aws: add further lambda examples

DevOps/AWS/AWS_Lambda/Code_examples/Handle_multiple_endpoints_single_lambda.md

@@ -0,0 +1,93 @@
+---
+categories:
+  - DevOps
+tags: [AWS, aws-lambda, backend]
+---
+
+# Handle multiple API Gateway endpoints in a single lambda
+
+With the following config we have a single lambda (`/query-waktime`) with multiple endpoints:
+
+```yml
+Resources:
+  QueryWakatimeFunction:
+    Type: AWS::Serverless::Function
+    Properties:
+      CodeUri: src/query-wakatime/
+      Handler: index.handler
+      Events:
+        MainMetrics:
+          Type: Api
+          Properties:
+            Path: /query-wakatime/main-metrics
+            Method: get
+            Auth:
+              Authorizer: AWS_IAM
+        Durations:
+          Type: Api
+          Properties:
+            Path: /query-wakatime/durations
+            Method: get
+            Auth:
+              Authorizer: AWS_IAM
+        TodayOnly:
+          Type: Api
+          Properties:
+            Path: /query-wakatime/today-only
+            Method: get
+            Auth:
+              Authorizer: AWS_IAM
+```
+
+Our endpoints are as follows:
+
+- `/query-wakatime/main-metrics`
+- `/query-wakatime/durations`
+- `/query-wakatime/today-only`
+
+Each returns a different dataset from an external API. The lambda function makes a different request to the API based on the endpoint it receives and the time period that is passed as a query string parameter, e.g. `/query-wakatime?range=last_7_days`.
+
+Below is a template for concisely handling requests to the different endpoints in the single lambda function wihout excessive repetition.
+
+```js
+const getEndpoint = (path: string, timePeriod?: string | undefined) => {
+  const basePath = "/users/current";
+  switch (path) {
+    case "/query-wakatime/main-metrics":
+      return `${basePath}/stats/${timePeriod}`;
+    case "/query-wakatime/durations":
+      return `${basePath}/summaries?range=${timePeriod}`;
+    case "/query-wakatime/today-only":
+      return `${basePath}/status_bar/today`;
+  }
+};
+
+export const handler = async (event) => {
+  const fetchClient = new FetchClient("https://wakatime.com/api/v1/");
+  const path = event.path;
+  const timePeriod = event.queryStringParameters?.timePeriod;
+  const endpoint = getEndpoint(path, timePeriod);
+
+  const init: RequestInit = {
+    headers: {
+      Authorization: `Basic ${encodedApiKey}`,
+    },
+  };
+
+  if (!endpoint) {
+    throw new Error("Endpoint is undefined")
+  }
+
+ let data = await fetchClient.get(endpoint, init)
+ let dataJson = (await data.json()) as string
+
+ response = {
+    statusCode: 200,
+    body: JSON.stringify(dataJson),
+    headers: responseHeaders,
+    }
+};
+
+
+
+```