From ae527b9d866520696f5c03b02c00651c7b6617fc Mon Sep 17 00:00:00 2001
From: Aponia <brianmv@uci.edu>
Date: Mon, 16 Oct 2023 16:46:21 -0700
Subject: [PATCH] =?UTF-8?q?feat:=20=E2=9C=A8=20warming=20body=20in=20lambd?=
 =?UTF-8?q?a=20lib?=
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---
 apps/api/bronya.config.ts  |  9 +--------
 libs/lambda/src/handler.ts | 30 ++++++++++++++++++++++++++++++
 libs/lambda/src/index.ts   |  2 ++
 libs/lambda/src/request.ts |  7 +++++++
 4 files changed, 40 insertions(+), 8 deletions(-)
 create mode 100644 libs/lambda/src/handler.ts
 create mode 100644 libs/lambda/src/request.ts

diff --git a/apps/api/bronya.config.ts b/apps/api/bronya.config.ts
index d53e8d87..9c082989 100644
--- a/apps/api/bronya.config.ts
+++ b/apps/api/bronya.config.ts
@@ -4,7 +4,7 @@ import { join, resolve } from "node:path";
 import { Api, type ApiConstructProps } from "@bronya.js/api-construct";
 import { createApiCliPlugins } from "@bronya.js/api-construct/plugins/cli";
 import { isCdk } from "@bronya.js/core";
-import { logger } from "@libs/lambda";
+import { logger, warmingRequestBody } from "@libs/lambda";
 import { LambdaIntegration, ResponseType } from "aws-cdk-lib/aws-apigateway";
 import { Certificate } from "aws-cdk-lib/aws-certificatemanager";
 import { RuleTargetInput, Rule, Schedule } from "aws-cdk-lib/aws-events";
@@ -79,13 +79,6 @@ const prismaSchema = resolve(libsDbDirectory, "prisma", prismaSchemaFile);
  */
 const prismaQueryEngineFile = "libquery_engine-linux-arm64-openssl-1.0.x.so.node";
 
-/**
- * The body of a warming request.
- *
- * TODO: actually recognize warming requests in the route handlers.
- */
-const warmingRequestBody = { body: "warming request" };
-
 /**
  * Shared ESBuild options.
  */
diff --git a/libs/lambda/src/handler.ts b/libs/lambda/src/handler.ts
new file mode 100644
index 00000000..b882008a
--- /dev/null
+++ b/libs/lambda/src/handler.ts
@@ -0,0 +1,30 @@
+import type { APIGatewayProxyEvent, Context, APIGatewayProxyResult } from "aws-lambda";
+
+import { warmingRequestBody } from "./request";
+import { createOKResult, createErrorResult } from "./response";
+
+export type ResponseHelpers = {
+  ok: typeof createOKResult;
+  error: typeof createErrorResult;
+};
+
+export type ExtendedApiGatewayHandler = (
+  event: APIGatewayProxyEvent,
+  context: Context,
+  res: ResponseHelpers,
+) => APIGatewayProxyResult | Promise<APIGatewayProxyResult>;
+
+export function createHandler(handler: ExtendedApiGatewayHandler): ExtendedApiGatewayHandler {
+  return async function (event, context) {
+    const res: ResponseHelpers = {
+      ok: (payload, headers, requestId) => createOKResult(payload, headers, requestId),
+      error: (statusCode, e, requestId) => createErrorResult(statusCode, e, requestId),
+    };
+
+    if (event.body === JSON.stringify(warmingRequestBody)) {
+      return res.ok("Successfully warmed!", event.headers, context.awsRequestId);
+    }
+
+    return handler(event, context, res);
+  };
+}
diff --git a/libs/lambda/src/index.ts b/libs/lambda/src/index.ts
index 4747115a..13471763 100644
--- a/libs/lambda/src/index.ts
+++ b/libs/lambda/src/index.ts
@@ -2,3 +2,5 @@ export * from "./logger";
 export * from "./compress";
 export * from "./response";
 export * from "./constants";
+export * from "./request";
+export * from "./handler";
diff --git a/libs/lambda/src/request.ts b/libs/lambda/src/request.ts
new file mode 100644
index 00000000..a824b231
--- /dev/null
+++ b/libs/lambda/src/request.ts
@@ -0,0 +1,7 @@
+/**
+ * The body of a warming request.
+ *
+ * A warming request is periodically sent to ensure that the Lambda function is active.
+ * Ideally, it wouldn't trigger any expensive computations.
+ */
+export const warmingRequestBody = { body: "warming request" };