Introduce typed D&D spell artifacts

internal/modules/dnd/codec/spells/codec.go

@@ -0,0 +1,110 @@
+package spells
+
+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.spells"
+	SchemaName    = "notarius_dnd_spells_v1"
+	SchemaVersion = "v1"
+	MediaType     = "application/json"
+)
+
+//go:embed assets/schemas/dnd_spells.v1.json
+var schemaAssets embed.FS
+
+var _ contracts.ArtifactCodec[dnd.SpellList] = (*Codec)(nil)
+
+type Codec struct{}
+
+func New() *Codec { return &Codec{} }
+
+func (c *Codec) Kind() contracts.ArtifactKind { return dnd.SpellListKind }
+
+func (c *Codec) Schema() contracts.ArtifactSchema {
+	raw, err := schemaAssets.ReadFile("assets/schemas/dnd_spells.v1.json")
+	if err != nil {
+		return contracts.ArtifactSchema{}
+	}
+	return contracts.ArtifactSchema{ID: SchemaID, Name: SchemaName, Version: SchemaVersion, JSONSchema: raw}
+}
+
+func (c *Codec) MediaType() string { return MediaType }
+
+func (c *Codec) Encode(value dnd.SpellList) ([]byte, error) {
+	if err := validate(value); err != nil {
+		return nil, fmt.Errorf("encode dnd spell list: %w", err)
+	}
+	return c.EncodeCandidate(value)
+}
+
+// EncodeCandidate provides the same stable representation before typed
+// validators have approved a value on the temporary raw downstream path.
+func (c *Codec) EncodeCandidate(value dnd.SpellList) ([]byte, error) {
+	content, err := json.Marshal(value)
+	if err != nil {
+		return nil, fmt.Errorf("encode dnd spell list: %w", err)
+	}
+	return content, nil
+}
+
+func (c *Codec) Decode(content []byte) (dnd.SpellList, error) {
+	decoder := json.NewDecoder(bytes.NewReader(content))
+	decoder.DisallowUnknownFields()
+	var value dnd.SpellList
+	if err := decoder.Decode(&value); err != nil {
+		return dnd.SpellList{}, fmt.Errorf("decode dnd spell list: %w", err)
+	}
+	var trailing any
+	if err := decoder.Decode(&trailing); err != io.EOF {
+		return dnd.SpellList{}, fmt.Errorf("decode dnd spell list: multiple JSON values")
+	}
+	if err := validate(value); err != nil {
+		return dnd.SpellList{}, fmt.Errorf("decode dnd spell list: %w", err)
+	}
+	return value, nil
+}
+
+func validate(value dnd.SpellList) error {
+	if value.SpellCasts == nil {
+		return fmt.Errorf("spell_casts must be present")
+	}
+	for index, spell := range value.SpellCasts {
+		if strings.TrimSpace(spell.Caster) == "" {
+			return fmt.Errorf("spell_casts[%d].caster must not be empty", index)
+		}
+		if strings.TrimSpace(spell.Spell) == "" {
+			return fmt.Errorf("spell_casts[%d].spell must not be empty", index)
+		}
+		if strings.TrimSpace(spell.Effect) == "" {
+			return fmt.Errorf("spell_casts[%d].effect must not be empty", index)
+		}
+		if strings.TrimSpace(spell.NarrativeDescription) == "" {
+			return fmt.Errorf("spell_casts[%d].narrative_description must not be empty", index)
+		}
+		if len(spell.SourceRefs) == 0 {
+			return fmt.Errorf("spell_casts[%d].source_refs must not be empty", index)
+		}
+		for refIndex, ref := range spell.SourceRefs {
+			if strings.TrimSpace(ref.SourceID) == "" {
+				return fmt.Errorf("spell_casts[%d].source_refs[%d].source_id must not be empty", index, refIndex)
+			}
+			if ref.StartUnitID <= 0 {
+				return fmt.Errorf("spell_casts[%d].source_refs[%d].start_unit_id must be positive", index, refIndex)
+			}
+			if ref.EndUnitID <= 0 {
+				return fmt.Errorf("spell_casts[%d].source_refs[%d].end_unit_id must be positive", index, refIndex)
+			}
+		}
+	}
+	return nil
+}