Add prepare to prefetch

Author: Jake Harding

doc/bloodhound.md

@@ -225,6 +225,13 @@ When configuring `prefetch`, the following options are available.
 * `thumbprint` – A string used for thumbprinting prefetched data. If this
   doesn't match what's stored in local storage, the data will be refetched.
 
+* `prepare` – A function that provides a hook to allow you to prepare the 
+  settings object passed to `transport` when a request is about to be made. 
+  The function signature should be `prepare(settings)` where `settings` is the 
+  default settings object created internally by the Bloodhound instance. The 
+  `prepare` function should return a settings object. Defaults to the 
+  [identity function].
+
 * `transform` – A function with the signature `transform(response)` that allows
   you to transform the prefetch response before the Bloodhound instance operates 
   on it. Defaults to the [identity function].

src/bloodhound/options_parser.js

@@ -49,6 +49,7 @@ var oParser = (function() {
       cache: true,
       cacheKey: null,
       thumbprint: '',
+      prepare: _.identity,
       transform: _.identity,
       transport: null
     };
@@ -98,7 +99,7 @@ var oParser = (function() {
     // DEPRECATED: filter will be dropped in v1
     o.transform = o.filter || o.transform;
 
-    o.prepare = toPrepare(o);
+    o.prepare = toRemotePrepare(o);
     o.limiter = toLimiter(o);
     o.transport = o.transport ? callbackToDeferred(o.transport) : $.ajax;
 
@@ -110,7 +111,7 @@ var oParser = (function() {
     return o;
   }
 
-  function toPrepare(o) {
+  function toRemotePrepare(o) {
     var prepare, replace, wildcard;
 
     prepare = o.prepare;

src/bloodhound/prefetch.js

@@ -19,6 +19,7 @@ var Prefetch = (function() {
     this.url = o.url;
     this.ttl = o.ttl;
     this.cache = o.cache;
+    this.prepare = o.prepare;
     this.transform = o.transform;
     this.transport = o.transport;
     this.thumbprint = o.thumbprint;
@@ -69,11 +70,12 @@ var Prefetch = (function() {
     },
 
     fromNetwork: function(cb) {
-      var that = this;
+      var that = this, settings;
 
       if (!cb) { return; }
 
-      this.transport(this._settings()).fail(onError).done(onResponse);
+      settings = this.prepare(this._settings());
+      this.transport(settings).fail(onError).done(onResponse);
 
       function onError() { cb(true); }
       function onResponse(resp) { cb(null, that.transform(resp)); }

test/bloodhound/prefetch_spec.js

@@ -108,6 +108,18 @@ describe('Prefetch', function() {
       });
     });
 
+    it('should transform request settings with prepare', function() {
+      var spy;
+
+      spy = jasmine.createSpy();
+      spyOn(this.prefetch, 'prepare').andReturn({ foo: 'bar' });
+      spyOn(this.prefetch, 'transport').andReturn($.Deferred());
+
+      this.prefetch.fromNetwork(spy);
+
+      expect(this.prefetch.transport).toHaveBeenCalledWith({ foo: 'bar' });
+    });
+
     it('should transform the response using transform', function() {
       var spy;