'use strict';

const crypto = require('crypto');
const { v4: uuidv4 } = require('uuid');

// ─── 常量 ───
const HANDSHAKE_EXPIRE_MS = 5 * 60 * 1000; // 5分钟
const HEARTBEAT_INTERVAL_MS = 30 * 1000;  // 30秒
const CONNECTION_EXPIRE_MS = 24 * 60 * 60 * 1000; // 24小时

// ─── 内存存储 ───
const pendingHandshakes = new Map(); // handshakeId → { initiatorId, targetId, createdAt, tempKey }
const activeConnections = new Map(); // connectionId → { initiatorId, targetId, createdAt, lastHeartbeat, sharedKey }

/**
 * 初始化握手
 * @param {string} initiatorId - 发起方Agent ID
 * @param {string} targetId - 目标Agent ID
 * @param {string} token - 会话token
 * @returns {{handshakeId: string, tempKey: string, expiresAt: string}}
 */
function initiateHandshake(initiatorId, targetId, token) {
  if (!initiatorId || !targetId || !token) {
    throw new Error('缺少必要参数');
  }

  // 验证会话token
  // TODO: 集成现有会话验证系统

  const handshakeId = uuidv4();
  const tempKey = crypto.randomBytes(32).toString('hex');
  const expiresAt = Date.now() + HANDSHAKE_EXPIRE_MS;

  pendingHandshakes.set(handshakeId, {
    initiatorId,
    targetId,
    tempKey,
    createdAt: Date.now(),
    expiresAt
  });

  return {
    handshakeId,
    tempKey,
    expiresAt: new Date(expiresAt).toISOString()
  };
}

/**
 * 完成握手
 * @param {string} handshakeId - 握手ID
 * @param {string} targetId - 目标Agent ID
 * @param {string} targetKey - 目标Agent临时密钥
 * @param {string} token - 会话token
 * @returns {{connectionId: string, sharedKey: string, expiresAt: string}}
 */
function completeHandshake(handshakeId, targetId, targetKey, token) {
  if (!handshakeId || !targetId || !targetKey || !token) {
    throw new Error('缺少必要参数');
  }

  const handshake = pendingHandshakes.get(handshakeId);
  if (!handshake) {
    throw new Error('无效的握手ID');
  }

  if (Date.now() > handshake.expiresAt) {
    pendingHandshakes.delete(handshakeId);
    throw new Error('握手已过期');
  }

  if (handshake.targetId !== targetId) {
    throw new Error('目标Agent不匹配');
  }

  // 验证临时密钥
  if (handshake.tempKey !== targetKey) {
    throw new Error('无效的临时密钥');
  }

  // 生成共享密钥
  const connectionId = uuidv4();
  const sharedKey = crypto.randomBytes(32).toString('hex');
  const expiresAt = Date.now() + CONNECTION_EXPIRE_MS;

  activeConnections.set(connectionId, {
    initiatorId: handshake.initiatorId,
    targetId: handshake.targetId,
    sharedKey,
    createdAt: Date.now(),
    lastHeartbeat: Date.now(),
    expiresAt
  });

  // 清理握手
  pendingHandshakes.delete(handshakeId);

  return {
    connectionId,
    sharedKey,
    expiresAt: new Date(expiresAt).toISOString()
  };
}

/**
 * 心跳检测
 * @param {string} connectionId - 连接ID
 * @param {string} token - 会话token
 * @returns {{alive: boolean, expiresAt: string}}
 */
function heartbeat(connectionId, token) {
  if (!connectionId || !token) {
    throw new Error('缺少必要参数');
  }

  const connection = activeConnections.get(connectionId);
  if (!connection) {
    throw new Error('无效的连接ID');
  }

  if (Date.now() > connection.expiresAt) {
    activeConnections.delete(connectionId);
    throw new Error('连接已过期');
  }

  connection.lastHeartbeat = Date.now();

  return {
    alive: true,
    expiresAt: new Date(connection.expiresAt).toISOString()
  };
}

/**
 * 断开连接
 * @param {string} connectionId - 连接ID
 * @param {string} token - 会话token
 * @returns {{success: boolean}}
 */
function disconnect(connectionId, token) {
  if (!connectionId || !token) {
    throw new Error('缺少必要参数');
  }

  activeConnections.delete(connectionId);
  return { success: true };
}

/**
 * 验证连接
 * @param {string} connectionId - 连接ID
 * @param {string} sharedKey - 共享密钥
 * @returns {{valid: boolean, initiatorId?: string, targetId?: string}}
 */
function validateConnection(connectionId, sharedKey) {
  if (!connectionId || !sharedKey) {
    return { valid: false };
  }

  const connection = activeConnections.get(connectionId);
  if (!connection) {
    return { valid: false };
  }

  if (Date.now() > connection.expiresAt) {
    activeConnections.delete(connectionId);
    return { valid: false };
  }

  if (connection.sharedKey !== sharedKey) {
    return { valid: false };
  }

  return {
    valid: true,
    initiatorId: connection.initiatorId,
    targetId: connection.targetId
  };
}

module.exports = {
  initiateHandshake,
  completeHandshake,
  heartbeat,
  disconnect,
  validateConnection
};