# All files / src/utils xhr-loader.js

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72.97% Branches 27/37
100% Functions 1/1
70.24% Lines 59/84

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     /**
     * XHR based logger
    */

    import { logger } from '../utils/logger';

    const { performance, XMLHttpRequest } = window;

    class XhrLoader {
      constructor (config) {
        Iif (config && config.xhrSetup) {
          this.xhrSetup = config.xhrSetup;
        }
      }

      destroy () {
        this.abort();
        this.loader = null;
      }

      abort () {
        let loader = this.loader;
        if (loader && loader.readyState !== 4) {
          this.stats.aborted = true;
          loader.abort();
        }

        window.clearTimeout(this.requestTimeout);
        this.requestTimeout = null;
        window.clearTimeout(this.retryTimeout);
        this.retryTimeout = null;
      }

      load (context, config, callbacks) {
        this.context = context;
        this.config = config;
        this.callbacks = callbacks;
        this.stats = { trequest: performance.now(), retry: 0 };
        this.retryDelay = config.retryDelay;
        this.loadInternal();
      }

      loadInternal () {
        let xhr, context = this.context;
        xhr = this.loader = new XMLHttpRequest();

        let stats = this.stats;
        stats.tfirst = 0;
        stats.loaded = 0;
        const xhrSetup = this.xhrSetup;

        try {
          Iif (xhrSetup) {
            try {
              xhrSetup(xhr, context.url);
            } catch (e) {
              // fix xhrSetup: (xhr, url) => {xhr.setRequestHeader("Content-Language", "test");}
              // not working, as xhr.setRequestHeader expects xhr.readyState === OPEN
              xhr.open('GET', context.url, true);
              xhrSetup(xhr, context.url);
            }
          }
          Eif (!xhr.readyState) {
            xhr.open('GET', context.url, true);
          }
        } catch (e) {
          // IE11 throws an exception on xhr.open if attempting to access an HTTP resource over HTTPS
          this.callbacks.onError({ code: xhr.status, text: e.message }, context, xhr);
          return;
        }

        Iif (context.rangeEnd) {
          xhr.setRequestHeader('Range', 'bytes=' + context.rangeStart + '-' + (context.rangeEnd - 1));
        }

        xhr.onreadystatechange = this.readystatechange.bind(this);
        xhr.onprogress = this.loadprogress.bind(this);
        xhr.responseType = context.responseType;

        // setup timeout before we perform request
        this.requestTimeout = window.setTimeout(this.loadtimeout.bind(this), this.config.timeout);
        xhr.send();
      }

      readystatechange (event) {
        let xhr = event.currentTarget,
          readyState = xhr.readyState,
          stats = this.stats,
          context = this.context,
          config = this.config;

        // don't proceed if xhr has been aborted
        if (stats.aborted) {
          return;
        }

        // >= HEADERS_RECEIVED
        Eif (readyState >= 2) {
          // clear xhr timeout and rearm it if readyState less than 4
          window.clearTimeout(this.requestTimeout);
          if (stats.tfirst === 0) {
            stats.tfirst = Math.max(performance.now(), stats.trequest);
          }

          if (readyState === 4) {
            let status = xhr.status;
            // http status between 200 to 299 are all successful
            Iif (status >= 200 && status < 300) {
              stats.tload = Math.max(stats.tfirst, performance.now());
              let data, len;
              if (context.responseType === 'arraybuffer') {
                data = xhr.response;
                len = data.byteLength;
              } else {
                data = xhr.responseText;
                len = data.length;
              }
              stats.loaded = stats.total = len;
              let response = { url: xhr.responseURL, data: data };
              this.callbacks.onSuccess(response, stats, context, xhr);
            } else {
              // if max nb of retries reached or if http status between 400 and 499 (such error cannot be recovered, retrying is useless), return error
              Eif (stats.retry >= config.maxRetry || (status >= 400 && status < 499)) {
                logger.error(`${status} while loading ${context.url}`);
                this.callbacks.onError({ code: status, text: xhr.statusText }, context, xhr);
              } else {
                // retry
                logger.warn(`${status} while loading ${context.url}, retrying in ${this.retryDelay}...`);
                // aborts and resets internal state
                this.destroy();
                // schedule retry
                this.retryTimeout = window.setTimeout(this.loadInternal.bind(this), this.retryDelay);
                // set exponential backoff
                this.retryDelay = Math.min(2 * this.retryDelay, config.maxRetryDelay);
                stats.retry++;
              }
            }
          } else {
            // readyState >= 2 AND readyState !==4 (readyState = HEADERS_RECEIVED || LOADING) rearm timeout as xhr not finished yet
            this.requestTimeout = window.setTimeout(this.loadtimeout.bind(this), config.timeout);
          }
        }
      }

      loadtimeout () {
        logger.warn(`timeout while loading ${this.context.url}`);
        this.callbacks.onTimeout(this.stats, this.context, null);
      }

      loadprogress (event) {
        let xhr = event.currentTarget,
          stats = this.stats;

        stats.loaded = event.loaded;
        Iif (event.lengthComputable) {
          stats.total = event.total;
        }

        let onProgress = this.callbacks.onProgress;
        if (onProgress) {
          // third arg is to provide on progress data
          onProgress(stats, this.context, null, xhr);
        }
      }
    }

    export default XhrLoader;