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

# CASAN Plan-16 SEC-20 (ARCH-04 / ARCH-09) — toolchain verification, fail-closed.
#
# Gate verdicts depend on external binaries. A missing tool (silent no-op) or a
# PATH-shadowed fake (attacker-controlled verdict) must refuse, not run. Proves:
#   * present toolchain passes,
#   * a missing required tool fails,
#   * a required tool planted INSIDE the workspace is rejected (shadow),
#   * with a trusted-dir allowlist, a tool outside it is rejected,
#   * harness-preflight fails closed when the toolchain check fails.
#
# Deterministic; hermetic; no model/network.

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
PROJECT_ROOT="$(cd "$SCRIPT_DIR/../.." && pwd)"
BASH_DIR="$PROJECT_ROOT/.specify/scripts/bash"
TV="$BASH_DIR/toolchain-verify.sh"
WORK="$(mktemp -d)"
trap 'rm -rf "$WORK"; rm -rf "$PROJECT_ROOT/.specify/_sec20probe"' 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-20: toolchain verification fail-closed ====="

[[ "$(rc_of bash "$TV")" -eq 0 ]] \
  && pass "present toolchain passes" || fail "present toolchain rejected"

[[ "$(rc_of bash "$TV" definitely_missing_tool_xyz)" -ne 0 ]] \
  && pass "missing required tool → refuse (ARCH-09)" || fail "missing tool not refused"

# Plant a fake required tool INSIDE the workspace, put it first on PATH.
PROBE="$PROJECT_ROOT/.specify/_sec20probe"; mkdir -p "$PROBE"
printf '#!/bin/sh\necho fake\n' > "$PROBE/awk"; chmod +x "$PROBE/awk"
RC="$(set +e; PATH="$PROBE:$PATH" bash "$TV" awk >/dev/null 2>&1; echo $?)"
[[ "$RC" -ne 0 ]] && pass "in-workspace planted binary → refuse (shadow, ARCH-04)" \
  || fail "workspace-shadowed binary accepted"

# Allowlist mode: a fake tool in a temp dir outside the trusted dirs is rejected.
printf '#!/bin/sh\necho fake\n' > "$WORK/grep"; chmod +x "$WORK/grep"
RC="$(set +e; PATH="$WORK:$PATH" CASAN_TOOLCHAIN_TRUSTED_DIRS="/usr/bin:/bin:/usr/local/bin:/opt/homebrew/bin" bash "$TV" grep >/dev/null 2>&1; echo $?)"
[[ "$RC" -ne 0 ]] && pass "untrusted-dir binary rejected under allowlist" \
  || fail "untrusted-dir binary accepted under allowlist"

# harness-preflight fails closed when toolchain-verify fails (planted required tool).
printf '#!/bin/sh\necho fake\n' > "$PROBE/openssl"; chmod +x "$PROBE/openssl"
RC="$(set +e; PATH="$PROBE:$PATH" bash "$BASH_DIR/harness-preflight.sh" "$WORK/none" --model local >/dev/null 2>&1; echo $?)"
[[ "$RC" -ne 0 ]] && pass "harness-preflight blocks on shadowed toolchain" \
  || fail "preflight did not block on shadowed toolchain"

echo ""
echo "===== SEC-20 SUMMARY: PASS=$PASS FAIL=$FAIL ====="
[[ "$FAIL" -eq 0 ]] || exit 1