seahaven-slack-bot/lib/constructs/slack-handler.ts

import * as cdk from 'aws-cdk-lib';
import { Construct } from 'constructs';
import * as lambda from 'aws-cdk-lib/aws-lambda';
import * as lambdaNodejs from 'aws-cdk-lib/aws-lambda-nodejs';
import * as apigatewayv2 from 'aws-cdk-lib/aws-apigatewayv2';
import { HttpLambdaIntegration } from 'aws-cdk-lib/aws-apigatewayv2-integrations';
import * as dynamodb from 'aws-cdk-lib/aws-dynamodb';
import * as iam from 'aws-cdk-lib/aws-iam';
import * as secretsmanager from 'aws-cdk-lib/aws-secretsmanager';
import * as route53 from 'aws-cdk-lib/aws-route53';
import * as route53Targets from 'aws-cdk-lib/aws-route53-targets';
import * as acm from 'aws-cdk-lib/aws-certificatemanager';
import * as path from 'path';

export interface SlackHandlerProps {
  accountId: string;
  region: string;
  agentId: string;
  agentAliasId: string;
  conversationTable: dynamodb.Table;
  wildcardCertArn: string;
}

export class SlackHandlerConstruct extends Construct {
  public readonly webhookLambda: lambdaNodejs.NodejsFunction;
  public readonly processorLambda: lambdaNodejs.NodejsFunction;
  public readonly api: apigatewayv2.HttpApi;

  constructor(scope: Construct, id: string, props: SlackHandlerProps) {
    super(scope, id);

    // Slack credentials secret (created manually — see README for structure)
    const slackSecret = secretsmanager.Secret.fromSecretNameV2(
      this, 'SlackSecret', 'seahaven/slack/credentials',
    );

    // ── Processor Lambda ──────────────────────────────────────────────────────
    // Async worker: calls Bedrock Agent, writes to DynamoDB, posts reply to Slack.
    // Timeout is generous — agent invocations with multi-step tool use can take 2–3 min.
    this.processorLambda = new lambdaNodejs.NodejsFunction(this, 'ProcessorFn', {
      functionName: 'seahaven-slack-processor',
      entry: path.join(__dirname, '../../lambda/slack-processor/index.ts'),
      handler: 'handler',
      runtime: lambda.Runtime.NODEJS_22_X,
      timeout: cdk.Duration.minutes(5),
      memorySize: 512,
      environment: {
        AGENT_ID: props.agentId,
        AGENT_ALIAS_ID: props.agentAliasId,
        CONVERSATION_TABLE: props.conversationTable.tableName,
        SLACK_SECRET_ARN: slackSecret.secretArn,
        REGION: props.region,
      },
      bundling: {
        externalModules: ['@aws-sdk/*'],
        minify: true,
        sourceMap: false,
      },
    });

    slackSecret.grantRead(this.processorLambda);
    props.conversationTable.grantReadWriteData(this.processorLambda);

    this.processorLambda.addToRolePolicy(new iam.PolicyStatement({
      actions: ['bedrock:InvokeAgent'],
      resources: [
        // Wildcard on agent alias — agentAliasId is a CDK token resolved at synth
        `arn:aws:bedrock:${props.region}:${props.accountId}:agent/${props.agentId}`,
        `arn:aws:bedrock:${props.region}:${props.accountId}:agent-alias/${props.agentId}/*`,
      ],
    }));

    // ── Webhook Lambda ────────────────────────────────────────────────────────
    // Synchronous: verifies Slack signature, returns 200 immediately, fires processor async.
    this.webhookLambda = new lambdaNodejs.NodejsFunction(this, 'WebhookFn', {
      functionName: 'seahaven-slack-webhook',
      entry: path.join(__dirname, '../../lambda/slack-webhook/index.ts'),
      handler: 'handler',
      runtime: lambda.Runtime.NODEJS_22_X,
      timeout: cdk.Duration.seconds(10),
      memorySize: 256,
      environment: {
        PROCESSOR_FUNCTION_NAME: this.processorLambda.functionName,
        SLACK_SECRET_ARN: slackSecret.secretArn,
      },
      bundling: {
        externalModules: ['@aws-sdk/*'],
        minify: true,
        sourceMap: false,
      },
    });

    slackSecret.grantRead(this.webhookLambda);
    this.processorLambda.grantInvoke(this.webhookLambda);

    // ── HTTP API (API Gateway v2) ──────────────────────────────────────────────
    this.api = new apigatewayv2.HttpApi(this, 'Api', {
      apiName: 'seahaven-slack-webhook',
      description: 'Receives Slack event webhook calls for Sea Haven bot',
    });

    this.api.addRoutes({
      path: '/slack/events',
      methods: [apigatewayv2.HttpMethod.POST],
      integration: new HttpLambdaIntegration('WebhookIntegration', this.webhookLambda),
    });

    // ── Custom domain: bot.seahaven.com ───────────────────────────────────────
    const certificate = acm.Certificate.fromCertificateArn(
      this, 'WildcardCert', props.wildcardCertArn,
    );

    const hostedZone = route53.HostedZone.fromLookup(this, 'SeahavenZone', {
      domainName: 'seahaven.com',
    });

    const customDomain = new apigatewayv2.DomainName(this, 'CustomDomain', {
      domainName: 'bot.seahaven.com',
      certificate,
    });

    new apigatewayv2.ApiMapping(this, 'ApiMapping', {
      api: this.api,
      domainName: customDomain,
      stage: this.api.defaultStage!,
    });

    new route53.ARecord(this, 'BotDnsRecord', {
      zone: hostedZone,
      recordName: 'bot',
      target: route53.RecordTarget.fromAlias(
        new route53Targets.ApiGatewayv2DomainProperties(
          customDomain.regionalDomainName,
          customDomain.regionalHostedZoneId,
        ),
      ),
    });

    new cdk.CfnOutput(scope, 'SlackWebhookUrl', {
      value: 'https://bot.seahaven.com/slack/events',
      description: 'Paste this into Slack app → Event Subscriptions → Request URL',
    });
  }
}