import invariant from 'invariant'
import isEmpty from 'lodash/isEmpty'
import isFunction from 'lodash/isFunction'
import isString from 'lodash/isString'
import conformsTo from 'lodash/conformsTo'

import checkStore from './checkStore'
import { DAEMON, ONCE_TILL_UNMOUNT, RESTART_ON_REMOUNT } from './constants'

const allowedModes = [RESTART_ON_REMOUNT, DAEMON, ONCE_TILL_UNMOUNT]

const checkKey = (key) =>
  invariant(
    isString(key) && !isEmpty(key),
    '(app/utils...) injectSaga: Expected `key` to be a non empty string'
  )

const checkDescriptor = (descriptor) => {
  const shape = {
    saga: isFunction,
    mode: (mode) => isString(mode) && allowedModes.includes(mode)
  }
  invariant(
    conformsTo(descriptor, shape),
    '(app/utils...) injectSaga: Expected a valid saga descriptor'
  )
}

export function injectSagaFactory (store, isValid) {
  return function injectSaga (key, descriptor: { saga?: any, mode?: string } = {}, args?: any) {
    if (!isValid) { checkStore(store) }

    const newDescriptor = {
      ...descriptor,
      mode: descriptor.mode || DAEMON
    }
    const { saga, mode } = newDescriptor

    checkKey(key)
    checkDescriptor(newDescriptor)

    let hasSaga = Reflect.has(store.injectedSagas, key)

    if (process.env.NODE_ENV !== 'production') {
      const oldDescriptor = store.injectedSagas[key]
      // enable hot reloading of daemon and once-till-unmount sagas
      if (hasSaga && oldDescriptor.saga !== saga) {
        oldDescriptor.task.cancel()
        hasSaga = false
      }
    }

    if (
      !hasSaga ||
      (hasSaga && mode !== DAEMON && mode !== ONCE_TILL_UNMOUNT)
    ) {
      /* eslint-disable no-param-reassign */
      store.injectedSagas[key] = {
        ...newDescriptor,
        task: store.runSaga(saga, args)
      }
      /* eslint-enable no-param-reassign */
    }
  }
}

export function ejectSagaFactory (store, isValid) {
  return function ejectSaga (key) {
    if (!isValid) { checkStore(store) }

    checkKey(key)

    if (Reflect.has(store.injectedSagas, key)) {
      const descriptor = store.injectedSagas[key]
      if (descriptor.mode && descriptor.mode !== DAEMON) {
        descriptor.task.cancel()
        // Clean up in production in development we need `descriptor.saga` for hot reloading
        if (process.env.NODE_ENV === 'production') {
          // Need some value to be able to detect `ONCE_TILL_UNMOUNT` sagas in `injectSaga`
          store.injectedSagas[key] = 'done' // eslint-disable-line no-param-reassign
        }
      }
    }
  }
}

export default function getInjectors (store) {
  checkStore(store)

  return {
    injectSaga: injectSagaFactory(store, true),
    ejectSaga: ejectSagaFactory(store, true)
  }
}