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

function currentUserId(ctx) {
  return ctx.state.user ? ctx.state.user.id : null
}

async function getCart(ctx) {
  const userId = currentUserId(ctx)
  if (!userId) {
    ctx.status = 401
    ctx.body = { code: 401, message: '未登录' }
    return
  }

  const sql = `
    SELECT
      c.id,
      c.goods_id,
      c.quantity,
      c.weight,
      c.selected,
      g.name as goods_name,
      g.price,
      g.unit,
      g.stock,
      g.images,
      g.pricing_type
    FROM carts c
    LEFT JOIN goods g ON c.goods_id = g.id
    WHERE c.user_id = ? AND g.status != 0
  `

  const items = await query(sql, [userId])

  const cartItems = items.map(item => {
    let images = []
    try {
      images = item.images ? JSON.parse(item.images) : []
    } catch {}

    return {
      id: item.goods_id,
      name: item.goods_name,
      price: parseFloat(item.price),
      unit: item.unit,
      stock: item.stock,
      images: images,
      pricingType: item.pricing_type,
      quantity: item.quantity,
      weight: item.weight,
      selected: item.selected === 1
    }
  })

  ctx.body = { code: 200, data: cartItems }
}

async function addToCart(ctx) {
  const userId = currentUserId(ctx)
  if (!userId) {
    ctx.status = 401
    ctx.body = { code: 401, message: '未登录' }
    return
  }
  const { goodsId, quantity, weight } = ctx.request.body || {}

  if (!goodsId) {
    ctx.body = { code: 400, message: '缺少商品ID' }
    return
  }

  const qty = sanitizeInt(quantity, 1, 1, 9999)
  if (qty === null) {
    ctx.body = { code: 400, message: '数量必须是 1-9999 之间的整数' }
    return
  }
  const wgt = weight !== undefined && weight !== null ? parseFloat(weight) : null
  if (wgt !== null && (isNaN(wgt) || wgt < 0)) {
    ctx.body = { code: 400, message: '重量必须为非负数' }
    return
  }

  await transaction(async (conn) => {
    const [rows] = await conn.execute('SELECT * FROM carts WHERE user_id = ? AND goods_id = ? FOR UPDATE', [userId, goodsId])
    if (rows.length > 0) {
      await conn.execute('UPDATE carts SET quantity = quantity + ?, weight = ?, updated_at = NOW() WHERE user_id = ? AND goods_id = ?', [qty, wgt, userId, goodsId])
    } else {
      await conn.execute('INSERT INTO carts (user_id, goods_id, quantity, weight) VALUES (?, ?, ?, ?)', [userId, goodsId, qty, wgt])
    }
  })

  ctx.body = { code: 200, message: '添加成功' }
}

async function updateCartItem(ctx) {
  const userId = currentUserId(ctx)
  if (!userId) {
    ctx.status = 401
    ctx.body = { code: 401, message: '未登录' }
    return
  }
  const { goodsId, quantity, weight, selected } = ctx.request.body || {}

  if (!goodsId) {
    ctx.body = { code: 400, message: '缺少商品ID' }
    return
  }

  const updates = []
  const params = []

  if (quantity !== undefined) {
    const qty = sanitizeInt(quantity, 1, 0, 9999)
    if (qty === null) {
      ctx.body = { code: 400, message: '数量必须是 0-9999 之间的整数' }
      return
    }
    updates.push('quantity = ?')
    params.push(qty)
  }

  if (weight !== undefined) {
    const wgt = weight === null ? null : parseFloat(weight)
    if (wgt !== null && (isNaN(wgt) || wgt < 0)) {
      ctx.body = { code: 400, message: '重量必须为非负数' }
      return
    }
    updates.push('weight = ?')
    params.push(wgt)
  }

  if (selected !== undefined) {
    updates.push('selected = ?')
    params.push(selected ? 1 : 0)
  }

  if (updates.length === 0) {
    ctx.body = { code: 400, message: '没有需要更新的字段' }
    return
  }

  params.push(userId, goodsId)

  const result = await query(
    `UPDATE carts SET ${updates.join(', ')}, updated_at = NOW() WHERE user_id = ? AND goods_id = ?`,
    params
  )

  if (result.affectedRows === 0) {
    ctx.body = { code: 404, message: '购物车中不存在该商品' }
    return
  }
  ctx.body = { code: 200, message: '更新成功' }
}

async function removeFromCart(ctx) {
  const userId = currentUserId(ctx)
  if (!userId) {
    ctx.status = 401
    ctx.body = { code: 401, message: '未登录' }
    return
  }
  const { goodsId } = ctx.request.body || {}

  if (!goodsId) {
    ctx.body = { code: 400, message: '缺少商品ID' }
    return
  }

  await query('DELETE FROM carts WHERE user_id = ? AND goods_id = ?', [userId, goodsId])
  ctx.body = { code: 200, message: '删除成功' }
}

async function clearCart(ctx) {
  const userId = currentUserId(ctx)
  if (!userId) {
    ctx.status = 401
    ctx.body = { code: 401, message: '未登录' }
    return
  }
  await query('DELETE FROM carts WHERE user_id = ?', [userId])
  ctx.body = { code: 200, message: '清空成功' }
}

async function syncCart(ctx) {
  const userId = currentUserId(ctx)
  if (!userId) {
    ctx.status = 401
    ctx.body = { code: 401, message: '未登录' }
    return
  }
  const { cart } = ctx.request.body || {}

  if (!Array.isArray(cart)) {
    ctx.body = { code: 400, message: '购物车数据格式错误' }
    return
  }
  if (cart.length > 100) {
    ctx.body = { code: 400, message: '购物车商品数不能超过 100' }
    return
  }

  await transaction(async (conn) => {
    await conn.execute('DELETE FROM carts WHERE user_id = ?', [userId])
    if (cart.length > 0) {
      const values = cart.map(item => [
        userId,
        item.id || item.goods_id,
        sanitizeInt(item.quantity, 1, 1, 9999) || 1,
        item.weight || null,
        1
      ])
      const placeholders = values.map(() => '(?, ?, ?, ?, ?)').join(', ')
      const flatParams = values.flat()
      await conn.execute(
        `INSERT INTO carts (user_id, goods_id, quantity, weight, selected) VALUES ${placeholders}`,
        flatParams
      )
    }
  })

  ctx.body = { code: 200, message: '同步成功' }
}

module.exports = {
  getCart,
  addToCart,
  updateCartItem,
  removeFromCart,
  clearCart,
  syncCart
}