All files / src fetch.js

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92.38% Branches 97/105
95.45% Functions 42/44
97.62% Lines 123/126
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// @flow
import get from 'lodash/get'
import isObject from 'lodash/isObject'
if (typeof (fetch) === 'undefined') {
  require('isomorphic-fetch')
}
 
// Generic fetch type
const GFT = '__FETCH__'
 
// ID that gets incremented for each fetch
let FETCH_ID = 0
 
// Get's the next fetch ID, which can be passed in to `fetch`, and allows for
// tracking the fetch or aborting it.
export const getID = () => ++FETCH_ID
 
// Active fetches, can still be aborted
const activeFetches = {
  [GFT]: []
}
 
// Remove a fetch from the active pool
const removeFetch = (sig) => {
  if (sig.type === GFT) {
    activeFetches[GFT].splice(activeFetches[GFT].indexOf(sig.id), 1)
  } else {
    delete activeFetches[sig.type]
  }
}
 
// Check if a fetch is still active
export const isActive = (sig) => {
  if (sig.type === GFT) return activeFetches[GFT].includes(sig.id)
  if (activeFetches[sig.type] === undefined) return false
  if (sig.id === undefined) return true
  return activeFetches[sig.type] === sig.id
}
 
// Action types
export const ABORTED_FETCH = 'aborted fetch'
export const ABORT_FETCH_FAILED = 'abort fetch failed'
export const INCREMENT_FETCH = 'increment outstanding fetches'
export const DECREMENT_FETCH = 'decrement outstanding fetches'
export const FETCH = 'fetch'
export const FETCH_MULTIPLE = 'fetch multiple'
export const FETCH_ERROR = 'fetch error'
 
// Simple action creator
const createAction = (type) => (payload) => ({type, payload})
 
// Main actions to be dispatched
export const fetchAction = createAction(FETCH)
export const fetchMultiple = createAction(FETCH_MULTIPLE)
export default fetchAction
 
// Internally dispatched actions
const abortedFetch = createAction(ABORTED_FETCH)
const abortFetchFailed = createAction(ABORT_FETCH_FAILED)
const fetchError = createAction(FETCH_ERROR)
 
/**
 * Call decrement and dispatch "aborted" and "decrement" actions. If `id` is
 * not set, cancel all fetches for the given type.
 */
export const abortFetch = (sig) => {
  if (isActive(sig)) {
    return [
      abortedFetch(sig),
      decrementFetches(sig)
    ]
  } else {
    return abortFetchFailed(sig)
  }
}
 
// Abort all active fetches
export const abortAllFetches = () =>
  Object.keys(activeFetches).reduce((aborts, fetchType) => {
    if (fetchType === GFT) {
      return [
        ...aborts,
        ...activeFetches[GFT].map(id => abortFetch({type: GFT, id}))
      ]
    } else {
      return [
        ...aborts,
        abortFetch({type: fetchType, id: activeFetches[fetchType]})
      ]
    }
  }, [])
 
/**
 * Send an increment action and add the fetch to the active list. This will also
 * abort a previous fetch of the same type if it exists.
 */
const incrementFetches = (payload) => {
  const actions = [{
    type: INCREMENT_FETCH,
    payload
  }]
 
  if (payload.type === GFT) activeFetches[GFT].push(payload.id)
  else {
    if (activeFetches[payload.type] !== undefined) {
      actions.push(abortFetch({
        type: payload.type,
        id: activeFetches[payload.type]
      }))
    }
    activeFetches[payload.type] = payload.id
  }
 
  return actions
}
 
/**
 * Send a decrement action and remove the fetch from the active list.
 */
const decrementFetches = (signature) => {
  removeFetch(signature)
 
  return {
    type: DECREMENT_FETCH,
    payload: signature
  }
}
 
// Redux middleware
export const middleware = (store) => (next) => (action) => {
  switch (get(action, 'type')) {
    case FETCH:
      return store.dispatch(runFetchAction(action.payload, store.getState()))
    case FETCH_MULTIPLE:
      return store.dispatch(runFetchMultiple(action.payload, store.getState()))
    default:
      return next(action)
  }
}
 
/**
 * Calls fetch, adds Auth and Content header if needed. Automatically parses
 * content based on type.
 *
 * @returns Promise
 */
function runFetch ({
  signature,
  options = {},
  retry = false,
  url
}, state) {
  const headers = {
    ...createAuthorizationHeader(state),
    ...createContentHeader(options.body),
    ...(options.headers || {})
  }
 
  const filteredHeaders = {}
 
  // Allow removing generated headers by specifiying { header: null } in
  // options.headers. Do this in two steps because otherwise we're modifying
  // the object as we're iterating over it.
  Object.keys(headers)
    .filter(key => headers[key] !== null && headers[key] !== undefined)
    .forEach(key => { filteredHeaders[key] = headers[key] })
 
  return fetch(url, {
    ...options,
    body: serialize(options.body),
    headers: filteredHeaders
  })
    .then(checkStatus)
    .then(createResponse)
    .then(async (response) =>
      (retry && isActive(signature) && await retry(response))E
        ? runFetch({signature, options, retry, url}, state)
        : response)
}
 
/**
 * Part of Redux action cycle. Returns an array of actions.
 */
function runFetchAction ({
  type = GFT,
  id = getID(),
  next,
  options = {},
  retry = false,
  url
}, state) {
  // Fetch signature based on the `type` and `id`
  const signature = {type, id}
 
  // If next does not exist or only takes a response, dispatch on error
  const dispatchFetchError = !next || next.length < 2
 
  // Wrap next so that we can parse the response
  const wrappedNext = wrapNext(next)
 
  return [
    incrementFetches({type, id, options, url}),
    runFetch({signature, options, retry, url}, state)
      .then((response) => {
        if (isActive(signature)) {
          return [
            decrementFetches(signature),
            wrappedNext(null, response)
          ]
        }
      })
      .catch((error) => {
        return createErrorResponse(error)
          .then((response) => {
            if (isActive(signature)) {
              const actions = [
                decrementFetches(signature),
                wrappedNext(error, response)
              ]
              if (dispatchFetchError) actions.push(fetchError(response))
              return actions
            }
          })
      })
  ]
}
 
/**
 * @returns Array of actions
 */
function runFetchMultiple ({
  type = GFT,
  id = getID(), // One ID for all fetch IDs in a fetch multiple
  fetches,
  next
}, state) {
  const signature = {type, id}
  const dispatchFetchError = !next || next.length < 2
  const wrappedNext = wrapNext(next)
 
  return [
    incrementFetches({type, id, fetches}),
    Promise.all(fetches.map((fetch) => runFetch({...fetch, signature}, state)))
      .then((responses) => {
        if (isActive(signature)) {
          return [
            decrementFetches(signature),
            wrappedNext(null, responses)
          ]
        }
      })
      .catch((error) =>
        createErrorResponse(error)
          .then((response) => {
        E    if (isActive(signature)) {
              const actions = [
                decrementFetches(signature),
                wrappedNext(error, response)
              ]
              if (dispatchFetchError) actions.push(fetchError(response))
              return actions
            }
          }))
  ]
}
 
/**
 * TODO: Expose this function to allow for customization.
 */
function createAuthorizationHeader (state) {
  return state.user && state.user.idToken
    ? {Authorization: `bearer ${state.user.idToken}`}
    : {}
}
 
function checkStatus (res) {
  if (res.status >= 200 && res.status < 300) {
    return res
  } else {
    throw res
  }
}
 
function createContentHeader (body) {
  if (body instanceof window.FormData) {
    return {}
  } else if (isObject(body)) {
    return {
      'Accept': 'application/json',
      'Content-Type': 'application/json;charset=UTF-8'
    }
  } else {
    return {}
  }
}
 
function createErrorResponse (res) {
  return res.headers
    ? createResponse(res)
    : Promise.resolve(res)
}
 
function createResponse (res) {
  return deserialize(res)
    .then((value) => {
      res.value = value
      return res
    })
    .catch((err) => {
      res.value = err
      return res
    })
}
 
async function deserialize (res) {
  const header =
    `${res.headers.get('Content-Type')} ${res.headers.get('Content')}`
  if (header.indexOf('json') > -1) return res.json()E
  if (header.indexOf('octet-stream') > -1) return res.arrayBuffer()
  if (header.indexOf('text') > -1) return res.text()
}
 
function serialize (body) {
  if (body instanceof window.FormData) {
    return body
  } else if (isObject(body)) {
    return JSON.stringify(body)
  } else {
    return body
  }
}
 
function wrapNext (next) {
  return function (error, response) {
    Eif (next) {
      if (next.length > 1) {
        return next(error, response)
      } else if (!error) {
        return next(response)
      }
    }
  }
}