Add D&D scene description codec

internal/modules/dnd/codec/scenedescriptions/codec.go

@@ -0,0 +1,134 @@
+package scenedescriptions
+
+import (
+	"bytes"
+	"embed"
+	"encoding/json"
+	"fmt"
+	"io"
+	"strings"
+
+	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
+	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd"
+)
+
+const (
+	SchemaID      = "notarius.dnd.scene_descriptions"
+	SchemaName    = "notarius_dnd_scene_descriptions_v1"
+	SchemaVersion = "v1"
+	MediaType     = "application/json"
+)
+
+//go:embed assets/schemas/dnd_scene_descriptions.v1.json
+var schemaAssets embed.FS
+
+var _ contracts.ArtifactCodec[dnd.SceneDescriptionList] = (*Codec)(nil)
+
+type Codec struct{}
+
+func New() *Codec { return &Codec{} }
+
+func (c *Codec) Kind() contracts.ArtifactKind { return dnd.SceneDescriptionListKind }
+
+func (c *Codec) Schema() contracts.ArtifactSchema {
+	raw, err := schemaAssets.ReadFile("assets/schemas/dnd_scene_descriptions.v1.json")
+	if err != nil {
+		return contracts.ArtifactSchema{}
+	}
+	return contracts.ArtifactSchema{
+		ID:         SchemaID,
+		Name:       SchemaName,
+		Version:    SchemaVersion,
+		JSONSchema: append([]byte(nil), raw...),
+	}
+}
+
+func (c *Codec) MediaType() string { return MediaType }
+
+func (c *Codec) Metadata(value dnd.SceneDescriptionList) map[string]any {
+	return map[string]any{"scene_count": len(value.Scenes)}
+}
+
+func (c *Codec) Encode(value dnd.SceneDescriptionList) ([]byte, error) {
+	if err := validate(value); err != nil {
+		return nil, fmt.Errorf("encode dnd scene description list: %w", err)
+	}
+	return c.EncodeCandidate(value)
+}
+
+// EncodeCandidate provides the durable representation before typed validators
+// have approved a value.
+func (c *Codec) EncodeCandidate(value dnd.SceneDescriptionList) ([]byte, error) {
+	content, err := json.Marshal(value)
+	if err != nil {
+		return nil, fmt.Errorf("encode dnd scene description list: %w", err)
+	}
+	return content, nil
+}
+
+func (c *Codec) Decode(content []byte) (dnd.SceneDescriptionList, error) {
+	value, err := c.DecodeCandidate(content)
+	if err != nil {
+		return dnd.SceneDescriptionList{}, err
+	}
+	if err := validate(value); err != nil {
+		return dnd.SceneDescriptionList{}, fmt.Errorf("decode dnd scene description list: %w", err)
+	}
+	return value, nil
+}
+
+// DecodeCandidate reads one strict durable JSON value before typed validators
+// have approved it.
+func (c *Codec) DecodeCandidate(content []byte) (dnd.SceneDescriptionList, error) {
+	decoder := json.NewDecoder(bytes.NewReader(content))
+	decoder.DisallowUnknownFields()
+	var value dnd.SceneDescriptionList
+	if err := decoder.Decode(&value); err != nil {
+		return dnd.SceneDescriptionList{}, fmt.Errorf("decode dnd scene description list: %w", err)
+	}
+	var trailing any
+	if err := decoder.Decode(&trailing); err != io.EOF {
+		return dnd.SceneDescriptionList{}, fmt.Errorf("decode dnd scene description list: multiple JSON values")
+	}
+	return value, nil
+}
+
+func validate(value dnd.SceneDescriptionList) error {
+	if value.Scenes == nil {
+		return fmt.Errorf("scenes must be present")
+	}
+	for index, scene := range value.Scenes {
+		prefix := fmt.Sprintf("scenes[%d]", index)
+		if strings.TrimSpace(scene.ID) == "" {
+			return fmt.Errorf("%s.id must not be empty", prefix)
+		}
+		if !validSceneKind(scene.Kind) {
+			return fmt.Errorf("%s.kind must be supported", prefix)
+		}
+		if strings.TrimSpace(scene.Title) == "" {
+			return fmt.Errorf("%s.title must not be empty", prefix)
+		}
+		if strings.TrimSpace(scene.Summary) == "" {
+			return fmt.Errorf("%s.summary must not be empty", prefix)
+		}
+		if strings.TrimSpace(scene.SourceRef.SourceID) == "" {
+			return fmt.Errorf("%s.source_ref.source_id must not be empty", prefix)
+		}
+		if scene.SourceRef.StartUnitID <= 0 {
+			return fmt.Errorf("%s.source_ref.start_unit_id must be positive", prefix)
+		}
+		if scene.SourceRef.EndUnitID <= 0 {
+			return fmt.Errorf("%s.source_ref.end_unit_id must be positive", prefix)
+		}
+	}
+	return nil
+}
+
+func validSceneKind(value dnd.SceneKind) bool {
+	switch value {
+	case dnd.SceneKindCombat, dnd.SceneKindNarrative, dnd.SceneKindRecap, dnd.SceneKindMeta:
+		return true
+	default:
+		return false
+	}
+}