import { isEmpty } from 'lodash'
import * as Bluebird from 'bluebird'

import { database as db } from '../../initializers/database'
import { logger, makeSecureRequest } from '../../helpers'
import { AbstractRequestClass, AbstractRequestToPodClass, PodInstance } from '../../models'
import {
  API_VERSION,
  REQUESTS_IN_PARALLEL,
  REQUESTS_INTERVAL
} from '../../initializers'

interface RequestsObjects<U> {
  [ id: string ]: {
    toPod: PodInstance
    endpoint: string
    ids: number[] // ids
    datas: U[]
  }
}

abstract class AbstractRequestScheduler <T> {
  requestInterval: number
  limitPods: number
  limitPerPod: number

  protected lastRequestTimestamp: number
  protected timer: NodeJS.Timer
  protected description: string

  constructor () {
    this.lastRequestTimestamp = 0
    this.timer = null
    this.requestInterval = REQUESTS_INTERVAL
  }

  abstract getRequestModel (): AbstractRequestClass<T>
  abstract getRequestToPodModel (): AbstractRequestToPodClass
  abstract buildRequestsObjects (requestsGrouped: T): RequestsObjects<any>

  activate () {
    logger.info('Requests scheduler activated.')
    this.lastRequestTimestamp = Date.now()

    this.timer = setInterval(() => {
      this.lastRequestTimestamp = Date.now()
      this.makeRequests()
    }, this.requestInterval)
  }

  deactivate () {
    logger.info('Requests scheduler deactivated.')
    clearInterval(this.timer)
    this.timer = null
  }

  forceSend () {
    logger.info('Force requests scheduler sending.')
    this.makeRequests()
  }

  remainingMilliSeconds () {
    if (this.timer === null) return -1

    return REQUESTS_INTERVAL - (Date.now() - this.lastRequestTimestamp)
  }

  remainingRequestsCount () {
    return this.getRequestModel().countTotalRequests()
  }

  flush () {
    return this.getRequestModel().removeAll()
  }

  // ---------------------------------------------------------------------------

  // Make a requests to friends of a certain type
  protected async makeRequest (toPod: PodInstance, requestEndpoint: string, requestsToMake: any) {
    const params = {
      toPod: toPod,
      method: 'POST' as 'POST',
      path: '/api/' + API_VERSION + '/remote/' + requestEndpoint,
      data: requestsToMake // Requests we need to make
    }

    // Make multiple retry requests to all of pods
    // The function fire some useful callbacks
    try {
      const { response } = await makeSecureRequest(params)

      // 400 because if the other pod is not up to date, it may not understand our request
      if ([ 200, 201, 204, 400 ].indexOf(response.statusCode) === -1) {
        throw new Error('Status code not 20x or 400 : ' + response.statusCode)
      }
    } catch (err) {
      logger.error('Error sending secure request to %s pod.', toPod.host, err)

      throw err
    }
  }

    // Make all the requests of the scheduler
  protected async makeRequests () {
    let requestsGrouped: T

    try {
      requestsGrouped = await this.getRequestModel().listWithLimitAndRandom(this.limitPods, this.limitPerPod)
    } catch (err) {
      logger.error('Cannot get the list of "%s".', this.description, { error: err.stack })
      throw err
    }

    // We want to group requests by destinations pod and endpoint
    const requestsToMake = this.buildRequestsObjects(requestsGrouped)

    // If there are no requests, abort
    if (isEmpty(requestsToMake) === true) {
      logger.info('No "%s" to make.', this.description)
      return { goodPods: [], badPods: [] }
    }

    logger.info('Making "%s" to friends.', this.description)

    const goodPods: number[] = []
    const badPods: number[] = []

    await Bluebird.map(Object.keys(requestsToMake), async hashKey => {
      const requestToMake = requestsToMake[hashKey]
      const toPod: PodInstance = requestToMake.toPod

      try {
        await this.makeRequest(toPod, requestToMake.endpoint, requestToMake.datas)
        logger.debug('Removing requests for pod %s.', requestToMake.toPod.id, { requestsIds: requestToMake.ids })
        goodPods.push(requestToMake.toPod.id)

        this.afterRequestHook()

        // Remove the pod id of these request ids
        await this.getRequestToPodModel()
          .removeByRequestIdsAndPod(requestToMake.ids, requestToMake.toPod.id)
      } catch (err) {
        badPods.push(requestToMake.toPod.id)
        logger.info('Cannot make request to %s.', toPod.host, err)
      }
    }, { concurrency: REQUESTS_IN_PARALLEL })

    this.afterRequestsHook()

    // All the requests were made, we update the pods score
    db.Pod.updatePodsScore(goodPods, badPods)
  }

  protected afterRequestHook () {
   // Nothing to do, let children re-implement it
  }

  protected afterRequestsHook () {
   // Nothing to do, let children re-implement it
  }
}

// ---------------------------------------------------------------------------

export {
  AbstractRequestScheduler,
  RequestsObjects
}