Expose and document scale parameter (#90)

README.md

@@ -305,8 +305,16 @@ Sample configuration:
 ```yaml
 type: mqtt
 topic: mbmd/sdm1-1/Power
-timeout: 30s
-payload: ${var:%.2f}
+timeout: 30s # don't accept values older than timeout
+scale: 0.001 # floating point factor applied to result, e.g. for kW to W conversion
+```
+
+Sample write configuration:
+
+```yaml
+type: mqtt
+topic: mbmd/charger/maxcurrent
+payload: ${var:%d}
 ```
 
 For write access, the data is provided using the `payload` attribute. If `payload` is missing, the value will be written in default format.
@@ -344,6 +352,7 @@ method: GET # default HTTP method
 headers:
 - content-type: application/json
 jq: .data.tuples[0][1] # parse response json
+scale: 0.001 # floating point factor applied to result, e.g. for kW to W conversion
 ```
 
 Sample write configuration:

provider/config.go

@@ -20,7 +20,7 @@ type Config struct {
 // mqttConfig is the specific mqtt getter/setter configuration
 type mqttConfig struct {
 	Topic, Payload string // Payload only applies to setters
-	Multiplier     float64
+	Scale          float64
 	Timeout        time.Duration
 }
 
@@ -42,8 +42,8 @@ func mqttFromConfig(log *util.Logger, other map[string]interface{}) mqttConfig {
 	var pc mqttConfig
 	util.DecodeOther(log, other, &pc)
 
-	if pc.Multiplier == 0 {
-		pc.Multiplier = 1
+	if pc.Scale == 0 {
+		pc.Scale = 1
 	}
 
 	return pc
@@ -67,7 +67,7 @@ func NewFloatGetterFromConfig(log *util.Logger, config Config) (res FloatGetter)
 		res = NewHTTPProviderFromConfig(log, config.Other).FloatGetter
 	case "mqtt":
 		pc := mqttFromConfig(log, config.Other)
-		res = MQTT.FloatGetter(pc.Topic, pc.Multiplier, pc.Timeout)
+		res = MQTT.FloatGetter(pc.Topic, pc.Scale, pc.Timeout)
 	case "script":
 		pc := scriptFromConfig(log, config.Other)
 		res = NewScriptProvider(pc.Timeout).FloatGetter(pc.Cmd)
@@ -90,7 +90,7 @@ func NewIntGetterFromConfig(log *util.Logger, config Config) (res IntGetter) {
 		res = NewHTTPProviderFromConfig(log, config.Other).IntGetter
 	case "mqtt":
 		pc := mqttFromConfig(log, config.Other)
-		res = MQTT.IntGetter(pc.Topic, int64(pc.Multiplier), pc.Timeout)
+		res = MQTT.IntGetter(pc.Topic, int64(pc.Scale), pc.Timeout)
 	case "script":
 		pc := scriptFromConfig(log, config.Other)
 		res = NewScriptProvider(pc.Timeout).IntGetter(pc.Cmd)

provider/http.go

@@ -86,7 +86,7 @@ func (p *HTTP) FloatGetter() (float64, error) {
 	}
 
 	f, err := strconv.ParseFloat(s, 64)
-	if err == nil && p.scale > 0 {
+	if err == nil && p.scale != 0 {
 		f *= p.scale
 	}
 

provider/mqtt.go

@@ -105,12 +105,12 @@ func (m *MqttClient) listen(topic string, callback func(string)) {
 }
 
 // FloatGetter creates handler for float64 from MQTT topic that returns cached value
-func (m *MqttClient) FloatGetter(topic string, multiplier float64, timeout time.Duration) FloatGetter {
+func (m *MqttClient) FloatGetter(topic string, scale float64, timeout time.Duration) FloatGetter {
 	h := &msgHandler{
-		log:        m.log,
-		topic:      topic,
-		multiplier: multiplier,
-		timeout:    timeout,
+		log:     m.log,
+		topic:   topic,
+		scale:   scale,
+		timeout: timeout,
 	}
 
 	m.Listen(topic, h.Receive)
@@ -118,12 +118,12 @@ func (m *MqttClient) FloatGetter(topic string, multiplier float64, timeout time.
 }
 
 // IntGetter creates handler for int64 from MQTT topic that returns cached value
-func (m *MqttClient) IntGetter(topic string, multiplier int64, timeout time.Duration) IntGetter {
+func (m *MqttClient) IntGetter(topic string, scale int64, timeout time.Duration) IntGetter {
 	h := &msgHandler{
-		log:        m.log,
-		topic:      topic,
-		multiplier: float64(multiplier),
-		timeout:    timeout,
+		log:     m.log,
+		topic:   topic,
+		scale:   float64(scale),
+		timeout: timeout,
 	}
 
 	m.Listen(topic, h.Receive)
@@ -213,14 +213,14 @@ func (m *MqttClient) WaitForToken(token mqtt.Token) {
 }
 
 type msgHandler struct {
-	log        *util.Logger
-	once       sync.Once
-	mux        sync.Mutex
-	updated    time.Time
-	timeout    time.Duration
-	multiplier float64
-	topic      string
-	payload    string
+	log     *util.Logger
+	once    sync.Once
+	mux     sync.Mutex
+	updated time.Time
+	timeout time.Duration
+	scale   float64
+	topic   string
+	payload string
 }
 
 func (h *msgHandler) Receive(payload string) {
@@ -263,7 +263,7 @@ func (h *msgHandler) floatGetter() (float64, error) {
 		return 0, fmt.Errorf("%s invalid: '%s'", h.topic, h.payload)
 	}
 
-	return h.multiplier * val, nil
+	return h.scale * val, nil
 }
 
 func (h *msgHandler) intGetter() (int64, error) {