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* AudioAssetLoader - Handles audio asset loading with retry logic and format fallback
* Implements production-ready asset loading strategies for Black Trigram
*/
import type { AudioAsset } from "./types";
export type LoadPriority = "critical" | "high" | "normal" | "low";
export interface LoadOptions {
readonly priority?: LoadPriority;
readonly maxRetries?: number;
readonly retryDelay?: number;
readonly timeout?: number;
}
export interface LoadResult {
readonly success: boolean;
readonly audio?: HTMLAudioElement;
readonly error?: Error;
readonly attemptCount: number;
readonly loadTime: number;
readonly formatUsed?: string;
}
export interface BatchLoadProgress {
readonly total: number;
readonly loaded: number;
readonly failed: number;
readonly currentAsset?: string;
readonly progress: number;
}
export class AudioAssetLoader {
private loadAttempts: Map<string, number> = new Map();
private loadCache: Map<string, HTMLAudioElement> = new Map();
private loadingPromises: Map<string, Promise<LoadResult>> = new Map();
/**
* Load a single audio asset with retry logic and format fallback
*/
async loadAsset(
asset: AudioAsset,
options: LoadOptions = {}
): Promise<LoadResult> {
const {
priority = "normal",
maxRetries = 3,
retryDelay = 1000,
timeout = 10000,
} = options;
// Check cache first
const cached = this.loadCache.get(asset.id);
if (cached) {
return {
success: true,
audio: cached,
attemptCount: 0,
loadTime: 0,
formatUsed: cached.src,
};
}
// Check if already loading
const existingPromise = this.loadingPromises.get(asset.id);
if (existingPromise) {
return existingPromise;
}
const startTime = performance.now();
const loadPromise = this.loadWithRetry(
asset,
maxRetries,
retryDelay,
timeout,
priority
);
this.loadingPromises.set(asset.id, loadPromise);
try {
const result = await loadPromise;
this.loadingPromises.delete(asset.id);
if (result.success && result.audio) {
this.loadCache.set(asset.id, result.audio);
}
return {
...result,
loadTime: performance.now() - startTime,
};
} catch (error) {
this.loadingPromises.delete(asset.id);
return {
success: false,
error: error instanceof Error ? error : new Error(String(error)),
attemptCount: this.loadAttempts.get(asset.id) ?? 0,
loadTime: performance.now() - startTime,
};
}
}
/**
* Load asset with exponential backoff retry
*/
private async loadWithRetry(
asset: AudioAsset,
maxRetries: number,
baseRetryDelay: number,
timeout: number,
priority: LoadPriority
): Promise<LoadResult> {
let lastError: Error | null = null;
const attemptCount = this.loadAttempts.get(asset.id) ?? 0;
this.loadAttempts.set(asset.id, attemptCount + 1);
// Try all available formats with fallback
const formats = this.getFormatsToTry(asset);
for (let attempt = 0; attempt < maxRetries; attempt++) {
for (const format of formats) {
try {
const audio = await this.tryLoadFormat(format, timeout, priority);
this.loadAttempts.delete(asset.id);
return {
success: true,
audio,
attemptCount: attempt + 1,
loadTime: 0, // Will be set by caller
formatUsed: format,
};
} catch (error) {
lastError = error instanceof Error ? error : new Error(String(error));
console.warn(
`Failed to load ${asset.id} format ${format} on attempt ${attempt + 1}:`,
error
);
}
}
// Exponential backoff before retry
if (attempt < maxRetries - 1) {
const delay = baseRetryDelay * Math.pow(2, attempt);
await this.sleep(delay);
}
}
// All retries failed, return silent placeholder
console.error(
`All attempts failed for ${asset.id}, using silent placeholder`
);
return {
success: false,
audio: this.createSilentPlaceholder(),
error: lastError ?? new Error("All load attempts failed"),
attemptCount: maxRetries,
loadTime: 0,
formatUsed: "placeholder",
};
}
/**
* Get formats to try in order of preference
*/
private getFormatsToTry(asset: AudioAsset): string[] {
const formats: string[] = [];
// Try asset URL first
Eif (asset.url) {
formats.push(asset.url);
}
// Try variations if available
if ("variations" in asset && Array.isArray(asset.variations)) {
formats.push(...asset.variations);
}
// Format fallback: webm → mp3 → wav
if (asset.url.endsWith(".webm")) {
const mp3Url = asset.url.replace(".webm", ".mp3");
Eif (!formats.includes(mp3Url)) {
formats.push(mp3Url);
}
}
return formats;
}
/**
* Try loading a specific format with timeout
*/
private tryLoadFormat(
url: string,
timeout: number,
_priority: LoadPriority
): Promise<HTMLAudioElement> {
return new Promise((resolve, reject) => {
const audio = new Audio();
audio.preload = "auto";
let timeoutId: NodeJS.Timeout | null = null;
let resolved = false;
const onLoad = () => {
if (resolved) return;
resolved = true;
Eif (timeoutId) clearTimeout(timeoutId);
resolve(audio);
};
const onError = () => {
Iif (resolved) return;
resolved = true;
Eif (timeoutId) clearTimeout(timeoutId);
audio.src = "";
reject(new Error(`Failed to load: ${url}`));
};
timeoutId = setTimeout(() => {
Iif (resolved) return;
resolved = true;
audio.src = "";
reject(new Error(`Load timeout after ${timeout}ms`));
}, timeout);
audio.addEventListener("canplaythrough", onLoad, { once: true });
audio.addEventListener("error", onError, { once: true });
audio.src = url;
audio.load();
});
}
/**
* Batch load multiple assets
*/
async batchLoad(
assets: readonly AudioAsset[],
options: LoadOptions = {},
onProgress?: (progress: BatchLoadProgress) => void
): Promise<LoadResult[]> {
const results: LoadResult[] = [];
let loaded = 0;
let failed = 0;
for (const asset of assets) {
onProgress?.({
total: assets.length,
loaded,
failed,
currentAsset: asset.id,
progress: (loaded + 1) / assets.length, // +1 to reflect current asset being loaded
});
const result = await this.loadAsset(asset, options);
results.push(result);
if (result.success) {
loaded++;
} else {
failed++;
}
}
onProgress?.({
total: assets.length,
loaded,
failed,
progress: 1.0,
});
return results;
}
/**
* Preload assets by priority level
*/
async preloadByPriority(
assets: readonly AudioAsset[],
priority: LoadPriority
): Promise<LoadResult[]> {
// Filter assets by priority if they have metadata
const priorityAssets = assets.filter(
(asset) =>
"preloadPriority" in asset && asset.preloadPriority === priority
);
if (priorityAssets.length === 0) {
return [];
}
return this.batchLoad(priorityAssets, { priority });
}
/**
* Unload an asset and free memory
* @param assetId - ID of the asset to unload
* @returns true if the asset was cached and unloaded, false if not found
*/
unloadAsset(assetId: string): boolean {
const audio = this.loadCache.get(assetId);
Eif (audio) {
audio.pause();
audio.src = "";
audio.load(); // Reset to release memory
this.loadCache.delete(assetId);
this.loadAttempts.delete(assetId);
return true;
}
return false;
}
/**
* Get cached audio element
* @param assetId - ID of the asset to retrieve
* @returns The cached audio element or undefined if not found
*/
getCached(assetId: string): HTMLAudioElement | undefined {
return this.loadCache.get(assetId);
}
/**
* Check if asset is cached
* @param assetId - ID of the asset to check
* @returns true if the asset is in cache, false otherwise
*/
isCached(assetId: string): boolean {
return this.loadCache.has(assetId);
}
/**
* Get total number of cached assets
* @returns The number of assets currently in cache
*/
getCacheSize(): number {
return this.loadCache.size;
}
/**
* Clear all cached assets and free memory
*/
clearCache(): void {
this.loadCache.forEach((audio) => {
audio.pause();
audio.src = "";
audio.load();
});
this.loadCache.clear();
this.loadAttempts.clear();
this.loadingPromises.clear();
}
/**
* Create a silent audio placeholder for failed loads
*/
private createSilentPlaceholder(): HTMLAudioElement {
const audio = new Audio();
// Valid 16-bit 44.1kHz mono silent WAV file (0.1s duration = 4410 samples)
// This is a properly formatted WAV file with actual silent audio data
// RIFF header + fmt chunk + data chunk with 4410 samples of 0x00 (16-bit silence)
audio.src =
"data:audio/wav;base64,UklGRuQRAABXQVZFZm10IBAAAAABAAEARKwAAIhYAQACABAAZGF0YQARAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
return audio;
}
/**
* Sleep utility for retry delays
*/
private sleep(ms: number): Promise<void> {
return new Promise((resolve) => setTimeout(resolve, ms));
}
/**
* Get loading statistics including cache size, loading count, and total attempts
* @returns Object with cached count, loading count, and total attempts
*/
getStatistics(): {
readonly cached: number;
readonly loading: number;
readonly totalAttempts: number;
} {
return {
cached: this.loadCache.size,
loading: this.loadingPromises.size,
totalAttempts: Array.from(this.loadAttempts.values()).reduce(
(sum, val) => sum + val,
0
),
};
}
}
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