re organizer project

backend/internal/service/url.go

@@ -0,0 +1,46 @@
+package service
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"time"
+)
+
+type URLService struct {
+	secret     string
+	serverHost string
+}
+
+func NewURLService(secret, serverHost string) *URLService {
+	return &URLService{secret: secret, serverHost: serverHost}
+}
+
+func (s *URLService) sign(fileID string, expires int64) string {
+	data := fmt.Sprintf("%s:%d", fileID, expires)
+	mac := hmac.New(sha256.New, []byte(s.secret))
+	mac.Write([]byte(data))
+	return hex.EncodeToString(mac.Sum(nil))
+}
+
+func (s *URLService) GenerateDownloadURL(fileUUID string) string {
+	expires := time.Now().Add(10 * time.Minute).Unix()
+	sig := s.sign(fileUUID, expires)
+
+	return fmt.Sprintf(
+		"%s/api/v1/files/%s?expires=%d&sig=%s",
+		s.serverHost,
+		fileUUID,
+		expires,
+		sig,
+	)
+}
+
+func (s *URLService) Validate(fileID, sig string, expires int64) bool {
+	if time.Now().Unix() > expires {
+		return false
+	}
+	expected := s.sign(fileID, expires)
+	return hmac.Equal([]byte(sig), []byte(expected))
+}