Allowed multiple plugins for one scheme

This modified the networking engine to store every plugin it is given
for a scheme, and adds a priority system to pick which of the plugins
to use.

Issue #829

Change-Id: I21a8a534383f2be898160d609d77efecfc2b684b

lib/net/http_plugin.js

@@ -111,6 +111,8 @@ shaka.net.HttpPlugin = function(uri, request) {
 };
 
 
-shaka.net.NetworkingEngine.registerScheme('http', shaka.net.HttpPlugin);
-shaka.net.NetworkingEngine.registerScheme('https', shaka.net.HttpPlugin);
+shaka.net.NetworkingEngine.registerScheme('http', shaka.net.HttpPlugin,
+    shaka.net.NetworkingEngine.PluginPriority.FALLBACK);
+shaka.net.NetworkingEngine.registerScheme('https', shaka.net.HttpPlugin,
+    shaka.net.NetworkingEngine.PluginPriority.FALLBACK);
 

lib/net/networking_engine.js

@@ -73,25 +73,66 @@ shaka.net.NetworkingEngine.RequestType = {
 };
 
 
+/**
+ * Priority level for network scheme plugins.
+ * If multiple plugins are provided for the same scheme, only the
+ * highest-priority one is used.
+ *
+ * @enum {number}
+ * @export
+ */
+shaka.net.NetworkingEngine.PluginPriority = {
+  FALLBACK: 1,
+  PREFERRED: 2,
+  APPLICATION: 3
+};
+
+
+/**
+ * @typedef {{
+ *   plugin: shakaExtern.SchemePlugin,
+ *   priority: number
+ * }}
+ * @property {shakaExtern.SchemePlugin} plugin
+ *   The associated plugin.
+ * @property {number} priority
+ *   The plugin's priority.
+ */
+shaka.net.NetworkingEngine.SchemeObject;
+
+
 /**
  * Contains the scheme plugins.
  *
- * @private {!Object.<string, ?shakaExtern.SchemePlugin>}
+ * @private {!Object.<string, shaka.net.NetworkingEngine.SchemeObject>}
  */
 shaka.net.NetworkingEngine.schemes_ = {};
 
 
 /**
  * Registers a scheme plugin.  This plugin will handle all requests with the
  * given scheme.  If a plugin with the same scheme already exists, it is
- * replaced.
+ * replaced, unless the existing plugin is of higher priority.
+ * If no priority is provided, this defaults to the highest priority of
+ * APPLICATION.
  *
  * @param {string} scheme
  * @param {shakaExtern.SchemePlugin} plugin
+ * @param {number=} opt_priority
  * @export
  */
-shaka.net.NetworkingEngine.registerScheme = function(scheme, plugin) {
-  shaka.net.NetworkingEngine.schemes_[scheme] = plugin;
+shaka.net.NetworkingEngine.registerScheme =
+    function(scheme, plugin, opt_priority) {
+  goog.asserts.assert(opt_priority == undefined || opt_priority > 0,
+      'explicit priority must be > 0');
+  var priority =
+      opt_priority || shaka.net.NetworkingEngine.PluginPriority.APPLICATION;
+  var existing = shaka.net.NetworkingEngine.schemes_[scheme];
+  if (!existing || priority >= existing.priority)
+    shaka.net.NetworkingEngine.schemes_[scheme] = {
+      priority: priority,
+      plugin: plugin
+    };
 };
 
 
@@ -354,7 +395,8 @@ shaka.net.NetworkingEngine.prototype.send_ = function(
     request.uris[index] = uri.toString();
   }
 
-  var plugin = shaka.net.NetworkingEngine.schemes_[scheme];
+  var object = shaka.net.NetworkingEngine.schemes_[scheme];
+  var plugin = object ? object.plugin : null;
   if (!plugin) {
     return Promise.reject(new shaka.util.Error(
         shaka.util.Error.Severity.CRITICAL,

test/net/networking_engine_unit.js

@@ -43,6 +43,15 @@ describe('NetworkingEngine', /** @suppress {accessControls} */ function() {
     };
   });
 
+  function makeResolveScheme(spyName) {
+    return jasmine.createSpy(spyName).and.callFake(
+        function() {
+          return Promise.resolve({
+            uri: '', data: new ArrayBuffer(5), headers: {}
+          });
+        });
+  }
+
   beforeEach(function() {
     fakeProtocol = 'http:';
     error = new shaka.util.Error(
@@ -51,18 +60,15 @@ describe('NetworkingEngine', /** @suppress {accessControls} */ function() {
         shaka.util.Error.Code.HTTP_ERROR);
 
     networkingEngine = new shaka.net.NetworkingEngine();
-    resolveScheme = jasmine.createSpy('resolve scheme').and.callFake(
-        function() {
-          return Promise.resolve({
-            uri: '', data: new ArrayBuffer(5), headers: {}
-          });
-        });
+    resolveScheme = makeResolveScheme('resolve scheme');
     rejectScheme = jasmine.createSpy('reject scheme')
         .and.callFake(function() { return Promise.reject(error); });
     shaka.net.NetworkingEngine.registerScheme(
-        'resolve', Util.spyFunc(resolveScheme));
+        'resolve', Util.spyFunc(resolveScheme),
+        shaka.net.NetworkingEngine.PluginPriority.FALLBACK);
     shaka.net.NetworkingEngine.registerScheme(
-        'reject', Util.spyFunc(rejectScheme));
+        'reject', Util.spyFunc(rejectScheme),
+        shaka.net.NetworkingEngine.PluginPriority.FALLBACK);
   });
 
   afterEach(function() {
@@ -263,13 +269,54 @@ describe('NetworkingEngine', /** @suppress {accessControls} */ function() {
   });
 
   describe('request', function() {
-    it('uses registered schemes', function(done) {
-      networkingEngine.request(requestType, createRequest('resolve://foo'))
+    function testResolve(schemeSpy) {
+      return networkingEngine.request(
+          requestType, createRequest('resolve://foo'))
           .catch(fail)
           .then(function() {
-            expect(resolveScheme).toHaveBeenCalled();
-            done();
+            expect(schemeSpy).toHaveBeenCalled();
           });
+    }
+
+    it('uses registered schemes', function(done) {
+      testResolve(resolveScheme).then(done);
+    });
+
+    it('uses registered scheme plugins in order of priority', function(done) {
+      var applicationResolveScheme =
+          makeResolveScheme('application resolve scheme');
+      shaka.net.NetworkingEngine.registerScheme(
+          'resolve', Util.spyFunc(applicationResolveScheme),
+          shaka.net.NetworkingEngine.PluginPriority.APPLICATION);
+      var preferredResolveScheme =
+          makeResolveScheme('preferred resolve scheme');
+      shaka.net.NetworkingEngine.registerScheme(
+          'resolve', Util.spyFunc(preferredResolveScheme),
+          shaka.net.NetworkingEngine.PluginPriority.PREFERRED);
+
+      testResolve(applicationResolveScheme).then(done);
+    });
+
+    it('uses newest scheme plugin in case of tie in priority', function(done) {
+      var secondResolveScheme = makeResolveScheme('second resolve scheme');
+      shaka.net.NetworkingEngine.registerScheme(
+          'resolve', Util.spyFunc(secondResolveScheme),
+          shaka.net.NetworkingEngine.PluginPriority.FALLBACK);
+
+      testResolve(secondResolveScheme).then(done);
+    });
+
+    it('defaults new scheme plugins to application priority', function(done) {
+      var secondResolveScheme = makeResolveScheme('second resolve scheme');
+      shaka.net.NetworkingEngine.registerScheme(
+          'resolve', Util.spyFunc(secondResolveScheme));
+      var preferredResolveScheme =
+          makeResolveScheme('preferred resolve scheme');
+      shaka.net.NetworkingEngine.registerScheme(
+          'resolve', Util.spyFunc(preferredResolveScheme),
+          shaka.net.NetworkingEngine.PluginPriority.PREFERRED);
+
+      testResolve(secondResolveScheme).then(done);
     });
 
     it('can unregister scheme', function(done) {
@@ -280,6 +327,22 @@ describe('NetworkingEngine', /** @suppress {accessControls} */ function() {
           .then(done);
     });
 
+    it('unregister removes all plugins for scheme at once', function(done) {
+      var preferredResolveScheme =
+          makeResolveScheme('preferred resolve scheme');
+      shaka.net.NetworkingEngine.registerScheme(
+          'resolve', Util.spyFunc(preferredResolveScheme),
+          shaka.net.NetworkingEngine.PluginPriority.PREFERRED);
+
+      shaka.net.NetworkingEngine.unregisterScheme('resolve');
+      networkingEngine.request(requestType, createRequest('resolve://foo'))
+          .then(fail)
+          .catch(function() {
+            expect(resolveScheme).not.toHaveBeenCalled();
+            expect(preferredResolveScheme).not.toHaveBeenCalled();
+          }).then(done);
+    });
+
     it('rejects if scheme does not exist', function(done) {
       networkingEngine.request(requestType, createRequest('foo://foo'))
           .then(fail)