v2 final

v2/context.go

@@ -0,0 +1,114 @@
+package serverevents
+
+import (
+	di "git.apihub24.de/admin/generic-di"
+	"sync"
+	"time"
+)
+
+func init() {
+	di.Injectable(newContext)
+}
+
+type IContext interface {
+	SetId(id string)
+	GetId() string
+	Set(key string, data any)
+	Get(key string) (any, bool)
+	RemoveMetaData(key string)
+	CleanupIn(lifetime time.Duration)
+	Dispatch(eventName string, data any, filter func(c IContext) bool)
+	IsCaller(c IContext) bool
+}
+
+type context struct {
+	id       string
+	metadata map[string]any
+	timer    *time.Timer
+	emitter  IEventEmitter
+	mutex    sync.RWMutex
+}
+
+func newContext() IContext {
+	return &context{
+		id:       "",
+		metadata: make(map[string]any),
+		timer:    nil,
+		emitter:  di.Inject[IEventEmitter](),
+		mutex:    sync.RWMutex{},
+	}
+}
+
+func (context *context) SetId(id string) {
+	context.mutex.Lock()
+	defer context.mutex.Unlock()
+
+	if context.timer != nil {
+		context.timer.Stop()
+		context.timer = nil
+	}
+	context.id = id
+}
+
+func (context *context) GetId() string {
+	return context.id
+}
+
+func (context *context) IsCaller(c IContext) bool {
+	return context.id == c.GetId()
+}
+
+func (context *context) Set(key string, data any) {
+	context.mutex.Lock()
+	defer context.mutex.Unlock()
+
+	context.metadata[key] = data
+}
+
+func (context *context) Get(key string) (any, bool) {
+	context.mutex.RLock()
+	defer context.mutex.RUnlock()
+
+	v, ok := context.metadata[key]
+	return v, ok
+}
+
+func (context *context) RemoveMetaData(key string) {
+	context.mutex.Lock()
+	defer context.mutex.Unlock()
+
+	if _, ok := context.metadata[key]; ok {
+		delete(context.metadata, key)
+	}
+}
+
+func (context *context) CleanupIn(lifetime time.Duration) {
+	context.mutex.Lock()
+	defer context.mutex.Unlock()
+
+	if context.timer != nil {
+		context.timer.Stop()
+	}
+	context.timer = time.NewTimer(lifetime)
+	go func(currentId string) {
+		<-context.timer.C
+
+		context.mutex.Lock()
+		defer context.mutex.Unlock()
+
+		if context.timer != nil {
+			di.Destroy[IContext](context.id)
+			context.timer = nil
+		}
+	}(context.id)
+}
+
+func (context *context) Dispatch(eventName string, data any, filter func(c IContext) bool) {
+	ev := Event{
+		Type:          eventName,
+		Data:          data,
+		IsBackendOnly: filter == nil,
+		Filter:        filter,
+	}
+	context.emitter.Emit(ev)
+}

v2/context_helper.go

@@ -0,0 +1,19 @@
+package serverevents
+
+func CreateMetaDataFilter[T any](c IContext, metaDataSelector func(IContext) T, vgl func(a T, b T) bool) func(context IContext) bool {
+	return func(context IContext) bool {
+		metaA := metaDataSelector(c)
+		metaB := metaDataSelector(context)
+		return vgl(metaA, metaB)
+	}
+}
+
+func MetadataAs[T any](context IContext, key string) (T, bool) {
+	var v T
+	tmp, ok := context.Get(key)
+	if tmp == nil {
+		return v, false
+	}
+	res, ok := tmp.(T)
+	return res, ok
+}

v2/event.go

@@ -4,4 +4,5 @@ type Event struct {
 	Type          string                `json:"type"`
 	Data          any                   `json:"data"`
 	IsBackendOnly bool                  `json:"-"`
+	Filter        func(c IContext) bool `json:"-"`
 }

v2/handler.go

@@ -0,0 +1,6 @@
+package serverevents
+
+type IEventHandler interface {
+	CanExecute(IContext) bool
+	Handle(IContext)
+}

v2/implementation_test/events/greeter.go

@@ -0,0 +1,37 @@
+package events
+
+import (
+	"fmt"
+	serverevents "git.apihub24.de/admin/server_events/v2"
+)
+
+func withSameUserName(context serverevents.IContext) func(context serverevents.IContext) bool {
+	return serverevents.CreateMetaDataFilter(context, func(c serverevents.IContext) string {
+		userName, _ := serverevents.MetadataAs[string](context, "UserName")
+		return userName
+	}, func(a string, b string) bool {
+		return a == b
+	})
+}
+
+type greeting struct {
+	Message string
+}
+
+type greeterEventHandler struct{}
+
+func (handler greeterEventHandler) CanExecute(context serverevents.IContext) bool {
+	_, ok := serverevents.MetadataAs[string](context, "UserName")
+	return ok
+}
+
+func (handler greeterEventHandler) Handle(context serverevents.IContext) {
+	userName, _ := serverevents.MetadataAs[string](context, "UserName")
+	context.Dispatch("greet", greeting{
+		Message: fmt.Sprintf("Hello, %s", userName),
+	}, withSameUserName(context))
+}
+
+func NewGreeterEventHandler() serverevents.IEventHandler {
+	return &greeterEventHandler{}
+}

v2/implementation_test/events/ping.go

@@ -0,0 +1,19 @@
+package events
+
+import (
+	serverevents "git.apihub24.de/admin/server_events/v2"
+)
+
+type pingEventHandler struct{}
+
+func NewPingEventHandler() serverevents.IEventHandler {
+	return &pingEventHandler{}
+}
+
+func (p pingEventHandler) CanExecute(context serverevents.IContext) bool {
+	return true
+}
+
+func (p pingEventHandler) Handle(context serverevents.IContext) {
+	context.Dispatch("pong", nil, context.IsCaller)
+}

v2/implementation_test/main.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	di "git.apihub24.de/admin/generic-di"
+	serverevents "git.apihub24.de/admin/server_events/v2"
+	"git.apihub24.de/admin/server_events/v2/implementation_test/events"
+	"log"
+	"net/http"
+	"time"
+)
+
+func main() {
+	serverEventsMiddleware := di.Inject[serverevents.IMiddleware]()
+	eventRegistration := di.Inject[serverevents.IEventHandlerRegistration]()
+
+	eventRegistration.Add("ping", events.NewPingEventHandler)
+	eventRegistration.Add("greet all", events.NewGreeterEventHandler)
+
+	serverEventsMiddleware.Use(serverevents.MiddlewareOptions{
+		Path:            "/events",
+		ContextLifetime: 500 * time.Second,
+	}, nil)
+
+	log.Fatal(http.ListenAndServe(":8080", nil))
+}

v2/middleware.go

@@ -1,11 +1,12 @@
 package serverevents
 
 import (
-	"encoding/json"
 	"fmt"
 	di "git.apihub24.de/admin/generic-di"
 	"github.com/gorilla/websocket"
 	"net/http"
+	"sync"
+	"time"
 )
 
 func init() {
@@ -14,18 +15,24 @@ func init() {
 
 type MiddlewareOptions struct {
 	Path            string
+	ContextLifetime time.Duration
 }
 
-type IServerEventsMiddleware interface {
-	Use(MiddlewareOptions, *http.ServeMux)
+type IMiddleware interface {
+	Use(options MiddlewareOptions, mux *http.ServeMux)
 }
 
 type serverEventsMiddleware struct {
+	options           MiddlewareOptions
 	upgrader          websocket.Upgrader
 	streamSubscribers map[string]bool
+	emitter           IEventEmitter
+	parser            IMessageParser
+	registration      IEventHandlerRegistration
+	mutex             sync.Mutex
 }
 
-func newServerEventsMiddleware() IServerEventsMiddleware {
+func newServerEventsMiddleware() IMiddleware {
 	return &serverEventsMiddleware{
 		upgrader: websocket.Upgrader{
 			CheckOrigin: func(r *http.Request) bool {
@@ -33,17 +40,21 @@ func newServerEventsMiddleware() IServerEventsMiddleware {
 			},
 		},
 		streamSubscribers: make(map[string]bool),
+		emitter:           di.Inject[IEventEmitter](),
+		parser:            di.Inject[IMessageParser](),
+		registration:      di.Inject[IEventHandlerRegistration](),
+		mutex:             sync.Mutex{},
 	}
 }
 
 func (middleware *serverEventsMiddleware) Use(options MiddlewareOptions, muxer *http.ServeMux) {
+	middleware.options = options
 	middleware.selectMethod(options.Path, func(w http.ResponseWriter, r *http.Request) {
 		middleware.handleEventStream(w, r)
 	}, muxer)
 }
 
 func (middleware *serverEventsMiddleware) handleEventStream(w http.ResponseWriter, r *http.Request) {
-	emitter := di.Inject[IEventEmitter]()
 	conn, err := middleware.upgrader.Upgrade(w, r, nil)
 	if err != nil {
 		fmt.Println("Error upgrading:", err)
@@ -54,31 +65,64 @@ func (middleware *serverEventsMiddleware) handleEventStream(w http.ResponseWrite
 		_ = conn.Close()
 	}()
 	id := r.URL.Query().Get("id")
+	context := di.Inject[IContext](id)
+	context.SetId(id)
 
+	// Locks the mutex before accessing 'middleware.streamSubscribers',
+	// to prevent race conditions when reading/writing to the map.
+	// This ensures that only one goroutine checks/registers at a time.
+	// defer can't be used here as the stream listens for messages in an infinite loop
+	middleware.mutex.Lock()
 	if _, ok := middleware.streamSubscribers[id]; !ok {
-		subscription := emitter.OnAll(func(event Event) {
-			if !event.IsBackendOnly {
-				jsonData, jsonErr := json.Marshal(event)
-				if jsonErr != nil {
-					fmt.Println("Error make json string", jsonErr)
+		subscription := middleware.emitter.OnAll(func(ev Event) {
+			// trigger the Backend Handlers
+			handler, getHandlerErr := middleware.registration.GetHandler(ev.Type)
+			if getHandlerErr != nil {
+				println(fmt.Sprintf("no Handler found for Event %s", ev.Type))
+			} else {
+				if handler.CanExecute(context) {
+					handler.Handle(context)
+				}
+			}
+
+			if ev.IsBackendOnly || ev.Filter == nil || !ev.Filter(context) {
+				// the Event is Backend only or there is no socket (context) Filter
+				// to send to all Sockets deliver context Filter with returns bool
 				return
 			}
-				_ = conn.WriteMessage(websocket.TextMessage, jsonData)
+			jsonData, jsonErr := middleware.parser.ToString(ev)
+			if jsonErr != nil {
+				println(fmt.Sprintf("Error parse event %s %s", jsonErr.Error(), ev.Type))
+				return
 			}
+			_ = conn.WriteMessage(websocket.TextMessage, []byte(jsonData))
 		})
 		defer func() {
+			// Blocks the mutex again, as this block also accesses 'middleware.streamSubscribers'.
+			// This is crucial to avoid race conditions when removing entries,
+			// while new connections may be established.
+			// defer cannot be used here either
+			middleware.mutex.Lock()
 			subscription.Unsubscribe()
 			delete(middleware.streamSubscribers, id)
+
+			// starts the Cleanup Process
+			context.CleanupIn(middleware.options.ContextLifetime)
+			middleware.mutex.Unlock()
 		}()
 		middleware.streamSubscribers[id] = true
 	}
+	middleware.mutex.Unlock()
 
 	ctx := r.Context()
 	for {
-		_, _, err := conn.ReadMessage()
+		messageType, data, err := conn.ReadMessage()
 		if err != nil {
 			return
 		}
+		if middleware.HandleMessage(conn, messageType, data) {
+			return
+		}
 		select {
 		case <-ctx.Done():
 			return
@@ -93,3 +137,31 @@ func (middleware *serverEventsMiddleware) selectMethod(path string, todo http.Ha
 		muxer.HandleFunc(path, todo)
 	}
 }
+
+func (middleware *serverEventsMiddleware) HandleMessage(conn *websocket.Conn, messageType int, data []byte) bool {
+	switch messageType {
+	case websocket.PingMessage:
+		pongErr := conn.WriteMessage(websocket.PongMessage, []byte{})
+		if pongErr != nil {
+			println(fmt.Sprintf("error on send PongMessage: %s", pongErr.Error()))
+		}
+		break
+	case websocket.CloseMessage:
+		// return true to close the Websocket
+		return true
+	case websocket.TextMessage:
+		ev, parseErr := middleware.parser.FromString(string(data))
+		if parseErr != nil {
+			println(fmt.Sprintf("error on parse Event: %s data: %s", parseErr.Error(), string(data)))
+			return false
+		}
+		// Event was dispatched over the Websocket so not send it back to Client!
+		ev.IsBackendOnly = true
+		middleware.emitter.Emit(ev)
+		break
+	case websocket.BinaryMessage:
+		println(fmt.Sprintf("BinaryMessages are not supported"))
+		break
+	}
+	return false
+}

v2/parser.go

@@ -0,0 +1,35 @@
+package serverevents
+
+import (
+	"encoding/json"
+	di "git.apihub24.de/admin/generic-di"
+)
+
+func init() {
+	di.Injectable(newMessageParser)
+}
+
+type IMessageParser interface {
+	ToString(event Event) (string, error)
+	FromString(eventStr string) (Event, error)
+}
+
+type messageParser struct{}
+
+func newMessageParser() IMessageParser {
+	return &messageParser{}
+}
+
+func (parser *messageParser) ToString(event Event) (string, error) {
+	stream, marshalErr := json.Marshal(event)
+	if marshalErr != nil {
+		return "", marshalErr
+	}
+	return string(stream), nil
+}
+
+func (parser *messageParser) FromString(eventStr string) (Event, error) {
+	var ev Event
+	unmarshalErr := json.Unmarshal([]byte(eventStr), &ev)
+	return ev, unmarshalErr
+}

v2/registration.go

@@ -0,0 +1,57 @@
+package serverevents
+
+import (
+	"fmt"
+	di "git.apihub24.de/admin/generic-di"
+	"sync"
+)
+
+func init() {
+	di.Injectable(newEventHandlerRegistration)
+}
+
+type IEventHandlerRegistration interface {
+	Add(eventType string, creator func() IEventHandler)
+	GetHandler(eventType string) (IEventHandler, error)
+}
+
+type eventHandlerRegistration struct {
+	creators  map[string]func() IEventHandler
+	instances map[string]IEventHandler
+	mutex     sync.RWMutex
+}
+
+func newEventHandlerRegistration() IEventHandlerRegistration {
+	return &eventHandlerRegistration{
+		creators:  make(map[string]func() IEventHandler),
+		instances: make(map[string]IEventHandler),
+		mutex:     sync.RWMutex{},
+	}
+}
+
+func (registration *eventHandlerRegistration) Add(eventType string, creator func() IEventHandler) {
+	registration.mutex.Lock()
+	defer registration.mutex.Unlock()
+
+	if _, ok := registration.instances[eventType]; ok {
+		delete(registration.instances, eventType)
+	}
+	if _, ok := registration.creators[eventType]; ok {
+		delete(registration.creators, eventType)
+	}
+	registration.creators[eventType] = creator
+}
+
+func (registration *eventHandlerRegistration) GetHandler(eventType string) (IEventHandler, error) {
+	registration.mutex.RLock()
+	defer registration.mutex.RUnlock()
+
+	if creator, ok := registration.creators[eventType]; ok {
+		if instance, ok := registration.instances[eventType]; ok {
+			return instance, nil
+		}
+		registration.instances[eventType] = creator()
+		return registration.instances[eventType], nil
+	}
+	return nil, fmt.Errorf("no instance of IEventHandler registered for Event %s! please call Registration Add in a init function to register your EventHandler", eventType)
+}