epub.js/src/store.js

import EventEmitter from "event-emitter";
import localforage from "localforage";
import { defer, isXml, parse } from "./utils/core";
import mime from "./utils/mime";
import Path from "./utils/path";
import httpRequest from "./utils/request";

/**
 * Handles saving and requesting files from local storage
 * @class
 * @param {string} name This should be the name of the application for modals
 * @param {function} [requester]
 * @param {function} [resolver]
 */
class Store {
  constructor(name, requester, resolver) {
    this.urlCache = {};
    this.storage = undefined;
    this.name = name;
    this.requester = requester || httpRequest;
    this.resolver = resolver;
    this.online = true;

    this.checkRequirements();
    this.addListeners();
  }

  /**
   * Checks to see if localForage exists in global namspace,
   * Requires localForage if it isn't there
   * @private
   */
  checkRequirements() {
    try {
      let store;
      if (typeof localforage === "undefined") {
        store = localforage;
      }
      this.storage = store.createInstance({
        name: this.name,
      });
    } catch (e) {
      throw new Error("localForage lib not loaded");
    }
  }

  /**
   * Add online and offline event listeners
   * @private
   */
  addListeners() {
    this._status = this.status.bind(this);
    window.addEventListener("online", this._status);
    window.addEventListener("offline", this._status);
  }

  /**
   * Remove online and offline event listeners
   * @private
   */
  removeListeners() {
    window.removeEventListener("online", this._status);
    window.removeEventListener("offline", this._status);
    this._status = undefined;
  }

  /**
   * Update the online / offline status
   * @private
   */
  status(event) {
    let online = navigator.onLine;
    this.online = online;
    if (online) {
      this.emit("online", this);
    } else {
      this.emit("offline", this);
    }
  }

  /**
   * Add all of a book resources to the store
   * @param  {Resources} resources  book resources
   * @param  {boolean} [force] force resaving resources
   * @return {Promise<object>} store objects
   */
  add(resources, force) {
    let mapped = resources.resources.map((item) => {
      let { href } = item;
      let url = this.resolver(href);
      let encodedUrl = window.encodeURIComponent(url);

      return this.storage.getItem(encodedUrl).then((item) => {
        if (!item || force) {
          return this.requester(url, "binary").then((data) => {
            return this.storage.setItem(encodedUrl, data);
          });
        } else {
          return item;
        }
      });
    });
    return Promise.all(mapped);
  }

  /**
   * Put binary data from a url to storage
   * @param  {string} url  a url to request from storage
   * @param  {boolean} [withCredentials]
   * @param  {object} [headers]
   * @return {Promise<Blob>}
   */
  put(url, withCredentials, headers) {
    let encodedUrl = window.encodeURIComponent(url);

    return this.storage.getItem(encodedUrl).then((result) => {
      if (!result) {
        return this.requester(url, "binary", withCredentials, headers).then(
          (data) => {
            return this.storage.setItem(encodedUrl, data);
          }
        );
      }
      return result;
    });
  }

  /**
   * Request a url
   * @param  {string} url  a url to request from storage
   * @param  {string} [type] specify the type of the returned result
   * @param  {boolean} [withCredentials]
   * @param  {object} [headers]
   * @return {Promise<Blob | string | JSON | Document | XMLDocument>}
   */
  request(url, type, withCredentials, headers) {
    if (this.online) {
      // From network
      return this.requester(url, type, withCredentials, headers).then(
        (data) => {
          // save to store if not present
          this.put(url);
          return data;
        }
      );
    } else {
      // From store
      return this.retrieve(url, type);
    }
  }

  /**
   * Request a url from storage
   * @param  {string} url  a url to request from storage
   * @param  {string} [type] specify the type of the returned result
   * @return {Promise<Blob | string | JSON | Document | XMLDocument>}
   */
  retrieve(url, type) {
    var response;
    var path = new Path(url);

    // If type isn't set, determine it from the file extension
    if (!type) {
      type = path.extension;
    }

    if (type == "blob") {
      response = this.getBlob(url);
    } else {
      response = this.getText(url);
    }

    return response.then((r) => {
      var deferred = new defer();
      var result;
      if (r) {
        result = this.handleResponse(r, type);
        deferred.resolve(result);
      } else {
        deferred.reject({
          message: "File not found in storage: " + url,
          stack: new Error().stack,
        });
      }
      return deferred.promise;
    });
  }

  /**
   * Handle the response from request
   * @private
   * @param  {any} response
   * @param  {string} [type]
   * @return {any} the parsed result
   */
  handleResponse(response, type) {
    var r;

    if (type == "json") {
      r = JSON.parse(response);
    } else if (isXml(type)) {
      r = parse(response, "text/xml");
    } else if (type == "xhtml") {
      r = parse(response, "application/xhtml+xml");
    } else if (type == "html" || type == "htm") {
      r = parse(response, "text/html");
    } else {
      r = response;
    }

    return r;
  }

  /**
   * Get a Blob from Storage by Url
   * @param  {string} url
   * @param  {string} [mimeType]
   * @return {Blob}
   */
  getBlob(url, mimeType) {
    let encodedUrl = window.encodeURIComponent(url);

    return this.storage.getItem(encodedUrl).then(function (uint8array) {
      if (!uint8array) return;

      mimeType = mimeType || mime.lookup(url);

      return new Blob([uint8array], { type: mimeType });
    });
  }

  /**
   * Get Text from Storage by Url
   * @param  {string} url
   * @param  {string} [mimeType]
   * @return {string}
   */
  getText(url, mimeType) {
    let encodedUrl = window.encodeURIComponent(url);

    mimeType = mimeType || mime.lookup(url);

    return this.storage.getItem(encodedUrl).then(function (uint8array) {
      var deferred = new defer();
      var reader = new FileReader();
      var blob;

      if (!uint8array) return;

      blob = new Blob([uint8array], { type: mimeType });

      reader.addEventListener("loadend", () => {
        deferred.resolve(reader.result);
      });

      reader.readAsText(blob, mimeType);

      return deferred.promise;
    });
  }

  /**
   * Get a base64 encoded result from Storage by Url
   * @param  {string} url
   * @param  {string} [mimeType]
   * @return {string} base64 encoded
   */
  getBase64(url, mimeType) {
    let encodedUrl = window.encodeURIComponent(url);

    mimeType = mimeType || mime.lookup(url);

    return this.storage.getItem(encodedUrl).then((uint8array) => {
      var deferred = new defer();
      var reader = new FileReader();
      var blob;

      if (!uint8array) return;

      blob = new Blob([uint8array], { type: mimeType });

      reader.addEventListener("loadend", () => {
        deferred.resolve(reader.result);
      });
      reader.readAsDataURL(blob, mimeType);

      return deferred.promise;
    });
  }

  /**
   * Create a Url from a stored item
   * @param  {string} url
   * @param  {object} [options.base64] use base64 encoding or blob url
   * @return {Promise} url promise with Url string
   */
  createUrl(url, options) {
    var deferred = new defer();
    var _URL = window.URL || window.webkitURL || window.mozURL;
    var tempUrl;
    var response;
    var useBase64 = options && options.base64;

    if (url in this.urlCache) {
      deferred.resolve(this.urlCache[url]);
      return deferred.promise;
    }

    if (useBase64) {
      response = this.getBase64(url);

      if (response) {
        response.then(
          function (tempUrl) {
            this.urlCache[url] = tempUrl;
            deferred.resolve(tempUrl);
          }.bind(this)
        );
      }
    } else {
      response = this.getBlob(url);

      if (response) {
        response.then(
          function (blob) {
            tempUrl = _URL.createObjectURL(blob);
            this.urlCache[url] = tempUrl;
            deferred.resolve(tempUrl);
          }.bind(this)
        );
      }
    }

    if (!response) {
      deferred.reject({
        message: "File not found in storage: " + url,
        stack: new Error().stack,
      });
    }

    return deferred.promise;
  }

  /**
   * Revoke Temp Url for a archive item
   * @param  {string} url url of the item in the store
   */
  revokeUrl(url) {
    var _URL = window.URL || window.webkitURL || window.mozURL;
    var fromCache = this.urlCache[url];
    if (fromCache) _URL.revokeObjectURL(fromCache);
  }

  destroy() {
    var _URL = window.URL || window.webkitURL || window.mozURL;
    for (let fromCache in this.urlCache) {
      _URL.revokeObjectURL(fromCache);
    }
    this.urlCache = {};
    this.removeListeners();
  }
}

EventEmitter(Store.prototype);

export default Store;