zordius/yfetch

import { stringify } from 'query-string'
import debug from 'debug'

const debugStart = debug('yfetch:start')
const debugRaw = debug('yfetch:raw')
const debugResult = debug('yfetch:result')
const debugError = debug('yfetch:error')

export class YfetchError extends Error {}

export const JSON_HEADER = {
  Accept: 'application/json',
  'Content-Type': 'application/json'
}

// Support simple opts.query , opts.base and opts.url logic
// Support opts.json headers
// return fetch() arguments
export const transformFetchOptions = ({ query, headers, base = '', url = '', ...opts }) => {
  const queryString = stringify(query)
  const urlString = base + url + (queryString ? `?${queryString}` : '')
  const H = opts.json ? JSON_HEADER : {}

  return [urlString, { headers: { ...H, ...headers }, ...opts }]
}

// Support opts.json, send debug yfetch:result
export const transformFetchResult = ({ fetchArgs, ...response }) => {
  if (fetchArgs[1].json) {
    try {
      response.body = JSON.parse(response.body)
      response.parsed = true
    } catch (E) {
      if (!fetchArgs[1].ignoreJsonError) {
        throw new Error(`Can not JSON parse response body: "${response.body}"`)
      }
    }
  }

  debugResult('url: %s - status: %s - body: %O', response.url, response.status, response.body)

  return { ...response, fetchArgs }
}

// Support opts.error
export const transformFetchStatusError = ({ fetchArgs, ...response }) => {
  if (fetchArgs[1].error &&
      fetchArgs[1].error.indexOf &&
      fetchArgs[1].error.indexOf(response.status) > -1) {
    throw new YfetchError(`Response Code ${response.status} means Error (includes: ${fetchArgs[1].error.join(',')})`)
  }

  return { ...response, fetchArgs }
}

// handle response.text() promise, make response simple, keep response.fetchArgs
// send debug yfetch:raw
const transformForContext = fetchArgs => (response = {}) => {
  const { url, status, statusText, headers = [], ok, size } = response
  const H = {}

  headers.forEach((v, k) => {
    H[k] = v
  })

  const job = response.text ? response.text() : (fetchArgs[1].jsonp ? response.json() : Promise.resolve())

  return job
    .then((body) => {
      debugRaw('url: %s - status: %s - size: %s - header: %o - body: %s', url, status, size, H, body)

      return {
        url,
        status,
        statusText,
        ok,
        size,
        body,
        fetchArgs,
        headers: H
      }
    })
}

// keep error.fetchArgs and error.response , send debug yfetch:error
// const transformFetchError = (fetchArgs, { response = {} }) => (error) => {
const transformFetchError = (fetchArgs, R) => (error) => {
  const response = R.response || {}
  debugError('url: %s - status: %s - size: %s - body: %s - %O', fetchArgs[0], response.status, response.size, response.body, error)
  error.fetchArgs = fetchArgs
  error.response = response
  throw error
}

// The main yfetch function
export const yfetch = (opts = {}) => {
  const fetchArgs = transformFetchOptions(opts)
  const R = {}

  const storeResponse = (response) => {
    R.response = response
    return response
  }

  debugStart('url: %s - args: %O', fetchArgs[0], fetchArgs[1])
  return ((global.fetchJsonp && fetchArgs[1].jsonp)
    ? global.fetchJsonp(...fetchArgs)
    : global.fetch(...fetchArgs))
    .then(transformForContext(fetchArgs))
    .then(storeResponse)
    .then(transformFetchResult)
    .then(storeResponse)
    .then(transformFetchStatusError)
    .catch(transformFetchError(fetchArgs, R))
}

// as default
export default yfetch