feat: add NewWatcherWithConfig() (#25)

* feat: Added configuration-based constructors

* fix: keyName is not specified.

* test: new test for NewWatcherWithConfig()

* doc: NewWatcherWithConfig() usage

README.md

@@ -45,6 +45,49 @@ func main() {
 }
 ```
 
+## Simple Example（Configuration Mode）
+
+```go
+package main
+
+import (
+    "log"
+
+    casbin "github.com/casbin/casbin/v2"
+    etcdwatcher "github.com/casbin/etcd-watcher/v2"
+)
+
+func updateCallback(rev string) {
+    log.Println("New revision detected:", rev)
+}
+
+func main() {
+    // Initialize the watcher.
+    // Use the configuration file as the parameter
+	w, _ := etcdwatcher.NewWatcherWithConfig(etcdwatcher.WatcherConfig{
+		Hosts: []string{"http://127.0.0.1:2379"},
+		Key:   "/casbin",
+		User:  "root",
+		Pass:  "123",
+	})
+
+    // Initialize the enforcer.
+    e, _ := casbin.NewEnforcer("examples/rbac_model.conf", "examples/rbac_policy.csv")
+
+    // Set the watcher for the enforcer.
+    e.SetWatcher(w)
+
+    // By default, the watcher's callback is automatically set to the
+    // enforcer's LoadPolicy() in the SetWatcher() call.
+    // We can change it by explicitly setting a callback.
+    w.SetUpdateCallback(updateCallback)
+
+    // Update the policy to test the effect.
+    // You should see "[New revision detected: X]" in the log.
+    e.SavePolicy()
+}
+```
+
 ## Getting Help
 
 - [Casbin](https://github.com/casbin/casbin)

watcher.go

@@ -35,6 +35,16 @@ type Watcher struct {
 	keyName     string
 	password    string
 	lastSentRev int64
+	conf        *WatcherConfig
+}
+
+type WatcherConfig struct {
+	Hosts                []string
+	Key                  string `json:",default=casbin_watcher"`
+	User                 string
+	Pass                 string
+	DialKeepAliveTimeout time.Duration `json:",default=10"`
+	DialTimeout          time.Duration `json:",default=30"`
 }
 
 // finalizer is the destructor for Watcher.
@@ -70,6 +80,30 @@ func NewWatcher(endpoints []string, keyName string, password ...string) (persist
 	return w, nil
 }
 
+// NewWatcherWithConfig is a configurable Watcher constructor
+func NewWatcherWithConfig(config WatcherConfig) (persist.Watcher, error) {
+	w := &Watcher{}
+	w.running = true
+	w.callback = nil
+	w.keyName = config.Key
+	w.conf = &config
+
+	// Create the client.
+	err := w.createClient()
+	if err != nil {
+		return nil, err
+	}
+
+	// Call the destructor when the object is released.
+	runtime.SetFinalizer(w, finalizer)
+
+	go func() {
+		_ = w.startWatch()
+	}()
+
+	return w, nil
+}
+
 // Close closes the Watcher.
 func (w *Watcher) Close() {
 	finalizer(w)
@@ -84,6 +118,17 @@ func (w *Watcher) createClient() error {
 		Password:             w.password,
 	}
 
+	if w.conf != nil {
+		cfg = client.Config{
+			Endpoints: w.conf.Hosts,
+			// set timeout per request to fail fast when the target endpoints is unavailable
+			DialTimeout:          time.Second * w.conf.DialTimeout,
+			DialKeepAliveTimeout: time.Second * w.conf.DialKeepAliveTimeout,
+			Username:             w.conf.User,
+			Password:             w.conf.Pass,
+		}
+	}
+
 	c, err := client.New(cfg)
 	if err != nil {
 		return err

watcher_test.go

@@ -30,6 +30,13 @@ func TestWatcher(t *testing.T) {
 	// Use the endpoints of etcd cluster as parameter.
 	updater, _ := NewWatcher([]string{"http://127.0.0.1:2379"}, "/casbin")
 
+	withConfigUpdater, _ := NewWatcherWithConfig(WatcherConfig{
+		Hosts: []string{"http://127.0.0.1:2379"},
+		Key:   "/casbin",
+		User:  "",
+		Pass:  "",
+	})
+
 	// listener represents any other Casbin enforcer instance that watches the change of policy in DB.
 	listener, _ := NewWatcher([]string{"http://127.0.0.1:2379"}, "/casbin")
 	// listener should set a callback that gets called when policy changes.
@@ -41,6 +48,11 @@ func TestWatcher(t *testing.T) {
 		panic(err)
 	}
 
+	err = withConfigUpdater.Update()
+	if err != nil {
+		panic(err)
+	}
+
 	// Now the listener's callback updateCallback() should be called,
 	// because it receives the notification of policy update.
 	// You should see "[New revision detected: X]" in the log.