import { EventEmitter } from 'events';
import { SNS } from 'aws-sdk';

import { Config } from '../Config';
import { LogLevels } from './Logger';


export interface Notifier extends EventEmitter {
  sendInfo(summary: string, event: Object, cb?: {(err?: Error)}): any;
  sendWarn(summary: string, event: Object, cb?: {(err?: Error)}): any;
  sendError(summary: string, event: Object, cb?: {(err?: Error)}): any;
}
export interface SNSNotiferConfig {
  snsTopicName: string;
  region: string;
  awsAccountId: string;
  silenceNotifier: boolean;
  snsClient: SNS | null;
}


export class SNSNotifier extends EventEmitter implements Notifier {

  config: SNSNotiferConfig;
  snsClient: SNS;
  mainConfig: Config;

  constructor(config: SNSNotiferConfig, mainConfig: Config) {
    super();
    this.config = config;
    this.mainConfig = mainConfig;
    this.snsClient = config.snsClient || new SNS({region: this.config.region});
  }

  sendInfo(summary: string, event: Object, cb?: {(err?: Error, resp?: SNS.PublishResponse)}) {
    this.sendLevel('info', summary, event, cb);
  }

  sendWarn(summary: string, event: Object, cb?: {(err?: Error, resp?: SNS.PublishResponse)}) {
    this.sendLevel('warn', summary, event, cb);
  }

  sendError(summary: string, event: Object, cb?: {(err?: Error, resp?: SNS.PublishResponse)}) {
    this.sendLevel('error', summary, event, cb);
  }

  getArn(): string {
    return `arn:aws:sns:${this.config.region}:${this.config.awsAccountId}:${this.config.snsTopicName}`;
  }

  sendLevel(level: LogLevels, summary: string, event: any, cb?: {(err?: Error, resp?: SNS.PublishResponse)}) {
    let params = {
      TopicArn: this.getArn(),
      Message: this.buildMessage(level, summary, event),
      Subject: level + ' - ' + summary
    };
    if (this.config.silenceNotifier) {
      return;
    }
    cb = cb || ((err?: Error, resp?: SNS.PublishResponse) => {
        if (err) {
          return this.emit('error', err);
        }
        this.emit('response', resp);
      });
    this.snsClient.publish(params, cb);

  }

  buildMessage(level: LogLevels, summary: string, event: any): string {
    let msg = JSON.stringify({
      domain: this.mainConfig.domainName,
      level: level,
      summary: summary,
      event: event
    });
    return msg;
  }
}