"use strict";

// Set up Apache OpenWhisk Client SDK
const openwhisk = require('openwhisk');
const options = {
  apihost: <INSERT_HOSTNAME>,
  api_key: <INSERT_API_KEY>
}
const ow = openwhisk(options)

const rand_int = () => Math.floor(Math.random() * 100)

// Promise-ify setTimeout
const delay = async ms => new Promise(resolve => setTimeout(resolve, ms))

// Returns function which checks whether max elapsed time has passed
// since instance creation.
const elapsed_time = max => {
  const start = new Date().getTime()

  return () => {
    const now = new Date().getTime()
    return (now - start) > max
  }
}

// Perform non-blocking action invocation and poll activation result using returned activation id.
// `activations.get()` will return result if action has finished and result is available.
// HTTP 404 returned when activation has not finished, wait and re-check after delay.
// All other errors code are fatal and should be thrown to caller.
//
// Parameters include delay_ms which controls polling delay and max_time
// which indicates maximum allowable waiting time for action to finish.
const invoke_and_poll = async (action, params, delay_ms, max_time) => {
  const time_has_elapsed = elapsed_time(max_time)
  const activation = await ow.actions.invoke({name: action, params})
  console.log(`new activation id: ${activation.activationId}`)
  let result = null

  while (!result) {
    try {
      result = await ow.activations.get({ name: activation.activationId })
      console.log(`activation result (${activation.activationId}) now available!`)
    } catch (err) {
      if (err.statusCode !== 404) {
        throw err
      }
      console.log(`activation result (${activation.activationId}) not available yet`)
    }
    await delay(delay_ms)
    if (time_has_elapsed()) throw new Error(`Maximum polling duration has elapsed (${result.activationId})`)
  }

  return result
}

// Action invocation with retries when activation result indicates a failure
// result.response.success boolean value shows whether action result suceeded or failed
// retries parameter configures the maximum number of allowable retries 
const invoke_with_retries = async (invoke, retries) => {
  let result = null
  let max_invocations = retries + 1
  const actvs = []
  do {
    if (max_invocations == 0) throw new Error(`Exhaused all available retries. ${actvs}`)
    result = await invoke()
    actvs.push(result.activationId)
    console.log('action invocation succeeded:', result.response.success)
    max_invocations--
  } while (!result.response.success)

  console.log('action result:', result.response.result)
  return result
}


;(async () => {
  // 100 invocations, 1 second between polls, 15 second maximum polling time, 15 maximum retries
  const polling_delay_ms = 1000
  const polling_timeout_ms = 1000 * 15
  const maximum_retries = 5
  const invocations = 200

  // Generate input data for N invocations.
  const input = new Array(invocations).fill(null).map(() => {
    return { a: rand_int(), b: rand_int() }
  })

  // Fire polling invocation with retries for each input value
  const output = input.map(async params => {
    const ow_invoke = () => invoke_and_poll('sum', params, polling_delay_ms, polling_timeout_ms)
    const result = await invoke_with_retries(ow_invoke, maximum_retries)
    console.log(`${params.a} + ${params.b} = ${result.response.result.sum}`)
    return result
  })

  // Wait for all results to be returned!
  const all_results = await Promise.all(output)
  console.log(all_results.map(result => result.response.result))
})();