Tighten NPC interaction validation and consistency

internal/modules/dnd/shared/diagnostics/diagnostics.go

@@ -6,10 +6,13 @@ import (
 	"fmt"
 	"strconv"
 	"strings"
+
+	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
 )
 
 const (
 	MaxIssues         = 20
+	MaxWarnings       = 20
 	MaxDisplayedRunes = 128
 	MaxMessageBytes   = 4096
 )
@@ -37,6 +40,28 @@ func Aggregate(prefix string, issues []string) string {
 	return aggregateMessage(prefix, displayed, len(issues)-len(displayed))
 }
 
+// LimitWarnings returns at most MaxWarnings warnings, reserving the final
+// position for a deterministic omission summary when truncation is required.
+func LimitWarnings(warnings []contracts.Warning, scope, reasonCode string) []contracts.Warning {
+	if warnings == nil {
+		return nil
+	}
+	if len(warnings) <= MaxWarnings {
+		bounded := make([]contracts.Warning, len(warnings))
+		copy(bounded, warnings)
+		return bounded
+	}
+	displayed := MaxWarnings - 1
+	bounded := make([]contracts.Warning, displayed, MaxWarnings)
+	copy(bounded, warnings[:displayed])
+	bounded = append(bounded, contracts.Warning{
+		Scope:      scope,
+		ReasonCode: reasonCode,
+		Message:    fmt.Sprintf("%d additional warning(s) omitted", len(warnings)-displayed),
+	})
+	return bounded
+}
+
 func aggregateMessage(prefix string, issues []string, omitted int) string {
 	message := prefix + ": " + strings.Join(issues, ", ")
 	if omitted > 0 {

internal/modules/dnd/shared/diagnostics/diagnostics_test.go

@@ -2,9 +2,12 @@ package diagnostics
 
 import (
 	"fmt"
+	"reflect"
 	"strings"
 	"testing"
 	"unicode/utf8"
+
+	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
 )
 
 func TestAggregateEnforcesByteBudgetAndReportsOmissions(t *testing.T) {
@@ -26,3 +29,25 @@ func TestAggregateEnforcesByteBudgetAndReportsOmissions(t *testing.T) {
 		t.Fatalf("Aggregate() = %q, want %q", message, wantOmitted)
 	}
 }
+
+func TestLimitWarningsBoundsOutputAndReportsOmissions(t *testing.T) {
+	warnings := make([]contracts.Warning, MaxWarnings+3)
+	for index := range warnings {
+		warnings[index] = contracts.Warning{ReasonCode: fmt.Sprintf("warning-%d", index)}
+	}
+	before := append([]contracts.Warning(nil), warnings...)
+
+	got := LimitWarnings(warnings, "records", "warnings_omitted")
+	if len(got) != MaxWarnings {
+		t.Fatalf("LimitWarnings() count = %d, want %d", len(got), MaxWarnings)
+	}
+	summary := got[len(got)-1]
+	wantOmitted := len(warnings) - (MaxWarnings - 1)
+	if summary.Scope != "records" || summary.ReasonCode != "warnings_omitted" ||
+		summary.Message != fmt.Sprintf("%d additional warning(s) omitted", wantOmitted) {
+		t.Fatalf("summary = %#v", summary)
+	}
+	if !reflect.DeepEqual(warnings, before) {
+		t.Fatal("LimitWarnings() mutated its input")
+	}
+}