import * as cdk from "@aws-cdk/core";
import {Duration} from "@aws-cdk/core";
import * as sns from "@aws-cdk/aws-sns";
import * as subs from "@aws-cdk/aws-sns-subscriptions";
import * as cw from "@aws-cdk/aws-cloudwatch";
import {ComparisonOperator} from "@aws-cdk/aws-cloudwatch";
import * as actions from "@aws-cdk/aws-cloudwatch-actions";

export class CloudwatchAlarmsStack extends cdk.Stack {
  constructor(scope: cdk.Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const topic = this.createTopic('foo@example.com');
    this.alertOnLambdaProducesAnyError(topic, 'lambda-a');
    this.alertOnLambdaProducesAnyError(topic, 'lambda-b');
  }

  createTopic(notifyEmail: string) {
    const topic = new sns.Topic(this, 'oly-monitoring', {
      displayName: 'OlyServiceMonitoring',
    });
    topic.addSubscription(
        new subs.EmailSubscription(notifyEmail),
    );
    return topic;
  }

  alertOnLambdaProducesAnyError(topic: sns.Topic, lambdaName: string) {
    const alarm = new cw.Alarm(this, `any-errors-${lambdaName}`, {
      alarmName: `any-errors-${lambdaName}`,
      actionsEnabled: true,
      alarmDescription: `Notify for any errors logged for the lambda function ${lambdaName}`,
      threshold: 1,
      evaluationPeriods: 1,
      comparisonOperator: ComparisonOperator.GREATER_THAN_OR_EQUAL_TO_THRESHOLD,

      metric: new cw.Metric({
        namespace: 'AWS/Lambda',
        metricName: 'Errors',
        dimensionsMap: {
          'FunctionName': lambdaName,
        },
        statistic: 'min',
        period: Duration.minutes(1),
      }),
    });

    alarm.addAlarmAction(new actions.SnsAction(topic));
  }

}