//@flow

import AWS from 'aws-sdk'

import System from './System'
import Module from './Module'
import { throwUnsetArg } from './errorUtils'

const { MODULE_NAME, debug, log, warn, error, noteGauge, noteCount, noteTimer, trackOp } = new Module(__filename) // eslint-disable-line no-unused-vars

class AWSError extends Error {

  message: string
  code: string
  time: string
  statusCode: number
  retryable: boolean
  data: ?any

  
  constructor(err: Error, opName: string, data: ?any) {
    // $FlowIgnore    
    const message = `AWS Op '${opName}' threw '${err.code}': ${err.message}`

    super(message)

    this.message = message
    // $FlowIgnore
    this.code = err.code
    // $FlowIgnore
    this.time = err.time
    // $FlowIgnore
    this.statusCode = err.statusCode
    // $FlowIgnore
    this.retryable = err.retryable

    this.data = data
  }
}

type ClientConfig = {
  region: string,
}

type AWSOpOptions = {
  args?: ?Array<any>,
  opName?: ?string,
  region?: ?string,
  errorHandlers?: ?{ 
    [code: string]: {
      type: 'ignore' | 'retry',
      tries?: ?number,
      action?: ?(err: AWSError) => Promise<void>,
    }
  },
  noLog?: ?boolean,
}

export default class AWSClient {

  constructor() {
    const awsConfig = System.getConfig().aws
    if (!awsConfig)
      throw new Error('aws system config is unset')

    AWS.config.region = awsConfig.defaultRegion
    
    // support local execution
    if (awsConfig.profile) {
      log('Using profile', { profile: awsConfig.profile })
      AWS.config.credentials = new AWS.SharedIniFileCredentials({ profile: awsConfig.profile })
    }
  }

  async runSES<D, E> (
    func: (service: AWS.SES) => AWS.Request<D, E>,
    options: ?AWSOpOptions,
  ): Promise<{ result: D, code?: ?string }> {
    return await this._runOp(
      'SES',
      (clientConfig: ClientConfig) => new AWS.SES(clientConfig),
      func,
      options)
  }

  async runS3<D, E> (
    func: (service: AWS.S3) => AWS.Request<D, E>,
    options: ?AWSOpOptions,
  ): Promise<{ result: D, code?: ?string }> {
    return await this._runOp(
      'S3',
      (clientConfig: ClientConfig) => new AWS.S3(clientConfig),
      func,
      options)
  }

  async runDocumentClient<D, E> (
    func: (service: AWS.DynamoDB.DocumentClient) => AWS.Request<D, E>,
    options: ?AWSOpOptions,
  ): Promise<{ result: D, code?: ?string }> {
    return await this._runOp(
      'DocumentClient',
      (clientConfig: ClientConfig) => new AWS.DynamoDB.DocumentClient({ convertEmptyValues: true, ...clientConfig }),
      func,
      options)
  }

  async runDynamoDB<D, E> (
    func: (service: AWS.DynamoDB) => AWS.Request<D, E>,
    options: ?AWSOpOptions,
  ): Promise<{ result: D, code?: ?string }> {
    return await this._runOp(
      'DynamoDB',
      (clientConfig: ClientConfig) => new AWS.DynamoDB(clientConfig),
      func,
      options)
  }

  async runApplicationAutoScaling<D, E> (
    func: (service: AWS.ApplicationAutoScaling) => AWS.Request<D, E>,
    options: ?AWSOpOptions,
  ): Promise<{ result: D, code?: ?string }> {
    return await this._runOp(
      'ApplicationAutoScaling',
      (clientConfig: ClientConfig) => new AWS.ApplicationAutoScaling(clientConfig),
      func,
      options)
  }

  async runCloudFront<D, E> (
    func: (service: AWS.CloudFront) => AWS.Request<D, E>,
    options: ?AWSOpOptions,
  ): Promise<{ result: D, code?: ?string }> {
    return await this._runOp(
      'CloudFront',
      (clientConfig: ClientConfig) => new AWS.CloudFront(clientConfig),
      func,
      options)
  }

  async runAthena<D, E> (
    func: (service: AWS.Athena) => AWS.Request<D, E>,
    options: ?AWSOpOptions,
  ): Promise<{ result: D, code?: ?string }> {
    return await this._runOp(
      'Athena',
      (clientConfig: ClientConfig) => new AWS.Athena(clientConfig),
      func,
      options)
  }

  async runSQS<D, E> (
    func: (service: AWS.SQS) => AWS.Request<D, E>,
    options: ?AWSOpOptions,
  ): Promise<{ result: D, code?: ?string }> {
    return await this._runOp(
      'SQS',
      (clientConfig: ClientConfig) => new AWS.SQS(clientConfig),
      func,
      options)
  }

  async runCloudWatch<D, E> (
    func: (service: AWS.SQS) => AWS.Request<D, E>,
    options: ?AWSOpOptions,
  ): Promise<{ result: D, code?: ?string }> {
    return await this._runOp(
      'CloudWatch',
      (clientConfig: ClientConfig) => new AWS.CloudWatch(clientConfig),
      func,
      options)
  }

  async runFirehose<D, E> (
    func: (service: AWS.SQS) => AWS.Request<D, E>,
    options: ?AWSOpOptions,
  ): Promise<{ result: D, code?: ?string }> {
    return await this._runOp(
      'Firehose',
      (clientConfig: ClientConfig) => new AWS.Firehose(clientConfig),
      func,
      options)
  }

  async runES<D, E>(
    func: (service: AWS.ES) => AWS.Request<D, E>,
    options: ?AWSOpOptions,
  ): Promise<{ result: D, code?: ?string }> {
    return await this._runOp(
      'Firehose',
      (clientConfig: ClientConfig) => new AWS.ES(clientConfig),
      func,
      options)
  }

  async _runOp<D, E> (
    serviceName: string,
    serviceGenerator: (clientConfig: ClientConfig) => Object,
    func: (service: Object) => AWS.Request<D, E>,
    options: ?AWSOpOptions,
  ): Promise<{ result: D, code?: ?string }> {
    const awsConfig = System.getConfig().aws
    if (!awsConfig)
      throw new Error('aws config not set in system config')
    const region = awsConfig.defaultRegion || (options || {}).region || throwUnsetArg('aws region')

    options = options || {}
    options.errorHandlers = options.errorHandlers || {}

    const credentials = AWS.config.credentials
    let start = 0
    let opName = 'unknown-operation'
    try {
      // TODO: recreate only when creds expire?
      const service = serviceGenerator({ credentials: credentials, region: region })
      const req = func(service)
      if (req === undefined)
        throw new Error(`AWS runXXX method call on service '${serviceName}' is missing, did you user 'return'?`)
      // $FlowIgnore
      opName = options.opName || req['operation']

      if (!options.noLog)
        debug(`AWS operation started...`, {serviceName, opName} )

      let result: D
      let success = false
      let code: ?string
      do {
        try {
          start = Date.now()
          result = await req.promise()
          success = true
        } catch (err) {
          // $FlowIgnore
          const errorHandler = options.errorHandlers[err.code]
          if (!errorHandler) 
            throw err
          switch (errorHandler.type) {
          case 'retry':
            try {
              errorHandler.tries = errorHandler.tries || 1
              if (errorHandler.tries-- > 0 && errorHandler.action) {
                await errorHandler.action(err)
              }
            } catch (err2) {
              err2.leadingError = err
              throw err2
            }
            break
          case 'ignore':
            code = err.code
            success = true
            log(`${serviceName} op '${opName}' completed with an ignorable error code`, { code: code, ms: Date.now() - start })
            break
          default:
            throw new Error(`Unexpected errorHandler type: '${errorHandler.type}'`)
          }
        }
      } while (!success)

      if (!options.noLog)
        debug(`AWS operation completed`, { serviceName, opName, ms: Date.now() - start })
      noteCount(`${MODULE_NAME}.${serviceName}.${opName}.success`, 1)
      // $FlowIgnore   
      return {
        result: result,
        code: code,
      }
    } catch (err) {
      log(`${serviceName} op '${opName}' failed`, { err, args: options.args })
      noteCount(`${MODULE_NAME}.${serviceName}.${opName}.fail`, 1)
      throw new AWSError(err, `${serviceName}.${opName}`, { args: options.args })
    } finally {
      noteTimer(`${MODULE_NAME}.${serviceName}.${opName}`, Date.now() - start)
    }
  }
}