import { config, CloudWatchLogs } from 'aws-sdk'
import { OnModuleInit, Injectable } from '@nestjs/common'
import { format } from 'date-fns'

@Injectable()
export class CloudWatchService implements OnModuleInit {
  private _CloudWatchLogs: CloudWatchLogs

  onModuleInit(): void {
    config.update({
      region: process.env.AWS_SNS_REGION,
    })
    this._CloudWatchLogs = new CloudWatchLogs()
  }

  async putLog(message: string, logName: string): Promise<void> {
    const logGroupName = '/aws/lambda/' + logName + '-' + process.env.STAGE
    const logStreamName = format(new Date(), 'yyyy/MM/dd-HH-mm')

    try {
      await this._CloudWatchLogs.createLogGroup({ logGroupName }).promise()
    } catch (e) {}

    try {
      await this._CloudWatchLogs.createLogStream({ logGroupName, logStreamName }).promise()
    } catch (e) {}

    const sequenceToken = await this.getNextSeqToken(logGroupName, logStreamName)

    const params = {
      logEvents: [
        {
          message,
          timestamp: new Date().getTime(),
        },
      ],
      logGroupName,
      logStreamName,
      sequenceToken,
    }

    try {
      await this._CloudWatchLogs.putLogEvents(params).promise()
    } catch (e) {}
  }

  async getNextSeqToken(logGroupName: string, logStreamName: string): Promise<string | null> {
    const response = await this._CloudWatchLogs
      .describeLogStreams({ logGroupName, logStreamNamePrefix: logStreamName })
      .promise()

    if (response?.logStreams && response?.logStreams?.[0]?.logStreamName == logStreamName)
      return response.logStreams[0].uploadSequenceToken

    return null
  }
}