"use strict";

/**
 * 告警记录存储
 *
 * 告警记录结构：
 * {
 *   id: "alert_xxx",
 *   rule_id: "rule_cpu_critical",
 *   rule_name: "CPU 使用率过高",
 *   device_id: "host_xxx",
 *   device_name: "核心交换机-01",
 *   metric: "cpu_usage",
 *   metric_value: "85",
 *   threshold: "80",
 *   level: "critical",
 *   message: "核心交换机-01 CPU 使用率 85%，超过阈值 80%",
 *   triggered_at: timestamp,
 *   status: "active",
 *   acknowledged_by: null,
 *   acknowledged_at: null,
 *   resolved_at: null,
 *   resolved_reason: null,
 *   note: null,
 * }
 */

const { STORAGE_KEY_ALERT_RECORDS, STORAGE_KEY_ALERT_COUNTERS } = require("./storageKeys.cjs");
const { ALERT_RECORD_STATUS, ALERT_LEVELS } = require("./types.cjs");

const MAX_ALERTS = 2000;

let _alerts = null;
let _counters = null; // 防抖动计数器 { "deviceId_ruleId": count }

function _ensureLoaded(readFn) {
  if (_alerts === null) {
    const raw = readFn(STORAGE_KEY_ALERT_RECORDS);
    _alerts = raw ? _safeParse(raw, []) : [];
  }
  if (_counters === null) {
    const raw = readFn(STORAGE_KEY_ALERT_COUNTERS);
    _counters = raw ? _safeParse(raw, {}) : {};
  }
}

function _safeParse(text, def) {
  try { return JSON.parse(text); }
  catch (e) { return def; }
}

function _saveAlerts(writeFn) {
  if (_alerts.length > MAX_ALERTS) {
    // 只保留最近的
    _alerts = _alerts.sort((a, b) => b.triggered_at - a.triggered_at).slice(0, MAX_ALERTS);
  }
  writeFn(STORAGE_KEY_ALERT_RECORDS, JSON.stringify(_alerts));
}

function _saveCounters(writeFn) {
  writeFn(STORAGE_KEY_ALERT_COUNTERS, JSON.stringify(_counters));
}

// ---------- 告警触发（带防抖动） ----------

/**
 * 处理告警：检查是否满足持续次数，满足则创建/更新告警记录
 * @param {object} device - 设备信息 { device_id, device_name }
 * @param {object} rule - 告警规则
 * @param {number|string} metricValue - 当前指标值
 * @param {boolean} isTriggered - 是否触发（指标值 > 阈值）
 * @returns {object|null} 新创建或恢复的告警记录，无变化则返回 null
 */
function processAlert(readFn, writeFn, device, rule, metricValue, isTriggered) {
  _ensureLoaded(readFn);

  const counterKey = `${device.device_id}_${rule.id}`;
  const activeAlert = _findActiveAlert(device.device_id, rule.id);

  if (isTriggered) {
    // 触发：计数 +1
    _counters[counterKey] = (_counters[counterKey] || 0) + 1;
    _saveCounters(writeFn);

    // 达到持续次数且没有活跃告警 → 创建告警
    if (_counters[counterKey] >= rule.duration && !activeAlert) {
      const alert = _createAlert(device, rule, metricValue);
      _alerts.push(alert);
      _saveAlerts(writeFn);
      return { ...alert, action: "triggered" };
    }

    // 已有活跃告警 → 更新指标值
    if (activeAlert) {
      activeAlert.metric_value = String(metricValue);
      activeAlert.message = _buildMessage(device.device_name, rule, metricValue);
      _saveAlerts(writeFn);
      return { ...activeAlert, action: "updated" };
    }

    return null;
  } else {
    // 未触发：重置计数
    if (_counters[counterKey]) {
      delete _counters[counterKey];
      _saveCounters(writeFn);
    }

    // 有活跃告警 → 自动恢复
    if (activeAlert && activeAlert.status === ALERT_RECORD_STATUS.ACTIVE) {
      activeAlert.status = ALERT_RECORD_STATUS.RESOLVED;
      activeAlert.resolved_at = Date.now();
      activeAlert.resolved_reason = "auto_recover";
      _saveAlerts(writeFn);
      return { ...activeAlert, action: "resolved" };
    }

    return null;
  }
}

function _findActiveAlert(deviceId, ruleId) {
  return _alerts.find(
    (a) =>
      a.device_id === deviceId &&
      a.rule_id === ruleId &&
      (a.status === ALERT_RECORD_STATUS.ACTIVE ||
        a.status === ALERT_RECORD_STATUS.ACKNOWLEDGED)
  );
}

function _createAlert(device, rule, metricValue) {
  return {
    id: `alert_${Date.now()}_${Math.random().toString(36).slice(2, 8)}`,
    rule_id: rule.id,
    rule_name: rule.name,
    device_id: device.device_id,
    device_name: device.device_name || device.device_id,
    metric: rule.metric,
    metric_value: String(metricValue),
    threshold: rule.threshold,
    level: rule.level,
    message: _buildMessage(device.device_name || device.device_id, rule, metricValue),
    triggered_at: Date.now(),
    status: ALERT_RECORD_STATUS.ACTIVE,
    acknowledged_by: null,
    acknowledged_at: null,
    resolved_at: null,
    resolved_reason: null,
    note: null,
  };
}

function _buildMessage(deviceName, rule, metricValue) {
  const unit = rule.metric.includes("_usage") ? "%" : "";
  return `${deviceName} ${rule.name}，当前值 ${metricValue}${unit}，阈值 ${rule.threshold}${unit}`;
}

// ---------- 告警查询 ----------

function listAlerts(readFn, options = {}) {
  _ensureLoaded(readFn);
  let result = [..._alerts];

  if (options.status) {
    result = result.filter((a) => a.status === options.status);
  }
  if (options.level) {
    result = result.filter((a) => a.level === options.level);
  }
  if (options.device_id) {
    result = result.filter((a) => a.device_id === options.device_id);
  }

  return result.sort((a, b) => b.triggered_at - a.triggered_at).slice(0, options.limit || 100);
}

function getActiveAlerts(readFn) {
  return listAlerts(readFn, { status: ALERT_RECORD_STATUS.ACTIVE });
}

function getAlert(readFn, alertId) {
  _ensureLoaded(readFn);
  return _alerts.find((a) => a.id === alertId) || null;
}

// ---------- 告警处理 ----------

function acknowledgeAlert(readFn, writeFn, alertId, operator = "system") {
  _ensureLoaded(readFn);
  const alert = _alerts.find((a) => a.id === alertId);
  if (!alert) return null;

  alert.status = ALERT_RECORD_STATUS.ACKNOWLEDGED;
  alert.acknowledged_by = operator;
  alert.acknowledged_at = Date.now();
  _saveAlerts(writeFn);
  return { ...alert };
}

function resolveAlert(readFn, writeFn, alertId, reason = "manual", operator = "system") {
  _ensureLoaded(readFn);
  const alert = _alerts.find((a) => a.id === alertId);
  if (!alert) return null;

  alert.status = ALERT_RECORD_STATUS.RESOLVED;
  alert.resolved_at = Date.now();
  alert.resolved_reason = reason;
  alert.acknowledged_by = alert.acknowledged_by || operator;
  alert.acknowledged_at = alert.acknowledged_at || Date.now();
  _saveAlerts(writeFn);
  return { ...alert };
}

function closeAlert(readFn, writeFn, alertId, note = "") {
  _ensureLoaded(readFn);
  const alert = _alerts.find((a) => a.id === alertId);
  if (!alert) return null;

  alert.status = ALERT_RECORD_STATUS.CLOSED;
  alert.note = note;
  if (!alert.resolved_at) {
    alert.resolved_at = Date.now();
    alert.resolved_reason = "closed";
  }
  _saveAlerts(writeFn);
  return { ...alert };
}

function updateNote(readFn, writeFn, alertId, note) {
  _ensureLoaded(readFn);
  const alert = _alerts.find((a) => a.id === alertId);
  if (!alert) return null;

  alert.note = note;
  _saveAlerts(writeFn);
  return { ...alert };
}

// ---------- 统计 ----------

function getAlertStats(readFn) {
  _ensureLoaded(readFn);

  const active = _alerts.filter((a) => a.status === ALERT_RECORD_STATUS.ACTIVE);
  return {
    total: _alerts.length,
    active: active.length,
    active_critical: active.filter((a) => a.level === ALERT_LEVELS.CRITICAL).length,
    active_warning: active.filter((a) => a.level === ALERT_LEVELS.WARNING).length,
    active_info: active.filter((a) => a.level === ALERT_LEVELS.INFO).length,
    acknowledged: _alerts.filter((a) => a.status === ALERT_RECORD_STATUS.ACKNOWLEDGED).length,
    resolved: _alerts.filter((a) => a.status === ALERT_RECORD_STATUS.RESOLVED).length,
    closed: _alerts.filter((a) => a.status === ALERT_RECORD_STATUS.CLOSED).length,
  };
}

// ---------- 重置（测试用） ----------
function _resetForTest() {
  _alerts = null;
  _counters = null;
}

module.exports = {
  // 告警触发
  processAlert,
  // 查询
  listAlerts,
  getActiveAlerts,
  getAlert,
  // 处理
  acknowledgeAlert,
  resolveAlert,
  closeAlert,
  updateNote,
  // 统计
  getAlertStats,
  // 内部
  _resetForTest,
};