refactor(queue): improve queues

* fix race condition for registering handler
* add close method
* use generics to reduce duplication
* rename packages to drop underscore for go convention
* rename interface to drop stutter with package name

Signed-off-by: ferhat elmas <elmas.ferhat@gmail.com>

Author: ferhatelmas

cmd/wire_gen.go

@@ -0,0 +1,120 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package queue
+
+import (
+	"context"
+	"sync"
+
+	"github.com/segmentfault/pacman/log"
+)
+
+// Queue is a generic message queue service that processes messages asynchronously.
+// It is thread-safe and supports graceful shutdown.
+type Queue[T any] struct {
+	name    string
+	queue   chan T
+	handler func(ctx context.Context, msg T) error
+	mu      sync.RWMutex
+	closed  bool
+	wg      sync.WaitGroup
+}
+
+// New creates a new queue with the given name and buffer size.
+func New[T any](name string, bufferSize int) *Queue[T] {
+	q := &Queue[T]{
+		name:  name,
+		queue: make(chan T, bufferSize),
+	}
+	q.startWorker()
+	return q
+}
+
+// Send enqueues a message to be processed asynchronously.
+// It will block if the queue is full.
+func (q *Queue[T]) Send(ctx context.Context, msg T) {
+	q.mu.RLock()
+	closed := q.closed
+	q.mu.RUnlock()
+
+	if closed {
+		log.Warnf("[%s] queue is closed, dropping message", q.name)
+		return
+	}
+
+	select {
+	case q.queue <- msg:
+		log.Debugf("[%s] enqueued message: %+v", q.name, msg)
+	case <-ctx.Done():
+		log.Warnf("[%s] context cancelled while sending message", q.name)
+	}
+}
+
+// RegisterHandler sets the handler function for processing messages.
+// This is thread-safe and can be called at any time.
+func (q *Queue[T]) RegisterHandler(handler func(ctx context.Context, msg T) error) {
+	q.mu.Lock()
+	defer q.mu.Unlock()
+	q.handler = handler
+}
+
+// Close gracefully shuts down the queue, waiting for pending messages to be processed.
+func (q *Queue[T]) Close() {
+	q.mu.Lock()
+	if q.closed {
+		q.mu.Unlock()
+		return
+	}
+	q.closed = true
+	q.mu.Unlock()
+
+	close(q.queue)
+	q.wg.Wait()
+	log.Infof("[%s] queue closed", q.name)
+}
+
+// startWorker starts the background goroutine that processes messages.
+func (q *Queue[T]) startWorker() {
+	q.wg.Add(1)
+	go func() {
+		defer q.wg.Done()
+		for msg := range q.queue {
+			q.processMessage(msg)
+		}
+	}()
+}
+
+// processMessage handles a single message with proper synchronization.
+func (q *Queue[T]) processMessage(msg T) {
+	q.mu.RLock()
+	handler := q.handler
+	q.mu.RUnlock()
+
+	if handler == nil {
+		log.Warnf("[%s] no handler registered, dropping message: %+v", q.name, msg)
+		return
+	}
+
+	// Use background context for async processing
+	// TODO: Consider adding timeout or using a derived context
+	if err := handler(context.TODO(), msg); err != nil {
+		log.Errorf("[%s] handler error: %v", q.name, err)
+	}
+}