97 lines
2.1 KiB
Go
97 lines
2.1 KiB
Go
package main
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import (
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"encoding/json"
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"fmt"
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"io"
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"log"
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"net/http"
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"os"
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"path/filepath"
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"time"
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)
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var dataFile *os.File
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var berlinTZ *time.Location
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type VoltageData struct {
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Voltage float64 `json:"voltage"`
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}
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func init() {
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var err error
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berlinTZ, err = time.LoadLocation("Europe/Berlin")
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if err != nil {
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log.Fatalf("Failed to load Berlin timezone: %v", err)
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}
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}
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func initDataFile() {
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// Ensure the data/ directory exists
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if err := os.MkdirAll("data", os.ModePerm); err != nil {
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log.Fatalf("Failed to create data directory: %v", err)
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}
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// Generate a filename with timestamp in Berlin local time
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filename := filepath.Join("data", fmt.Sprintf("voltages_%s.csv", time.Now().In(berlinTZ).Format("20060102_150405")))
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file, err := os.OpenFile(filename, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
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if err != nil {
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log.Fatalf("Failed to open data file: %v", err)
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}
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dataFile = file
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log.Printf("Logging voltage data to %s\n", filename)
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// Write CSV header
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_, _ = dataFile.WriteString("timestamp,voltage\n")
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}
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func handler(w http.ResponseWriter, r *http.Request) {
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if r.Method != http.MethodPost {
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http.Error(w, "POST only", http.StatusMethodNotAllowed)
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return
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}
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body, err := io.ReadAll(r.Body)
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if err != nil {
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http.Error(w, "read error", http.StatusBadRequest)
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return
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}
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defer r.Body.Close()
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// Parse JSON
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var v VoltageData
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if err := json.Unmarshal(body, &v); err != nil {
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http.Error(w, "invalid JSON", http.StatusBadRequest)
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return
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}
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// Get current timestamp in Berlin
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timestamp := time.Now().In(berlinTZ).Format("2006-01-02 15:04:05.000")
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// Print voltage to console
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fmt.Printf("Received voltage: %f at %s\n", v.Voltage, timestamp)
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// Append CSV line to file
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if dataFile != nil {
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if _, err := dataFile.WriteString(fmt.Sprintf("%s,%.6f\n", timestamp, v.Voltage)); err != nil {
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log.Printf("Failed to write to file: %v", err)
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}
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}
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w.WriteHeader(http.StatusOK)
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w.Write([]byte("ok"))
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}
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func main() {
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initDataFile()
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defer dataFile.Close()
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http.HandleFunc("/data", handler)
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addr := ":8080"
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log.Println("Listening on", addr)
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log.Fatal(http.ListenAndServe(addr, nil))
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}
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