94 lines
2.4 KiB
TypeScript
94 lines
2.4 KiB
TypeScript
import { createHash } from 'crypto';
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import { existsSync, mkdirSync, statSync, createReadStream, writeFileSync } from 'fs';
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import { join } from 'path';
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import type { Readable } from 'stream';
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const MAX_AGE_MS = 24 * 60 * 60 * 1000; // 24 hours
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export class ScreenshotCache {
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private dir: string;
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constructor(dir: string) {
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this.dir = dir;
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if (!existsSync(dir)) {
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mkdirSync(dir, { recursive: true });
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}
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}
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/**
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* Build a cache key by quantizing view params and hashing.
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* - lat/lon quantized to 2 decimal places
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* - zoom quantized to integer
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* - filters and POI categories sorted alphabetically
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*/
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buildKey(params: URLSearchParams): string {
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const normalized: Record<string, string> = {};
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// Quantize lat/lon/zoom
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const lat = params.get('lat');
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const lon = params.get('lon');
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const zoom = params.get('zoom');
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if (lat && lon && zoom) {
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normalized.lat = parseFloat(lat).toFixed(2);
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normalized.lon = parseFloat(lon).toFixed(2);
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normalized.zoom = Math.round(parseFloat(zoom)).toString();
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}
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// Sort filters
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const filters = params.getAll('filter').sort();
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if (filters.length > 0) {
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normalized.filters = filters.join(',');
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}
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// Sort POI categories
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const pois = params.getAll('poi').sort();
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if (pois.length > 0) {
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normalized.poi = pois.join(',');
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}
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if (params.get('tab')) {
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normalized.tab = params.get('tab')!;
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}
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if (params.get('og')) {
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normalized.og = params.get('og')!;
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}
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if (params.get('path')) {
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normalized.path = params.get('path')!;
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}
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const input = JSON.stringify(normalized);
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const hash = createHash('sha256').update(input).digest('hex').substring(0, 16);
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return hash;
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}
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getPath(key: string): string {
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return join(this.dir, `${key}.jpg`);
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}
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/**
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* Returns a readable stream if a fresh cached file exists, null otherwise.
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*/
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get(key: string): Readable | null {
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const path = this.getPath(key);
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if (!existsSync(path)) return null;
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try {
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const stat = statSync(path);
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const age = Date.now() - stat.mtimeMs;
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if (age > MAX_AGE_MS) return null;
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return createReadStream(path);
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} catch {
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return null;
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}
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}
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/**
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* Write screenshot bytes to cache.
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*/
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set(key: string, data: Buffer): void {
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const path = this.getPath(key);
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writeFileSync(path, data);
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}
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}
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