From f2cc660c8f8ee31379b012994ee2a4109db4374c Mon Sep 17 00:00:00 2001
From: Noooste <83548733+Noooste@users.noreply.github.com>
Date: Mon, 20 Apr 2026 00:01:31 +0200
Subject: [PATCH] feat(apierr): parse Garage structured error responses into
 UpstreamError

---
 backend/internal/apierr/parse.go      | 53 ++++++++++++++++++
 backend/internal/apierr/parse_test.go | 79 +++++++++++++++++++++++++++
 2 files changed, 132 insertions(+)
 create mode 100644 backend/internal/apierr/parse.go
 create mode 100644 backend/internal/apierr/parse_test.go

diff --git a/backend/internal/apierr/parse.go b/backend/internal/apierr/parse.go
new file mode 100644
index 0000000..04aa7d6
--- /dev/null
+++ b/backend/internal/apierr/parse.go
@@ -0,0 +1,53 @@
+package apierr
+
+import (
+	"encoding/json"
+	"io"
+
+	"github.com/Noooste/azuretls-client"
+)
+
+// garageErrBody mirrors Garage's JSON error envelope.
+type garageErrBody struct {
+	Code    string `json:"code"`
+	Message string `json:"message"`
+	Region  string `json:"region"`
+	Path    string `json:"path"`
+}
+
+// ParseGarage returns nil for 2xx responses. For non-2xx it reads the body
+// once, JSON-decodes the structured Garage error envelope, and returns a
+// *UpstreamError. Malformed bodies are preserved verbatim in Message.
+//
+// ParseGarage DOES NOT close resp.RawBody on the success path — callers that
+// decode the success body (decodeResponse in services/admin.go) still need
+// access and are responsible for closing. On the error path the body is fully
+// consumed before return.
+func ParseGarage(resp *azuretls.Response) error {
+	if resp.StatusCode >= 200 && resp.StatusCode < 300 {
+		return nil
+	}
+
+	bodyBytes, _ := io.ReadAll(resp.RawBody)
+
+	ue := &UpstreamError{
+		HTTPStatus: resp.StatusCode,
+		Source:     "garage",
+	}
+
+	var parsed garageErrBody
+	if len(bodyBytes) > 0 && json.Unmarshal(bodyBytes, &parsed) == nil && parsed.Code != "" {
+		ue.Code = parsed.Code
+		ue.Message = parsed.Message
+		ue.Details = map[string]string{}
+		if parsed.Region != "" {
+			ue.Details["region"] = parsed.Region
+		}
+		if parsed.Path != "" {
+			ue.Details["path"] = parsed.Path
+		}
+	} else {
+		ue.Message = string(bodyBytes)
+	}
+	return ue
+}
diff --git a/backend/internal/apierr/parse_test.go b/backend/internal/apierr/parse_test.go
new file mode 100644
index 0000000..c24f75a
--- /dev/null
+++ b/backend/internal/apierr/parse_test.go
@@ -0,0 +1,79 @@
+package apierr
+
+import (
+	"bytes"
+	"io"
+	"strings"
+	"testing"
+
+	"github.com/Noooste/azuretls-client"
+)
+
+func fakeResp(status int, body string) *azuretls.Response {
+	return &azuretls.Response{
+		StatusCode: status,
+		RawBody:    io.NopCloser(bytes.NewBufferString(body)),
+	}
+}
+
+func TestParseGarage_Success(t *testing.T) {
+	resp := fakeResp(200, `{"foo":"bar"}`)
+	if err := ParseGarage(resp); err != nil {
+		t.Fatalf("ParseGarage(2xx) returned %v, want nil", err)
+	}
+}
+
+func TestParseGarage_StructuredError(t *testing.T) {
+	body := `{"code":"BucketNotEmpty","message":"Tried to delete a non-empty bucket","region":"eu-west-1","path":"/v2/DeleteBucket"}`
+	resp := fakeResp(409, body)
+
+	err := ParseGarage(resp)
+	ue, ok := err.(*UpstreamError)
+	if !ok {
+		t.Fatalf("ParseGarage returned %T, want *UpstreamError", err)
+	}
+	if ue.HTTPStatus != 409 {
+		t.Errorf("HTTPStatus = %d, want 409", ue.HTTPStatus)
+	}
+	if ue.Code != "BucketNotEmpty" {
+		t.Errorf("Code = %q, want BucketNotEmpty", ue.Code)
+	}
+	if ue.Message != "Tried to delete a non-empty bucket" {
+		t.Errorf("Message = %q", ue.Message)
+	}
+	if ue.Source != "garage" {
+		t.Errorf("Source = %q, want garage", ue.Source)
+	}
+	if ue.Details["region"] != "eu-west-1" || ue.Details["path"] != "/v2/DeleteBucket" {
+		t.Errorf("Details = %v", ue.Details)
+	}
+}
+
+func TestParseGarage_MalformedBody(t *testing.T) {
+	resp := fakeResp(500, "not json at all")
+
+	err := ParseGarage(resp)
+	ue, ok := err.(*UpstreamError)
+	if !ok {
+		t.Fatalf("ParseGarage returned %T, want *UpstreamError", err)
+	}
+	if ue.HTTPStatus != 500 || ue.Code != "" {
+		t.Errorf("HTTPStatus=%d Code=%q, want 500 and empty code", ue.HTTPStatus, ue.Code)
+	}
+	if !strings.Contains(ue.Message, "not json at all") {
+		t.Errorf("Message = %q, expected raw body", ue.Message)
+	}
+}
+
+func TestParseGarage_EmptyBody(t *testing.T) {
+	resp := fakeResp(502, "")
+
+	err := ParseGarage(resp)
+	ue, ok := err.(*UpstreamError)
+	if !ok {
+		t.Fatalf("ParseGarage returned %T, want *UpstreamError", err)
+	}
+	if ue.HTTPStatus != 502 {
+		t.Errorf("HTTPStatus = %d, want 502", ue.HTTPStatus)
+	}
+}