Handle XHR response error (#137)

* Move the XHR callback to a separate file
* Trigger an error event if the response cannot be parsed.
* Add tests for handle-response.js

index.js

@@ -142,6 +142,8 @@ Pjax.prototype = {
 
   doRequest: require("./lib/send-request.js"),
 
+  handleResponse: require("./lib/proto/handle-response.js"),
+
   loadUrl: function(href, options) {
     options = typeof options === "object" ?
       extend({}, this.options, options) :
@@ -155,66 +157,7 @@ Pjax.prototype = {
     trigger(document, "pjax:send", options)
 
     // Do the request
-    this.request = this.doRequest(href, options, function(html, request) {
-      // Fail if unable to load HTML via AJAX
-      if (html === false) {
-        trigger(document, "pjax:complete pjax:error", options)
-
-        return
-      }
-
-      // push scroll position to history
-      var currentState = window.history.state || {}
-      window.history.replaceState({
-          url: currentState.url || window.location.href,
-          title: currentState.title || document.title,
-          uid: currentState.uid || newUid(),
-          scrollPos: [document.documentElement.scrollLeft || document.body.scrollLeft,
-            document.documentElement.scrollTop || document.body.scrollTop]
-        },
-        document.title, window.location)
-
-      var oldHref = href
-      if (request.responseURL) {
-        if (href !== request.responseURL) {
-          href = request.responseURL
-        }
-      }
-      else if (request.getResponseHeader("X-PJAX-URL")) {
-        href = request.getResponseHeader("X-PJAX-URL")
-      }
-      else if (request.getResponseHeader("X-XHR-Redirected-To")) {
-        href = request.getResponseHeader("X-XHR-Redirected-To")
-      }
-
-      // Add back the hash if it was removed
-      var a = document.createElement("a")
-      a.href = oldHref
-      var oldHash = a.hash
-      a.href = href
-      if (oldHash && !a.hash) {
-        a.hash = oldHash
-        href = a.href
-      }
-
-      this.state.href = href
-      this.state.options = clone(options)
-
-      try {
-        this.loadContent(html, options)
-      }
-      catch (e) {
-        if (!this.options.debug) {
-          if (console && console.error) {
-            console.error("Pjax switch fail: ", e)
-          }
-          return this.latestChance(href)
-        }
-        else {
-          throw e
-        }
-      }
-    }.bind(this))
+    this.request = this.doRequest(href, options, this.handleResponse.bind(this))
   },
 
   afterAllSwitches: function() {