// routes/contracts.js —— 合同管理 CRUD
const { pool } = require('../db')

function pagination(query) {
  const page = Math.max(Number(query.page) || 1, 1)
  const pageSize = Math.min(Math.max(Number(query.pageSize) || 10, 1), 100)
  const offset = (page - 1) * pageSize
  return { page, pageSize, offset }
}

// 列表查询时 JOIN 客户名和员工名
const LIST_SELECT = `
  SELECT
    c.*,
    cu.name AS customer_name,
    e.name  AS employee_name
  FROM contracts c
    LEFT JOIN customers cu ON c.customer_id = cu.id
    LEFT JOIN employees e  ON c.employee_id = e.id
`

// 单条查询时用同样的 JOIN
const DETAIL_SELECT = LIST_SELECT

// GET /api/contracts —— 列表
async function list(req, res) {
  try {
    const { page, pageSize, offset } = pagination(req.query)
    const { status, customer_name, contract_no, employee_name } = req.query

    let where = 'WHERE 1=1'
    const params = []

    if (status) {
      where += ' AND c.status = ?'
      params.push(status)
    }
    if (customer_name) {
      where += ' AND cu.name LIKE ?'
      params.push(`%${customer_name}%`)
    }
    if (contract_no) {
      where += ' AND c.contract_no LIKE ?'
      params.push(`%${contract_no}%`)
    }
    if (employee_name) {
      where += ' AND e.name LIKE ?'
      params.push(`%${employee_name}%`)
    }

    const [[{ total }]] = await pool.query(
      `SELECT COUNT(*) AS total FROM contracts c
         LEFT JOIN customers cu ON c.customer_id = cu.id
         LEFT JOIN employees e  ON c.employee_id = e.id
       ${where}`,
      params
    )

    const [rows] = await pool.query(
      `${LIST_SELECT} ${where} ORDER BY c.id DESC LIMIT ? OFFSET ?`,
      [...params, pageSize, offset]
    )

    res.json({
      code: 0,
      message: 'ok',
      data: {
        list: rows,
        total,
        page,
        pageSize,
        totalPages: Math.ceil(total / pageSize),
      },
    })
  } catch (e) {
    console.error('[contracts list] error:', e)
    res.status(500).json({ code: 500, message: e.message })
  }
}

// GET /api/contracts/:id —— 详情
async function detail(req, res) {
  try {
    const [rows] = await pool.query(
      `${DETAIL_SELECT} WHERE c.id = ?`,
      [req.params.id]
    )
    if (rows.length === 0) {
      return res.status(404).json({ code: 404, message: '合同不存在' })
    }
    res.json({ code: 0, message: 'ok', data: rows[0] })
  } catch (e) {
    console.error('[contracts detail] error:', e)
    res.status(500).json({ code: 500, message: e.message })
  }
}

// POST /api/contracts —— 新增
async function create(req, res) {
  const {
    customer_id, contract_name, contract_no, contract_content,
    amount, effective_date, expiry_date, employee_id, status, remark,
  } = req.body || {}

  if (!customer_id) {
    return res.status(400).json({ code: 400, message: '客户ID必填' })
  }
  if (!contract_name) {
    return res.status(400).json({ code: 400, message: '合同名称必填' })
  }

  try {
    // 校验客户是否存在
    const [cust] = await pool.query('SELECT id FROM customers WHERE id = ?', [customer_id])
    if (cust.length === 0) {
      return res.status(400).json({ code: 400, message: '关联客户不存在' })
    }
    // 校验业务员（如果填了）
    if (employee_id) {
      const [emp] = await pool.query('SELECT id FROM employees WHERE id = ?', [employee_id])
      if (emp.length === 0) {
        return res.status(400).json({ code: 400, message: '关联业务员不存在' })
      }
    }

    const [result] = await pool.query(
      `INSERT INTO contracts
         (customer_id, contract_name, contract_no, contract_content, amount, effective_date, expiry_date, employee_id, status, remark)
       VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
      [customer_id, contract_name,
        contract_no || null,
        contract_content || null,
        amount !== undefined ? amount : null,
        effective_date || null,
        expiry_date || null,
        employee_id || null,
        status || '生效',
        remark || null]
    )

    const [rows] = await pool.query(`${DETAIL_SELECT} WHERE c.id = ?`, [result.insertId])
    res.json({ code: 0, message: 'ok', data: rows[0] })
  } catch (e) {
    console.error('[contracts create] error:', e)
    res.status(500).json({ code: 500, message: e.message })
  }
}

// PUT /api/contracts/:id —— 更新
async function update(req, res) {
  const { id } = req.params
  const fields = [
    'customer_id', 'contract_name', 'contract_no', 'contract_content',
    'amount', 'effective_date', 'expiry_date', 'employee_id', 'status', 'remark',
  ]

  try {
    const [existing] = await pool.query('SELECT id FROM contracts WHERE id = ?', [id])
    if (existing.length === 0) {
      return res.status(404).json({ code: 404, message: '合同不存在' })
    }

    // 如果更新了 customer_id 或 employee_id，需要校验
    if (req.body.customer_id) {
      const [cust] = await pool.query('SELECT id FROM customers WHERE id = ?', [req.body.customer_id])
      if (cust.length === 0) {
        return res.status(400).json({ code: 400, message: '关联客户不存在' })
      }
    }
    if (req.body.employee_id) {
      const [emp] = await pool.query('SELECT id FROM employees WHERE id = ?', [req.body.employee_id])
      if (emp.length === 0) {
        return res.status(400).json({ code: 400, message: '关联业务员不存在' })
      }
    }

    const sets = []
    const params = []
    for (const f of fields) {
      if (req.body[f] !== undefined) {
        sets.push(`${f} = ?`)
        params.push(req.body[f])
      }
    }
    if (sets.length === 0) {
      return res.status(400).json({ code: 400, message: '没有需要更新的字段' })
    }

    params.push(id)
    await pool.query(`UPDATE contracts SET ${sets.join(', ')} WHERE id = ?`, params)

    const [rows] = await pool.query(`${DETAIL_SELECT} WHERE c.id = ?`, [id])
    res.json({ code: 0, message: 'ok', data: rows[0] })
  } catch (e) {
    console.error('[contracts update] error:', e)
    res.status(500).json({ code: 500, message: e.message })
  }
}

// DELETE /api/contracts/:id —— 删除
async function remove(req, res) {
  const { id } = req.params
  try {
    const [existing] = await pool.query('SELECT id FROM contracts WHERE id = ?', [id])
    if (existing.length === 0) {
      return res.status(404).json({ code: 404, message: '合同不存在' })
    }
    await pool.query('DELETE FROM contracts WHERE id = ?', [id])
    res.json({ code: 0, message: 'ok' })
  } catch (e) {
    console.error('[contracts delete] error:', e)
    // 如果因为外键约束（customer_id 被 after_sales 引用）导致删除失败
    if (e.code === 'ER_ROW_IS_REFERENCED_2') {
      return res.status(400).json({ code: 400, message: '该合同关联了售后记录，无法删除' })
    }
    res.status(500).json({ code: 500, message: e.message })
  }
}

module.exports = { list, detail, create, update, remove }