From eb3855915cbe8ace4ecb22746f01a384eb950887 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1=C5=A1=20Ml=C3=A1dek?= <t@mldk.cz>
Date: Mon, 28 Jul 2025 11:03:00 +0200
Subject: [PATCH] feat: implement unified AssetLoader service for prioritized
 image and audio loading

---
 src/components/AudioArea.vue   |  30 ++--
 src/components/VideoScroll.vue |  19 +-
 src/services/AssetLoader.ts    | 306 +++++++++++++++++++++++++++++++++
 3 files changed, 335 insertions(+), 20 deletions(-)
 create mode 100644 src/services/AssetLoader.ts

diff --git a/src/components/AudioArea.vue b/src/components/AudioArea.vue
index 1b3078f..f9b45a6 100644
--- a/src/components/AudioArea.vue
+++ b/src/components/AudioArea.vue
@@ -5,7 +5,7 @@
 <script lang="ts">
 import { defineComponent, PropType, ref, watch } from "vue";
 import { BoundingBox } from "@/components/SVGContent.vue";
-import { queueAudioForLoading } from "@/services/AudioLoader";
+import { queueAudioForLoading } from "@/services/AssetLoader";
 
 export default defineComponent({
   name: "AudioArea",
@@ -23,6 +23,7 @@ export default defineComponent({
     const audio = ref<HTMLAudioElement | null>(null);
     const audioSrc = ref<string>(""); // Ref to hold audio source after preloading
     const isPreloaded = ref<boolean>(false);
+    const distance = ref<number>(0);
 
     console.debug(`[AUDIOAREA] Initializing ${props.definition.src}...`);
     console.debug(props.definition);
@@ -31,24 +32,23 @@ export default defineComponent({
     // Use the global audio loading queue to throttle concurrent loads
     const preloadAudio = (src: string) => {
       console.debug(`[AUDIOAREA] Queueing audio for preload: ${src}`);
-
-      // Set audioSrc to empty initially
       audioSrc.value = "";
 
-      // Queue the audio for loading through our global service
-      // Our improved AudioLoader will cache and deduplicate requests
-      queueAudioForLoading(src)
-        .then((blobUrl) => {
+      queueAudioForLoading(
+        src,
+        () => distance.value,
+        (blobUrl) => {
           // Use blob URL to avoid keeping connections open
           audioSrc.value = blobUrl;
           isPreloaded.value = true;
           console.debug(`[AUDIOAREA] Successfully preloaded audio: ${src}`);
-        })
-        .catch((error) => {
+        },
+        (error) => {
           console.error(`[AUDIOAREA] Error preloading audio: ${error}`);
           // Fall back to original source if preloading fails
           audioSrc.value = src;
-        });
+        }
+      );
     };
 
     // Start preloading when component is created
@@ -64,12 +64,12 @@ export default defineComponent({
 
       const x = props.bbox.x + props.bbox.w / 2;
       const y = props.bbox.y + props.bbox.h / 2;
-      const distance = Math.sqrt(
-        Math.pow(x - props.definition.cx, 2) +
-          Math.pow(y - props.definition.cy, 2)
+      distance.value = Math.hypot(
+        x - props.definition.cx,
+        y - props.definition.cy
       );
 
-      if (distance < props.definition.radius) {
+      if (distance.value < props.definition.radius) {
         if (audio.value!.paused) {
           console.debug(
             `[AUDIOAREA] Entered audio area "${props.definition.src}", starting playback...`
@@ -77,7 +77,7 @@ export default defineComponent({
           audio.value!.play();
         }
         const volume =
-          (props.definition.radius - distance) / props.definition.radius;
+          (props.definition.radius - distance.value) / props.definition.radius;
         audio.value!.volume =
           volume * (props.bbox.z < 1 ? props.bbox.z * vol_x + vol_b : 1);
       } else {
diff --git a/src/components/VideoScroll.vue b/src/components/VideoScroll.vue
index 8d3c3fb..e126ea9 100644
--- a/src/components/VideoScroll.vue
+++ b/src/components/VideoScroll.vue
@@ -18,7 +18,7 @@
 <script lang="ts">
 import { defineComponent, PropType } from "vue";
 import { rotate } from "@/utils";
-import { queueImageForLoading } from "@/services/ImageLoader";
+import { queueImageForLoading } from "@/services/AssetLoader";
 
 export default defineComponent({
   name: "VideoScroll",
@@ -97,10 +97,19 @@ export default defineComponent({
           element.classList.add("visible");
           if (!element.src && element.dataset.src) {
             // Queue the image for loading through the global service
-            const self = this;
-            queueImageForLoading(element, function() {
-              self.handleImageLoad(element);
-            });
+            // Calculate the image's position to prioritize closer images
+            queueImageForLoading(
+              element,
+              () => {
+                return Math.hypot(
+                  element.getBoundingClientRect().left - window.innerWidth / 2,
+                  element.getBoundingClientRect().top - window.innerHeight / 2
+                );
+              },
+              () => {
+                this.handleImageLoad(element);
+              }
+            );
 
             // Add a fallback to show the image after a timeout even if not fully loaded
             setTimeout(() => {
diff --git a/src/services/AssetLoader.ts b/src/services/AssetLoader.ts
new file mode 100644
index 0000000..01a2b5a
--- /dev/null
+++ b/src/services/AssetLoader.ts
@@ -0,0 +1,306 @@
+/**
+ * Unified Asset Loader service that handles both image and audio loading
+ * Uses a priority queue to prioritize assets based on type and proximity
+ */
+
+// Configuration
+const MAX_CONCURRENT_IMAGE_LOADS = 5;
+const MAX_CONCURRENT_AUDIO_LOADS = 1;
+const RETRY_DELAY_MS = 200;
+
+// Types
+export enum AssetType {
+  IMAGE = "image",
+  AUDIO = "audio",
+}
+
+export interface ImageAsset {
+  type: AssetType.IMAGE;
+  element: HTMLImageElement;
+  getDistance: () => number;
+  onComplete: () => void;
+}
+
+export interface AudioAsset {
+  type: AssetType.AUDIO;
+  src: string;
+  getDistance: () => number;
+  onComplete: (blobUrl: string) => void;
+  onError: (error: Error) => void;
+}
+
+type Asset = ImageAsset | AudioAsset;
+
+// State
+let activeImageLoads = 0;
+let activeAudioLoads = 0;
+
+const assetQueue: Asset[] = [];
+
+const loadedAudioCache: Record<string, string> = {};
+const pendingAudioLoads: Set<string> = new Set();
+
+/**
+ * Check if there are any assets queued or actively loading
+ */
+export function hasQueuedAssets(): boolean {
+  return assetQueue.length > 0 || activeImageLoads > 0 || activeAudioLoads > 0;
+}
+
+/**
+ * Check if there are any images queued or actively loading
+ */
+export function hasQueuedImages(): boolean {
+  return (
+    assetQueue.some((asset) => asset.type === AssetType.IMAGE) ||
+    activeImageLoads > 0
+  );
+}
+
+/**
+ * Queue an image for loading, respecting the global concurrent loading limit
+ */
+export function queueImageForLoading(
+  element: HTMLImageElement,
+  getDistance: () => number,
+  onComplete?: () => void
+) {
+  if (!element.dataset.src) {
+    console.warn("[AssetLoader] Element has no data-src attribute");
+    return;
+  }
+
+  // Add to queue
+  assetQueue.push({
+    type: AssetType.IMAGE,
+    element,
+    onComplete: onComplete || (() => {}),
+    getDistance,
+  });
+
+  // Try to process queue
+  processQueue();
+}
+
+/**
+ * Queue an audio file for loading, respecting the global concurrent loading limit
+ * Returns a promise that resolves with the blob URL when loading is complete
+ */
+export function queueAudioForLoading(
+  src: string,
+  getDistance: () => number,
+  onComplete?: (blobUrl: string) => void,
+  onError?: (error: Error) => void
+): Promise<string> {
+  // Return cached result immediately if available
+  if (loadedAudioCache[src]) {
+    console.debug(`[AssetLoader] Using cached audio for ${src}`);
+    const blobUrl = loadedAudioCache[src];
+    if (onComplete) setTimeout(() => onComplete(blobUrl), 0);
+    return Promise.resolve(blobUrl);
+  }
+
+  // Create promise for this request
+  return new Promise((resolve, reject) => {
+    // If this source is already being loaded, add to queue with same source
+    // It will be grouped during loading
+    const asset: AudioAsset = {
+      type: AssetType.AUDIO,
+      src,
+      onComplete: (blobUrl) => {
+        if (onComplete) onComplete(blobUrl);
+        resolve(blobUrl);
+      },
+      onError: (error) => {
+        if (onError) onError(error);
+        reject(error);
+      },
+      getDistance,
+    };
+
+    // Add to queue
+    assetQueue.push(asset);
+
+    // Track pending loads
+    if (!pendingAudioLoads.has(src)) {
+      pendingAudioLoads.add(src);
+    }
+
+    // Try to process queue
+    processQueue();
+  });
+}
+
+/**
+ * Sort the queue based on priority
+ */
+function sortQueue(): void {
+  assetQueue.sort((a, b) => {
+    return a.getDistance() - b.getDistance();
+  });
+}
+
+/**
+ * Process the next items in the queue if we have capacity
+ */
+function processQueue(): void {
+  sortQueue();
+
+  // First, attempt to process image assets
+  while (
+    activeImageLoads < MAX_CONCURRENT_IMAGE_LOADS &&
+    assetQueue.length > 0
+  ) {
+    // Look for the highest priority image
+    const imageIndex = assetQueue.findIndex(
+      (asset) => asset.type === AssetType.IMAGE
+    );
+    if (imageIndex === -1) break; // No more images in the queue
+
+    const asset = assetQueue.splice(imageIndex, 1)[0] as ImageAsset;
+    loadImage(asset.element, asset.onComplete);
+  }
+
+  // Only process audio if we have capacity and no images are prioritized
+  if (hasQueuedImages()) {
+    // Schedule a retry after a delay to check again for audio processing
+    setTimeout(processQueue, RETRY_DELAY_MS);
+    return;
+  }
+
+  // Process audio assets
+  const pendingAudios: Record<
+    string,
+    Array<{
+      onComplete: (blobUrl: string) => void;
+      onError: (error: Error) => void;
+    }>
+  > = {};
+
+  // Continue loading audio while respecting MAX_CONCURRENT_AUDIO_LOADS
+  while (
+    activeAudioLoads < MAX_CONCURRENT_AUDIO_LOADS &&
+    assetQueue.length > 0
+  ) {
+    const audioIndex = assetQueue.findIndex(
+      (asset) => asset.type === AssetType.AUDIO
+    );
+    if (audioIndex === -1) break; // No more audio in the queue
+
+    const asset = assetQueue.splice(audioIndex, 1)[0] as AudioAsset;
+
+    // If already cached, complete immediately without consuming a slot
+    if (loadedAudioCache[asset.src]) {
+      asset.onComplete(loadedAudioCache[asset.src]);
+      continue;
+    }
+
+    // Group by src to avoid duplicate loads
+    if (!pendingAudios[asset.src]) {
+      pendingAudios[asset.src] = [];
+      activeAudioLoads++;
+    }
+
+    pendingAudios[asset.src].push({
+      onComplete: asset.onComplete,
+      onError: asset.onError,
+    });
+  }
+
+  // Start loading each unique audio file
+  Object.entries(pendingAudios).forEach(([src, handlers]) => {
+    loadAudio(src, handlers);
+  });
+
+  // If we have more items in the queue, schedule another check
+  if (assetQueue.length > 0) {
+    setTimeout(processQueue, RETRY_DELAY_MS);
+  }
+}
+
+/**
+ * Internal function to handle the actual image loading
+ */
+function loadImage(element: HTMLImageElement, onComplete: () => void) {
+  // Increment active loads counter
+  activeImageLoads++;
+
+  const src = element.dataset.src;
+  console.debug(`[AssetLoader] Loading image ${src}`);
+
+  // Start loading the image
+  element.src = src!;
+
+  // Handle load completion
+  const handleCompletion = () => {
+    activeImageLoads--;
+    onComplete();
+    processQueue();
+  };
+
+  // Set handlers
+  element.onload = () => {
+    console.debug(`[AssetLoader] Loaded image ${src}`);
+    handleCompletion();
+  };
+
+  element.onerror = () => {
+    console.error(`[AssetLoader] Failed to load image ${src}`);
+    handleCompletion();
+  };
+}
+
+/**
+ * Internal function to handle the actual audio loading using fetch API
+ * This ensures the entire audio file is downloaded
+ * @param src The source URL to load
+ * @param handlers Array of handlers to call when loading completes or fails
+ */
+async function loadAudio(
+  src: string,
+  handlers: Array<{
+    onComplete: (blobUrl: string) => void;
+    onError: (error: Error) => void;
+  }>
+) {
+  console.debug(
+    `[AssetLoader] Loading audio ${src} (${handlers.length} listeners)`
+  );
+
+  try {
+    // Fetch the entire audio file
+    const response = await fetch(src);
+
+    if (!response.ok) {
+      throw new Error(`Failed to load audio: ${response.statusText}`);
+    }
+
+    // Convert to blob to ensure full download
+    const blob = await response.blob();
+
+    // Create a blob URL to use as the audio source
+    const blobUrl = URL.createObjectURL(blob);
+
+    // Store in cache
+    loadedAudioCache[src] = blobUrl;
+
+    console.debug(`[AssetLoader] Successfully loaded audio ${src}`);
+
+    // Call all completion handlers
+    handlers.forEach((handler) => handler.onComplete(blobUrl));
+  } catch (error) {
+    console.error(`[AssetLoader] Error loading audio: ${error}`);
+
+    // Call all error handlers
+    handlers.forEach((handler) => handler.onError(error as Error));
+  } finally {
+    // Remove from pending loads
+    pendingAudioLoads.delete(src);
+
+    // Decrement counter when audio is loaded (or failed)
+    activeAudioLoads--;
+
+    // Process next asset in queue if available
+    processQueue();
+  }
+}