func AmountGreaterThan1000(m *gdb.Model) *gdb.Model {
	return m.WhereGT("amount", 1000)
}

func PaidWithCreditCard(m *gdb.Model) *gdb.Model {
	return m.Where("pay_mode_sign", "credit_card")
}

func PaidWithCod(m *gdb.Model) *gdb.Model {
	return m.Where("pay_mode_sign", "cod")
}

func OrderStatus(statuses []string) func(m *gdb.Model) *gdb.Model {
	return func(m *gdb.Model) *gdb.Model {
		return m.Where("status", statuses)
	}
}

var (
	m = g.Model("product_order")
)

m.Handler(AmountGreaterThan1000, PaidWithCreditCard).Scan(&orders)
// SELECT * FROM `product_order` WHERE `amount`>1000 AND `pay_mode_sign`='credit_card'
// 查找所有金额大于 1000 的信用卡订单

m.Handler(AmountGreaterThan1000, PaidWithCod).Scan(&orders)
// SELECT * FROM `product_order` WHERE `amount`>1000 AND `pay_mode_sign`='cod'
// 查找所有金额大于 1000 的 COD 订单

m.Handler(AmountGreaterThan1000, OrderStatus([]string{"paid", "shipped"})).Scan(&orders)
// SELECT * FROM `product_order` WHERE `amount`>1000 AND `status` IN('paid','shipped')
// 查找所有金额大于1000 的已付款或已发货订单

func Paginate(r *ghttp.Request) func(m *gdb.Model) *gdb.Model {
	return func(m *gdb.Model) *gdb.Model {
		type Pagination struct {
			Page int
			Size int
		}
		var pagination Pagination
		_ = r.Parse(&pagination)
		switch {
		case pagination.Size > 100:
			pagination.Size = 100

		case pagination.Size <= 0:
			pagination.Size = 10
		}
		return m.Page(pagination.Page, pagination.Size)
	}
}

m.Handler(Paginate(r)).Scan(&users)
m.Handler(Paginate(r)).Scan(&articles)