FloorVisualizer/internal/handler/upload_handler.go

package handler

import (
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"time"
)

func Upload(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		writeErr(w, 405, "Method not allowed")
		return
	}
	if err := r.ParseMultipartForm(20 << 20); err != nil {
		writeErr(w, 400, "image too large (max 20MB)")
		return
	}
	file, _, err := r.FormFile("image")
	if err != nil {
		writeErr(w, 400, "missing image file")
		return
	}
	defer file.Close()

	data, err := io.ReadAll(file)
	if err != nil || len(data) == 0 {
		writeErr(w, 400, "failed to read image")
		return
	}

	ct := http.DetectContentType(data)
	if !strings.HasPrefix(ct, "image/") {
		writeErr(w, 400, "file is not an image")
		return
	}

	hash := sha256.Sum256(data)
	name := hex.EncodeToString(hash[:])[:16] + "_" + fmt.Sprintf("%d", time.Now().UnixNano())
	dir := "static/images"
	os.MkdirAll(dir, 0755)

	// Determine extension from content type
	ext := ".jpg"
	switch {
	case strings.Contains(ct, "png"):
		ext = ".png"
	case strings.Contains(ct, "webp"):
		ext = ".webp"
	case strings.Contains(ct, "gif"):
		ext = ".gif"
	case strings.Contains(ct, "svg"):
		ext = ".svg"
	}

	filePath := filepath.Join(dir, name+ext)
	if err := os.WriteFile(filePath, data, 0644); err != nil {
		writeErr(w, 500, "failed to save image")
		return
	}

	url := "/static/images/" + name + ext
	writeJSON(w, 200, map[string]string{"url": url, "filename": name + ext})
}