From 3b405bd9f648aa54f7a903761265073779789356 Mon Sep 17 00:00:00 2001
From: pancho horrillo <pedrofelipe.horrillo@bbva.com>
Date: Tue, 8 Oct 2019 15:06:08 +0200
Subject: [PATCH] Add ServeHTTP() method to swappableMux struct
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Roberto Abdelkader Martínez Pérez <robertomartinezp@gmail.com>
---
 internal/server/user/mux.go      | 11 ++--
 internal/server/user/mux_test.go | 90 ++++++++++++++++++++++++++++----
 2 files changed, 89 insertions(+), 12 deletions(-)

diff --git a/internal/server/user/mux.go b/internal/server/user/mux.go
index c47aaca..fb3919d 100644
--- a/internal/server/user/mux.go
+++ b/internal/server/user/mux.go
@@ -1,6 +1,7 @@
 package user
 
 import (
+	"net/http"
 	"sync"
 
 	"github.com/gorilla/mux"
@@ -8,18 +9,22 @@ import (
 
 type swappableMux struct {
 	m    sync.RWMutex
-	root mux.Router
+	root *mux.Router
 }
 
-func (sm *swappableMux) get() mux.Router {
+func (sm *swappableMux) get() *mux.Router {
 	sm.m.RLock()
 	defer sm.m.RUnlock()
 
 	return sm.root
 }
 
-func (sm *swappableMux) set(mux mux.Router) {
+func (sm *swappableMux) set(mux *mux.Router) {
 	sm.m.Lock()
 	sm.root = mux
 	sm.m.Unlock()
 }
+
+func (sm *swappableMux) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	sm.get().ServeHTTP(w, r)
+}
diff --git a/internal/server/user/mux_test.go b/internal/server/user/mux_test.go
index b7c96d2..08c8459 100644
--- a/internal/server/user/mux_test.go
+++ b/internal/server/user/mux_test.go
@@ -1,6 +1,8 @@
 package user
 
 import (
+	"net/http"
+	"net/http/httptest"
 	"reflect"
 	"testing"
 	"time"
@@ -30,7 +32,7 @@ func TestSwappableMuxGetWaitsForTheMutexToBeReleased(t *testing.T) {
 	sm.m.Lock()
 	defer sm.m.Unlock()
 
-	c := make(chan mux.Router)
+	c := make(chan *mux.Router)
 	go func() { c <- sm.get() }()
 
 	time.Sleep(10 * time.Millisecond)
@@ -48,7 +50,7 @@ func TestSwappableMuxGetIsAbleToReadWhileOthersAreReading(t *testing.T) {
 	sm.m.RLock()
 	defer sm.m.RUnlock()
 
-	c := make(chan mux.Router)
+	c := make(chan *mux.Router)
 	go func() { c <- sm.get() }()
 
 	time.Sleep(10 * time.Millisecond)
@@ -62,7 +64,7 @@ func TestSwappableMuxGetIsAbleToReadWhileOthersAreReading(t *testing.T) {
 
 func TestSwappableMuxSetSetsTheGivenMux(t *testing.T) {
 	sm := swappableMux{}
-	mux := mux.Router{
+	mux := &mux.Router{
 		KeepContext: true,
 	}
 
@@ -74,14 +76,14 @@ func TestSwappableMuxSetSetsTheGivenMux(t *testing.T) {
 	}
 }
 
-func TestSwappableMuxSetSetsADifferentInstance(t *testing.T) {
+func TestSwappableMuxSetSetsTheSameInstance(t *testing.T) {
 	sm := swappableMux{}
-	mux := mux.Router{}
+	mux := &mux.Router{}
 
 	sm.set(mux)
 
-	if &mux == &sm.root {
-		t.Error("Set mux is the same instance")
+	if mux != sm.root {
+		t.Error("Set mux is not the same instance")
 	}
 }
 
@@ -92,7 +94,7 @@ func TestSwappableMuxSetWaitsForWriterToReleaseMutex(t *testing.T) {
 	defer sm.m.Unlock()
 
 	c := make(chan bool)
-	go func() { sm.set(mux.Router{}); c <- true }()
+	go func() { sm.set(&mux.Router{}); c <- true }()
 
 	time.Sleep(10 * time.Millisecond)
 
@@ -110,7 +112,7 @@ func TestSwappableMuxSetWaitsForReadersToReleaseMutex(t *testing.T) {
 	defer sm.m.RUnlock()
 
 	c := make(chan bool)
-	go func() { sm.set(mux.Router{}); c <- true }()
+	go func() { sm.set(&mux.Router{}); c <- true }()
 
 	time.Sleep(10 * time.Millisecond)
 
@@ -120,3 +122,73 @@ func TestSwappableMuxSetWaitsForReadersToReleaseMutex(t *testing.T) {
 	default:
 	}
 }
+
+func TestServeHTTPCallsInnerMux(t *testing.T) {
+	called := false
+
+	mux := &mux.Router{}
+	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { called = true })
+
+	sm := swappableMux{root: mux}
+
+	req := httptest.NewRequest("GET", "/", nil)
+	w := httptest.NewRecorder()
+
+	sm.ServeHTTP(w, req)
+
+	if !called {
+		t.Error("Inner mux wasn't called")
+	}
+}
+
+// TODO: test that a read lock does not impede calling ServeHTTP
+
+func TestServeHTTPCanServeWhenMuxIsReadLocked(t *testing.T) {
+	called := false
+
+	mux := &mux.Router{}
+	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { called = true })
+
+	sm := swappableMux{root: mux}
+	sm.m.RLock()
+
+	req := httptest.NewRequest("GET", "/", nil)
+	w := httptest.NewRecorder()
+
+	go sm.ServeHTTP(w, req)
+
+	time.Sleep(10 * time.Millisecond)
+
+	if !called {
+		t.Error("Inner mux not called while mutex is read locked")
+	}
+}
+
+func TestServeHTTPCallsInnerMuxAfterAcquiringLock(t *testing.T) {
+	called := false
+
+	mux := &mux.Router{}
+	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { called = true })
+
+	sm := swappableMux{root: mux}
+	sm.m.Lock()
+
+	req := httptest.NewRequest("GET", "/", nil)
+	w := httptest.NewRecorder()
+
+	go sm.ServeHTTP(w, req)
+
+	time.Sleep(10 * time.Millisecond)
+
+	if called {
+		t.Fatal("Mutex not acquired")
+	}
+
+	sm.m.Unlock()
+
+	time.Sleep(10 * time.Millisecond)
+
+	if !called {
+		t.Error("Inner mux wasn't called after mutex released")
+	}
+}