data layer

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

@@ -0,0 +1,36 @@
+package handler
+
+import (
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+
+	"github.com/go-playground/validator/v10"
+
+	"github.com/dbiz/cdp/data-layer/api/internal/apperr"
+)
+
+var validate = validator.New(validator.WithRequiredStructEnabled())
+
+// decodeAndValidate reads JSON into `dst`, then runs validator tags. Returns
+// a wrapped AppError so handlers can pass it straight to writeError.
+func decodeAndValidate(r *http.Request, dst any) error {
+	dec := json.NewDecoder(r.Body)
+	dec.DisallowUnknownFields()
+	if err := dec.Decode(dst); err != nil {
+		if errors.Is(err, io.EOF) {
+			return apperr.BadRequest("request body is empty", "", err)
+		}
+		return apperr.BadRequest("invalid JSON: "+err.Error(), "", err)
+	}
+	if err := validate.Struct(dst); err != nil {
+		var verrs validator.ValidationErrors
+		if errors.As(err, &verrs) && len(verrs) > 0 {
+			ve := verrs[0]
+			return apperr.BadRequest("validation failed on "+ve.Field()+": "+ve.Tag(), ve.Field(), err)
+		}
+		return apperr.BadRequest("validation failed: "+err.Error(), "", err)
+	}
+	return nil
+}