const { query, transaction } = require('../config/database')
const { paginate } = require('../utils/pagination')

async function ensureStockLogTable() {
  await query(`
    CREATE TABLE IF NOT EXISTS stock_logs (
      id INT NOT NULL AUTO_INCREMENT,
      goods_id INT NOT NULL,
      change_type VARCHAR(20) NOT NULL COMMENT 'inbound/adjust/purchase/sale',
      delta INT NOT NULL,
      quantity_after INT NOT NULL,
      operator_id INT,
      remark VARCHAR(255),
      created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
      PRIMARY KEY (id),
      KEY goods_id (goods_id),
      KEY created_at (created_at)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='库存流水表'
  `)
}

// 获取库存列表
async function getStockList(ctx) {
  const keyword = ctx.query.keyword
  const threshold = parseInt(ctx.query.threshold) || 0

  let sql = `
    SELECT
      s.id,
      s.goods_id,
      g.name as goods_name,
      g.images as goods_image,
      g.unit as goods_unit,
      s.quantity,
      s.warehouse
    FROM stock s
    LEFT JOIN goods g ON s.goods_id = g.id
    WHERE 1=1
  `
  const params = []

  if (keyword) {
    sql += ' AND (g.name LIKE ? OR g.barcode LIKE ?)'
    params.push(`%${keyword}%`, `%${keyword}%`)
  }

  if (threshold > 0) {
    sql += ' AND s.quantity <= ?'
    params.push(threshold)
  }

  sql += ' ORDER BY s.quantity ASC'

  const result = await paginate(query, sql, params, ctx.query.page, ctx.query.pageSize)

  ctx.body = {
    code: 200,
    ...result
  }
}

// 调整库存
async function adjustStock(ctx) {
  const operator = ctx.state.user
  if (!operator) {
    ctx.status = 401
    ctx.body = { code: 401, message: '未登录' }
    return
  }
  const goodsId = parseInt(ctx.params.id)
  const { quantity, type, remark } = ctx.request.body || {}

  const qty = parseInt(quantity)
  if (!qty || qty <= 0 || qty > 100000) {
    ctx.body = { code: 400, message: '请输入 1-100000 之间的整数' }
    return
  }
  if (type !== 'add' && type !== 'sub') {
    ctx.body = { code: 400, message: 'type 必须是 add 或 sub' }
    return
  }

  await ensureStockLogTable()

  try {
    const newQuantity = await transaction(async (conn) => {
      const [rows] = await conn.execute('SELECT * FROM stock WHERE goods_id = ? FOR UPDATE', [goodsId])
      let current = rows[0]
      if (!current) {
        if (type === 'sub') {
          throw new Error('库存不足，无法减少')
        }
        await conn.execute(
          'INSERT INTO stock (goods_id, quantity, warehouse) VALUES (?, ?, ?)',
          [goodsId, qty, '默认仓库']
        )
        return qty
      }
      const delta = type === 'add' ? qty : -qty
      const next = current.quantity + delta
      if (next < 0) throw new Error('库存不足，无法减少')

      await conn.execute('UPDATE stock SET quantity = ? WHERE goods_id = ?', [next, goodsId])
      await conn.execute(
        'UPDATE goods SET stock = ? WHERE id = ?',
        [Math.max(0, next), goodsId]
      )
      await conn.execute(
        'INSERT INTO stock_logs (goods_id, change_type, delta, quantity_after, operator_id, remark) VALUES (?, ?, ?, ?, ?, ?)',
        [goodsId, 'adjust', delta, next, operator.id, remark || '库存调整']
      )
      return next
    })

    const [updated] = await query('SELECT * FROM stock WHERE goods_id = ?', [goodsId])
    ctx.body = { code: 200, data: updated, message: '库存调整成功', newQuantity }
  } catch (error) {
    ctx.status = 400
    ctx.body = { code: 400, message: error.message || '调整失败' }
  }
}

// 获取单个商品的库存
async function getStockByGoodsId(ctx) {
  const goodsId = ctx.params.id

  const stockRecords = await query('SELECT * FROM stock WHERE goods_id = ?', [goodsId])

  if (stockRecords.length > 0) {
    ctx.body = {
      code: 200,
      data: stockRecords[0]
    }
  } else {
    ctx.body = {
      code: 200,
      data: { goods_id: goodsId, quantity: 0, warehouse: '默认仓库' }
    }
  }
}

module.exports = {
  getStockList,
  adjustStock,
  getStockByGoodsId
}