Centralize D&D candidate JSON codecs

2026-07-25 13:05:02 +00:00
parent 8199d95dc1
commit d752c51aec
7 changed files with 100 additions and 95 deletions
--- a/internal/modules/dnd/codec/candidatejson/candidate_json.go
+++ b/internal/modules/dnd/codec/candidatejson/candidate_json.go
@@ -0,0 +1,38 @@
+// Package candidatejson provides strict JSON mechanics for D&D artifact
+// candidates before artifact-specific validation.
+package candidatejson
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+)
+
+// EncodeCandidate encodes a typed candidate with an artifact-specific error
+// label.
+func EncodeCandidate[T any](label string, value T) ([]byte, error) {
+	content, err := json.Marshal(value)
+	if err != nil {
+		return nil, fmt.Errorf("encode %s: %w", label, err)
+	}
+	return content, nil
+}
+
+// DecodeCandidate decodes exactly one typed JSON value while rejecting unknown
+// fields and trailing values with an artifact-specific error label.
+func DecodeCandidate[T any](label string, content []byte) (T, error) {
+	decoder := json.NewDecoder(bytes.NewReader(content))
+	decoder.DisallowUnknownFields()
+	var value T
+	if err := decoder.Decode(&value); err != nil {
+		var zero T
+		return zero, fmt.Errorf("decode %s: %w", label, err)
+	}
+	var trailing any
+	if err := decoder.Decode(&trailing); err != io.EOF {
+		var zero T
+		return zero, fmt.Errorf("decode %s: multiple JSON values", label)
+	}
+	return value, nil
+}
--- a/internal/modules/dnd/codec/candidatejson/candidate_json_test.go
+++ b/internal/modules/dnd/codec/candidatejson/candidate_json_test.go
@@ -0,0 +1,47 @@
+package candidatejson
+
+import (
+	"encoding/json"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+type testCandidate struct {
+	Items []string `json:"items"`
+}
+
+func TestCandidateJSON(t *testing.T) {
+	input := testCandidate{Items: []string{"one", "two"}}
+	content, err := EncodeCandidate("test candidate", input)
+	if err != nil {
+		t.Fatalf("EncodeCandidate() error = %v", err)
+	}
+	if !json.Valid(content) {
+		t.Fatalf("EncodeCandidate() = %q, want JSON", content)
+	}
+	for _, test := range []struct {
+		name    string
+		content []byte
+		want    testCandidate
+		wantErr string
+	}{
+		{name: "typed round trip", content: content, want: input},
+		{name: "unknown field", content: []byte(`{"items":[],"unexpected":true}`), wantErr: "unknown field"},
+		{name: "malformed JSON", content: []byte(`{"items":`), wantErr: "decode test candidate"},
+		{name: "trailing value", content: []byte(`{"items":[]} {}`), wantErr: "multiple JSON values"},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			got, err := DecodeCandidate[testCandidate]("test candidate", test.content)
+			if test.wantErr != "" {
+				if err == nil || !strings.Contains(err.Error(), test.wantErr) {
+					t.Fatalf("DecodeCandidate() error = %v, want %q", err, test.wantErr)
+				}
+				return
+			}
+			if err != nil || !reflect.DeepEqual(got, test.want) {
+				t.Fatalf("DecodeCandidate() = %#v, %v; want %#v", got, err, test.want)
+			}
+		})
+	}
+}
--- a/internal/modules/dnd/codec/combatturns/codec.go
+++ b/internal/modules/dnd/codec/combatturns/codec.go
@@ -1,15 +1,13 @@
 package combatturns

 import (
-	"bytes"
 	"embed"
-	"encoding/json"
 	"fmt"
-	"io"
 	"strings"

 	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
 	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd"
+	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/codec/candidatejson"
 )

 const (
@@ -59,11 +57,7 @@ func (c *Codec) Encode(value dnd.CombatTurnList) ([]byte, error) {
 // EncodeCandidate provides the durable representation before typed validators
 // have approved a value.
 func (c *Codec) EncodeCandidate(value dnd.CombatTurnList) ([]byte, error) {
-	content, err := json.Marshal(value)
-	if err != nil {
-		return nil, fmt.Errorf("encode dnd combat turn list: %w", err)
-	}
-	return content, nil
+	return candidatejson.EncodeCandidate("dnd combat turn list", value)
 }

 func (c *Codec) Decode(content []byte) (dnd.CombatTurnList, error) {
@@ -80,17 +74,7 @@ func (c *Codec) Decode(content []byte) (dnd.CombatTurnList, error) {
 // DecodeCandidate reads one strict durable JSON value before semantic
 // validators have approved it.
 func (c *Codec) DecodeCandidate(content []byte) (dnd.CombatTurnList, error) {
-	decoder := json.NewDecoder(bytes.NewReader(content))
-	decoder.DisallowUnknownFields()
-	var value dnd.CombatTurnList
-	if err := decoder.Decode(&value); err != nil {
-		return dnd.CombatTurnList{}, fmt.Errorf("decode dnd combat turn list: %w", err)
-	}
-	var trailing any
-	if err := decoder.Decode(&trailing); err != io.EOF {
-		return dnd.CombatTurnList{}, fmt.Errorf("decode dnd combat turn list: multiple JSON values")
-	}
-	return value, nil
+	return candidatejson.DecodeCandidate[dnd.CombatTurnList]("dnd combat turn list", content)
 }

 func validate(value dnd.CombatTurnList) error {
--- a/internal/modules/dnd/codec/npcinteractions/codec.go
+++ b/internal/modules/dnd/codec/npcinteractions/codec.go
@@ -2,15 +2,13 @@
 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"
+	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/codec/candidatejson"
 )

 const (
@@ -60,11 +58,7 @@ func (c *Codec) Encode(value dnd.NPCInteractionList) ([]byte, error) {
 // 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
+	return candidatejson.EncodeCandidate("dnd npc interaction list", value)
 }

 func (c *Codec) Decode(content []byte) (dnd.NPCInteractionList, error) {
@@ -81,17 +75,7 @@ func (c *Codec) Decode(content []byte) (dnd.NPCInteractionList, error) {
 // 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
+	return candidatejson.DecodeCandidate[dnd.NPCInteractionList]("dnd npc interaction list", content)
 }

 func validate(value dnd.NPCInteractionList) error {
--- a/internal/modules/dnd/codec/npcs/codec.go
+++ b/internal/modules/dnd/codec/npcs/codec.go
@@ -1,15 +1,13 @@
 package npcs

 import (
-	"bytes"
 	"embed"
-	"encoding/json"
 	"fmt"
-	"io"
 	"strings"

 	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
 	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd"
+	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/codec/candidatejson"
 	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/npcs/identity"
 )

@@ -60,11 +58,7 @@ func (c *Codec) Encode(value dnd.NPCList) ([]byte, error) {
 // EncodeCandidate provides the durable representation before semantic
 // validators have approved a value.
 func (c *Codec) EncodeCandidate(value dnd.NPCList) ([]byte, error) {
-	content, err := json.Marshal(value)
-	if err != nil {
-		return nil, fmt.Errorf("encode dnd npc list: %w", err)
-	}
-	return content, nil
+	return candidatejson.EncodeCandidate("dnd npc list", value)
 }

 func (c *Codec) Decode(content []byte) (dnd.NPCList, error) {
@@ -81,17 +75,7 @@ func (c *Codec) Decode(content []byte) (dnd.NPCList, error) {
 // DecodeCandidate reads one strict durable JSON value before semantic
 // validators have approved it.
 func (c *Codec) DecodeCandidate(content []byte) (dnd.NPCList, error) {
-	decoder := json.NewDecoder(bytes.NewReader(content))
-	decoder.DisallowUnknownFields()
-	var value dnd.NPCList
-	if err := decoder.Decode(&value); err != nil {
-		return dnd.NPCList{}, fmt.Errorf("decode dnd npc list: %w", err)
-	}
-	var trailing any
-	if err := decoder.Decode(&trailing); err != io.EOF {
-		return dnd.NPCList{}, fmt.Errorf("decode dnd npc list: multiple JSON values")
-	}
-	return value, nil
+	return candidatejson.DecodeCandidate[dnd.NPCList]("dnd npc list", content)
 }

 func validate(value dnd.NPCList) error {
--- a/internal/modules/dnd/codec/scenedescriptions/codec.go
+++ b/internal/modules/dnd/codec/scenedescriptions/codec.go
@@ -1,15 +1,13 @@
 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"
+	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/codec/candidatejson"
 )

 const (
@@ -59,11 +57,7 @@ func (c *Codec) Encode(value dnd.SceneDescriptionList) ([]byte, error) {
 // 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
+	return candidatejson.EncodeCandidate("dnd scene description list", value)
 }

 func (c *Codec) Decode(content []byte) (dnd.SceneDescriptionList, error) {
@@ -80,17 +74,7 @@ func (c *Codec) Decode(content []byte) (dnd.SceneDescriptionList, error) {
 // 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
+	return candidatejson.DecodeCandidate[dnd.SceneDescriptionList]("dnd scene description list", content)
 }

 func validate(value dnd.SceneDescriptionList) error {
--- a/internal/modules/dnd/codec/spells/codec.go
+++ b/internal/modules/dnd/codec/spells/codec.go
@@ -1,15 +1,13 @@
 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"
+	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/codec/candidatejson"
 )

 const (
@@ -54,11 +52,7 @@ func (c *Codec) Encode(value dnd.SpellList) ([]byte, error) {
 // EncodeCandidate provides the same stable representation before typed
 // validators have approved a value.
 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
+	return candidatejson.EncodeCandidate("dnd spell list", value)
 }

 func (c *Codec) Decode(content []byte) (dnd.SpellList, error) {
@@ -75,17 +69,7 @@ func (c *Codec) Decode(content []byte) (dnd.SpellList, error) {
 // DecodeCandidate reads the durable representation before semantic validators
 // have approved it.
 func (c *Codec) DecodeCandidate(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")
-	}
-	return value, nil
+	return candidatejson.DecodeCandidate[dnd.SpellList]("dnd spell list", content)
 }

 func validate(value dnd.SpellList) error {