feat: mail service

mail/internal/domain/template/model.go

@@ -0,0 +1,65 @@
+// Package template defines the logical template entity used by the
+// filesystem-backed Mail Service template catalog.
+package template
+
+import (
+	"fmt"
+	"strings"
+
+	"galaxy/mail/internal/domain/common"
+)
+
+// Template stores one locale-specific template bundle.
+type Template struct {
+	// TemplateID identifies the template family.
+	TemplateID common.TemplateID
+
+	// Locale stores the canonical locale of the template variant.
+	Locale common.Locale
+
+	// SubjectTemplate stores the subject template source.
+	SubjectTemplate string
+
+	// TextTemplate stores the plaintext body template source.
+	TextTemplate string
+
+	// HTMLTemplate stores the optional HTML body template source.
+	HTMLTemplate string
+
+	// Version stores the template version marker projected into the domain
+	// model.
+	Version string
+}
+
+// Validate reports whether Template satisfies the frozen Stage 2 structural
+// invariants.
+func (record Template) Validate() error {
+	if err := record.TemplateID.Validate(); err != nil {
+		return fmt.Errorf("template id: %w", err)
+	}
+	if err := record.Locale.Validate(); err != nil {
+		return fmt.Errorf("template locale: %w", err)
+	}
+	if record.SubjectTemplate == "" {
+		return fmt.Errorf("template subject template must not be empty")
+	}
+	if record.TextTemplate == "" {
+		return fmt.Errorf("template text template must not be empty")
+	}
+	if err := validateToken("template version", record.Version); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func validateToken(name string, value string) error {
+	switch {
+	case strings.TrimSpace(value) == "":
+		return fmt.Errorf("%s must not be empty", name)
+	case strings.TrimSpace(value) != value:
+		return fmt.Errorf("%s must not contain surrounding whitespace", name)
+	default:
+		return nil
+	}
+}