const { BillPayment, Bill } = require('../models');
const { Op } = require('sequelize');

// 获取账单的所有支付流水
const getPaymentsByBillId = async (req, res) => {
  try {
    const { billId } = req.params;
    const tenantId = req.user.tenantId;

    const payments = await BillPayment.findAll({
      where: {
        billId,
        tenantId,
        isDeleted: 0
      },
      order: [['paymentTime', 'DESC']]
    });

    res.status(200).json({
      code: 200,
      data: payments,
      message: 'success'
    });
  } catch (error) {
    console.error('获取支付流水失败:', error);
    res.status(500).json({ code: 500, error: error.message });
  }
};

// 创建支付流水（收款）
const createPayment = async (req, res) => {
  try {
    const { billId } = req.params;
    const { amount, paymentMethod, paymentTime, transactionNo, remark } = req.body;
    const tenantId = req.user.tenantId;
    const createBy = req.user.id;

    // 查找账单
    const bill = await Bill.findOne({
      where: { id: billId, tenantId, isDeleted: 0 }
    });

    if (!bill) {
      return res.status(404).json({ code: 404, error: '账单不存在' });
    }

    if (bill.status === 'paid') {
      return res.status(400).json({ code: 400, error: '该账单已收清，无法继续收款' });
    }

    if (bill.status === 'cancelled') {
      return res.status(400).json({ code: 400, error: '该账单已取消，无法收款' });
    }

    // 计算剩余应收金额
    const receivableAmount = parseFloat(bill.receivableAmount);
    const currentReceived = parseFloat(bill.receivedAmount || 0);
    const remainingAmount = receivableAmount - currentReceived;

    // 验证支付金额
    const paymentAmount = parseFloat(amount);
    if (paymentAmount <= 0) {
      return res.status(400).json({ code: 400, error: '支付金额必须大于0' });
    }

    if (paymentAmount > remainingAmount) {
      return res.status(400).json({
        code: 400,
        error: `支付金额不能超过剩余应收金额 ¥${remainingAmount.toFixed(2)}`
      });
    }

    // 创建支付流水
    const payment = await BillPayment.create({
      billId,
      amount: paymentAmount,
      paymentMethod,
      paymentTime: paymentTime || new Date(),
      transactionNo: transactionNo || null,
      remark: remark || null,
      tenantId,
      createBy,
      isDeleted: 0
    });

    // 更新账单的已收金额和状态
    const newReceivedAmount = currentReceived + paymentAmount;
    let newStatus = bill.status;

    if (newReceivedAmount >= receivableAmount) {
      newStatus = 'paid';
    } else if (newReceivedAmount > 0) {
      newStatus = 'partial';
    }

    await bill.update({
      receivedAmount: newReceivedAmount,
      status: newStatus,
      updateBy: createBy
    });

    res.status(201).json({
      code: 201,
      data: {
        payment,
        bill: {
          id: bill.id,
          receivedAmount: newReceivedAmount,
          status: newStatus
        }
      },
      message: '收款成功'
    });
  } catch (error) {
    console.error('创建支付流水失败:', error);
    res.status(500).json({ code: 500, error: error.message });
  }
};

// 删除支付流水（退款/撤销）
const deletePayment = async (req, res) => {
  try {
    const { id } = req.params;
    const tenantId = req.user.tenantId;
    const updateBy = req.user.id;

    const payment = await BillPayment.findOne({
      where: { id, tenantId, isDeleted: 0 }
    });

    if (!payment) {
      return res.status(404).json({ code: 404, error: '支付流水不存在' });
    }

    // 查找关联账单
    const bill = await Bill.findOne({
      where: { id: payment.billId, tenantId, isDeleted: 0 }
    });

    if (!bill) {
      return res.status(404).json({ code: 404, error: '关联账单不存在' });
    }

    // 软删除支付流水
    await payment.update({ isDeleted: 1 });

    // 重新计算账单的已收金额和状态
    const remainingPayments = await BillPayment.findAll({
      where: {
        billId: bill.id,
        tenantId,
        isDeleted: 0
      }
    });

    const newReceivedAmount = remainingPayments.reduce((sum, p) => {
      return sum + parseFloat(p.amount);
    }, 0);

    let newStatus = 'unpaid';
    if (newReceivedAmount >= parseFloat(bill.receivableAmount)) {
      newStatus = 'paid';
    } else if (newReceivedAmount > 0) {
      newStatus = 'partial';
    }

    await bill.update({
      receivedAmount: newReceivedAmount,
      status: newStatus,
      updateBy
    });

    res.status(200).json({
      code: 200,
      data: {
        bill: {
          id: bill.id,
          receivedAmount: newReceivedAmount,
          status: newStatus
        }
      },
      message: '支付流水已删除，账单状态已更新'
    });
  } catch (error) {
    console.error('删除支付流水失败:', error);
    res.status(500).json({ code: 500, error: error.message });
  }
};

// 获取支付流水统计
const getPaymentStatistics = async (req, res) => {
  try {
    const tenantId = req.user.tenantId;
    const { startDate, endDate } = req.query;

    const where = {
      tenantId,
      isDeleted: 0
    };

    if (startDate && endDate) {
      where.paymentTime = {
        [Op.between]: [new Date(startDate), new Date(endDate)]
      };
    }

    const payments = await BillPayment.findAll({
      where,
      attributes: ['paymentMethod', [sequelize.fn('SUM', sequelize.col('amount')), 'totalAmount'], [sequelize.fn('COUNT', sequelize.col('id')), 'count']],
      group: ['paymentMethod']
    });

    res.status(200).json({
      code: 200,
      data: payments,
      message: 'success'
    });
  } catch (error) {
    console.error('获取支付统计失败:', error);
    res.status(500).json({ code: 500, error: error.message });
  }
};

module.exports = {
  getPaymentsByBillId,
  createPayment,
  deletePayment,
  getPaymentStatistics
};