refactor(display): more scalable file preview file type routing

display/pkg/main.go

@@ -4,6 +4,9 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
+	"image"
+	"image/jpeg"
+	"image/png"
 	"log/slog"
 	"net"
 	"os"
@@ -178,3 +181,30 @@ func ResolveStorageFilePath(pathParam string) (string, bool, error) {
 
 	return fullPath, true, nil
 }
+
+func PreviewFile(fullPath string) (image.Image, error) {
+	var err error
+
+	f, err := os.Open(fullPath)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	ext := strings.ToLower(filepath.Ext(fullPath))
+	var img image.Image
+	switch ext {
+	case ".jpg", ".jpeg":
+		img, err = jpeg.Decode(f)
+	case ".png":
+		img, err = png.Decode(f)
+	default:
+		return nil, fmt.Errorf("unsupported file type for preview: %s", ext)
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	preview := resizeImage(img, 200, 200)
+	return preview, nil
+}