package semantic

import "testing"

// TestFastPathDerivationInvariant asserts that every development-pool row's
// stored fast-path flag exactly matches what the production fast path derives
// today (DeriveFastPath runs TryFastPath over the stage-0 grammars with the
// experiment's act allowlist). Frozen holdout rows are preserved verbatim
// across merges and are exempt — their drift is reported, never silently
// rewritten. A stale development value is a corpus-build error.
func TestFastPathDerivationInvariant(t *testing.T) {
	exs, err := LoadCorpus()
	if err != nil {
		t.Fatalf("load corpus: %v", err)
	}
	_, dev, _ := FrozenHoldoutSplit(exs)
	devSet := make(map[string]bool, len(dev))
	for _, e := range dev {
		devSet[e.SourceID] = true
	}

	stale := 0
	for _, e := range exs {
		if !devSet[e.SourceID] {
			continue
		}
		if got := DeriveFastPath(e.Text).Matched; got != e.FastPathResolved {
			t.Errorf("dev row %s (route=%s) fast_path_resolved=%v but router derives %v: %q",
				e.SourceID, e.Route, e.FastPathResolved, got, e.Text)
			stale++
		}
	}
	if stale > 0 {
		t.Fatalf("%d development rows have stale fast-path metadata", stale)
	}
}