From 93daf214e7aa58e2911919eb7859c15fc930d7ed Mon Sep 17 00:00:00 2001
From: Kohei Yoshino <kohei.yoshino@gmail.com>
Date: Tue, 17 Dec 2024 15:50:55 -0500
Subject: [PATCH] Implement infinite scroll for list items

---
 .../components/assets/list/asset-list.svelte  | 19 +++---
 .../components/common/infinite-scroll.svelte  | 65 +++++++++++++++++++
 src/lib/components/common/listing-grid.svelte |  9 ++-
 .../contents/list/entry-list.svelte           | 21 +++---
 .../components/contents/list/file-list.svelte | 10 +--
 .../components/search/search-results.svelte   | 18 ++---
 6 files changed, 106 insertions(+), 36 deletions(-)
 create mode 100644 src/lib/components/common/infinite-scroll.svelte

diff --git a/src/lib/components/assets/list/asset-list.svelte b/src/lib/components/assets/list/asset-list.svelte
index ebbdb936..4f7d4802 100644
--- a/src/lib/components/assets/list/asset-list.svelte
+++ b/src/lib/components/assets/list/asset-list.svelte
@@ -1,15 +1,16 @@
 <script>
   import { GridBody } from '@sveltia/ui';
-  import { sleep } from '@sveltia/utils/misc';
   import { _ } from 'svelte-i18n';
   import AssetListItem from '$lib/components/assets/list/asset-list-item.svelte';
   import DropZone from '$lib/components/assets/shared/drop-zone.svelte';
   import EmptyState from '$lib/components/common/empty-state.svelte';
+  import InfiniteScroll from '$lib/components/common/infinite-scroll.svelte';
   import ListContainer from '$lib/components/common/list-container.svelte';
   import ListingGrid from '$lib/components/common/listing-grid.svelte';
   import { globalAssetFolder, selectedAssetFolder, uploadingAssets } from '$lib/services/assets';
   import { assetGroups, currentView, listedAssets } from '$lib/services/assets/view';
 
+  $: viewType = $currentView.type;
   // Can’t upload assets if collection assets are saved at entry-relative paths
   $: uploadDisabled = !!$selectedAssetFolder?.entryRelative;
 </script>
@@ -28,19 +29,19 @@
     {#if Object.values($assetGroups).flat(1).length}
       <ListingGrid
         id="asset-list"
-        viewType={$currentView.type}
+        {viewType}
         aria-label={$_('assets')}
         aria-rowcount={$listedAssets.length}
       >
         {#each Object.entries($assetGroups) as [name, assets] (name)}
           <GridBody label={name !== '*' ? name : undefined}>
-            {#each assets as asset (asset.path)}
-              {#key asset.sha}
-                {#await sleep(0) then}
-                  <AssetListItem {asset} viewType={$currentView.type} />
-                {/await}
-              {/key}
-            {/each}
+            <InfiniteScroll items={assets} itemKey="path">
+              {#snippet renderItem(/** @type {Asset} */ asset)}
+                {#key asset.sha}
+                  <AssetListItem {asset} {viewType} />
+                {/key}
+              {/snippet}
+            </InfiniteScroll>
           </GridBody>
         {/each}
       </ListingGrid>
diff --git a/src/lib/components/common/infinite-scroll.svelte b/src/lib/components/common/infinite-scroll.svelte
new file mode 100644
index 00000000..037e5e21
--- /dev/null
+++ b/src/lib/components/common/infinite-scroll.svelte
@@ -0,0 +1,65 @@
+<!--
+  @component Enable infinite scroll for list items for better rendering performance.
+  @see https://svelte.dev/docs/svelte/v5-migration-guide#Snippets-instead-of-slots-Passing-data-back-up
+-->
+<script>
+  /**
+   * @typedef {object} Props
+   * @property {any[]} items - Item list.
+   * @property {string} itemKey - Item key used for the `each` loop.
+   * @property {number} [itemChunkSize] - Number of items to be loaded at once.
+   * @property {import('svelte').Snippet<[any]>} renderItem - Snippet to render each item.
+   */
+
+  /** @type {Props} */
+  let {
+    /* eslint-disable prefer-const */
+    items,
+    itemKey,
+    itemChunkSize = 25,
+    renderItem,
+    /* eslint-enable prefer-const */
+  } = $props();
+
+  /**
+   * @type {number}
+   */
+  let loadedItemSize = $state(itemChunkSize);
+
+  /**
+   * @type {HTMLElement | undefined}
+   */
+  let spinner = $state(undefined);
+
+  const loading = $derived(items.length > loadedItemSize);
+
+  const observer = new IntersectionObserver(([{ isIntersecting }]) => {
+    if (isIntersecting) {
+      if (loading) {
+        loadedItemSize += itemChunkSize;
+      } else {
+        observer.disconnect();
+      }
+    }
+  });
+
+  $effect(() => {
+    if (spinner) {
+      observer.observe(spinner);
+    }
+  });
+</script>
+
+{#each items.slice(0, loadedItemSize) as item (item[itemKey])}
+  {@render renderItem(item)}
+{/each}
+
+{#if loading}
+  <div role="none" class="spinner" bind:this={spinner}></div>
+{/if}
+
+<style>
+  .spinner {
+    height: 1px;
+  }
+</style>
diff --git a/src/lib/components/common/listing-grid.svelte b/src/lib/components/common/listing-grid.svelte
index 6fd124b8..8e705a9f 100644
--- a/src/lib/components/common/listing-grid.svelte
+++ b/src/lib/components/common/listing-grid.svelte
@@ -4,6 +4,7 @@
 -->
 <script>
   import { Grid } from '@sveltia/ui';
+  import { sleep } from '@sveltia/utils/misc';
 
   /**
    * View type.
@@ -13,9 +14,11 @@
 </script>
 
 <div role="none" class="{viewType}-view">
-  <Grid multiple clickToSelect={false} {...$$restProps}>
-    <slot />
-  </Grid>
+  {#await sleep(0) then}
+    <Grid multiple clickToSelect={false} {...$$restProps}>
+      <slot />
+    </Grid>
+  {/await}
 </div>
 
 <style lang="scss">
diff --git a/src/lib/components/contents/list/entry-list.svelte b/src/lib/components/contents/list/entry-list.svelte
index 5eb4d6dc..25fbd32c 100644
--- a/src/lib/components/contents/list/entry-list.svelte
+++ b/src/lib/components/contents/list/entry-list.svelte
@@ -1,8 +1,8 @@
 <script>
   import { Button, GridBody, Icon } from '@sveltia/ui';
-  import { sleep } from '@sveltia/utils/misc';
   import { _ } from 'svelte-i18n';
   import EmptyState from '$lib/components/common/empty-state.svelte';
+  import InfiniteScroll from '$lib/components/common/infinite-scroll.svelte';
   import ListContainer from '$lib/components/common/list-container.svelte';
   import ListingGrid from '$lib/components/common/listing-grid.svelte';
   import EntryListItem from '$lib/components/contents/list/entry-list-item.svelte';
@@ -28,15 +28,16 @@
         {#each $entryGroups as { name, entries } (name)}
           <!-- @todo Implement custom table column option that can replace summary template -->
           <GridBody label={name !== '*' ? name : undefined}>
-            {#each entries as entry (entry.id)}
-              {#await sleep(0) then}
-                {@const { locales } = entry}
-                {@const { content } = locales[defaultLocale] ?? Object.values(locales)[0] ?? {}}
-                {#if content}
-                  <EntryListItem {collection} {entry} {viewType} />
-                {/if}
-              {/await}
-            {/each}
+            <InfiniteScroll
+              items={entries.filter(
+                ({ locales }) => !!(locales[defaultLocale] ?? Object.values(locales)[0])?.content,
+              )}
+              itemKey="id"
+            >
+              {#snippet renderItem(/** @type {Entry} */ entry)}
+                <EntryListItem {collection} {entry} {viewType} />
+              {/snippet}
+            </InfiniteScroll>
           </GridBody>
         {/each}
       </ListingGrid>
diff --git a/src/lib/components/contents/list/file-list.svelte b/src/lib/components/contents/list/file-list.svelte
index 5e355c82..d3759187 100644
--- a/src/lib/components/contents/list/file-list.svelte
+++ b/src/lib/components/contents/list/file-list.svelte
@@ -1,8 +1,8 @@
 <script>
   import { GridCell, GridRow } from '@sveltia/ui';
-  import { sleep } from '@sveltia/utils/misc';
   import { _ } from 'svelte-i18n';
   import EmptyState from '$lib/components/common/empty-state.svelte';
+  import InfiniteScroll from '$lib/components/common/infinite-scroll.svelte';
   import ListContainer from '$lib/components/common/list-container.svelte';
   import ListingGrid from '$lib/components/common/listing-grid.svelte';
   import { goto } from '$lib/services/app/navigation';
@@ -16,8 +16,8 @@
       aria-label={$_('files')}
       aria-rowcount={$selectedCollection.files.length}
     >
-      {#each $selectedCollection.files as { name, label } (name)}
-        {#await sleep(0) then}
+      <InfiniteScroll items={$selectedCollection.files} itemKey="name">
+        {#snippet renderItem(/** @type {RawCollectionFile} */ { name, label })}
           <GridRow
             onclick={() => {
               goto(`/collections/${$selectedCollection?.name}/entries/${name}`);
@@ -27,8 +27,8 @@
               {label || name}
             </GridCell>
           </GridRow>
-        {/await}
-      {/each}
+        {/snippet}
+      </InfiniteScroll>
     </ListingGrid>
   {:else}
     <EmptyState>
diff --git a/src/lib/components/search/search-results.svelte b/src/lib/components/search/search-results.svelte
index cbfc1d13..3da2cf52 100644
--- a/src/lib/components/search/search-results.svelte
+++ b/src/lib/components/search/search-results.svelte
@@ -1,7 +1,7 @@
 <script>
   import { Group } from '@sveltia/ui';
-  import { sleep } from '@sveltia/utils/misc';
   import { _ } from 'svelte-i18n';
+  import InfiniteScroll from '$lib/components/common/infinite-scroll.svelte';
   import ListingGrid from '$lib/components/common/listing-grid.svelte';
   import AssetResultItem from '$lib/components/search/asset-result-item.svelte';
   import EntryResultItem from '$lib/components/search/entry-result-item.svelte';
@@ -23,11 +23,11 @@
             aria-rowcount={$searchResults.entries.length}
           >
             {#key $searchTerms}
-              {#each $searchResults.entries as entry (entry.id)}
-                {#await sleep(0) then}
+              <InfiniteScroll items={$searchResults.entries} itemKey="id">
+                {#snippet renderItem(/** @type {Entry} */ entry)}
                   <EntryResultItem {entry} />
-                {/await}
-              {/each}
+                {/snippet}
+              </InfiniteScroll>
             {/key}
           </ListingGrid>
         {:else}
@@ -45,11 +45,11 @@
             aria-rowcount={$searchResults.assets.length}
           >
             {#key $searchTerms}
-              {#each $searchResults.assets as asset (asset.path)}
-                {#await sleep(0) then}
+              <InfiniteScroll items={$searchResults.assets} itemKey="path">
+                {#snippet renderItem(/** @type {Asset} */ asset)}
                   <AssetResultItem {asset} />
-                {/await}
-              {/each}
+                {/snippet}
+              </InfiniteScroll>
             {/key}
           </ListingGrid>
         {:else}