import { Worker } from 'worker_threads'
import { v4 as uuidv4 } from 'uuid'
import { EventEmitter } from 'events'
import os from 'os'

import logger from './logger'

interface WorkerObj {
  worker: any
  index: number
  free: Boolean
}

interface PendingJob {
  workData: any
  doneEvent: any
  targetWorkerIndex?: number
}

const alertOnPendingCount = 10
const workerFile = './src/utils/classes.ts'
let workers: Array<WorkerObj>
const pendingJobs: {
  [id: string]: PendingJob
} = {}

const jobEvents = new EventEmitter()

jobEvents.on('jobDone', () => {
  processJob()
})

jobEvents.on('newJob', () => {
  processJob()
})

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

function handleWorkerError(worker: WorkerObj, err) {
  // TODO: restart worker if exited or things like that
  logger.Log('resourcePromise error', logger.GetColor('redbg'))
  console.error(err)
}

// TODO: accuire all workers here, and handle errors so they can be removed if threads exit
export function msgAllWorker(data: any): Promise<any> {
  logger.DebugLog('MSGING ALL WORKER', 'job', 1)
  return new Promise((resolve) => {
    const promises = []
    workers.forEach((worker) => {
      promises.push(doALongTask(data, worker.index))
    })
    Promise.all(promises).then((res) => {
      logger.DebugLog('MSGING ALL WORKER DONE', 'job', 1)
      resolve(res)
    })
  })
}

export function doALongTask(
  obj: any,
  targetWorkerIndex?: number
): Promise<any> {
  if (Object.keys(pendingJobs).length > alertOnPendingCount) {
    logger.Log(
      `More than ${alertOnPendingCount} callers waiting for free resource! (${
        Object.keys(pendingJobs).length
      })`,
      logger.GetColor('redbg')
    )
  }

  const jobId = uuidv4()
  // FIXME: delete doneEvent?
  const doneEvent = new EventEmitter()
  pendingJobs[jobId] = {
    workData: obj,
    targetWorkerIndex: targetWorkerIndex,
    doneEvent: doneEvent,
  }
  jobEvents.emit('newJob')
  return new Promise((resolve) => {
    doneEvent.once('done', (result) => {
      jobEvents.emit('jobDone')
      resolve(result)
    })
  })
}

export function initWorkerPool(initData: any): void {
  if (workers) {
    logger.Log('WORKERS ALREADY EXISTS', logger.GetColor('redbg'))
    return
  }
  workers = []
  const factory = {
    create: function(index) {
      return getAWorker(index, initData)
    },
    destroy: function(client) {
      client.worker.terminate()
    },
  }

  const threadCount = process.env.NS_THREAD_COUNT || os.cpus().length
  if (process.env.NS_THREAD_COUNT) {
    logger.Log(
      `Setting thread count from enviroment variable NS_WORKER_COUNT: '${threadCount}'`,
      logger.GetColor('red')
    )
  }

  for (let i = 0; i < threadCount; i++) {
    workers.push({
      worker: factory.create(i),
      index: i,
      free: true,
    })
  }
}

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

function processJob() {
  if (Object.keys(pendingJobs).length > 0) {
    // FIXME: FIFO OR ANYTHING ELSE (JOB PROCESSING ORDER)
    const keys = Object.keys(pendingJobs)
    let jobKey, freeWorker
    let i = 0
    while (!freeWorker && i < keys.length) {
      jobKey = keys[i]
      if (!isNaN(pendingJobs[jobKey].targetWorkerIndex)) {
        if (workers[pendingJobs[jobKey].targetWorkerIndex].free) {
          freeWorker = workers[pendingJobs[jobKey].targetWorkerIndex]
          logger.DebugLog(
            `RESERVING WORKER ${pendingJobs[jobKey].targetWorkerIndex}`,
            'job',
            1
          )
        }
      } else {
        freeWorker = workers.find((worker) => {
          return worker.free
        })
        if (freeWorker) {
          logger.DebugLog(
            `RESERVING FIRST AVAILABLE WORKER ${freeWorker.index}`,
            'job',
            1
          )
        }
      }
      i++
    }

    if (!freeWorker) {
      logger.DebugLog('NO FREE WORKER', 'job', 1)
      return
    }

    if (freeWorker.free) {
      freeWorker.free = false
    }
    const job = pendingJobs[jobKey]
    delete pendingJobs[jobKey]

    doSomething(freeWorker, job.workData)
      .then((res) => {
        freeWorker.free = true
        job.doneEvent.emit('done', res)
      })
      .catch(function(err) {
        handleWorkerError(freeWorker, err)
      })
  }
}

function getAWorker(i, initData) {
  const worker = workerTs(workerFile, {
    workerData: {
      workerIndex: i,
      initData: initData,
    },
  })

  worker.setMaxListeners(50)

  worker.on('error', (err) => {
    logger.Log('Worker error!', logger.GetColor('redbg'))
    console.error(err)
  })

  worker.on('exit', (code) => {
    // TODO: this is critical, whole server should stop, or child threads should be restarted
    logger.Log(
      `[MAIN]: worker #${i} exit code: ${code}`,
      code === 0 ? logger.GetColor('redbg') : logger.GetColor('green')
    )
  })
  return worker
}

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

function doSomething(currWorker, obj) {
  const { /* index, */ worker } = currWorker
  return new Promise((resolve) => {
    worker.postMessage(obj)
    worker.once('message', (msg) => {
      resolve(msg)
    })
  })
}

const workerTs = (file: string, wkOpts: any) => {
  wkOpts.eval = true
  if (!wkOpts.workerData) {
    wkOpts.workerData = {}
  }
  wkOpts.workerData.__filename = file
  return new Worker(
    `
            const wk = require('worker_threads');
            require('ts-node').register();
            let file = wk.workerData.__filename;
            delete wk.workerData.__filename;
            require(file);
        `,
    wkOpts
  )
}