From 65a7a7eef8e5abfda359330f9f852eec1ad5a0ad Mon Sep 17 00:00:00 2001
From: Andrej Mickov <andrej@ferdzo.xyz>
Date: Sun, 22 Feb 2026 13:02:22 +0100
Subject: [PATCH] S3 Error handling

---
 api/s3_errors.go | 97 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)
 create mode 100644 api/s3_errors.go

diff --git a/api/s3_errors.go b/api/s3_errors.go
new file mode 100644
index 0000000..8792621
--- /dev/null
+++ b/api/s3_errors.go
@@ -0,0 +1,97 @@
+package api
+
+import (
+	"encoding/xml"
+	"errors"
+	"fs/metadata"
+	"fs/models"
+	"net/http"
+)
+
+type s3APIError struct {
+	Status  int
+	Code    string
+	Message string
+}
+
+var (
+	s3ErrInvalidObjectKey = s3APIError{
+		Status:  http.StatusBadRequest,
+		Code:    "InvalidArgument",
+		Message: "Object key is required.",
+	}
+	s3ErrNotImplemented = s3APIError{
+		Status:  http.StatusNotImplemented,
+		Code:    "NotImplemented",
+		Message: "A header you provided implies functionality that is not implemented.",
+	}
+	s3ErrInternal = s3APIError{
+		Status:  http.StatusInternalServerError,
+		Code:    "InternalError",
+		Message: "We encountered an internal error. Please try again.",
+	}
+)
+
+func mapToS3Error(err error) s3APIError {
+	switch {
+	case errors.Is(err, metadata.ErrInvalidBucketName):
+		return s3APIError{
+			Status:  http.StatusBadRequest,
+			Code:    "InvalidBucketName",
+			Message: "The specified bucket is not valid.",
+		}
+	case errors.Is(err, metadata.ErrBucketAlreadyExists):
+		return s3APIError{
+			Status:  http.StatusConflict,
+			Code:    "BucketAlreadyOwnedByYou",
+			Message: "Your previous request to create the named bucket succeeded and you already own it.",
+		}
+	case errors.Is(err, metadata.ErrBucketNotFound):
+		return s3APIError{
+			Status:  http.StatusNotFound,
+			Code:    "NoSuchBucket",
+			Message: "The specified bucket does not exist.",
+		}
+	case errors.Is(err, metadata.ErrBucketNotEmpty):
+		return s3APIError{
+			Status:  http.StatusConflict,
+			Code:    "BucketNotEmpty",
+			Message: "The bucket you tried to delete is not empty.",
+		}
+	case errors.Is(err, metadata.ErrObjectNotFound):
+		return s3APIError{
+			Status:  http.StatusNotFound,
+			Code:    "NoSuchKey",
+			Message: "The specified key does not exist.",
+		}
+	default:
+		return s3ErrInternal
+	}
+}
+
+func writeS3Error(w http.ResponseWriter, r *http.Request, apiErr s3APIError, resource string) {
+	w.Header().Set("Content-Type", "application/xml; charset=utf-8")
+	w.WriteHeader(apiErr.Status)
+
+	if r != nil && r.Method == http.MethodHead {
+		return
+	}
+
+	payload := models.S3ErrorResponse{
+		Code:     apiErr.Code,
+		Message:  apiErr.Message,
+		Resource: resource,
+	}
+
+	out, err := xml.MarshalIndent(payload, "", "    ")
+	if err != nil {
+		return
+	}
+
+	_, _ = w.Write([]byte(xml.Header))
+	_, _ = w.Write(out)
+}
+
+func writeMappedS3Error(w http.ResponseWriter, r *http.Request, err error) {
+	writeS3Error(w, r, mapToS3Error(err), r.URL.Path)
+}