From 62ec810e6daa1a0347357687c5ef7742598b41ea Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Roberto=20Abdelkader=20Mart=C3=ADnez=20P=C3=A9rez?=
 <robertomartinezp@gmail.com>
Date: Sat, 5 Oct 2019 12:22:38 +0200
Subject: [PATCH] Implemented user server state aka route list

---
 internal/server/user/state.go      |  37 ++++++++
 internal/server/user/state_test.go | 136 +++++++++++++++++++++++++++++
 2 files changed, 173 insertions(+)
 create mode 100644 internal/server/user/state.go
 create mode 100644 internal/server/user/state_test.go

diff --git a/internal/server/user/state.go b/internal/server/user/state.go
new file mode 100644
index 0000000..726bb46
--- /dev/null
+++ b/internal/server/user/state.go
@@ -0,0 +1,37 @@
+package user
+
+import (
+	"sync"
+
+	"github.com/BBVA/kapow/internal/server/model"
+)
+
+type safeRouteList struct {
+	rs []model.Route
+	m  sync.RWMutex
+}
+
+var Routes = New()
+
+func New() safeRouteList {
+	return safeRouteList{}
+}
+
+func (srl *safeRouteList) Append(r model.Route) {
+	srl.m.Lock()
+	srl.rs = append(srl.rs, r)
+	srl.m.Unlock()
+}
+
+func (srl *safeRouteList) Snapshot() []model.Route {
+	srl.m.RLock()
+	defer srl.m.RUnlock()
+
+	if srl.rs == nil {
+		return nil
+	} else {
+		rs := make([]model.Route, len(srl.rs))
+		copy(rs, srl.rs)
+		return rs
+	}
+}
diff --git a/internal/server/user/state_test.go b/internal/server/user/state_test.go
new file mode 100644
index 0000000..2b67f3c
--- /dev/null
+++ b/internal/server/user/state_test.go
@@ -0,0 +1,136 @@
+package user
+
+import (
+	"github.com/BBVA/kapow/internal/server/model"
+	"reflect"
+	"testing"
+	"time"
+)
+
+func TestNewReturnAnEmptyStruct(t *testing.T) {
+	srl := New()
+
+	if len(srl.rs) != 0 {
+		t.Error("Unexpected member in slice")
+	}
+}
+
+func TestPackageHaveASingletonEmptyRouteList(t *testing.T) {
+	if !reflect.DeepEqual(Routes, New()) {
+		t.Error("Routes is not an empty safeRouteList")
+	}
+}
+
+func TestAppendAppendsANewRouteToTheList(t *testing.T) {
+	srl := New()
+
+	srl.Append(model.Route{})
+
+	if len(srl.rs) == 0 {
+		t.Error("Route not added to the list")
+	}
+}
+
+func TestAppendAdquiresMutexBeforeAdding(t *testing.T) {
+	srl := New()
+
+	srl.m.Lock()
+	defer srl.m.Unlock()
+	go srl.Append(model.Route{})
+
+	time.Sleep(10 * time.Millisecond)
+
+	if len(srl.rs) != 0 {
+		t.Error("Route added while mutex was adquired")
+	}
+}
+
+func TestAppendAddsRouteAfterMutexIsReleased(t *testing.T) {
+	srl := New()
+
+	srl.m.Lock()
+	go srl.Append(model.Route{})
+	srl.m.Unlock()
+
+	time.Sleep(10 * time.Millisecond)
+
+	if len(srl.rs) != 1 {
+		t.Error("Route not added after mutex release")
+	}
+}
+
+func TestSnapshotReturnTheCurrentListOfRoutes(t *testing.T) {
+	srl := New()
+	srl.Append(model.Route{Id: "FOO"})
+
+	rs := srl.Snapshot()
+
+	if !reflect.DeepEqual(srl.rs, rs) {
+		t.Error("Route list returned is not the current one")
+	}
+}
+
+func TestSnapshotReturnADeepCopyOfTheListWhenEmpty(t *testing.T) {
+	srl := New()
+
+	rs := srl.Snapshot()
+
+	if rs != nil {
+		t.Fatal("Route list copy is not empty")
+	}
+}
+
+func TestSnapshotReturnADeepCopyOfTheListWhenNonEmpty(t *testing.T) {
+	srl := New()
+	srl.Append(model.Route{Id: "FOO"})
+
+	rs := srl.Snapshot()
+
+	if &rs == &srl.rs {
+		t.Fatal("Route list is not a copy")
+	}
+
+	for i := 0; i < len(rs); i++ {
+		if &rs[i] == &srl.rs[i] {
+			t.Errorf("Route %q is not a copy", i)
+		}
+	}
+}
+
+func TestSnapshotWaitsForTheWriterToFinish(t *testing.T) {
+	srl := New()
+	srl.Append(model.Route{Id: "FOO"})
+
+	srl.m.Lock()
+	defer srl.m.Unlock()
+
+	c := make(chan []model.Route)
+	go func() { c <- srl.Snapshot() }()
+
+	time.Sleep(10 * time.Millisecond)
+
+	select {
+	case <-c:
+		t.Error("Route list readed while mutex was adquired")
+	default: // This default prevents the select from being blocking
+	}
+}
+
+func TestSnapshotNonBlockingReadWithOtherReaders(t *testing.T) {
+	srl := New()
+	srl.Append(model.Route{Id: "FOO"})
+
+	srl.m.RLock()
+	defer srl.m.RUnlock()
+
+	c := make(chan []model.Route)
+	go func() { c <- srl.Snapshot() }()
+
+	time.Sleep(10 * time.Millisecond)
+
+	select {
+	case <-c:
+	default: // This default prevents the select from being blocking
+		t.Error("Route list couldn't be readed while mutex was adquired for read")
+	}
+}