data layer

data-layer/api/internal/handler/render.go

@@ -0,0 +1,47 @@
+// Package handler holds HTTP handlers. Handlers parse the request, call into
+// service, and translate the result (or error) into an HTTP response.
+package handler
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/dbiz/cdp/data-layer/api/internal/apperr"
+)
+
+type errorResponse struct {
+	Error string `json:"error"`
+	Field string `json:"field,omitempty"`
+}
+
+func writeJSON(w http.ResponseWriter, status int, body any) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	_ = json.NewEncoder(w).Encode(body)
+}
+
+func writeError(w http.ResponseWriter, err error) {
+	if ae, ok := apperr.As(err); ok {
+		if ae.RetryAfter > 0 {
+			w.Header().Set("Retry-After", itoa(ae.RetryAfter))
+		}
+		writeJSON(w, ae.Code, errorResponse{Error: ae.Message, Field: ae.Field})
+		return
+	}
+	writeJSON(w, http.StatusInternalServerError, errorResponse{Error: "internal server error"})
+}
+
+func itoa(i int) string {
+	const digits = "0123456789"
+	if i == 0 {
+		return "0"
+	}
+	var buf [20]byte
+	pos := len(buf)
+	for i > 0 {
+		pos--
+		buf[pos] = digits[i%10]
+		i /= 10
+	}
+	return string(buf[pos:])
+}