Harden item occurrence grounding

internal/modules/dnd/shared/text_comparison.go

@@ -0,0 +1,28 @@
+package shared
+
+import (
+	"strings"
+
+	"golang.org/x/text/cases"
+	"golang.org/x/text/unicode/norm"
+)
+
+// TextComparisonPolicy identifies the shared D&D text-comparison semantics.
+// A semantic change requires a new value and a review of every dependent
+// identity, mapping, normalization, and validator policy.
+const TextComparisonPolicy = "dnd.text_comparison.v1"
+
+// ComparisonKey returns the D&D Unicode- and case-insensitive comparison key.
+func ComparisonKey(value string) string {
+	value = norm.NFKC.String(value)
+	value = strings.Map(func(r rune) rune {
+		switch r {
+		case '\u2018', '\u2019', '\u02bc':
+			return '\''
+		default:
+			return r
+		}
+	}, value)
+	value = strings.Join(strings.Fields(value), " ")
+	return cases.Fold().String(value)
+}