add --csv-file flag to write data to a csv file. fixes #22

- add csv-file flag
- when flag is populated, write csv data to that file and do not write data to influx.

Author: tedpearson

internal/app/csv.go

@@ -0,0 +1,58 @@
+package app
+
+import (
+	"encoding/csv"
+	"os"
+	"strconv"
+)
+
+func WriteCsv(records []ElectricUsage, csvFile string) error {
+	// Open the CSV file for writing
+	file, err := os.Create(csvFile)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	// Create a CSV writer
+	writer := csv.NewWriter(file)
+	defer writer.Flush()
+
+	// Write comments
+	_, err = file.WriteString(`# Notes:
+# MeterName will only be populated if there are multiple meters returned in the data.
+# StartUnixMillis and EndUnixMillis will only be in the correct timezone if you specify the correct timezone in the config.
+`)
+	if err != nil {
+		return err
+	}
+
+	// Write the header row
+	header := []string{"StartUnixMillis", "EndUnixMillis", "WattHours", "CostInCents", "MeterName"}
+	if err := writer.Write(header); err != nil {
+		return err
+	}
+
+	// Write the data rows
+	for _, record := range records {
+		meterName := ""
+		if record.MeterName != nil {
+			meterName = *record.MeterName
+		}
+		costInCents := ""
+		if record.CostInCents != nil {
+			costInCents = strconv.FormatInt(*record.CostInCents, 10)
+		}
+		row := []string{
+			strconv.FormatInt(record.StartTime.UnixMilli(), 10),
+			strconv.FormatInt(record.EndTime.UnixMilli(), 10),
+			strconv.FormatInt(record.WattHours, 10),
+			costInCents,
+			meterName,
+		}
+		if err := writer.Write(row); err != nil {
+			return err
+		}
+	}
+	return nil
+}

internal/app/main.go

@@ -47,6 +47,7 @@ func Main() error {
 	startFlag := flag.String("start", "", "Start date of period to extract from electric co.")
 	endFlag := flag.String("end", "", "End date of period to extract from electric co.")
 	debugFlag := flag.Bool("debug", false, "Enable to print out verbose debugging logs.")
+	csvFlag := flag.String("csv-file", "", "Path to output data in csv format, as an alternative to writing to influx")
 	flag.Parse()
 
 	debug = *debugFlag
@@ -119,10 +120,18 @@ func Main() error {
 	if err != nil {
 		return err
 	}
-	fmt.Println("Writing data to database...")
-	err = WriteMetrics(usage, config.InfluxDB)
-	if err != nil {
-		return err
+	if *csvFlag != "" {
+		fmt.Println("Writing data to csv file...")
+		err = WriteCsv(usage, *csvFlag)
+		if err != nil {
+			return err
+		}
+	} else {
+		fmt.Println("Writing data to database...")
+		err = WriteMetrics(usage, config.InfluxDB)
+		if err != nil {
+			return err
+		}
 	}
 	fmt.Println("Done")
 	return nil