feat: support calling AppSync from Lambda

Author: hoegertn

src/client/appsync.ts

@@ -0,0 +1,41 @@
+import { parse, UrlWithStringQuery } from 'url';
+import * as AWS from 'aws-sdk';
+import * as axios from 'axios';
+
+export class AppSyncClient {
+
+  protected readonly graphQlServerUri: UrlWithStringQuery;
+
+  constructor(protected readonly graphQlServerUrl: string, protected readonly awsRegion: string) {
+    this.graphQlServerUri = parse(this.graphQlServerUrl);
+    if (!this.graphQlServerUri.href) {
+      throw new Error('Invalid GraphQL server URL');
+    }
+  }
+
+  public async call(operationName: string, query: string, variables: any = {}): Promise<axios.AxiosResponse<any>> {
+    const post_body = {
+      operationName,
+      query,
+      variables,
+    };
+
+    const httpRequest = new AWS.HttpRequest(new AWS.Endpoint(this.graphQlServerUri.href!), this.awsRegion);
+    httpRequest.headers.host = this.graphQlServerUri.host!;
+    httpRequest.headers['Content-Type'] = 'application/json';
+    httpRequest.method = 'POST';
+    httpRequest.body = JSON.stringify(post_body);
+
+    await ((AWS.config.credentials as AWS.Credentials)?.getPromise());
+
+    // Signers is an internal API
+    const signer = new (AWS as any).Signers.V4(httpRequest, 'appsync', true);
+    signer.addAuthorization(AWS.config.credentials, (AWS as any).util.date.getDate());
+
+    const res = await axios.default.post(this.graphQlServerUri.href!, httpRequest.body, {
+      headers: httpRequest.headers,
+    });
+    return res;
+  }
+
+}

src/client/index.ts

@@ -0,0 +1 @@
+export * from './appsync';

src/index.ts

@@ -1,3 +1,4 @@
 export * as errors from './types/errors';
 export * as dynamodb from './dynamodb';
 export * as http from './http';
+export * as client from './client';