AWS CDK sample for Post to Slack in Step Functions using API Gateway

BaseStack.ts

import { PostSlackApiGwStack } from "./PostSlackApiGwStack";

...


    const postSlackGwStack = new PostSlackGwStack(scope, id, props);
    const postSlackGateway = postSlackGwStack.getApiGateway();

    const SLACK_APP_TOKEN = "xoxb-XXXXXXXXXX";

    const collPostSlackApiGatewayInputDefinition =
      new tasks.CallApiGatewayRestApiEndpoint(
        scope,
        "collPostSlackApiGatewayInputDefinition",
        {
          api: postSlackGateway,
          stageName: "prod",
          method: tasks.HttpMethod.POST,
          authType: tasks.AuthType.IAM_ROLE,
          headers: stepfunctions.TaskInput.fromObject({
            "x-Authorization": [`Bearer ${SLACK_APP_TOKEN}`],
          }),
          requestBody: stepfunctions.TaskInput.fromObject({
            channel: "#YOUR_CHANNEL",
            "text.$": "$.message",
          }),
        }
      );

PostSlackApiGwStack.ts

import * as cdk from "aws-cdk-lib";
import { Construct } from "constructs";
import * as apigateway from "aws-cdk-lib/aws-apigateway";

export class PostSlackApiGwStack {
  private postSlackApiGateway;

  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    ////////// API Gateway //////////
    this.postSlackApiGateway = new apigateway.RestApi(
      scope,
      "postSlackApiGateway",
      {}
    );
    this.postSlackApiGateway.root.addMethod(
      "POST",
      new apigateway.HttpIntegration("https://slack.com/api/chat.postMessage", {
        proxy: false,
        httpMethod: "POST",
        options: {
          requestParameters: {
            "integration.request.header.Authorization":
              "method.request.header.x-Authorization",
          },
          integrationResponses: [
            {
              statusCode: "200",
            },
          ],
        },
      }),
      {
        authorizationType: apigateway.AuthorizationType.IAM,
        requestParameters: {
          "method.request.header.x-Authorization": true,
        },
        methodResponses: [
          {
            statusCode: "200",
          },
        ],
      }
    );
  }

  getApiGateway() {
    return this.postSlackApiGateway;
  }
}