Add D&D NPC interaction artifact codec

internal/modules/dnd/codec/npcinteractions/assets/schemas/dnd_npc_interactions.v1.json

@@ -0,0 +1,50 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "notarius.dnd.npc_interactions",
+  "type": "object",
+  "additionalProperties": false,
+  "required": ["interactions"],
+  "properties": {
+    "interactions": {
+      "type": "array",
+      "items": {
+        "type": "object",
+        "additionalProperties": false,
+        "required": ["name", "kind", "source_refs"],
+        "properties": {
+          "name": {
+            "type": "string",
+            "minLength": 1
+          },
+          "kind": {
+            "type": "string",
+            "enum": ["mentioned", "noncombat_presence", "dialogue", "combat_ally", "combat_opponent", "other"]
+          },
+          "source_refs": {
+            "type": "array",
+            "minItems": 1,
+            "items": {
+              "type": "object",
+              "additionalProperties": false,
+              "required": ["source_id", "start_unit_id", "end_unit_id"],
+              "properties": {
+                "source_id": {
+                  "type": "string",
+                  "minLength": 1
+                },
+                "start_unit_id": {
+                  "type": "integer",
+                  "minimum": 1
+                },
+                "end_unit_id": {
+                  "type": "integer",
+                  "minimum": 1
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+}

internal/modules/dnd/codec/npcinteractions/codec.go

@@ -0,0 +1,140 @@
+// Package npcinteractions encodes durable D&D NPC interaction artifacts.
+package npcinteractions
+
+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.npc_interactions"
+	SchemaName    = "notarius_dnd_npc_interactions_v1"
+	SchemaVersion = "v1"
+	MediaType     = "application/json"
+)
+
+//go:embed assets/schemas/dnd_npc_interactions.v1.json
+var schemaAssets embed.FS
+
+var _ contracts.ArtifactCodec[dnd.NPCInteractionList] = (*Codec)(nil)
+
+type Codec struct{}
+
+func New() *Codec { return &Codec{} }
+
+func (c *Codec) Kind() contracts.ArtifactKind { return dnd.NPCInteractionListKind }
+
+func (c *Codec) Schema() contracts.ArtifactSchema {
+	raw, err := schemaAssets.ReadFile("assets/schemas/dnd_npc_interactions.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.NPCInteractionList) map[string]any {
+	return map[string]any{"interaction_count": len(value.Interactions)}
+}
+
+func (c *Codec) Encode(value dnd.NPCInteractionList) ([]byte, error) {
+	if err := validate(value); err != nil {
+		return nil, fmt.Errorf("encode dnd npc interaction list: %w", err)
+	}
+	return c.EncodeCandidate(value)
+}
+
+// EncodeCandidate provides the durable representation before semantic
+// validators have approved a value.
+func (c *Codec) EncodeCandidate(value dnd.NPCInteractionList) ([]byte, error) {
+	content, err := json.Marshal(value)
+	if err != nil {
+		return nil, fmt.Errorf("encode dnd npc interaction list: %w", err)
+	}
+	return content, nil
+}
+
+func (c *Codec) Decode(content []byte) (dnd.NPCInteractionList, error) {
+	value, err := c.DecodeCandidate(content)
+	if err != nil {
+		return dnd.NPCInteractionList{}, err
+	}
+	if err := validate(value); err != nil {
+		return dnd.NPCInteractionList{}, fmt.Errorf("decode dnd npc interaction list: %w", err)
+	}
+	return value, nil
+}
+
+// DecodeCandidate reads one strict durable JSON value before semantic
+// validators have approved it.
+func (c *Codec) DecodeCandidate(content []byte) (dnd.NPCInteractionList, error) {
+	decoder := json.NewDecoder(bytes.NewReader(content))
+	decoder.DisallowUnknownFields()
+	var value dnd.NPCInteractionList
+	if err := decoder.Decode(&value); err != nil {
+		return dnd.NPCInteractionList{}, fmt.Errorf("decode dnd npc interaction list: %w", err)
+	}
+	var trailing any
+	if err := decoder.Decode(&trailing); err != io.EOF {
+		return dnd.NPCInteractionList{}, fmt.Errorf("decode dnd npc interaction list: multiple JSON values")
+	}
+	return value, nil
+}
+
+func validate(value dnd.NPCInteractionList) error {
+	if value.Interactions == nil {
+		return fmt.Errorf("interactions must be present")
+	}
+	for index, interaction := range value.Interactions {
+		prefix := fmt.Sprintf("interactions[%d]", index)
+		if strings.TrimSpace(interaction.Name) == "" {
+			return fmt.Errorf("%s.name must not be empty", prefix)
+		}
+		if !validInteractionKind(interaction.Kind) {
+			return fmt.Errorf("%s.kind must be supported", prefix)
+		}
+		if len(interaction.SourceRefs) == 0 {
+			return fmt.Errorf("%s.source_refs must contain at least one reference", prefix)
+		}
+		for refIndex, ref := range interaction.SourceRefs {
+			refPrefix := fmt.Sprintf("%s.source_refs[%d]", prefix, refIndex)
+			if strings.TrimSpace(ref.SourceID) == "" {
+				return fmt.Errorf("%s.source_id must not be empty", refPrefix)
+			}
+			if ref.StartUnitID <= 0 {
+				return fmt.Errorf("%s.start_unit_id must be positive", refPrefix)
+			}
+			if ref.EndUnitID <= 0 {
+				return fmt.Errorf("%s.end_unit_id must be positive", refPrefix)
+			}
+		}
+	}
+	return nil
+}
+
+func validInteractionKind(value dnd.NPCInteractionKind) bool {
+	switch value {
+	case dnd.NPCInteractionKindMentioned,
+		dnd.NPCInteractionKindNoncombatPresence,
+		dnd.NPCInteractionKindDialogue,
+		dnd.NPCInteractionKindCombatAlly,
+		dnd.NPCInteractionKindCombatOpponent,
+		dnd.NPCInteractionKindOther:
+		return true
+	default:
+		return false
+	}
+}

internal/modules/dnd/codec/npcinteractions/codec_test.go

@@ -0,0 +1,183 @@
+package npcinteractions
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"os"
+	"reflect"
+	"strings"
+	"testing"
+
+	"gitea.maximumdirect.net/eric/notarius/internal/core/source"
+	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
+	"gitea.maximumdirect.net/eric/notarius/internal/framework/pipeline"
+	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd"
+)
+
+func validList() dnd.NPCInteractionList {
+	return dnd.NPCInteractionList{Interactions: []dnd.NPCInteraction{
+		{
+			Name: "Mira Thorn", Kind: dnd.NPCInteractionKindDialogue,
+			SourceRefs: []source.SourceRef{{SourceID: "session-alpha", StartUnitID: 1, EndUnitID: 2}},
+		},
+		{
+			Name: "Hooded Guard", Kind: dnd.NPCInteractionKindCombatOpponent,
+			SourceRefs: []source.SourceRef{{SourceID: "session-alpha", StartUnitID: 3, EndUnitID: 3}},
+		},
+	}}
+}
+
+func TestCodecMatchesMaintainedDurableFixture(t *testing.T) {
+	raw, err := os.ReadFile("testdata/dnd_npc_interactions.v1.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	codec := New()
+	value, err := codec.Decode(raw)
+	if err != nil {
+		t.Fatalf("Decode() error = %v", err)
+	}
+	if want := validList(); !reflect.DeepEqual(value, want) {
+		t.Fatalf("Decode() = %#v, want %#v", value, want)
+	}
+	encoded, err := codec.Encode(value)
+	if err != nil {
+		t.Fatalf("Encode() error = %v", err)
+	}
+	var compact bytes.Buffer
+	if err := json.Compact(&compact, raw); err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(encoded, compact.Bytes()) {
+		t.Fatalf("Encode() = %s, want %s", encoded, compact.Bytes())
+	}
+}
+
+func TestCodecOwnsDurableSchemaAndRegistersExactType(t *testing.T) {
+	codec := New()
+	schema := codec.Schema()
+	if codec.Kind() != dnd.NPCInteractionListKind || codec.MediaType() != MediaType {
+		t.Fatalf("codec identity = %q/%q", codec.Kind(), codec.MediaType())
+	}
+	if schema.ID != SchemaID || schema.Name != SchemaName || schema.Version != SchemaVersion || !json.Valid(schema.JSONSchema) {
+		t.Fatalf("schema = %#v", schema)
+	}
+	registry := pipeline.NewArtifactCodecRegistry()
+	if err := pipeline.RegisterArtifactCodec(registry, codec); err != nil {
+		t.Fatal(err)
+	}
+	spec, ok := registry.Spec(dnd.NPCInteractionListKind)
+	if !ok || spec.SchemaDigest != contracts.DigestArtifactSchema(schema) {
+		t.Fatalf("registered spec = %#v, %t", spec, ok)
+	}
+	if _, err := registry.Encode(dnd.NPCInteractionListKind, dnd.NPCList{}); err == nil {
+		t.Fatal("Encode() error = nil, want exact type rejection")
+	} else {
+		var typeErr *pipeline.ArtifactCodecTypeError
+		if !errors.As(err, &typeErr) {
+			t.Fatalf("Encode() error = %T, want ArtifactCodecTypeError", err)
+		}
+	}
+}
+
+func TestCodecSupportsEmptyListAndPreservesCollectionPresenceInCandidates(t *testing.T) {
+	codec := New()
+	empty := dnd.NPCInteractionList{Interactions: []dnd.NPCInteraction{}}
+	content, err := codec.Encode(empty)
+	if err != nil || string(content) != `{"interactions":[]}` {
+		t.Fatalf("Encode() = %s, %v", content, err)
+	}
+	for _, candidate := range []dnd.NPCInteractionList{
+		{},
+		empty,
+		{Interactions: []dnd.NPCInteraction{{Name: " ", Kind: "unsupported", SourceRefs: nil}}},
+		{Interactions: []dnd.NPCInteraction{{Name: " ", Kind: "unsupported", SourceRefs: []source.SourceRef{}}}},
+		{Interactions: []dnd.NPCInteraction{{Name: " ", Kind: "unsupported", SourceRefs: []source.SourceRef{{StartUnitID: 0, EndUnitID: -1}}}}},
+	} {
+		content, err := codec.EncodeCandidate(candidate)
+		if err != nil || !json.Valid(content) {
+			t.Fatalf("EncodeCandidate() = %s, %v", content, err)
+		}
+		decoded, err := codec.DecodeCandidate(content)
+		if err != nil || !reflect.DeepEqual(decoded, candidate) {
+			t.Fatalf("DecodeCandidate() = %#v, %v; want %#v", decoded, err, candidate)
+		}
+	}
+}
+
+func TestCodecStrictlyRejectsMalformedUnknownAndTrailingJSON(t *testing.T) {
+	validJSON := `{"interactions":[{"name":"Mira Thorn","kind":"dialogue","source_refs":[{"source_id":"session","start_unit_id":1,"end_unit_id":1}]}]}`
+	for _, test := range []struct{ name, raw, want string }{
+		{"malformed", `{`, "decode dnd npc interaction list"},
+		{"unknown top-level", `{"interactions":[],"unexpected":true}`, "unknown field"},
+		{"unknown interaction field", strings.Replace(validJSON, `"kind":"dialogue"`, `"kind":"dialogue","unexpected":true`, 1), "unknown field"},
+		{"unknown source reference field", strings.Replace(validJSON, `"end_unit_id":1`, `"end_unit_id":1,"unexpected":true`, 1), "unknown field"},
+		{"trailing", `{"interactions":[]} {}`, "multiple JSON values"},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			if _, err := New().Decode([]byte(test.raw)); err == nil || !strings.Contains(err.Error(), test.want) {
+				t.Fatalf("Decode() error = %v, want %q", err, test.want)
+			}
+		})
+	}
+}
+
+func TestCodecRejectsRequiredShapeEnumAndReferenceBoundaries(t *testing.T) {
+	tests := []struct {
+		name  string
+		value dnd.NPCInteractionList
+		want  string
+	}{
+		{"nil interactions", dnd.NPCInteractionList{}, "interactions must be present"},
+		{"blank name", mutate(validList(), func(v *dnd.NPCInteractionList) { v.Interactions[0].Name = " " }), "name must not be empty"},
+		{"unsupported kind", mutate(validList(), func(v *dnd.NPCInteractionList) { v.Interactions[0].Kind = "unsupported" }), "kind must be supported"},
+		{"nil source refs", mutate(validList(), func(v *dnd.NPCInteractionList) { v.Interactions[0].SourceRefs = nil }), "source_refs must contain"},
+		{"empty source ID", mutate(validList(), func(v *dnd.NPCInteractionList) { v.Interactions[0].SourceRefs[0].SourceID = " " }), "source_id must not be empty"},
+		{"non-positive start", mutate(validList(), func(v *dnd.NPCInteractionList) { v.Interactions[0].SourceRefs[0].StartUnitID = 0 }), "start_unit_id must be positive"},
+		{"non-positive end", mutate(validList(), func(v *dnd.NPCInteractionList) { v.Interactions[0].SourceRefs[0].EndUnitID = 0 }), "end_unit_id must be positive"},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			if _, err := New().Encode(test.value); err == nil || !strings.Contains(err.Error(), test.want) {
+				t.Fatalf("Encode() error = %v, want %q", err, test.want)
+			}
+		})
+	}
+}
+
+func TestCodecAcceptsEveryInteractionKind(t *testing.T) {
+	for _, kind := range []dnd.NPCInteractionKind{
+		dnd.NPCInteractionKindMentioned,
+		dnd.NPCInteractionKindNoncombatPresence,
+		dnd.NPCInteractionKindDialogue,
+		dnd.NPCInteractionKindCombatAlly,
+		dnd.NPCInteractionKindCombatOpponent,
+		dnd.NPCInteractionKindOther,
+	} {
+		value := validList()
+		value.Interactions[0].Kind = kind
+		if _, err := New().Encode(value); err != nil {
+			t.Fatalf("Encode(%q) error = %v", kind, err)
+		}
+	}
+}
+
+func TestCodecSchemaAndMetadataAreDefensive(t *testing.T) {
+	codec := New()
+	first := codec.Schema()
+	first.JSONSchema[0] = '['
+	if second := codec.Schema(); !json.Valid(second.JSONSchema) || second.JSONSchema[0] == '[' {
+		t.Fatal("Schema() returned shared bytes")
+	}
+	metadata := codec.Metadata(validList())
+	metadata["other"] = true
+	if next := codec.Metadata(validList()); len(next) != 1 || next["interaction_count"] != 2 {
+		t.Fatalf("Metadata() = %#v", next)
+	}
+}
+
+func mutate(value dnd.NPCInteractionList, change func(*dnd.NPCInteractionList)) dnd.NPCInteractionList {
+	change(&value)
+	return value
+}

internal/modules/dnd/codec/npcinteractions/testdata/dnd_npc_interactions.v1.json

@@ -0,0 +1,18 @@
+{
+  "interactions": [
+    {
+      "name": "Mira Thorn",
+      "kind": "dialogue",
+      "source_refs": [
+        {"source_id": "session-alpha", "start_unit_id": 1, "end_unit_id": 2}
+      ]
+    },
+    {
+      "name": "Hooded Guard",
+      "kind": "combat_opponent",
+      "source_refs": [
+        {"source_id": "session-alpha", "start_unit_id": 3, "end_unit_id": 3}
+      ]
+    }
+  ]
+}