quran/node_modules/redux-persist/es/createPersistoid.js

import { KEY_PREFIX, REHYDRATE } from './constants';
// @TODO remove once flow < 0.63 support is no longer required.
export default function createPersistoid(config) {
  // defaults
  var blacklist = config.blacklist || null;
  var whitelist = config.whitelist || null;
  var transforms = config.transforms || [];
  var throttle = config.throttle || 0;
  var storageKey = "".concat(config.keyPrefix !== undefined ? config.keyPrefix : KEY_PREFIX).concat(config.key);
  var storage = config.storage;
  var serialize;

  if (config.serialize === false) {
    serialize = function serialize(x) {
      return x;
    };
  } else if (typeof config.serialize === 'function') {
    serialize = config.serialize;
  } else {
    serialize = defaultSerialize;
  }

  var writeFailHandler = config.writeFailHandler || null; // initialize stateful values

  var lastState = {};
  var stagedState = {};
  var keysToProcess = [];
  var timeIterator = null;
  var writePromise = null;

  var update = function update(state) {
    // add any changed keys to the queue
    Object.keys(state).forEach(function (key) {
      if (!passWhitelistBlacklist(key)) return; // is keyspace ignored? noop

      if (lastState[key] === state[key]) return; // value unchanged? noop

      if (keysToProcess.indexOf(key) !== -1) return; // is key already queued? noop

      keysToProcess.push(key); // add key to queue
    }); //if any key is missing in the new state which was present in the lastState,
    //add it for processing too

    Object.keys(lastState).forEach(function (key) {
      if (state[key] === undefined && passWhitelistBlacklist(key) && keysToProcess.indexOf(key) === -1 && lastState[key] !== undefined) {
        keysToProcess.push(key);
      }
    }); // start the time iterator if not running (read: throttle)

    if (timeIterator === null) {
      timeIterator = setInterval(processNextKey, throttle);
    }

    lastState = state;
  };

  function processNextKey() {
    if (keysToProcess.length === 0) {
      if (timeIterator) clearInterval(timeIterator);
      timeIterator = null;
      return;
    }

    var key = keysToProcess.shift();
    var endState = transforms.reduce(function (subState, transformer) {
      return transformer.in(subState, key, lastState);
    }, lastState[key]);

    if (endState !== undefined) {
      try {
        stagedState[key] = serialize(endState);
      } catch (err) {
        console.error('redux-persist/createPersistoid: error serializing state', err);
      }
    } else {
      //if the endState is undefined, no need to persist the existing serialized content
      delete stagedState[key];
    }

    if (keysToProcess.length === 0) {
      writeStagedState();
    }
  }

  function writeStagedState() {
    // cleanup any removed keys just before write.
    Object.keys(stagedState).forEach(function (key) {
      if (lastState[key] === undefined) {
        delete stagedState[key];
      }
    });
    writePromise = storage.setItem(storageKey, serialize(stagedState)).catch(onWriteFail);
  }

  function passWhitelistBlacklist(key) {
    if (whitelist && whitelist.indexOf(key) === -1 && key !== '_persist') return false;
    if (blacklist && blacklist.indexOf(key) !== -1) return false;
    return true;
  }

  function onWriteFail(err) {
    // @TODO add fail handlers (typically storage full)
    if (writeFailHandler) writeFailHandler(err);

    if (err && process.env.NODE_ENV !== 'production') {
      console.error('Error storing data', err);
    }
  }

  var flush = function flush() {
    while (keysToProcess.length !== 0) {
      processNextKey();
    }

    return writePromise || Promise.resolve();
  }; // return `persistoid`


  return {
    update: update,
    flush: flush
  };
} // @NOTE in the future this may be exposed via config

function defaultSerialize(data) {
  return JSON.stringify(data);
}