feat(media): add phase5 media provider abstraction and stream credentials APIs

Backend/media/providers/mock.ts

@@ -0,0 +1,96 @@
+import { createHmac } from 'crypto';
+
+import type {
+  MediaProvider,
+  MediaPublishCredentials,
+  MediaSessionCreateInput,
+  MediaSessionCreateResult,
+  MediaSubscribeCredentials,
+} from '../types';
+
+const secret = process.env.BETTER_AUTH_SECRET;
+
+if (!secret) {
+  throw new Error('BETTER_AUTH_SECRET is required for mock media provider token signing');
+}
+
+const DEFAULT_TTL_SECONDS = 60 * 10;
+
+const signToken = (payload: Record<string, unknown>, ttlSeconds = DEFAULT_TTL_SECONDS): { token: string; expiresInSeconds: number } => {
+  const body = {
+    ...payload,
+    exp: Math.floor(Date.now() / 1000) + ttlSeconds,
+  };
+
+  const encoded = Buffer.from(JSON.stringify(body), 'utf8').toString('base64url');
+  const signature = createHmac('sha256', secret).update(encoded).digest('base64url');
+
+  return {
+    token: `${encoded}.${signature}`,
+    expiresInSeconds: ttlSeconds,
+  };
+};
+
+const getBaseUrl = (): string => process.env.MEDIA_MOCK_BASE_URL ?? process.env.BETTER_AUTH_URL ?? 'http://localhost:3000';
+
+export class MockMediaProvider implements MediaProvider {
+  name = 'mock';
+
+  async createSession(input: MediaSessionCreateInput): Promise<MediaSessionCreateResult> {
+    const mediaSessionId = `mock_${input.streamSessionId}`;
+    const baseUrl = getBaseUrl();
+
+    return {
+      provider: this.name,
+      mediaSessionId,
+      publishUrl: `${baseUrl}/media/mock/publish/${mediaSessionId}`,
+      subscribeUrl: `${baseUrl}/media/mock/subscribe/${mediaSessionId}`,
+    };
+  }
+
+  async issuePublishCredentials(input: {
+    mediaSessionId: string;
+    cameraDeviceId: string;
+    ownerUserId: string;
+  }): Promise<MediaPublishCredentials> {
+    const baseUrl = getBaseUrl();
+    const { token, expiresInSeconds } = signToken({
+      typ: 'publish',
+      provider: this.name,
+      mediaSessionId: input.mediaSessionId,
+      cameraDeviceId: input.cameraDeviceId,
+      ownerUserId: input.ownerUserId,
+    });
+
+    return {
+      provider: this.name,
+      mediaSessionId: input.mediaSessionId,
+      publishToken: token,
+      publishUrl: `${baseUrl}/media/mock/publish/${input.mediaSessionId}`,
+      expiresInSeconds,
+    };
+  }
+
+  async issueSubscribeCredentials(input: {
+    mediaSessionId: string;
+    viewerDeviceId: string;
+    ownerUserId: string;
+  }): Promise<MediaSubscribeCredentials> {
+    const baseUrl = getBaseUrl();
+    const { token, expiresInSeconds } = signToken({
+      typ: 'subscribe',
+      provider: this.name,
+      mediaSessionId: input.mediaSessionId,
+      viewerDeviceId: input.viewerDeviceId,
+      ownerUserId: input.ownerUserId,
+    });
+
+    return {
+      provider: this.name,
+      mediaSessionId: input.mediaSessionId,
+      subscribeToken: token,
+      subscribeUrl: `${baseUrl}/media/mock/subscribe/${input.mediaSessionId}`,
+      expiresInSeconds,
+    };
+  }
+}

Backend/media/service.ts

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+import { MockMediaProvider } from './providers/mock';
+import type { MediaProvider } from './types';
+
+const providerName = (process.env.MEDIA_PROVIDER ?? 'mock').toLowerCase();
+
+const createProvider = (): MediaProvider => {
+  switch (providerName) {
+    case 'mock':
+      return new MockMediaProvider();
+    default:
+      throw new Error(`Unsupported MEDIA_PROVIDER: ${providerName}`);
+  }
+};
+
+export const mediaProvider = createProvider();

Backend/media/types.ts

@@ -0,0 +1,44 @@
+export type MediaSessionCreateInput = {
+  streamSessionId: string;
+  ownerUserId: string;
+  cameraDeviceId: string;
+  requesterDeviceId: string;
+};
+
+export type MediaPublishCredentials = {
+  provider: string;
+  mediaSessionId: string;
+  publishToken: string;
+  publishUrl: string;
+  expiresInSeconds: number;
+};
+
+export type MediaSubscribeCredentials = {
+  provider: string;
+  mediaSessionId: string;
+  subscribeToken: string;
+  subscribeUrl: string;
+  expiresInSeconds: number;
+};
+
+export type MediaSessionCreateResult = {
+  provider: string;
+  mediaSessionId: string;
+  publishUrl: string;
+  subscribeUrl: string;
+};
+
+export interface MediaProvider {
+  name: string;
+  createSession(input: MediaSessionCreateInput): Promise<MediaSessionCreateResult>;
+  issuePublishCredentials(input: {
+    mediaSessionId: string;
+    cameraDeviceId: string;
+    ownerUserId: string;
+  }): Promise<MediaPublishCredentials>;
+  issueSubscribeCredentials(input: {
+    mediaSessionId: string;
+    viewerDeviceId: string;
+    ownerUserId: string;
+  }): Promise<MediaSubscribeCredentials>;
+}