service backend

api/ledger/internal/model/validation.go

@@ -0,0 +1,31 @@
+package ledger
+
+// ValidationIssue describes a single validation problem.
+type ValidationIssue struct {
+	Field string `json:"field"`
+	Code  string `json:"code"`
+	Msg   string `json:"msg"`
+}
+
+// ValidationError aggregates issues. Implements error without fmt/errors.
+type ValidationError struct {
+	Issues []ValidationIssue `json:"issues"`
+}
+
+func (e *ValidationError) Error() string {
+	if e == nil || len(e.Issues) == 0 {
+		return ""
+	}
+	if len(e.Issues) == 1 {
+		return e.Issues[0].Field + ": " + e.Issues[0].Msg
+	}
+	return "validation failed"
+}
+
+// veAdd appends a new issue into a (possibly nil) *ValidationError.
+func veAdd(e **ValidationError, field, code, msg string) {
+	if *e == nil {
+		*e = &ValidationError{Issues: make([]ValidationIssue, 0, 4)}
+	}
+	(*e).Issues = append((*e).Issues, ValidationIssue{Field: field, Code: code, Msg: msg})
+}