1 files changed, 69 insertions, 0 deletions
diff --git a/internal/behavior/desc.go b/internal/behavior/desc.go
index f6dbaf3..744b97e 100644
--- a/internal/behavior/desc.go
+++ b/internal/behavior/desc.go
@@ -1,8 +1,77 @@
 package behavior
 
+import (
+	"fmt"
+
+	"gopkg.in/yaml.v3"
+)
+
+// DescVariant is one alternative description, optionally gated by a condition.
 type DescVariant struct {
 	Text      string     `yaml:"text"`
 	Condition *Condition `yaml:"condition,omitempty"`
 }
 
+// DescList is an ordered list of description variants. The first variant whose
+// condition matches is shown.
+//
+// Content may author the common single, unconditional description two ways:
+// as a bare scalar (`description: "A dark room."`) or as a list of variants
+// (`description: [{text: "A dark room."}]`). MarshalYAML collapses a single
+// unconditional variant back to the scalar form so machine-written room files
+// stay close to what a human would type.
 type DescList []DescVariant
+
+func (d *DescList) UnmarshalYAML(value *yaml.Node) error {
+	switch value.Kind {
+	case yaml.ScalarNode:
+		var text string
+		if err := value.Decode(&text); err != nil {
+			return err
+		}
+		if text == "" {
+			*d = nil
+			return nil
+		}
+		*d = DescList{{Text: text}}
+		return nil
+	case yaml.SequenceNode:
+		out := make(DescList, 0, len(value.Content))
+		for _, item := range value.Content {
+			// Accept a bare string element as shorthand for a variant.
+			if item.Kind == yaml.ScalarNode {
+				var text string
+				if err := item.Decode(&text); err != nil {
+					return err
+				}
+				out = append(out, DescVariant{Text: text})
+				continue
+			}
+			var variant DescVariant
+			if err := item.Decode(&variant); err != nil {
+				return err
+			}
+			out = append(out, variant)
+		}
+		*d = out
+		return nil
+	case yaml.AliasNode:
+		return d.UnmarshalYAML(value.Alias)
+	case 0:
+		// An omitted/zero node leaves the list empty.
+		*d = nil
+		return nil
+	default:
+		return fmt.Errorf("description must be a string or a list of variants")
+	}
+}
+
+func (d DescList) MarshalYAML() (any, error) {
+	if len(d) == 0 {
+		return []DescVariant{}, nil
+	}
+	if len(d) == 1 && d[0].Condition == nil {
+		return d[0].Text, nil
+	}
+	return []DescVariant(d), nil
+}