Support arbitrary sensor IDs properly

The previous implementation of the Result type assumed a specific sensor
ID would be present when unmarshaling JSON, which isn't always going to
be the case.

This approach converts the type into an anonymous struct which properly
supports us setting a custom sensor ID for incoming power.

cmd/client/client.go

@@ -35,12 +35,10 @@ type APIResponse struct {
 	ID      int    `json:"id"`      // ID is the unique identifier of the response.
 	Type    string `json:"type"`    // Type is the type of the response.
 	Success bool   `json:"success"` // Success indicates whether the response was successful or not.
-	Result  struct {
-		ImportedElectricity []struct {
-			Start  int     `json:"start"`
-			End    int     `json:"end"`
-			Change float64 `json:"change"` // Change is the amount of electricity imported.
-		} `json:"sensor.smart_meter_electricity_import_2"`
+	Result  map[string][]struct {
+		Change float64 `json:"change"`
+		End    int64   `json:"end"`
+		Start  int64   `json:"start"`
 	} `json:"result"` // Result contains the data returned by the API.
 	Error struct {
 		Code    string `json:"code"`
@@ -239,18 +237,17 @@ func getResults(c *Client) ([][]float64, error) {
 	// What we're doing is creating an offset from the current *day* based on a multiple of
 	// 24 hours, each time we iterate through the a "row" of the results slice.
 	results := make([][]float64, c.Config.Days)
+	sensorID := viper.GetString("sensor_id")
+	if sensorID == "" {
+		return nil, fmt.Errorf("sensor_id is required")
+	}
 
 	for i := range results {
 		c.MessageID++
 
 		offset := time.Duration((i+1)*24) * time.Hour
 		start := time.Now().Add(-offset).Truncate(24 * time.Hour).Format("2006-01-02T15:04:05.000Z")
 
-		sensorID := viper.GetString("sensor_id")
-		if sensorID == "" {
-			return nil, fmt.Errorf("sensor_id is required")
-		}
-
 		msg := map[string]interface{}{
 			"id":            c.MessageID,
 			"type":          "recorder/statistics_during_period",
@@ -277,15 +274,9 @@ func getResults(c *Client) ([][]float64, error) {
 		if !data.Success {
 			return nil, fmt.Errorf("api response error: %v", data.Error)
 		}
-
-		if len(data.Result.ImportedElectricity) != hoursInADay {
-			return nil, fmt.Errorf("expected %d sets of results, got %d", hoursInADay, len(data.Result.ImportedElectricity))
-		}
-
 		changeSlice := make([]float64, hoursInADay)
-		log.Debug().Msgf("got %d results", len(data.Result.ImportedElectricity))
 		for j := range changeSlice {
-			changeSlice[j] = data.Result.ImportedElectricity[j].Change
+			changeSlice[j] = data.Result[sensorID][j].Change
 		}
 		results[i] = changeSlice
 	}