Region RemovePeer function implementation (#126)

cluster/region/region.go

@@ -112,7 +112,15 @@ func (r *region) AddPeer(peer string) error {
 }
 
 func (r *region) RemovePeer(peer string) error {
-	panic("implement me")
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	for i := 0; i < len(r.peers); i++ {
+		if r.peers[i] == peer {
+			r.peers = append(r.peers[:i], r.peers[i+1:]...)
+			return r.raft.DemoteVoter(raft.ServerID(peer), 0, 0).Error()
+		}
+	}
+	return errors.New("the specified peer does not exist")
 }
 
 func (r *region) GetSize() int64 {

cluster/region/region_test.go

@@ -125,6 +125,35 @@ func TestRegion_GetSize(t *testing.T) {
 	assert.Equal(t, int64(100), size)
 }
 
+func TestRegion_RemovePeer(t *testing.T) {
+	// Create a test region instance
+	region := NewTestRegion()
+	_ = []struct {
+		name          string
+		peers         []string
+		peerToAdd     string
+		expectedPeers []string
+		expectError   bool
+	}{
+		{
+			name:          "remove a peer",
+			peers:         region.GetPeers(),
+			peerToAdd:     "peer2",
+			expectedPeers: []string{"peer1"},
+			expectError:   false,
+		},
+		{
+			name:          "remove a non existing peer",
+			peers:         region.GetPeers(),
+			peerToAdd:     "peer3",
+			expectedPeers: []string{"peer1", "peer2"},
+			expectError:   true,
+		},
+	}
+	destroyRegion(region)
+
+}
+
 func TestRegion_AddPeer(t *testing.T) {
 	// Create a test region instance
 	region := NewTestRegion()