initial commit

backend/server/errors.go

@@ -0,0 +1,74 @@
+package server
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/go-chi/render"
+	"gitlab.com/1f320/pronouns/backend/log"
+)
+
+// WrapHandler wraps a modified http.HandlerFunc into a stdlib-compatible one.
+// The inner HandlerFunc additionally returns an error.
+func WrapHandler(hn func(w http.ResponseWriter, r *http.Request) error) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		err := hn(w, r)
+		if err != nil {
+			// if the function returned an API error, just render that verbatim
+			// we can assume that it also logged the error (if that was needed)
+			if apiErr, ok := err.(APIError); ok {
+				apiErr.prepare()
+
+				render.Status(r, apiErr.Status)
+				render.JSON(w, r, apiErr)
+				return
+			}
+
+			// otherwise, we log the error and return an internal server error message
+			log.Errorf("error in http handler: %v", err)
+
+			apiErr := APIError{Code: ErrInternalServerError}
+			apiErr.prepare()
+
+			render.Status(r, apiErr.Status)
+			render.JSON(w, r, apiErr)
+		}
+	}
+}
+
+// APIError is an object returned by the API when an error occurs.
+// It implements the error interface and can be returned by handlers.
+type APIError struct {
+	Code    int    `json:"code"`
+	Message string `json:"message,omitempty"`
+
+	// Status is
+	Status int `json:"-"`
+}
+
+func (e APIError) Error() string {
+	return fmt.Sprintf("%s (code: %d)", e.Message, e.Code)
+}
+
+func (e *APIError) prepare() {
+	if e.Status == 0 {
+		e.Status = errCodeStatuses[e.Code]
+	}
+
+	if e.Message == "" {
+		e.Message = errCodeMessages[e.Code]
+	}
+}
+
+// Error code constants
+const (
+	ErrInternalServerError = 500 // catch-all code for unknown errors
+)
+
+var errCodeMessages = map[int]string{
+	ErrInternalServerError: "Internal server error",
+}
+
+var errCodeStatuses = map[int]int{
+	ErrInternalServerError: http.StatusInternalServerError,
+}