refactor(backend): switch to DDD

backend/internal/interfaces/rest/handlers/error_handler.go

@@ -0,0 +1,44 @@
+package rest
+
+import (
+	"fmt"
+	"net/http"
+
+	"tanabata/internal/domain"
+)
+
+type ErrorResponse struct {
+	Error   string `json:"error"`
+	Code    string `json:"code,omitempty"`
+	Message string `json:"message,omitempty"`
+}
+
+type ErrorMapper struct{}
+
+func (m *ErrorMapper) MapError(err domain.DomainError) (int, ErrorResponse) {
+	switch err.Code {
+	case domain.ErrFileNotFound:
+		return http.StatusNotFound, ErrorResponse{
+			Error:   "Not Found",
+			Code:    string(err.Code),
+			Message: fmt.Sprintf("File %q not found", err.Details...),
+		}
+	case domain.ErrMIMENotSupported:
+		return http.StatusNotFound, ErrorResponse{
+			Error:   "MIME not supported",
+			Code:    string(err.Code),
+			Message: fmt.Sprintf("MIME not supported: %q", err.Details...),
+		}
+	case domain.ErrValidation:
+		return http.StatusNotFound, ErrorResponse{
+			Error:   "Bad Request",
+			Code:    string(err.Code),
+			Message: fmt.Sprintf("Invalid %s: %s", err.Details...),
+		}
+	}
+	return http.StatusInternalServerError, ErrorResponse{
+		Error:   "Internal Server Error",
+		Code:    string(err.Code),
+		Message: "An unexpected error occured",
+	}
+}