Add presigned S3 media URLs

src/common/interceptors/media-url.interceptor.ts

@@ -0,0 +1,63 @@
+import { CallHandler, ExecutionContext, Injectable, NestInterceptor } from '@nestjs/common';
+import { from, Observable, switchMap } from 'rxjs';
+import { MediaStorageService } from '../media/media-storage.service';
+
+@Injectable()
+export class MediaUrlInterceptor implements NestInterceptor {
+  constructor(private readonly mediaStorageService: MediaStorageService) {}
+
+  intercept(context: ExecutionContext, next: CallHandler): Observable<unknown> {
+    if (context.getType() !== 'http' || !this.mediaStorageService.shouldSignResponseUrls()) {
+      return next.handle();
+    }
+
+    return next
+      .handle()
+      .pipe(switchMap((data) => from(this.resolveValue(data, new WeakMap<object, unknown>()))));
+  }
+
+  private async resolveValue(value: unknown, seen: WeakMap<object, unknown>): Promise<unknown> {
+    if (typeof value === 'string') {
+      return this.mediaStorageService.resolveResponseUrl(value);
+    }
+
+    if (
+      value === null ||
+      typeof value !== 'object' ||
+      value instanceof Date ||
+      Buffer.isBuffer(value)
+    ) {
+      return value;
+    }
+
+    const existing = seen.get(value);
+    if (existing) {
+      return existing;
+    }
+
+    if (Array.isArray(value)) {
+      const result: unknown[] = [];
+      seen.set(value, result);
+      const entries = await Promise.all(value.map((entry) => this.resolveValue(entry, seen)));
+      result.push(...entries);
+      return result;
+    }
+
+    const serializable =
+      typeof (value as { toJSON?: unknown }).toJSON === 'function'
+        ? (value as { toJSON: () => unknown }).toJSON()
+        : value;
+    if (serializable !== value) {
+      return this.resolveValue(serializable, seen);
+    }
+
+    const result: Record<string, unknown> = {};
+    seen.set(value, result);
+    await Promise.all(
+      Object.entries(value).map(async ([key, entryValue]) => {
+        result[key] = await this.resolveValue(entryValue, seen);
+      }),
+    );
+    return result;
+  }
+}