feat: initial package implementation

src/index.ts

@@ -1,3 +1,67 @@
-export function helloWorld() {
-  return 'Hello World!';
+import {
+  ApolloServer,
+  BaseContext,
+  ContextFunction,
+  HeaderMap,
+} from '@apollo/server';
+import { parse } from 'url';
+import { http, type HttpFunction } from '@google-cloud/functions-framework';
+import type { WithRequired } from '@apollo/utils.withrequired';
+
+interface Options<Context extends BaseContext> {
+  context?: ContextFunction<Parameters<HttpFunction>, Context>;
+  functionName: string;
+}
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+const defaultContext: ContextFunction<[], any> = async () => ({});
+
+export function startServerAndCreateGoogleCloudFunctionsHandler(
+  server: ApolloServer<BaseContext>,
+  options: Options<BaseContext>,
+): any;
+export function startServerAndCreateGoogleCloudFunctionsHandler<
+  Context extends BaseContext,
+>(
+  server: ApolloServer<Context>,
+  options: WithRequired<Options<Context>, 'context'>,
+): any;
+export function startServerAndCreateGoogleCloudFunctionsHandler<
+  Context extends BaseContext,
+>(server: ApolloServer<Context>, options: Options<Context>) {
+  server.startInBackgroundHandlingStartupErrorsByLoggingAndFailingAllRequests();
+
+  const contextFunction = options?.context || defaultContext;
+  const handler = http(options.functionName, async (req, res) => {
+    const headers = new HeaderMap();
+
+    for (const [key, value] of Object.entries(req.headers)) {
+      if (typeof value === 'string') {
+        headers.set(key, value);
+      }
+    }
+
+    const httpGraphQLResponse = await server.executeHTTPGraphQLRequest({
+      context: () => contextFunction(req, res),
+      httpGraphQLRequest: {
+        body: req.body,
+        headers,
+        method: req.method || 'POST',
+        search: req.url ? parse(req.url).search || '' : '',
+      },
+    });
+
+    res.statusCode = httpGraphQLResponse.status || 200;
+
+    if (httpGraphQLResponse.body.kind === 'complete') {
+      res.send(httpGraphQLResponse.body.string);
+    } else {
+      for await (const chunk of httpGraphQLResponse.body.asyncIterator) {
+        res.write(chunk);
+      }
+      res.end();
+    }
+  });
+
+  return handler;
 }