Improve LogMonitor to handle empty writes and ensure buffer immutability

- Add a check to return immediately if the write buffer is empty
- Create a copy of new history data to ensure it is immutable
- Update the `GetHistory` method to use the `any` type for the buffer interface
- Add a test case to verify that the buffer remains unchanged
  even if the original message is modified after writing

proxy/logMonitor.go

@@ -30,13 +30,19 @@ func NewLogMonitorWriter(stdout io.Writer) *LogMonitor {
 }
 
 func (w *LogMonitor) Write(p []byte) (n int, err error) {
+	if len(p) == 0 {
+		return 0, nil
+	}
+
 	n, err = w.stdout.Write(p)
 	if err != nil {
 		return n, err
 	}
 
 	w.bufferMu.Lock()
-	w.buffer.Value = p
+	bufferCopy := make([]byte, len(p))
+	copy(bufferCopy, p)
+	w.buffer.Value = bufferCopy
 	w.buffer = w.buffer.Next()
 	w.bufferMu.Unlock()
 
@@ -49,7 +55,7 @@ func (w *LogMonitor) GetHistory() []byte {
 	defer w.bufferMu.RUnlock()
 
 	var history []byte
-	w.buffer.Do(func(p interface{}) {
+	w.buffer.Do(func(p any) {
 		if p != nil {
 			if content, ok := p.([]byte); ok {
 				history = append(history, content...)

proxy/logMonitor_test.go

@@ -1,6 +1,7 @@
 package proxy
 
 import (
+	"bytes"
 	"io"
 	"sync"
 	"testing"
@@ -61,3 +62,34 @@ func TestLogMonitor(t *testing.T) {
 		t.Errorf("Client2 expected %s, got: %s", expectedHistory, c2Data)
 	}
 }
+
+func TestWrite_ImmutableBuffer(t *testing.T) {
+	// Create a new LogMonitor instance
+	lm := NewLogMonitorWriter(io.Discard)
+
+	// Prepare a message to write
+	msg := []byte("Hello, World!")
+	lenmsg := len(msg)
+
+	// Write the message to the LogMonitor
+	n, err := lm.Write(msg)
+	if err != nil {
+		t.Fatalf("Write failed: %v", err)
+	}
+
+	if n != lenmsg {
+		t.Errorf("Expected %d bytes written but got %d", lenmsg, n)
+	}
+
+	// Change the original message
+	msg[0] = 'B' // This should not affect the buffer
+
+	// Get the history from the LogMonitor
+	history := lm.GetHistory()
+
+	// Check that the history contains the original message, not the modified one
+	expected := []byte("Hello, World!")
+	if !bytes.Equal(history, expected) {
+		t.Errorf("Expected history to be %q, got %q", expected, history)
+	}
+}