import React from 'react'
import { reducer, action, CONNECTION_STATE, INITIAL_STATE } from '../../common/state.mjs'

function getConfig () {
  return {
    endpoint: process.env.NODE_ENV === 'development' ? 'http://localhost:3030' : ''
  }
}
function useConfig () {
  return getConfig()
}

export function useCommand (defaultCommand, defaultArgs = {}) {
  const config = useConfig()
  const url = config.endpoint + '/command'
  const headers = { 'content-type': 'application/json' }
  const [pending, setPending] = React.useState(false)
  const [error, setError] = React.useState(null)
  const [success, setSuccess] = React.useState(null)
  return { pending, error, success, dispatch }
  async function dispatch (command = defaultCommand, args = defaultArgs) {
    setPending(true)
    try {
      const res = await fetch(url, {
        headers,
        method: 'post',
        body: JSON.stringify({ command, args })
      })
      const json = await res.json()
      if (json.error) throw new Error('Remote error: ' + json.details)
      setSuccess(json)
    } catch (err) {
      setError(error)
    } finally {
      setPending(false)
    }
  }
}

export function useRemoteState (opts = {}) {
  const { retryInterval = 1000 } = opts
  const config = useConfig()
  const [retry, setRetry] = React.useState(0)
  const url = config.endpoint + '/sse'
  const [state, dispatch] = React.useReducer(reducer, INITIAL_STATE)
  const es = React.useRef()

  function reconnect () {
    if (es.current) es.current.close()
    es.current = null
    setRetry(retry => retry + 1)
  }

  // setup event source
  React.useEffect(() => {
    if (es.current) return
    es.current = new EventSource(url)
  }, [retry])

  // process event source
  React.useEffect(() => {
    if (!es.current) return
    const eventSource = es.current
    eventSource.onmessage = (event) => {
      const action = JSON.parse(event.data)
      dispatch(action)
    }
    eventSource.onerror = () => {
      dispatch(action(CONNECTION_STATE, { error: `Failed to connect to backend` }))
      if (retryInterval) setTimeout(reconnect, retryInterval)
    }
  }, [es.current])

  return { state }
}