssetInteraction } from '$lib/stores/asset-interaction.svelte';
   import { assetViewingStore } from '$lib/stores/asset-viewing.store';
-  import { isSelectingAllAssets } from '$lib/stores/assets-store.svelte';
   import { mobileDevice } from '$lib/stores/mobile-device.svelte';
   import { isAssetViewerRoute } from '$lib/utils/navigation';
   import { getTimes, type ScrubberListener } from '$lib/utils/timeline-util';
@@ -25,7 +26,6 @@
   import { DateTime } from 'luxon';
   import { onDestroy, onMount, type Snippet } from 'svelte';
   import type { UpdatePayload } from 'vite';
-  import TimelineDateGroup from './TimelineDateGroup.svelte';
 
   interface Props {
     isSelectionMode?: boolean;
@@ -50,22 +50,12 @@
     album?: AlbumResponseDto | null;
     person?: PersonResponseDto | null;
     isShowDeleteConfirmation?: boolean;
-    onSelect?: (asset: TimelineAsset) => void;
+    onAssetOpen?: (asset: TimelineAsset, defaultAssetOpen: () => void) => void;
+    onAssetSelect?: (asset: TimelineAsset) => void;
     onEscape?: () => void;
     children?: Snippet;
     empty?: Snippet;
-    customLayout?: Snippet<[TimelineAsset]>;
-    onThumbnailClick?: (
-      asset: TimelineAsset,
-      timelineManager: TimelineManager,
-      dayGroup: DayGroup,
-      onClick: (
-        timelineManager: TimelineManager,
-        assets: TimelineAsset[],
-        groupTitle: string,
-        asset: TimelineAsset,
-      ) => void,
-    ) => void;
+    customThumbnailLayout?: Snippet<[TimelineAsset]>;
   }
 
   let {
@@ -82,12 +72,13 @@
     album = null,
     person = null,
     isShowDeleteConfirmation = $bindable(false),
-    onSelect = () => {},
+
+    onAssetSelect,
+    onAssetOpen,
     onEscape = () => {},
     children,
     empty,
-    customLayout,
-    onThumbnailClick,
+    customThumbnailLayout,
   }: Props = $props();
 
   timelineManager = new TimelineManager();
@@ -254,7 +245,6 @@
   });
 
   const updateIsScrolling = () => (timelineManager.scrolling = true);
-  // note: don't throttle, debounch, or otherwise do this function async - it causes flicker
 
   const topSectionResizeObserver: OnResizeCallback = ({ height }) => (timelineManager.topSectionHeight = height);
 
@@ -362,172 +352,6 @@
     }
   };
 
-  const handleSelectAsset = (asset: TimelineAsset) => {
-    if (!timelineManager.albumAssets.has(asset.id)) {
-      assetInteraction.selectAsset(asset);
-    }
-  };
-
-  let lastAssetMouseEvent: TimelineAsset | null = $state(null);
-
-  let shiftKeyIsDown = $state(false);
-
-  const onKeyDown = (event: KeyboardEvent) => {
-    if (event.key === 'Shift') {
-      event.preventDefault();
-      shiftKeyIsDown = true;
-    }
-  };
-
-  const onKeyUp = (event: KeyboardEvent) => {
-    if (event.key === 'Shift') {
-      event.preventDefault();
-      shiftKeyIsDown = false;
-    }
-  };
-  const handleSelectAssetCandidates = (asset: TimelineAsset | null) => {
-    if (asset) {
-      void selectAssetCandidates(asset);
-    }
-    lastAssetMouseEvent = asset;
-  };
-
-  const handleGroupSelect = (timelineManager: TimelineManager, group: string, assets: TimelineAsset[]) => {
-    if (assetInteraction.selectedGroup.has(group)) {
-      assetInteraction.removeGroupFromMultiselectGroup(group);
-      for (const asset of assets) {
-        assetInteraction.removeAssetFromMultiselectGroup(asset.id);
-      }
-    } else {
-      assetInteraction.addGroupToMultiselectGroup(group);
-      for (const asset of assets) {
-        handleSelectAsset(asset);
-      }
-    }
-
-    if (timelineManager.assetCount == assetInteraction.selectedAssets.length) {
-      isSelectingAllAssets.set(true);
-    } else {
-      isSelectingAllAssets.set(false);
-    }
-  };
-
-  const handleSelectAssets = async (asset: TimelineAsset) => {
-    if (!asset) {
-      return;
-    }
-    onSelect(asset);
-
-    if (singleSelect) {
-      timelineManager.scrollTo(0);
-      return;
-    }
-
-    const rangeSelection = assetInteraction.assetSelectionCandidates.length > 0;
-    const deselect = assetInteraction.hasSelectedAsset(asset.id);
-
-    // Select/deselect already loaded assets
-    if (deselect) {
-      for (const candidate of assetInteraction.assetSelectionCandidates) {
-        assetInteraction.removeAssetFromMultiselectGroup(candidate.id);
-      }
-      assetInteraction.removeAssetFromMultiselectGroup(asset.id);
-    } else {
-      for (const candidate of assetInteraction.assetSelectionCandidates) {
-        handleSelectAsset(candidate);
-      }
-      handleSelectAsset(asset);
-    }
-
-    assetInteraction.clearAssetSelectionCandidates();
-
-    if (assetInteraction.assetSelectionStart && rangeSelection) {
-      let startBucket = timelineManager.getMonthGroupByAssetId(assetInteraction.assetSelectionStart.id);
-      let endBucket = timelineManager.getMonthGroupByAssetId(asset.id);
-
-      if (startBucket === null || endBucket === null) {
-        return;
-      }
-
-      // Select/deselect assets in range (start,end)
-      let started = false;
-      for (const monthGroup of timelineManager.months) {
-        if (monthGroup === endBucket) {
-          break;
-        }
-        if (started) {
-          await timelineManager.loadMonthGroup(monthGroup.yearMonth);
-          for (const asset of monthGroup.assetsIterator()) {
-            if (deselect) {
-              assetInteraction.removeAssetFromMultiselectGroup(asset.id);
-            } else {
-              handleSelectAsset(asset);
-            }
-          }
-        }
-        if (monthGroup === startBucket) {
-          started = true;
-        }
-      }
-
-      // Update date group selection in range [start,end]
-      started = false;
-      for (const monthGroup of timelineManager.months) {
-        if (monthGroup === startBucket) {
-          started = true;
-        }
-        if (started) {
-          // Split month group into day groups and check each group
-          for (const dayGroup of monthGroup.dayGroups) {
-            const dayGroupTitle = dayGroup.groupTitle;
-            if (dayGroup.getAssets().every((a) => assetInteraction.hasSelectedAsset(a.id))) {
-              assetInteraction.addGroupToMultiselectGroup(dayGroupTitle);
-            } else {
-              assetInteraction.removeGroupFromMultiselectGroup(dayGroupTitle);
-            }
-          }
-        }
-        if (monthGroup === endBucket) {
-          break;
-        }
-      }
-    }
-
-    assetInteraction.setAssetSelectionStart(deselect ? null : asset);
-  };
-
-  const selectAssetCandidates = async (endAsset: TimelineAsset) => {
-    if (!shiftKeyIsDown) {
-      return;
-    }
-
-    const startAsset = assetInteraction.assetSelectionStart;
-    if (!startAsset) {
-      return;
-    }
-
-    const assets = assetsSnapshot(await timelineManager.retrieveRange(startAsset, endAsset));
-    assetInteraction.setAssetSelectionCandidates(assets);
-  };
-
-  $effect(() => {
-    if (!lastAssetMouseEvent) {
-      assetInteraction.clearAssetSelectionCandidates();
-    }
-  });
-
-  $effect(() => {
-    if (!shiftKeyIsDown) {
-      assetInteraction.clearAssetSelectionCandidates();
-    }
-  });
-
-  $effect(() => {
-    if (shiftKeyIsDown && lastAssetMouseEvent) {
-      void selectAssetCandidates(lastAssetMouseEvent);
-    }
-  });
-
   $effect(() => {
     if ($showAssetViewer) {
       const { localDateTime } = getTimes($viewingAsset.fileCreatedAt, DateTime.local().offset / 60);
@@ -536,8 +360,6 @@
   });
 </script>
 
-<svelte:document onkeydown={onKeyDown} onkeyup={onKeyUp} />
-
 <HotModuleReload
   onAfterUpdate={() => {
     const asset = page.url.searchParams.get('at');
@@ -573,21 +395,6 @@
     {viewportTopMonth}
     {onScrub}
     bind:scrubberWidth
-    onScrubKeyDown={(evt) => {
-      evt.preventDefault();
-      let amount = 50;
-      if (shiftKeyIsDown) {
-        amount = 500;
-      }
-      if (evt.key === 'ArrowUp') {
-        amount = -amount;
-        if (shiftKeyIsDown) {
-          scrollableElement?.scrollBy({ top: amount, behavior: 'smooth' });
-        }
-      } else if (evt.key === 'ArrowDown') {
-        scrollableElement?.scrollBy({ top: amount, behavior: 'smooth' });
-      }
-    }}
   />
 {/if}
 
@@ -643,20 +450,56 @@
           style:transform={`translate3d(0,${absoluteHeight}px,0)`}
           style:width="100%"
         >
-          <TimelineDateGroup
-            {withStacked}
-            {showArchiveIcon}
-            {assetInteraction}
+          <AssetSelectionController
             {timelineManager}
+            {assetInteraction}
             {isSelectionMode}
             {singleSelect}
-            {monthGroup}
-            onSelect={({ title, assets }) => handleGroupSelect(timelineManager, title, assets)}
-            onSelectAssetCandidates={handleSelectAssetCandidates}
-            onSelectAssets={handleSelectAssets}
-            {customLayout}
-            {onThumbnailClick}
-          />
+            {onAssetOpen}
+            {onAssetSelect}
+          >
+            {#snippet content({ onAssetOpen, onAssetSelect, onAssetHover })}
+              <DaySelectionController {assetInteraction} {onAssetSelect}>
+                {#snippet content({ onDayGroupSelect, onDayGroupAssetSelect })}
+                  <Month
+                    {assetInteraction}
+                    {customThumbnailLayout}
+                    {singleSelect}
+                    {monthGroup}
+                    manager={timelineManager}
+                    {onDayGroupSelect}
+                  >
+                    {#snippet thumbnail({ asset, position, dayGroup, groupIndex })}
+                      {@const isAssetSelectionCandidate = assetInteraction.hasSelectionCandidate(asset.id)}
+                      {@const isAssetSelected =
+                        assetInteraction.hasSelectedAsset(asset.id) || timelineManager.albumAssets.has(asset.id)}
+                      {@const isAssetDisabled = timelineManager.albumAssets.has(asset.id)}
+                      <Thumbnail
+                        showStackedIcon={withStacked}
+                        {showArchiveIcon}
+                        {asset}
+                        {groupIndex}
+                        onClick={() => onAssetOpen(asset)}
+                        onSelect={() => onDayGroupAssetSelect(dayGroup, asset)}
+                        onMouseEvent={(isMouseOver) => {
+                          if (isMouseOver) {
+                            onAssetHover(asset);
+                          } else {
+                            onAssetHover(null);
+                          }
+                        }}
+                        selected={isAssetSelected}
+                        selectionCandidate={isAssetSelectionCandidate}
+                        disabled={isAssetDisabled}
+                        thumbnailWidth={position.width}
+                        thumbnailHeight={position.height}
+                      />
+                    {/snippet}
+                  </Month>
+                {/snippet}
+              </DaySelectionController>
+            {/snippet}
+          </AssetSelectionController>
         </div>
       {/if}
     {/each}

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

@@ -1,246 +0,0 @@
-<script lang="ts">
-  import Thumbnail from '$lib/components/assets/thumbnail/thumbnail.svelte';
-  import type { DayGroup } from '$lib/managers/timeline-manager/day-group.svelte';
-  import type { MonthGroup } from '$lib/managers/timeline-manager/month-group.svelte';
-  import type { TimelineManager } from '$lib/managers/timeline-manager/timeline-manager.svelte';
-  import type { TimelineAsset } from '$lib/managers/timeline-manager/types';
-  import { assetSnapshot, assetsSnapshot } from '$lib/managers/timeline-manager/utils.svelte';
-  import type { AssetInteraction } from '$lib/stores/asset-interaction.svelte';
-  import { isSelectingAllAssets } from '$lib/stores/assets-store.svelte';
-  import { uploadAssetsStore } from '$lib/stores/upload';
-  import { navigate } from '$lib/utils/navigation';
-
-  import { mdiCheckCircle, mdiCircleOutline } from '@mdi/js';
-
-  import { fromTimelinePlainDate, getDateLocaleString } from '$lib/utils/timeline-util';
-  import { Icon } from '@immich/ui';
-  import { type Snippet } from 'svelte';
-  import { flip } from 'svelte/animate';
-  import { scale } from 'svelte/transition';
-
-  let { isUploading } = uploadAssetsStore;
-
-  interface Props {
-    isSelectionMode: boolean;
-    singleSelect: boolean;
-    withStacked: boolean;
-    showArchiveIcon: boolean;
-    monthGroup: MonthGroup;
-    timelineManager: TimelineManager;
-    assetInteraction: AssetInteraction;
-    customLayout?: Snippet<[TimelineAsset]>;
-
-    onSelect: ({ title, assets }: { title: string; assets: TimelineAsset[] }) => void;
-    onSelectAssets: (asset: TimelineAsset) => void;
-    onSelectAssetCandidates: (asset: TimelineAsset | null) => void;
-    onThumbnailClick?: (
-      asset: TimelineAsset,
-      timelineManager: TimelineManager,
-      dayGroup: DayGroup,
-      onClick: (
-        timelineManager: TimelineManager,
-        assets: TimelineAsset[],
-        groupTitle: string,
-        asset: TimelineAsset,
-      ) => void,
-    ) => void;
-  }
-
-  let {
-    isSelectionMode,
-    singleSelect,
-    withStacked,
-    showArchiveIcon,
-    monthGroup = $bindable(),
-    assetInteraction,
-    timelineManager,
-    customLayout,
-    onSelect,
-    onSelectAssets,
-    onSelectAssetCandidates,
-
-    onThumbnailClick,
-  }: Props = $props();
-
-  let isMouseOverGroup = $state(false);
-  let hoveredDayGroup = $state();
-
-  const transitionDuration = $derived.by(() =>
-    monthGroup.timelineManager.suspendTransitions && !$isUploading ? 0 : 150,
-  );
-  const scaleDuration = $derived(transitionDuration === 0 ? 0 : transitionDuration + 100);
-  const _onClick = (
-    timelineManager: TimelineManager,
-    assets: TimelineAsset[],
-    groupTitle: string,
-    asset: TimelineAsset,
-  ) => {
-    if (isSelectionMode || assetInteraction.selectionActive) {
-      assetSelectHandler(timelineManager, asset, assets, groupTitle);
-      return;
-    }
-    void navigate({ targetRoute: 'current', assetId: asset.id });
-  };
-
-  const handleSelectGroup = (title: string, assets: TimelineAsset[]) => onSelect({ title, assets });
-
-  const assetSelectHandler = (
-    timelineManager: TimelineManager,
-    asset: TimelineAsset,
-    assetsInDayGroup: TimelineAsset[],
-    groupTitle: string,
-  ) => {
-    onSelectAssets(asset);
-
-    // Check if all assets are selected in a group to toggle the group selection's icon
-    let selectedAssetsInGroupCount = assetsInDayGroup.filter((asset) =>
-      assetInteraction.hasSelectedAsset(asset.id),
-    ).length;
-
-    // if all assets are selected in a group, add the group to selected group
-    if (selectedAssetsInGroupCount == assetsInDayGroup.length) {
-      assetInteraction.addGroupToMultiselectGroup(groupTitle);
-    } else {
-      assetInteraction.removeGroupFromMultiselectGroup(groupTitle);
-    }
-
-    if (timelineManager.assetCount == assetInteraction.selectedAssets.length) {
-      isSelectingAllAssets.set(true);
-    } else {
-      isSelectingAllAssets.set(false);
-    }
-  };
-
-  const assetMouseEventHandler = (groupTitle: string, asset: TimelineAsset | null) => {
-    // Show multi select icon on hover on date group
-    hoveredDayGroup = groupTitle;
-
-    if (assetInteraction.selectionActive) {
-      onSelectAssetCandidates(asset);
-    }
-  };
-
-  function filterIntersecting<R extends { intersecting: boolean }>(intersectable: R[]) {
-    return intersectable.filter((int) => int.intersecting);
-  }
-
-  const getDayGroupFullDate = (dayGroup: DayGroup): string => {
-    const { month, year } = dayGroup.monthGroup.yearMonth;
-    const date = fromTimelinePlainDate({
-      year,
-      month,
-      day: dayGroup.day,
-    });
-    return getDateLocaleString(date);
-  };
-</script>
-
-{#each filterIntersecting(monthGroup.dayGroups) as dayGroup, groupIndex (dayGroup.day)}
-  {@const absoluteWidth = dayGroup.left}
-
-  <!-- svelte-ignore a11y_no_static_element_interactions -->
-  <section
-    class={[
-      { 'transition-all': !monthGroup.timelineManager.suspendTransitions },
-      !monthGroup.timelineManager.suspendTransitions && `delay-${transitionDuration}`,
-    ]}
-    data-group
-    style:position="absolute"
-    style:transform={`translate3d(${absoluteWidth}px,${dayGroup.top}px,0)`}
-    onmouseenter={() => {
-      isMouseOverGroup = true;
-      assetMouseEventHandler(dayGroup.groupTitle, null);
-    }}
-    onmouseleave={() => {
-      isMouseOverGroup = false;
-      assetMouseEventHandler(dayGroup.groupTitle, null);
-    }}
-  >
-    <!-- Date group title -->
-    <div
-      class="flex pt-7 pb-5 max-md:pt-5 max-md:pb-3 h-6 place-items-center text-xs font-medium text-immich-fg dark:text-immich-dark-fg md:text-sm"
-      style:width={dayGroup.width + 'px'}
-    >
-      {#if !singleSelect}
-        <div
-          class="hover:cursor-pointer transition-all duration-200 ease-out overflow-hidden w-0"
-          class:w-8={(hoveredDayGroup === dayGroup.groupTitle && isMouseOverGroup) ||
-            assetInteraction.selectedGroup.has(dayGroup.groupTitle)}
-          onclick={() => handleSelectGroup(dayGroup.groupTitle, assetsSnapshot(dayGroup.getAssets()))}
-          onkeydown={() => handleSelectGroup(dayGroup.groupTitle, assetsSnapshot(dayGroup.getAssets()))}
-        >
-          {#if assetInteraction.selectedGroup.has(dayGroup.groupTitle)}
-            <Icon icon={mdiCheckCircle} size="24" class="text-primary" />
-          {:else}
-            <Icon icon={mdiCircleOutline} size="24" color="#757575" />
-          {/if}
-        </div>
-      {/if}
-
-      <span class="w-full truncate first-letter:capitalize" title={getDayGroupFullDate(dayGroup)}>
-        {dayGroup.groupTitle}
-      </span>
-    </div>
-
-    <!-- Image grid -->
-    <div
-      data-image-grid
-      class="relative overflow-clip"
-      style:height={dayGroup.height + 'px'}
-      style:width={dayGroup.width + 'px'}
-    >
-      {#each filterIntersecting(dayGroup.viewerAssets) as viewerAsset (viewerAsset.id)}
-        {@const position = viewerAsset.position!}
-        {@const asset = viewerAsset.asset!}
-
-        <!-- {#if viewerAsset.intersecting} -->
-        <!-- note: don't remove data-asset-id - its used by web e2e tests -->
-        <div
-          data-asset-id={asset.id}
-          class="absolute"
-          style:top={position.top + 'px'}
-          style:left={position.left + 'px'}
-          style:width={position.width + 'px'}
-          style:height={position.height + 'px'}
-          out:scale|global={{ start: 0.1, duration: scaleDuration }}
-          animate:flip={{ duration: transitionDuration }}
-        >
-          <Thumbnail
-            showStackedIcon={withStacked}
-            {showArchiveIcon}
-            {asset}
-            {groupIndex}
-            onClick={(asset) => {
-              if (typeof onThumbnailClick === 'function') {
-                onThumbnailClick(asset, timelineManager, dayGroup, _onClick);
-              } else {
-                _onClick(timelineManager, dayGroup.getAssets(), dayGroup.groupTitle, asset);
-              }
-            }}
-            onSelect={(asset) => assetSelectHandler(timelineManager, asset, dayGroup.getAssets(), dayGroup.groupTitle)}
-            onMouseEvent={() => assetMouseEventHandler(dayGroup.groupTitle, assetSnapshot(asset))}
-            selected={assetInteraction.hasSelectedAsset(asset.id) ||
-              dayGroup.monthGroup.timelineManager.albumAssets.has(asset.id)}
-            selectionCandidate={assetInteraction.hasSelectionCandidate(asset.id)}
-            disabled={dayGroup.monthGroup.timelineManager.albumAssets.has(asset.id)}
-            thumbnailWidth={position.width}
-            thumbnailHeight={position.height}
-          />
-          {#if customLayout}
-            {@render customLayout(asset)}
-          {/if}
-        </div>
-        <!-- {/if} -->
-      {/each}
-    </div>
-  </section>
-{/each}
-
-<style>
-  section {
-    contain: layout paint style;
-  }
-  [data-image-grid] {
-    user-select: none;
-  }
-</style>

web/src/routes/(user)/albums/[albumId=id]/[[photos=photos]]/[[assetId=id]]/+page.svelte

@@ -441,7 +441,7 @@
         {isSelectionMode}
         {singleSelect}
         {showArchiveIcon}
-        {onSelect}
+        onAssetSelect={onSelect}
         onEscape={handleEscape}
       >
         {#if viewMode !== AlbumPageViewMode.SELECT_ASSETS}

web/src/routes/(user)/people/[personId]/[[photos=photos]]/[[assetId=id]]/+page.svelte

@@ -371,7 +371,7 @@
       {assetInteraction}
       isSelectionMode={viewMode === PersonPageViewMode.SELECT_PERSON}
       singleSelect={viewMode === PersonPageViewMode.SELECT_PERSON}
-      onSelect={handleSelectFeaturePhoto}
+      onAssetSelect={handleSelectFeaturePhoto}
       onEscape={handleEscape}
     >
       {#if viewMode === PersonPageViewMode.VIEW_ASSETS}

web/src/routes/(user)/utilities/geolocation/+page.svelte

@@ -5,7 +5,6 @@
   import Timeline from '$lib/components/timeline/Timeline.svelte';
   import { AssetAction } from '$lib/constants';
   import { authManager } from '$lib/managers/auth-manager.svelte';
-  import type { DayGroup } from '$lib/managers/timeline-manager/day-group.svelte';
   import { TimelineManager } from '$lib/managers/timeline-manager/timeline-manager.svelte';
   import type { TimelineAsset } from '$lib/managers/timeline-manager/types';
   import GeolocationUpdateConfirmModal from '$lib/modals/GeolocationUpdateConfirmModal.svelte';
@@ -110,17 +109,7 @@
     return !!asset.latitude && !!asset.longitude;
   };
 
-  const handleThumbnailClick = (
-    asset: TimelineAsset,
-    timelineManager: TimelineManager,
-    dayGroup: DayGroup,
-    onClick: (
-      timelineManager: TimelineManager,
-      assets: TimelineAsset[],
-      groupTitle: string,
-      asset: TimelineAsset,
-    ) => void,
-  ) => {
+  const handleAssetOpen = (asset: TimelineAsset, defaultAssetOpen: () => void) => {
     if (hasGps(asset)) {
       locationUpdated = true;
       setTimeout(() => {
@@ -128,9 +117,9 @@
       }, 1500);
       location = { latitude: asset.latitude!, longitude: asset.longitude! };
       void setQueryValue('at', asset.id);
-    } else {
-      onClick(timelineManager, dayGroup.getAssets(), dayGroup.groupTitle, asset);
+      return;
     }
+    defaultAssetOpen();
   };
 </script>
 
@@ -194,9 +183,9 @@
     removeAction={AssetAction.ARCHIVE}
     onEscape={handleEscape}
     withStacked
-    onThumbnailClick={handleThumbnailClick}
+    onAssetOpen={handleAssetOpen}
   >
-    {#snippet customLayout(asset: TimelineAsset)}
+    {#snippet customThumbnailLayout(asset: TimelineAsset)}
       {#if hasGps(asset)}
         <div class="absolute bottom-1 end-3 px-4 py-1 rounded-xl text-xs transition-colors bg-success text-black">
           {asset.city || $t('gps')}