#!/usr/bin/env bash
set -uo pipefail

# CASAN Plan-16 SEC-12 — drift-detect semantic invariants (beyond char-similarity).
#
# Char-similarity alone misses a SEMANTIC inversion: dropping a negation
# ("must NOT deploy" -> "must deploy") keeps similarity ~0.97 but flips the meaning,
# and previously passed. Now a candidate that removes negations present in the
# golden, or that drops a must-keep invariant, FAILS. Proves the flip is caught and
# identical/benign content still passes.
#
# Deterministic; hermetic.

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
source "$SCRIPT_DIR/../scripts/bash/casan-paths.sh"
PROJECT_ROOT="$CASAN_APP_ROOT"
DD="$CASAN_HARNESS_ROOT/scripts/bash/drift-detect.sh"
WORK="$(mktemp -d)"
trap 'rm -rf "$WORK"' EXIT

PASS=0; FAIL=0
pass() { echo "PASS: $1"; PASS=$((PASS + 1)); }
fail() { echo "FAIL: $1"; FAIL=$((FAIL + 1)); }
rc_of() { set +e; "$@" >/dev/null 2>&1; echo $?; set -e 2>/dev/null || true; }

echo "===== Plan-16 SEC-12: drift semantic invariants ====="

printf 'You MUST NOT deploy to production without explicit human approval.\n' > "$WORK/golden.txt"
printf 'You MUST deploy to production without explicit human approval.\n' > "$WORK/flip.txt"
cp "$WORK/golden.txt" "$WORK/same.txt"

# Negation flip: near-identical text (similarity ~0.97) but a "NOT" vanished.
[[ "$(rc_of bash "$DD" "$WORK/golden.txt" "$WORK/flip.txt" "$WORK/r1.json")" -ne 0 ]] \
  && pass "negation flip FAILS despite high similarity" \
  || fail "negation flip passed (semantic inversion missed)"
grep -q 'negation_dropped' "$WORK/r1.json" \
  && pass "report records the negation_dropped reason" || fail "reason not recorded"

# Identical golden/candidate still passes.
[[ "$(rc_of bash "$DD" "$WORK/golden.txt" "$WORK/same.txt" "$WORK/r2.json")" -eq 0 ]] \
  && pass "identical content passes (no false positive)" || fail "identical content flagged"

# must-keep invariant missing from candidate → FAIL.
printf 'MUST NOT deploy\n' > "$WORK/mustkeep.txt"
[[ "$(rc_of env CASAN_DRIFT_MUSTKEEP_FILE="$WORK/mustkeep.txt" bash "$DD" "$WORK/golden.txt" "$WORK/flip.txt" "$WORK/r3.json")" -ne 0 ]] \
  && pass "missing must-keep invariant FAILS" || fail "missing must-keep not detected"

# must-keep invariant present → pass.
printf 'production\n' > "$WORK/mustkeep2.txt"
[[ "$(rc_of env CASAN_DRIFT_MUSTKEEP_FILE="$WORK/mustkeep2.txt" bash "$DD" "$WORK/golden.txt" "$WORK/same.txt" "$WORK/r4.json")" -eq 0 ]] \
  && pass "present must-keep invariant passes" || fail "present must-keep wrongly failed"

echo ""
echo "===== SEC-12 SUMMARY: PASS=$PASS FAIL=$FAIL ====="
[[ "$FAIL" -eq 0 ]] || exit 1