feat(components/tiles): autoscroll between pages

src/lib/components/tiles/Tile.svelte

@@ -5,13 +5,55 @@ Metro-like tile. Must be in a group to display correctly.
 -->
 
 <script lang="ts">
+    import randomNumber from "$lib/utils/random-number";
     import { cva } from "class-variance-authority";
+    import { onDestroy, onMount } from "svelte";
 
     /**
-     * Base size for a icon in pixels.
+     * Base size of a icon in pixels.
      **/
     const ICON_BASE_SIZE = 45;
 
+    /**
+     * Icon sizes.
+     */
+    const ICON_SIZES = {
+        small: ICON_BASE_SIZE,
+        medium: ICON_BASE_SIZE * 2,
+        wide: ICON_BASE_SIZE * 2,
+        large: ICON_BASE_SIZE * 4,
+    };
+
+    /**
+     * Base size of a page in pixels.
+     */
+    const PAGE_BASE_SIZE = 75;
+
+    /**
+     * Page heights.
+     */
+    const PAGE_HEIGHTS = {
+        small: PAGE_BASE_SIZE,
+        medium: PAGE_BASE_SIZE * 2,
+        wide: PAGE_BASE_SIZE * 2,
+        large: PAGE_BASE_SIZE * 4,
+    };
+
+    /**
+     * Max scroll interval delay in milliseconds.
+     */
+    const SCROLL_INTERVAL_MAX = 10 * 1000;
+
+    /**
+     * Min scroll interval delay in milliseconds.
+     */
+    const SCROLL_INTERVAL_MIN = SCROLL_INTERVAL_MAX / 2;
+
+    /**
+     * Tile element.
+     */
+    let element: HTMLElement;
+
     /**
      * Properties.
      */
@@ -45,43 +87,88 @@ Metro-like tile. Must be in a group to display correctly.
     /**
      * Tile style.
      **/
-    const style = cva(["bg-(--tile-color)", "overflow-y-hidden"], {
-        variants: {
-            size: {
-                small: ["row-span-1", "col-span-1"],
-                medium: ["row-span-2", "col-span-2"],
-                wide: ["row-span-2", "col-span-4"],
-                large: ["row-span-4", "col-span-4"],
+    const style = cva(
+        ["bg-(--tile-color)", "overflow-y-hidden", "scroll-smooth"],
+        {
+            variants: {
+                size: {
+                    small: ["row-span-1", "col-span-1"],
+                    medium: ["row-span-2", "col-span-2"],
+                    wide: ["row-span-2", "col-span-4"],
+                    large: ["row-span-4", "col-span-4"],
+                },
             },
         },
-    });
+    );
 
     /**
-     * Icon size. Based on tile's size.
+     * Icon size.
      */
-    let iconSize: string = $state("0");
-    switch (size) {
-        case "small":
-            iconSize = `${ICON_BASE_SIZE}px`;
-            break;
-        case "medium":
-        case "wide":
-            iconSize = `${ICON_BASE_SIZE * 2}px`;
-            break;
-        case "large":
-            iconSize = `${ICON_BASE_SIZE * 4}px`;
-            break;
+    const iconSize = ICON_SIZES[size];
+
+    /**
+     * Page height.
+     */
+    const pageHeight = PAGE_HEIGHTS[size];
+
+    /**
+     * Scroll side. Positive value is down, negative value is up.
+     */
+    let scrollSide = 1;
+
+    /**
+     * Get page count based on scroll height.
+     */
+    const getPageCount = () => Math.floor(element.scrollHeight / pageHeight);
+
+    /**
+     * Scroll between pages. Used by scroll interval.
+     */
+    function scrollPages() {
+        if (element.clientHeight === element.scrollHeight - pageHeight) {
+            scrollSide = -scrollSide;
+        }
+
+        element.scrollBy({ top: pageHeight * scrollSide });
     }
+
+    /**
+     * Scroll interval.
+     */
+    let scrollInterval: NodeJS.Timeout;
+
+    onMount(() => {
+        if (size === "small" || getPageCount() === 1) {
+            return;
+        }
+
+        const scrollDelay = randomNumber(
+            SCROLL_INTERVAL_MIN,
+            SCROLL_INTERVAL_MAX,
+        );
+
+        scrollInterval = setInterval(scrollPages, scrollDelay);
+    });
+
+    onDestroy(() => {
+        if (!scrollInterval) {
+            return;
+        }
+
+        clearInterval(scrollInterval);
+    });
 </script>
 
 <div
     class={style({ size })}
     style="
-        --tile-icon-size: {iconSize};
+        --tile-icon-size: {iconSize}px;
+        --tile-page-height: {pageHeight}px;
         --tile-name-display: {size !== 'small' ? 'inline' : 'none'};
         grid-row-start: {row};
         grid-column-start: {column};
     "
+    bind:this={element}
 >
     {@render children()}
 </div>