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

# Verify the tamper-evident central tool-call audit log:
#   1. recompute the SHA-256 hash chain
#   2. confirm the stored head equals the computed head
#   3. verify the head's RSA signature
# Usage: verify-tool-audit.sh [tool-calls.jsonl]

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
source "$SCRIPT_DIR/casan-paths.sh"
PROJECT_ROOT="$CASAN_APP_ROOT"
LOG="${1:-$CASAN_STATE_ROOT/logs/audit/tool-calls.jsonl}"

if [[ ! -f "$LOG" ]]; then
  echo "TOOL_AUDIT_MISSING file=$LOG" >&2
  exit 1
fi

COMPUTED_HEAD="$(python - "$LOG" <<'PY'
import hashlib, json, sys
path = sys.argv[1]
prev = ""
count = 0
with open(path, encoding="utf-8") as f:
    for line_no, line in enumerate(f, 1):
        if not line.strip():
            continue
        rec = json.loads(line)
        if rec.get("previous_record_hash", "") != prev:
            raise SystemExit(f"TOOL_AUDIT_CHAIN_BROKEN line={line_no}")
        stored = rec.pop("record_hash", "")
        core = json.dumps(rec, sort_keys=True, separators=(",", ":"))
        expected = hashlib.sha256((prev + "|" + core).encode()).hexdigest()
        if expected != stored:
            raise SystemExit(f"TOOL_AUDIT_HASH_MISMATCH line={line_no}")
        prev = stored
        count += 1
sys.stderr.write(f"TOOL_AUDIT_INTEGRITY_OK records={count}\n")
sys.stdout.write(prev)
PY
)"

AUDIT_DIR="$(dirname "$LOG")"
HEAD_FILE="$AUDIT_DIR/tool-calls-head.txt"
HEAD_SIG="$AUDIT_DIR/tool-calls-head.sig"
AUDIT_PUB="$CASAN_GOVERNANCE_ROOT/audit-public.pem"

if [[ -f "$HEAD_FILE" && -f "$HEAD_SIG" && -f "$AUDIT_PUB" ]] && command -v openssl >/dev/null 2>&1; then
  if [[ "$(cat "$HEAD_FILE")" != "$COMPUTED_HEAD" ]]; then
    echo "TOOL_AUDIT_HEAD_MISMATCH computed=$COMPUTED_HEAD" >&2
    exit 1
  fi
  if ! openssl dgst -sha256 -verify "$AUDIT_PUB" -signature "$HEAD_SIG" "$HEAD_FILE" >/dev/null 2>&1; then
    echo "TOOL_AUDIT_HEAD_SIGNATURE_INVALID head=$COMPUTED_HEAD" >&2
    exit 1
  fi
  echo "TOOL_AUDIT_VALID anchor=signed last_hash=$COMPUTED_HEAD"
else
  # SEC-01 (H-01): enforced mode treats a missing/unverifiable signature as FAIL.
  # Self-contained (this script is copied into sandboxes by tests — no common.sh).
  if [[ "${CASAN_PROFILE:-}" == "prod" || "${CASAN_VERIFY_STRICT:-}" == "1" ]]; then
    MISSING=""
    [[ -f "$HEAD_FILE" ]] || MISSING="$MISSING head-file"
    [[ -f "$HEAD_SIG" ]] || MISSING="$MISSING head-sig"
    [[ -f "$AUDIT_PUB" ]] || MISSING="$MISSING pubkey"
    command -v openssl >/dev/null 2>&1 || MISSING="$MISSING openssl"
    echo "TOOL_AUDIT_UNSIGNED_STRICT_FAIL last_hash=$COMPUTED_HEAD missing=${MISSING# }" >&2
    exit 1
  fi
  echo "TOOL_AUDIT_VALID anchor=unsigned last_hash=$COMPUTED_HEAD"
fi