feat: added DECRBY command support

echovault/api_generic.go

@@ -476,13 +476,34 @@ func (server *EchoVault) Decr(key string) (int, error) {
 func (server *EchoVault) IncrBy(key string, value string) (int, error) {
 	// Construct the command
 	cmd := []string{"INCRBY", key, value}
-
 	// Execute the command
 	b, err := server.handleCommand(server.context, internal.EncodeCommand(cmd), nil, false, true)
 	if err != nil {
 		return 0, err
 	}
+	// Parse the integer response
+	return internal.ParseIntegerResponse(b)
+}
 
+// DecrBy decrements the integer value of the specified key by the given increment.
+// If the key does not exist, it is created with an initial value of 0 before decrementing.
+// If the value stored at the key is not an integer, an error is returned.
+//
+// Parameters:
+//
+// `key` - string - The key whose value is to be decremented.
+//
+// `increment` - int - The amount by which to decrement the key's value. This can be a positive or negative integer.
+//
+// Returns: The new value of the key after the decrement operation as an integer.
+func (server *EchoVault) DecrBy(key string, value string) (int, error) {
+	// Construct the command
+	cmd := []string{"DECRBY", key, value}
+	// Execute the command
+	b, err := server.handleCommand(server.context, internal.EncodeCommand(cmd), nil, false, true)
+	if err != nil {
+		return 0, err
+	}
 	// Parse the integer response
 	return internal.ParseIntegerResponse(b)
 }

echovault/api_generic_test.go

@@ -974,11 +974,11 @@ func TestEchoVault_INCR(t *testing.T) {
 			}
 			got, err := server.Incr(tt.key)
 			if (err != nil) != tt.wantErr {
-				t.Errorf("TTL() error = %v, wantErr %v", err, tt.wantErr)
+				t.Errorf("INCR() error = %v, wantErr %v", err, tt.wantErr)
 				return
 			}
 			if got != tt.want {
-				t.Errorf("TTL() got = %v, want %v", got, tt.want)
+				t.Errorf("INCR() got = %v, want %v", got, tt.want)
 			}
 		})
 	}
@@ -1038,11 +1038,11 @@ func TestEchoVault_DECR(t *testing.T) {
 			}
 			got, err := server.Decr(tt.key)
 			if (err != nil) != tt.wantErr {
-				t.Errorf("TTL() error = %v, wantErr %v", err, tt.wantErr)
+				t.Errorf("DECR() error = %v, wantErr %v", err, tt.wantErr)
 				return
 			}
 			if got != tt.want {
-				t.Errorf("TTL() got = %v, want %v", got, tt.want)
+				t.Errorf("DECR() got = %v, want %v", got, tt.want)
 			}
 		})
 	}
@@ -1116,3 +1116,71 @@ func TestEchoVault_INCRBY(t *testing.T) {
 		})
 	}
 }
+
+func TestEchoVault_DECRBY(t *testing.T) {
+	server := createEchoVault()
+
+	tests := []struct {
+		name         string
+		key          string
+		decrement    string
+		presetValues map[string]internal.KeyData
+		want         int
+		wantErr      bool
+	}{
+		{
+			name:         "1. Decrement non-existent key by 4",
+			key:          "DecrByKey1",
+			decrement:    "4",
+			presetValues: nil,
+			want:         -4,
+			wantErr:      false,
+		},
+		{
+			name:      "2. Decrement existing key with integer value by 3",
+			key:       "DecrByKey2",
+			decrement: "3",
+			presetValues: map[string]internal.KeyData{
+				"DecrByKey2": {Value: "-5"},
+			},
+			want:    -8,
+			wantErr: false,
+		},
+		{
+			name:      "3. Decrement existing key with non-integer value by 2",
+			key:       "DecrByKey3",
+			decrement: "2",
+			presetValues: map[string]internal.KeyData{
+				"DecrByKey3": {Value: "not_an_int"},
+			},
+			want:    0,
+			wantErr: true,
+		},
+		{
+			name:      "4. Decrement existing key with int64 value by 7",
+			key:       "DecrByKey4",
+			decrement: "7",
+			presetValues: map[string]internal.KeyData{
+				"DecrByKey4": {Value: int64(10)}},
+			want:    3,
+			wantErr: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.presetValues != nil {
+				for k, d := range tt.presetValues {
+					presetKeyData(server, context.Background(), k, d)
+				}
+			}
+			got, err := server.DecrBy(tt.key, tt.decrement)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("DecrBy() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if got != tt.want {
+				t.Errorf("DecrBy() got = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

internal/modules/generic/commands.go

@@ -529,6 +529,58 @@ func handleIncrBy(params internal.HandlerFuncParams) ([]byte, error) {
 	return []byte(fmt.Sprintf(":%d\r\n", newValue)), nil
 }
 
+func handleDecrBy(params internal.HandlerFuncParams) ([]byte, error) {
+	// Extract key from command
+	keys, err := decrByKeyFunc(params.Command)
+	if err != nil {
+		return nil, err
+	}
+
+	// Parse decrement value
+	decrValue, err := strconv.ParseInt(params.Command[2], 10, 64)
+	if err != nil {
+		return nil, errors.New("decrement value is not an integer or out of range")
+	}
+
+	key := keys.WriteKeys[0]
+	values := params.GetValues(params.Context, []string{key}) // Get the current values for the specified keys
+	currentValue, ok := values[key]                           // Check if the key exists
+
+	var newValue int64
+	var currentValueInt int64
+
+	// Check if the key exists and its current value
+	if !ok || currentValue == nil {
+		// If key does not exist, initialize it with the decrement value
+		newValue = decrValue * -1
+	} else {
+		// Use type switch to handle different types of currentValue
+		switch v := currentValue.(type) {
+		case string:
+			currentValueInt, err = strconv.ParseInt(v, 10, 64) // Parse the string to int64
+			if err != nil {
+				return nil, errors.New("value is not an integer or out of range")
+			}
+		case int:
+			currentValueInt = int64(v) // Convert int to int64
+		case int64:
+			currentValueInt = v // Use int64 value directly
+		default:
+			fmt.Printf("unexpected type for currentValue: %T\n", currentValue)
+			return nil, errors.New("unexpected type for currentValue") // Handle unexpected types
+		}
+		newValue = currentValueInt - decrValue // decrement the value by the specified amount
+	}
+
+	// Set the new incremented value
+	if err := params.SetValues(params.Context, map[string]interface{}{key: fmt.Sprintf("%d", newValue)}); err != nil {
+		return nil, err
+	}
+
+	// Prepare response with the actual new value
+	return []byte(fmt.Sprintf(":%d\r\n", newValue)), nil
+}
+
 func Commands() []internal.Command {
 	return []internal.Command{
 		{
@@ -733,5 +785,17 @@ An error is returned if the key contains a value of the wrong type or contains a
 			KeyExtractionFunc: incrByKeyFunc,
 			HandlerFunc:       handleIncrBy,
 		},
+		{
+			Command:    "decrby",
+			Module:     constants.GenericModule,
+			Categories: []string{constants.KeyspaceCategory, constants.WriteCategory, constants.FastCategory},
+			Description: `(DECRBY key decrement) 
+The DECRBY command reduces the value stored at the specified key by the specified decrement. 
+If the key does not exist, it is initialized with a value of 0 before performing the operation. 
+If the key's value is not of the correct type or cannot be represented as an integer, an error is returned.`,
+			Sync:              true,
+			KeyExtractionFunc: decrByKeyFunc,
+			HandlerFunc:       handleDecrBy,
+		},
 	}
 }

internal/modules/generic/commands_test.go

@@ -2266,4 +2266,131 @@ func Test_Generic(t *testing.T) {
 			})
 		}
 	})
+
+	t.Run("Test_HandlerDECRBY", func(t *testing.T) {
+		t.Parallel()
+		conn, err := internal.GetConnection("localhost", port)
+		if err != nil {
+			t.Error(err)
+			return
+		}
+		defer func() {
+			_ = conn.Close()
+		}()
+		client := resp.NewConn(conn)
+
+		tests := []struct {
+			name             string
+			key              string
+			decrement        string
+			presetValue      interface{}
+			command          []resp.Value
+			expectedResponse int64
+			expectedError    error
+		}{
+			{
+				name:             "1. Decrement non-existent key by 4",
+				key:              "DecrByKey1",
+				decrement:        "4",
+				presetValue:      nil,
+				command:          []resp.Value{resp.StringValue("DECRBY"), resp.StringValue("DecrByKey1"), resp.StringValue("4")},
+				expectedResponse: -4,
+				expectedError:    nil,
+			},
+			{
+				name:             "2. Decrement existing key with integer value by 3",
+				key:              "DecrByKey2",
+				decrement:        "3",
+				presetValue:      "5",
+				command:          []resp.Value{resp.StringValue("DECRBY"), resp.StringValue("DecrByKey2"), resp.StringValue("3")},
+				expectedResponse: 2,
+				expectedError:    nil,
+			},
+			{
+				name:             "3. Decrement existing key with non-integer value by 2",
+				key:              "DecrByKey3",
+				decrement:        "2",
+				presetValue:      "not_an_int",
+				command:          []resp.Value{resp.StringValue("DECRBY"), resp.StringValue("DecrByKey3"), resp.StringValue("2")},
+				expectedResponse: 0,
+				expectedError:    errors.New("value is not an integer or out of range"),
+			},
+			{
+				name:             "4. Decrement existing key with int64 value by 7",
+				key:              "DecrByKey4",
+				decrement:        "7",
+				presetValue:      int64(10),
+				command:          []resp.Value{resp.StringValue("DECRBY"), resp.StringValue("DecrByKey4"), resp.StringValue("7")},
+				expectedResponse: 3,
+				expectedError:    nil,
+			},
+			{
+				name:             "5. Command too short",
+				key:              "DecrByKey5",
+				presetValue:      nil,
+				command:          []resp.Value{resp.StringValue("DECRBY"), resp.StringValue("DecrByKey5")},
+				expectedResponse: 0,
+				expectedError:    errors.New(constants.WrongArgsResponse),
+			},
+			{
+				name:        "6. Command too long",
+				key:         "DecrKey6",
+				presetValue: nil,
+				command: []resp.Value{
+					resp.StringValue("DECRBY"),
+					resp.StringValue("DecrKey6"),
+					resp.StringValue("3"),
+					resp.StringValue("extra_arg"),
+				},
+				expectedResponse: 0,
+				expectedError:    errors.New(constants.WrongArgsResponse),
+			},
+		}
+
+		for _, test := range tests {
+			t.Run(test.name, func(t *testing.T) {
+				if test.presetValue != nil {
+					command := []resp.Value{resp.StringValue("SET"), resp.StringValue(test.key), resp.StringValue(fmt.Sprintf("%v", test.presetValue))}
+					if err = client.WriteArray(command); err != nil {
+						t.Error(err)
+					}
+					res, _, err := client.ReadValue()
+					if err != nil {
+						t.Error(err)
+					}
+					if !strings.EqualFold(res.String(), "OK") {
+						t.Errorf("expected preset response to be OK, got %s", res.String())
+					}
+				}
+
+				if err = client.WriteArray(test.command); err != nil {
+					t.Error(err)
+				}
+
+				res, _, err := client.ReadValue()
+				if err != nil {
+					t.Error(err)
+				}
+
+				if test.expectedError != nil {
+					if !strings.Contains(res.Error().Error(), test.expectedError.Error()) {
+						t.Errorf("expected error \"%s\", got \"%s\"", test.expectedError.Error(), err.Error())
+					}
+					return
+				}
+
+				if err != nil {
+					t.Error(err)
+				} else {
+					responseInt, err := strconv.ParseInt(res.String(), 10, 64)
+					if err != nil {
+						t.Errorf("error parsing response to int64: %s", err)
+					}
+					if responseInt != test.expectedResponse {
+						t.Errorf("expected response %d, got %d", test.expectedResponse, responseInt)
+					}
+				}
+			})
+		}
+	})
 }

internal/modules/generic/key_funcs.go

@@ -163,3 +163,12 @@ func incrByKeyFunc(cmd []string) (internal.KeyExtractionFuncResult, error) {
 		WriteKeys: []string{cmd[1]},
 	}, nil
 }
+
+func decrByKeyFunc(cmd []string) (internal.KeyExtractionFuncResult, error) {
+	if len(cmd) != 3 {
+		return internal.KeyExtractionFuncResult{}, errors.New(constants.WrongArgsResponse)
+	}
+	return internal.KeyExtractionFuncResult{
+		WriteKeys: []string{cmd[1]},
+	}, nil
+}