import { Router, Response } from 'express'
import { randomInt } from 'crypto'
import pool from '../db/connection'
import { AuthRequest } from '../middleware/auth'

const router = Router()

/** 生成 6 位随机邀请码（密码学安全） */
function generateInviteCode(): string {
  const chars = 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789'
  let code = ''
  for (let i = 0; i < 6; i++) {
    code += chars.charAt(randomInt(chars.length))
  }
  return code
}

/** 创建群组 */
router.post('/', async (req: AuthRequest, res: Response) => {
  try {
    const { name } = req.body
    const trimmedName = typeof name === 'string' ? name.trim() : ''
    if (!trimmedName) {
      return res.status(400).json({ code: 40001, message: '群组名称不能为空' })
    }
    if (trimmedName.length > 100) {
      return res.status(400).json({ code: 40001, message: '群组名称不能超过100个字符' })
    }

    // 生成唯一邀请码
    let inviteCode = generateInviteCode()
    let attempts = 0
    while (attempts < 10) {
      const [existing] = await pool.query('SELECT id FROM `groups` WHERE invite_code = ?', [inviteCode])
      if ((existing as any[]).length === 0) break
      inviteCode = generateInviteCode()
      attempts++
    }

    const conn = await pool.getConnection()
    try {
      await conn.beginTransaction()

      const [result] = await conn.query(
        'INSERT INTO `groups` (name, invite_code, created_by) VALUES (?, ?, ?)',
        [trimmedName, inviteCode, req.userId]
      )
      const groupId = (result as any).insertId

      // 创建者自动成为 owner
      await conn.query(
        'INSERT INTO group_members (group_id, user_id, role) VALUES (?, ?, ?)',
        [groupId, req.userId, 'owner']
      )

      await conn.commit()
      res.json({ code: 0, data: { id: groupId, invite_code: inviteCode } })
    } catch (err) {
      await conn.rollback()
      throw err
    } finally {
      conn.release()
    }
  } catch (err) {
    console.error('[Group] POST error:', err)
    res.status(500).json({ code: 50000, message: '服务器错误' })
  }
})

/** 获取用户的群组列表 */
router.get('/', async (req: AuthRequest, res: Response) => {
  try {
    const [rows] = await pool.query(
      `SELECT g.id, g.name, g.invite_code, g.created_by, g.created_at,
              gm.role, gm.nickname as my_nickname,
              (SELECT COUNT(*) FROM group_members WHERE group_id = g.id) as member_count
       FROM \`groups\` g
       INNER JOIN group_members gm ON g.id = gm.group_id AND gm.user_id = ?
       ORDER BY g.created_at DESC`,
      [req.userId]
    )
    res.json({ code: 0, data: rows })
  } catch (err) {
    console.error('[Group] GET error:', err)
    res.status(500).json({ code: 50000, message: '服务器错误' })
  }
})

/** 通过邀请码加入群组 */
router.post('/join', async (req: AuthRequest, res: Response) => {
  try {
    const { invite_code } = req.body
    if (!invite_code || typeof invite_code !== 'string' || invite_code.length > 10) {
      return res.status(400).json({ code: 40001, message: '邀请码无效' })
    }

    const [groupRows] = await pool.query(
      'SELECT id, name FROM `groups` WHERE invite_code = ?',
      [invite_code.toUpperCase()]
    )
    const group = (groupRows as any[])[0]
    if (!group) {
      return res.status(404).json({ code: 40400, message: '邀请码无效' })
    }

    // 使用 INSERT IGNORE 避免并发加入时的竞态条件
    const [result] = await pool.query(
      'INSERT IGNORE INTO group_members (group_id, user_id, role) VALUES (?, ?, ?)',
      [group.id, req.userId, 'member']
    )
    if ((result as any).affectedRows === 0) {
      return res.status(400).json({ code: 40002, message: '你已经是该群组成员' })
    }

    res.json({ code: 0, data: { group_id: group.id, name: group.name } })
  } catch (err) {
    console.error('[Group] join error:', err)
    res.status(500).json({ code: 50000, message: '服务器错误' })
  }
})

/** 退出群组 */
router.post('/:id/leave', async (req: AuthRequest, res: Response) => {
  try {
    const groupId = req.params.id

    // 检查是否是成员
    const [memberRows] = await pool.query(
      'SELECT role FROM group_members WHERE group_id = ? AND user_id = ?',
      [groupId, req.userId]
    )
    const member = (memberRows as any[])[0]
    if (!member) {
      return res.status(404).json({ code: 40400, message: '你不是该群组成员' })
    }

    // owner 不能退出，只能解散
    if (member.role === 'owner') {
      return res.status(400).json({ code: 40003, message: '群主不能退出，请先转让或解散群组' })
    }

    const conn = await pool.getConnection()
    try {
      await conn.beginTransaction()

      // 清除该用户在该群组的记录标签
      await conn.query(
        'UPDATE transactions SET group_id = NULL WHERE user_id = ? AND group_id = ?',
        [req.userId, groupId]
      )

      // 删除成员关系
      await conn.query(
        'DELETE FROM group_members WHERE group_id = ? AND user_id = ?',
        [groupId, req.userId]
      )

      await conn.commit()
      res.json({ code: 0 })
    } catch (err) {
      await conn.rollback()
      throw err
    } finally {
      conn.release()
    }
  } catch (err) {
    console.error('[Group] leave error:', err)
    res.status(500).json({ code: 50000, message: '服务器错误' })
  }
})

/** 解散群组（仅 owner） */
router.delete('/:id', async (req: AuthRequest, res: Response) => {
  try {
    const [groupRows] = await pool.query(
      'SELECT created_by FROM `groups` WHERE id = ?',
      [req.params.id]
    )
    const group = (groupRows as any[])[0]
    if (!group) {
      return res.status(404).json({ code: 40400, message: '群组不存在' })
    }
    if (group.created_by !== req.userId) {
      return res.status(403).json({ code: 40300, message: '仅群主可解散群组' })
    }

    const conn = await pool.getConnection()
    try {
      await conn.beginTransaction()

      // 清除该群组所有记录的标签
      await conn.query('UPDATE transactions SET group_id = NULL WHERE group_id = ?', [req.params.id])

      // 删除群组（CASCADE 自动清理 group_members）
      await conn.query('DELETE FROM `groups` WHERE id = ?', [req.params.id])

      await conn.commit()
      res.json({ code: 0 })
    } catch (err) {
      await conn.rollback()
      throw err
    } finally {
      conn.release()
    }
  } catch (err) {
    console.error('[Group] DELETE error:', err)
    res.status(500).json({ code: 50000, message: '服务器错误' })
  }
})

/** 刷新邀请码（仅 owner） */
router.post('/:id/refresh-code', async (req: AuthRequest, res: Response) => {
  try {
    const groupId = req.params.id

    // 验证是否是群主
    const [groupRows] = await pool.query(
      'SELECT created_by FROM `groups` WHERE id = ?',
      [groupId]
    )
    const group = (groupRows as any[])[0]
    if (!group) {
      return res.status(404).json({ code: 40400, message: '群组不存在' })
    }
    if (group.created_by !== req.userId) {
      return res.status(403).json({ code: 40300, message: '仅群主可刷新邀请码' })
    }

    // 生成新的唯一邀请码
    let inviteCode = generateInviteCode()
    let attempts = 0
    while (attempts < 10) {
      const [existing] = await pool.query('SELECT id FROM `groups` WHERE invite_code = ?', [inviteCode])
      if ((existing as any[]).length === 0) break
      inviteCode = generateInviteCode()
      attempts++
    }

    await pool.query('UPDATE `groups` SET invite_code = ? WHERE id = ?', [inviteCode, groupId])
    res.json({ code: 0, data: { invite_code: inviteCode } })
  } catch (err) {
    console.error('[Group] refresh-code error:', err)
    res.status(500).json({ code: 50000, message: '服务器错误' })
  }
})

/** 获取成员列表 */
router.get('/:id/members', async (req: AuthRequest, res: Response) => {
  try {
    const groupId = req.params.id

    // 验证用户是否是群组成员
    const [memberCheck] = await pool.query(
      'SELECT id FROM group_members WHERE group_id = ? AND user_id = ?',
      [groupId, req.userId]
    )
    if ((memberCheck as any[]).length === 0) {
      return res.status(403).json({ code: 40300, message: '无权访问此群组' })
    }

    const [members] = await pool.query(
      `SELECT gm.user_id, gm.role, gm.created_at as joined_at,
              u.nickname, u.avatar_url
       FROM group_members gm
       LEFT JOIN users u ON gm.user_id = u.id
       WHERE gm.group_id = ?
       ORDER BY gm.role DESC, gm.created_at ASC`,
      [groupId]
    )

    res.json({ code: 0, data: members })
  } catch (err) {
    console.error('[Group] members error:', err)
    res.status(500).json({ code: 50000, message: '服务器错误' })
  }
})

/** 移除成员（仅 owner） */
router.delete('/:id/members/:userId', async (req: AuthRequest, res: Response) => {
  try {
    const groupId = req.params.id
    const targetUserId = Number(req.params.userId)

    // 不能移除自己
    if (targetUserId === req.userId) {
      return res.status(400).json({ code: 40001, message: '不能移除自己' })
    }

    // 验证是否是群主
    const [groupRows] = await pool.query(
      'SELECT created_by FROM `groups` WHERE id = ?',
      [groupId]
    )
    const group = (groupRows as any[])[0]
    if (!group) {
      return res.status(404).json({ code: 40400, message: '群组不存在' })
    }
    if (group.created_by !== req.userId) {
      return res.status(403).json({ code: 40300, message: '仅群主可移除成员' })
    }

    const conn = await pool.getConnection()
    try {
      await conn.beginTransaction()

      // 清除该成员在群组的记录标签
      await conn.query(
        'UPDATE transactions SET group_id = NULL WHERE user_id = ? AND group_id = ?',
        [targetUserId, groupId]
      )

      // 删除成员关系
      await conn.query(
        'DELETE FROM group_members WHERE group_id = ? AND user_id = ?',
        [groupId, targetUserId]
      )

      await conn.commit()
      res.json({ code: 0 })
    } catch (err) {
      await conn.rollback()
      throw err
    } finally {
      conn.release()
    }
  } catch (err) {
    console.error('[Group] remove member error:', err)
    res.status(500).json({ code: 50000, message: '服务器错误' })
  }
})

export default router