88 lines
2.2 KiB
TypeScript
88 lines
2.2 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/lng quantized to 2 decimal places
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* - zoom quantized to integer
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* - filters sorted alphabetically
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*/
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buildKey(params: Record<string, string>): string {
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const normalized: Record<string, string> = {};
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// Parse and quantize the view param (lat,lng,zoom)
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if (params.v) {
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const parts = params.v.split(',');
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if (parts.length === 3) {
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const lat = parseFloat(parts[0]).toFixed(2);
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const lng = parseFloat(parts[1]).toFixed(2);
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const zoom = Math.round(parseFloat(parts[2])).toString();
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normalized.v = `${lat},${lng},${zoom}`;
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} else {
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normalized.v = params.v;
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}
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}
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// Sort filters
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if (params.f) {
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const segments = params.f.split(',').sort();
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normalized.f = segments.join(',');
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}
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if (params.poi) {
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const cats = params.poi.split(',').sort();
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normalized.poi = cats.join(',');
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}
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if (params.tab) {
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normalized.tab = params.tab;
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}
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const input = JSON.stringify(normalized);
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const hash = createHash('sha256').update(input).digest('hex').substring(0, 16);
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return hash;
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}
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getPath(key: string): string {
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return join(this.dir, `${key}.png`);
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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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