added option to remove single registered hook handler

tools/hook/hook.go

@@ -2,7 +2,10 @@ package hook
 
 import (
 	"errors"
+	"fmt"
 	"sync"
+
+	"github.com/pocketbase/pocketbase/tools/security"
 )
 
 var StopPropagation = errors.New("Event hook propagation stopped")
@@ -10,36 +13,65 @@ var StopPropagation = errors.New("Event hook propagation stopped")
 // Handler defines a hook handler function.
 type Handler[T any] func(e T) error
 
+// handlerPair defines a pair of string id and Handler.
+type handlerPair[T any] struct {
+	id      string
+	handler Handler[T]
+}
+
 // Hook defines a concurrent safe structure for handling event hooks
 // (aka. callbacks propagation).
 type Hook[T any] struct {
 	mux      sync.RWMutex
-	handlers []Handler[T]
+	handlers []*handlerPair[T]
 }
 
 // PreAdd registers a new handler to the hook by prepending it to the existing queue.
-func (h *Hook[T]) PreAdd(fn Handler[T]) {
+//
+// Returns an autogenerated hook id that could be used later to remove the hook with Hook.Remove(id).
+func (h *Hook[T]) PreAdd(fn Handler[T]) string {
 	h.mux.Lock()
 	defer h.mux.Unlock()
 
+	id := generateHookId()
+
 	// minimize allocations by shifting the slice
 	h.handlers = append(h.handlers, nil)
 	copy(h.handlers[1:], h.handlers)
-	h.handlers[0] = fn
+	h.handlers[0] = &handlerPair[T]{id, fn}
+
+	return id
 }
 
 // Add registers a new handler to the hook by appending it to the existing queue.
-func (h *Hook[T]) Add(fn Handler[T]) {
+//
+// Returns an autogenerated hook id that could be used later to remove the hook with Hook.Remove(id).
+func (h *Hook[T]) Add(fn Handler[T]) string {
 	h.mux.Lock()
 	defer h.mux.Unlock()
 
-	h.handlers = append(h.handlers, fn)
+	id := generateHookId()
+
+	h.handlers = append(h.handlers, &handlerPair[T]{id, fn})
+
+	return id
 }
 
-// Reset removes all registered handlers.
-//
-// @todo for consistency with other Go methods consider renaming it to Clear.
-func (h *Hook[T]) Reset() {
+// Remove removes a single hook handler by its id.
+func (h *Hook[T]) Remove(id string) {
+	h.mux.Lock()
+	defer h.mux.Unlock()
+
+	for i := len(h.handlers) - 1; i >= 0; i-- {
+		if h.handlers[i].id == id {
+			h.handlers = append(h.handlers[:i], h.handlers[i+1:]...)
+			return
+		}
+	}
+}
+
+// RemoveAll removes all registered handlers.
+func (h *Hook[T]) RemoveAll() {
 	h.mux.Lock()
 	defer h.mux.Unlock()
 
@@ -57,14 +89,24 @@ func (h *Hook[T]) Reset() {
 // - any non-nil error is returned in one of the handlers
 func (h *Hook[T]) Trigger(data T, oneOffHandlers ...Handler[T]) error {
 	h.mux.RLock()
-	handlers := make([]Handler[T], 0, len(h.handlers)+len(oneOffHandlers))
+
+	handlers := make([]*handlerPair[T], 0, len(h.handlers)+len(oneOffHandlers))
 	handlers = append(handlers, h.handlers...)
-	handlers = append(handlers, oneOffHandlers...)
-	// unlock is not deferred to avoid deadlocks when Trigger is called recursive by the handlers
+
+	// append the one off handlers
+	for i, oneOff := range oneOffHandlers {
+		handlers = append(handlers, &handlerPair[T]{
+			id:      fmt.Sprintf("@%d", i),
+			handler: oneOff,
+		})
+	}
+
+	// unlock is not deferred to avoid deadlocks in case Trigger
+	// is called recursively by the handlers
 	h.mux.RUnlock()
 
-	for _, fn := range handlers {
-		err := fn(data)
+	for _, item := range handlers {
+		err := item.handler(data)
 		if err == nil {
 			continue
 		}
@@ -78,3 +120,7 @@ func (h *Hook[T]) Trigger(data T, oneOffHandlers ...Handler[T]) error {
 
 	return nil
 }
+
+func generateHookId() string {
+	return security.PseudorandomString(8)
+}