Add screenshot server

og-screenshot/src/cache.ts

@@ -0,0 +1,88 @@
+import { createHash } from 'crypto';
+import { existsSync, mkdirSync, statSync, createReadStream, writeFileSync } from 'fs';
+import { join } from 'path';
+import type { Readable } from 'stream';
+
+const MAX_AGE_MS = 24 * 60 * 60 * 1000; // 24 hours
+
+export class ScreenshotCache {
+  private dir: string;
+
+  constructor(dir: string) {
+    this.dir = dir;
+    if (!existsSync(dir)) {
+      mkdirSync(dir, { recursive: true });
+    }
+  }
+
+  /**
+   * Build a cache key by quantizing view params and hashing.
+   * - lat/lng quantized to 2 decimal places
+   * - zoom quantized to integer
+   * - filters sorted alphabetically
+   */
+  buildKey(params: Record<string, string>): string {
+    const normalized: Record<string, string> = {};
+
+    // Parse and quantize the view param (lat,lng,zoom)
+    if (params.v) {
+      const parts = params.v.split(',');
+      if (parts.length === 3) {
+        const lat = parseFloat(parts[0]).toFixed(2);
+        const lng = parseFloat(parts[1]).toFixed(2);
+        const zoom = Math.round(parseFloat(parts[2])).toString();
+        normalized.v = `${lat},${lng},${zoom}`;
+      } else {
+        normalized.v = params.v;
+      }
+    }
+
+    // Sort filters
+    if (params.f) {
+      const segments = params.f.split(',').sort();
+      normalized.f = segments.join(',');
+    }
+
+    if (params.poi) {
+      const cats = params.poi.split(',').sort();
+      normalized.poi = cats.join(',');
+    }
+
+    if (params.tab) {
+      normalized.tab = params.tab;
+    }
+
+    const input = JSON.stringify(normalized);
+    const hash = createHash('sha256').update(input).digest('hex').substring(0, 16);
+    return hash;
+  }
+
+  getPath(key: string): string {
+    return join(this.dir, `${key}.png`);
+  }
+
+  /**
+   * Returns a readable stream if a fresh cached file exists, null otherwise.
+   */
+  get(key: string): Readable | null {
+    const path = this.getPath(key);
+    if (!existsSync(path)) return null;
+
+    try {
+      const stat = statSync(path);
+      const age = Date.now() - stat.mtimeMs;
+      if (age > MAX_AGE_MS) return null;
+      return createReadStream(path);
+    } catch {
+      return null;
+    }
+  }
+
+  /**
+   * Write screenshot bytes to cache.
+   */
+  set(key: string, data: Buffer): void {
+    const path = this.getPath(key);
+    writeFileSync(path, data);
+  }
+}