feat(cloudwatch-actions): support alarm lambda action

packages/aws-cdk-lib/aws-cloudwatch-actions/lib/lambda.ts

@@ -0,0 +1,47 @@
+import { Construct } from 'constructs';
+import * as cloudwatch from '../../aws-cloudwatch';
+import * as lambda from '../../aws-lambda';
+import { Stack } from '../../core';
+
+/**
+ * Use an Lambda action as an Alarm action
+ */
+export class LambdaAction implements cloudwatch.IAlarmAction {
+  private lambdaFunction: lambda.IAlias | lambda.IVersion
+  constructor(
+    lambdaFunction: lambda.IAlias | lambda.IVersion,
+  ) {
+    this.lambdaFunction = lambdaFunction;
+  }
+
+  /**
+   * Returns an alarm action configuration to use an Lambda action as an alarm action
+   *
+   * @see: https://docs.aws.amazon.com/AmazonCloudWatch/latest/APIReference/API_PutMetricAlarm.html
+   *
+   */
+  bind(_scope: Construct, _alarm: cloudwatch.IAlarm): cloudwatch.AlarmActionConfig {
+    if (this.lambdaFunction.stack.account === Stack.of(_scope).account) {
+      new lambda.CfnPermission(_scope, 'AlarmPermission', {
+        sourceAccount: Stack.of(_scope).account,
+        action: 'lambda:InvokeFunction',
+        sourceArn: _alarm.alarmArn,
+        principal: 'lambda.alarms.cloudwatch.amazonaws.com',
+        functionName: this.lambdaFunction.functionName,
+      });
+    }
+    if ((this.lambdaFunction as lambda.IAlias).aliasName) {
+      return {
+        alarmActionArn: `arn:${Stack.of(this.lambdaFunction.stack).partition}:lambda:${Stack.of(this.lambdaFunction.stack).region}:${Stack.of(this.lambdaFunction.stack).account}:function:${this.lambdaFunction.functionName}:${(this.lambdaFunction as lambda.IAlias).aliasName}`,
+      };
+    } else if ((this.lambdaFunction as lambda.IAlias).version) {
+      return {
+        alarmActionArn: `arn:${Stack.of(this.lambdaFunction.stack).partition}:lambda:${Stack.of(this.lambdaFunction.stack).region}:${Stack.of(this.lambdaFunction.stack).account}:function:${this.lambdaFunction.functionName}:${(this.lambdaFunction as lambda.IAlias).version}`,
+      };
+    } else {
+      return {
+        alarmActionArn: `arn:${Stack.of(this.lambdaFunction.stack).partition}:lambda:${Stack.of(this.lambdaFunction.stack).region}:${Stack.of(this.lambdaFunction.stack).account}:function:${this.lambdaFunction.functionName}`,
+      };
+    }
+  }
+}