Better makefile, plotting, saving the data, and cleanup

main.go

@@ -1,12 +1,39 @@
 package main
 
 import (
+	"encoding/json"
 	"fmt"
 	"io"
 	"log"
 	"net/http"
+	"os"
+	"path/filepath"
+	"time"
 )
 
+var dataFile *os.File
+
+type VoltageData struct {
+	Voltage float64 `json:"voltage"`
+}
+
+func initDataFile() {
+	// Ensure the data/ directory exists
+	if err := os.MkdirAll("data", os.ModePerm); err != nil {
+		log.Fatalf("Failed to create data directory: %v", err)
+	}
+
+	// Generate a filename with timestamp
+	filename := filepath.Join("data", fmt.Sprintf("voltages_%s.txt", time.Now().Format("20060102_150405")))
+	file, err := os.OpenFile(filename, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
+	if err != nil {
+		log.Fatalf("Failed to open data file: %v", err)
+	}
+
+	dataFile = file
+	log.Printf("Logging voltage data to %s\n", filename)
+}
+
 func handler(w http.ResponseWriter, r *http.Request) {
 	if r.Method != http.MethodPost {
 		http.Error(w, "POST only", http.StatusMethodNotAllowed)
@@ -20,13 +47,31 @@ func handler(w http.ResponseWriter, r *http.Request) {
 	}
 	defer r.Body.Close()
 
-	fmt.Println("Received:", string(body))
+	// Parse JSON
+	var v VoltageData
+	if err := json.Unmarshal(body, &v); err != nil {
+		http.Error(w, "invalid JSON", http.StatusBadRequest)
+		return
+	}
+
+	// Print voltage to console
+	fmt.Println("Received voltage:", v.Voltage)
+
+	// Append voltage number to file
+	if dataFile != nil {
+		if _, err := dataFile.WriteString(fmt.Sprintf("%f\n", v.Voltage)); err != nil {
+			log.Printf("Failed to write to file: %v", err)
+		}
+	}
 
 	w.WriteHeader(http.StatusOK)
 	w.Write([]byte("ok"))
 }
 
 func main() {
+	initDataFile()
+	defer dataFile.Close()
+
 	http.HandleFunc("/data", handler)
 
 	addr := ":8080"