Initial ServiceWorker Cache API polyfill.

Source/modules/serviceworkers/polyfills/cachePolyfill.js

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// A simple, incomplete implementation of the Cache API, intended to facilitate
+// end to end serviceworker testing.
+
+// See https://slightlyoff.github.io/ServiceWorker/spec/service_worker/index.html#cache
+
+// FIXME: Support AbstractResponse/OpaqueResponse correctly.
+// FIXME: Serialize the cache.
+// FIXME: Implement CacheStorage API.
+// FIXME: Bind all function references.
+(function (global) {
+    var _castToRequest = function (item) {
+        if (typeof item === 'string') {
+            item = new Request({
+                url: item,
+            });
+        }
+        return item;
+    };
+
+    var Cache = function() {
+        // An object containing a property for each HTTP fetch method. Those
+        // referenced objects contain a property for each URL, which is the
+        // Response.
+        this.entriesByMethod = {};
+    };
+
+    // FIXME: Should this be in the spec?
+    Cache.prototype.keys = function() {
+        var that = this;
+
+        return Promise.resolve(Array.prototype.concat.apply([], Object.keys(this.entriesByMethod).map(function (method) {

[jsbell, 2014/06/06 17:25:31]

Maybe extract the Array.prototype.concat.apply([], x) magic into a flatten()
helper, for readability?

+            return Object.keys(that.entriesByMethod[method]).map(function (url) {
+                return new Request({method: method, url: url});

[gavinp, 2014/06/06 21:39:55]

Have I followed the standard indentation practice for closing my lambda form
here? I personally prefer this form:

                return new Request({method: method, url: url})})})))};

However, the Google JavaScript coding standard is at best vague on this subject,
but I think it's not right. Did I make the right call?

+            });
+        })));
+    };
+
+    // FIXME: Implement this.
+    // FIXME: Should spec rename each --> forEach?
+    Cache.prototype.forEach = Promise.reject.bind(Promise, 'Cache.prototype.forEach() not implemented.');
+    Cache.prototype.each = Promise.reject.bind(Promise, 'Cache.prototype.each() not implemented.');
+
+    Cache.prototype.put = function (request, response) {
+        request = _castToRequest(request);

[jsbell, 2014/06/06 17:25:31]

Consider doing this inside the new Promise(function(r,r) { .. }) body, so that
if this throws the method will convert the exception to a rejection rather than
throwing. (Here and below)

[gavinp, 2014/06/06 21:39:55]

Done.

+
+        var that = this;
+        return new Promise(function (resolve, reject) {
+            if (!that.entriesByMethod.hasOwnProperty(request.method)) {
+                that.entriesByMethod[request.method] = {};
+            }
+
+            var entriesByUrl = that.entriesByMethod[request.method];
+            entriesByUrl[request.url] = response;
+
+            resolve();
+        });
+    };
+
+    // FIXME: Implement this.
+    Cache.prototype.add = Promise.reject.bind(Promise, 'Cache.prototype.add() not implemented.');
+
+    // FIXME: Add QueryParams argument.
+    Cache.prototype.delete = function (request) {
+        request = _castToRequest(request);
+
+        var that = this;
+        return new Promise(function (resolve, reject) {
+            if (!that.entriesByMethod.hasOwnProperty(request.method)) {
+                reject('not found');

[jsbell, 2014/06/06 17:25:31]

This seems inconsistent - we reject if the *method* is not found, but not if the
*url* is not found?

It should probably be idempotent and just resolve() if the method is not found.

[gavinp, 2014/06/06 21:39:55]

Done.

+                return;
+            }
+
+            var entriesByUrl = that.entriesByMethod[request.method];
+            delete entriesByUrl[request.url];
+            resolve();
+        });
+    };
+
+    // FIXME: Add QueryParams argument.
+    Cache.prototype.match = function (request) {
+        request = _castToRequest(request);
+
+        var that = this;
+        return new Promise(function (resolve, reject) {
+            if (!that.entriesByMethod.hasOwnProperty(request.method)) {
+                reject('not found');
+                return;
+            }
+
+            var entriesByUrl = that.entriesByMethod[request.method];
+
+            if (!entriesByUrl.hasOwnProperty(request.url)) {
+                reject('not found');
+                return;
+            }
+
+            var entry = entriesByUrl[request.url];
+            resolve(entry);
+        });
+    };
+
+    // FIXME: Implement this.
+    Cache.prototype.matchAll = Promise.reject.bind(Promise, 'Cache.prototype.matchAll not implemented.');
+
+    global.Cache = global.Cache || Cache;
+}(self));  // window or worker global scope.