From 10a31bd84103e272f5afa599093b6dfe167f2bb5 Mon Sep 17 00:00:00 2001
From: alex <53851759+alxxjohn@users.noreply.github.com>
Date: Tue, 18 Aug 2026 17:21:55 -0400
Subject: [PATCH] fix(quality): skip impossible clone windows

---
 .../codeguard/checks/quality/quality_clone.go     | 10 ++++++++++
 .../checks/quality/quality_clone_test.go          | 15 +++++++++++++++
 2 files changed, 25 insertions(+)
 create mode 100644 internal/codeguard/checks/quality/quality_clone_test.go

diff --git a/internal/codeguard/checks/quality/quality_clone.go b/internal/codeguard/checks/quality/quality_clone.go
index 20b8c36b..71475fb0 100644
--- a/internal/codeguard/checks/quality/quality_clone.go
+++ b/internal/codeguard/checks/quality/quality_clone.go
@@ -88,6 +88,16 @@ const cloneWindowMultiplier uint64 = 6364136223846793005
 // candidates are identical to the old per-window byte hashing.
 func cloneWindowIndex(docs []cloneDocument, threshold int) cloneIndex {
 	index := make(cloneIndex)
+	hasWindow := false
+	for _, doc := range docs {
+		if len(doc.Tokens) >= threshold {
+			hasWindow = true
+			break
+		}
+	}
+	if !hasWindow {
+		return index
+	}
 	// top = multiplier^(threshold-1), the weight of the token leaving the
 	// window on each slide.
 	top := uint64(1)
diff --git a/internal/codeguard/checks/quality/quality_clone_test.go b/internal/codeguard/checks/quality/quality_clone_test.go
new file mode 100644
index 00000000..06b537d5
--- /dev/null
+++ b/internal/codeguard/checks/quality/quality_clone_test.go
@@ -0,0 +1,15 @@
+package quality
+
+import "testing"
+
+func TestCloneWindowIndexSkipsMultiplierForOversizedThreshold(t *testing.T) {
+	docs := []cloneDocument{
+		{Tokens: []cloneToken{{Hash: 1}}},
+		{Tokens: []cloneToken{{Hash: 1}}},
+	}
+	threshold := int(^uint(0) >> 1)
+
+	if index := cloneWindowIndex(docs, threshold); len(index) != 0 {
+		t.Fatalf("cloneWindowIndex() returned %d windows, want 0", len(index))
+	}
+}