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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 | /**
* Subtitle Cache Service
*
* Provides caching and preloading functionality for subtitle files
* to enable instant subtitle switching without delays.
*/
interface CachedSubtitle {
url: string;
content: string;
timestamp: number;
}
class SubtitleCacheService {
private cache: Map<string, CachedSubtitle> = new Map();
private maxCacheSize: number = 50; // Maximum number of subtitles to cache
private maxCacheAge: number = 1000 * 60 * 30; // 30 minutes
/**
* Preload all subtitles for a content item
*/
async preloadSubtitles(subtitles: Array<{ url: string; language: string; label: string }>): Promise<void> {
const promises = subtitles.map(sub => this.fetchAndCache(sub.url));
await Promise.all(promises).catch(() => {});
}
/**
* Fetch and cache a subtitle file
*/
private async fetchAndCache(url: string): Promise<string> {
// Check if already cached and not expired
const cached = this.cache.get(url);
if (cached && (Date.now() - cached.timestamp) < this.maxCacheAge) {
return cached.content;
}
const response = await fetch(url, {
credentials: 'include',
headers: {
'Accept': 'text/vtt,text/plain,*/*'}});
if (!response.ok) {
throw new Error(`HTTP ${response.status}: ${response.statusText}`);
}
const content = await response.text();
// Store in cache
this.cache.set(url, {
url,
content,
timestamp: Date.now()});
// Enforce cache size limit
this.enforceMaxCacheSize();
return content;
}
/**
* Get a subtitle from cache or fetch it
*/
async getSubtitle(url: string): Promise<string> {
return this.fetchAndCache(url);
}
/**
* Check if a subtitle is cached
*/
isCached(url: string): boolean {
const cached = this.cache.get(url);
if (!cached) return false;
// Check if expired
if ((Date.now() - cached.timestamp) >= this.maxCacheAge) {
this.cache.delete(url);
return false;
}
return true;
}
/**
* Get cached subtitle content without fetching
*/
getCachedContent(url: string): string | null {
const cached = this.cache.get(url);
if (!cached) return null;
// Check if expired
if ((Date.now() - cached.timestamp) >= this.maxCacheAge) {
this.cache.delete(url);
return null;
}
return cached.content;
}
/**
* Create a blob URL from cached subtitle content
*/
createBlobUrl(url: string): string | null {
const content = this.getCachedContent(url);
if (!content) return null;
const blob = new Blob([content], { type: 'text/vtt' });
return URL.createObjectURL(blob);
}
/**
* Enforce maximum cache size by removing oldest entries
*/
private enforceMaxCacheSize(): void {
if (this.cache.size <= this.maxCacheSize) return;
// Sort by timestamp (oldest first)
const entries = Array.from(this.cache.entries()).sort(
(a, b) => a[1].timestamp - b[1].timestamp
);
// Remove oldest entries until we're under the limit
const toRemove = entries.slice(0, this.cache.size - this.maxCacheSize);
toRemove.forEach(([url]) => {
this.cache.delete(url);
});
}
/**
* Clear all cached subtitles
*/
clearCache(): void {
this.cache.clear();
}
/**
* Clear expired cache entries
*/
clearExpired(): void {
const now = Date.now();
for (const [url, cached] of this.cache.entries()) {
if ((now - cached.timestamp) >= this.maxCacheAge) {
this.cache.delete(url);
}
}
}
/**
* Get cache statistics
*/
getStats(): { size: number; maxSize: number; urls: string[] } {
return {
size: this.cache.size,
maxSize: this.maxCacheSize,
urls: Array.from(this.cache.keys())};
}
}
// Export singleton instance
export const subtitleCache = new SubtitleCacheService();
// Periodically clear expired entries (every 5 minutes)
if (typeof window !== 'undefined') {
setInterval(() => {
subtitleCache.clearExpired();
}, 1000 * 60 * 5);
}
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