'use strict';
/**
 * fail-mode.js — fail-open/fail-closed 决策 API (P1-FAIL-MODE-V1)
 *
 * 红队识别风险: 关键 hook 普遍 fail-open（异常即放行）→ 攻击者构造慢路径或异常即逃逸守卫。
 *
 * 设计:
 *   - feature-flags.json 中读取 features['bookworm.security.failClosed'].mode
 *   - mode='off' / 不存在: 完全无操作（保留原 fail-open 行为）
 *   - mode='warn': 记录 evolution-log violation 但放行
 *   - mode='enforce': 调用方应据此 process.exit(1)
 *
 * Usage:
 *   const { failModeDecide } = require('./lib/fail-mode.js');
 *   try { ... } catch (e) {
 *     const action = failModeDecide('security-startup-guard', e);
 *     if (action === 'reject') process.exit(1);
 *     // else: 原 fail-open 路径
 *   }
 */

const fs = require('fs');
const path = require('path');

const ROOT = path.join(__dirname, '..', '..');
const FLAGS = path.join(ROOT, 'feature-flags.json');
const EVOLUTION_LOG = path.join(ROOT, 'evolution-log.jsonl');
const FLAG_FEATURE = 'bookworm.security.failClosed';

let _cachedFlags = null;
let _cacheMtime = 0;

function loadFlags() {
  try {
    const stat = fs.statSync(FLAGS);
    if (_cachedFlags && stat.mtimeMs === _cacheMtime) return _cachedFlags;
    const raw = JSON.parse(fs.readFileSync(FLAGS, 'utf8'));
    _cachedFlags = raw && raw.features ? raw.features : {};
    _cacheMtime = stat.mtimeMs;
    return _cachedFlags;
  } catch (_) {
    return {};
  }
}

/**
 * 决策 API
 * @param {string} hookName - 调用方标识，如 'security-startup-guard'
 * @param {Error|object} ctx - 异常或上下文
 * @returns {'noop'|'warn'|'reject'}
 */
function failModeDecide(hookName, ctx) {
  const flags = loadFlags();
  const cfg = flags[FLAG_FEATURE];
  const mode = cfg && cfg.mode ? cfg.mode : 'off';

  if (mode === 'off' || !cfg || cfg.enabled === false) return 'noop';

  if (mode === 'warn') {
    // 仅记录，不拒绝
    try {
      const entry = {
        ts: new Date().toISOString(),
        type: 'failmode.violation',
        hook: hookName,
        ctxMessage: ctx && ctx.message ? String(ctx.message).slice(0, 200) : null,
        mode: 'warn',
      };
      fs.appendFileSync(EVOLUTION_LOG, JSON.stringify(entry) + '\n');
    } catch (_) { /* best effort */ }
    return 'warn';
  }

  if (mode === 'enforce') {
    try {
      const entry = {
        ts: new Date().toISOString(),
        type: 'failmode.rejected',
        hook: hookName,
        ctxMessage: ctx && ctx.message ? String(ctx.message).slice(0, 200) : null,
        mode: 'enforce',
      };
      fs.appendFileSync(EVOLUTION_LOG, JSON.stringify(entry) + '\n');
    } catch (_) {}
    return 'reject';
  }

  return 'noop';
}

/**
 * 当前 mode 查询
 */
function getMode() {
  const flags = loadFlags();
  const cfg = flags[FLAG_FEATURE];
  if (!cfg || cfg.enabled === false) return 'off';
  return cfg.mode || 'off';
}

module.exports = { failModeDecide, getMode, __sentinel: 'P1-FAIL-MODE-V1' };