api/bucket-policy: Refactor, Handler test. (#2071)

PR contains,
- New setup utilities for running object handler tests. Here is why they are essential, 
    - Unit tests have to be run in isolation without being have to be associated with other functionalities which are not under test. 
    - The integration tests follows the philosophy of running a Test Server and registers all handlers and fires HTTP requests over the socket to simulate the system functionality under usual work load scenarios and test for correctness. But this philosophy cannot be adopted for running unit tests for HTTP handlers. 
    - Running Unit tests for API handlers, 
        - Shouldn't run a test server. Should purely call the handlers `ServeHTTP` under isolation. 
        - Shouldn't register all handlers, should only register handlers under test and so that the system is close to be in an isolated setup. 

- As an example PutBucketPolicy test is illustrated using the new setup. Exhaustive cases has to be added and has been listen in TODO for now.

test-utils_test.go

@@ -36,6 +36,8 @@ import (
 	"testing"
 	"time"
 	"unicode/utf8"
+
+	router "github.com/gorilla/mux"
 )
 
 // The Argument to TestServer should satidy the interface.
@@ -111,36 +113,43 @@ func StartTestServer(t TestErrHandler, instanceType string) TestServer {
 	if err != nil {
 		t.Fatalf("Failed obtaining Temp Backend: <ERROR> %s", err)
 	}
-	testServer.Disks = erasureDisks
-	// Obtain temp root.
-	root, err := getTestRoot()
+
+	credentials, root, err := initTestConfig("us-east-1")
 	if err != nil {
-		t.Fatalf("Failed obtaining Temp Root for the backend Backend: <ERROR> %s", err)
+		t.Fatalf("%s", err)
 	}
 	testServer.Root = root
 	testServer.Disks = erasureDisks
-	// Initialize server config.
-	initConfig()
-	// Get credential.
-	credentials := serverConfig.GetCredential()
 	testServer.AccessKey = credentials.AccessKeyID
 	testServer.SecretKey = credentials.SecretAccessKey
-	// Set a default region.
-	serverConfig.SetRegion("us-east-1")
-
-	// Do this only once here.
-	setGlobalConfigPath(root)
-
-	err = serverConfig.Save()
-	if err != nil {
-		t.Fatalf(err.Error())
-	}
 	// Run TestServer.
 	testServer.Server = httptest.NewServer(configureServerHandler(serverCmdConfig{exportPaths: erasureDisks}))
 
 	return testServer
 }
 
+// Configure the server for the test run.
+func initTestConfig(bucketLocation string) (credential, string, error) {
+	// Initialize server config.
+	initConfig()
+	// Get credential.
+	credentials := serverConfig.GetCredential()
+	// Set a default region.
+	serverConfig.SetRegion(bucketLocation)
+	rootPath, err := getTestRoot()
+	if err != nil {
+		return credential{}, "", err
+	}
+	// Do this only once here.
+	setGlobalConfigPath(rootPath)
+
+	err = serverConfig.Save()
+	if err != nil {
+		return credential{}, "", err
+	}
+	return credentials, rootPath, nil
+}
+
 // Deleting the temporary backend and stopping the server.
 func (testServer TestServer) Stop() {
 	removeAll(testServer.Root)
@@ -595,14 +604,14 @@ type objTestDiskNotFoundType func(obj ObjectLayer, instanceType string, dirs []s
 func ExecObjectLayerTest(t *testing.T, objTest objTestType) {
 	objLayer, fsDir, err := getSingleNodeObjectLayer()
 	if err != nil {
-		t.Fatalf("Initialization of object layer failed for single node setup: %s", err.Error())
+		t.Fatalf("Initialization of object layer failed for single node setup: %s", err)
 	}
 	// Executing the object layer tests for single node setup.
 	objTest(objLayer, singleNodeTestStr, t)
 
 	objLayer, fsDirs, err := getXLObjectLayer()
 	if err != nil {
-		t.Fatalf("Initialization of object layer failed for XL setup: %s", err.Error())
+		t.Fatalf("Initialization of object layer failed for XL setup: %s", err)
 	}
 	// Executing the object layer tests for XL.
 	objTest(objLayer, xLTestStr, t)
@@ -614,7 +623,7 @@ func ExecObjectLayerTest(t *testing.T, objTest objTestType) {
 func ExecObjectLayerDiskNotFoundTest(t *testing.T, objTest objTestDiskNotFoundType) {
 	objLayer, fsDirs, err := getXLObjectLayer()
 	if err != nil {
-		t.Fatalf("Initialization of object layer failed for XL setup: %s", err.Error())
+		t.Fatalf("Initialization of object layer failed for XL setup: %s", err)
 	}
 	// Executing the object layer tests for XL.
 	objTest(objLayer, xLTestStr, fsDirs, t)
@@ -629,9 +638,54 @@ type objTestStaleFilesType func(obj ObjectLayer, instanceType string, dirs []str
 func ExecObjectLayerStaleFilesTest(t *testing.T, objTest objTestStaleFilesType) {
 	objLayer, fsDirs, err := getXLObjectLayer()
 	if err != nil {
-		t.Fatalf("Initialization of object layer failed for XL setup: %s", err.Error())
+		t.Fatalf("Initialization of object layer failed for XL setup: %s", err)
 	}
 	// Executing the object layer tests for XL.
 	objTest(objLayer, xLTestStr, fsDirs, t)
 	defer removeRoots(fsDirs)
 }
+
+// Takes in XL/FS object layer, and the list of API end points to be tested/required, registers the API end points and returns the HTTP handler.
+// Need isolated registration of API end points while writing unit tests for end points.
+// All the API end points are registered only for the default case.
+func initTestAPIEndPoints(objLayer ObjectLayer, apiFunctions []string) http.Handler {
+	// initialize a new mux router.
+	// goriilla/mux is the library used to register all the routes and handle them.
+	muxRouter := router.NewRouter()
+	// All object storage operations are registered as HTTP handlers on `objectAPIHandlers`.
+	// When the handlers get a HTTP request they use the underlyting ObjectLayer to perform operations.
+	api := objectAPIHandlers{
+		ObjectAPI: objLayer,
+	}
+	// API Router.
+	apiRouter := muxRouter.NewRoute().PathPrefix("/").Subrouter()
+	// Bucket router.
+	bucket := apiRouter.PathPrefix("/{bucket}").Subrouter()
+	// Iterate the list of API functions requested for and register them in mux HTTP handler.
+	for _, apiFunction := range apiFunctions {
+		switch apiFunction {
+		// Register PutBucket Policy handler.
+		case "PutBucketPolicy":
+			bucket.Methods("PUT").HandlerFunc(api.PutBucketPolicyHandler).Queries("policy", "")
+
+			// Register Delete bucket HTTP policy handler.
+		case "DeleteBucketPolicy":
+			bucket.Methods("DELETE").HandlerFunc(api.DeleteBucketPolicyHandler).Queries("policy", "")
+
+			// Register Get Bucket policy HTTP Handler.
+		case "GetBucketPolicy":
+			bucket.Methods("GET").HandlerFunc(api.GetBucketPolicyHandler).Queries("policy", "")
+
+			// Register Post Bucket policy function.
+		case "PostBucketPolicy":
+			bucket.Methods("POST").HeadersRegexp("Content-Type", "multipart/form-data*").HandlerFunc(api.PostPolicyBucketHandler)
+
+			// Register all api endpoints by default.
+		default:
+			registerAPIRouter(muxRouter, api)
+			// No need to register any more end points, all the end points are registered.
+			break
+		}
+	}
+	return muxRouter
+}