package responsex

import "math"

type Pagination struct {
	Page       int64 `json:"page"`
	Size       int64 `json:"size"`
	TotalPage  int64 `json:"total_page"`
	TotalCount int64 `json:"total_count"`
}

// 计算DB分页偏移量
// page/size 小于等于 0 时取默认值（page=1，size=10），保证 offset/limit 永远合法
func GetOffset(page, size int) (offset int, limit int) {
	if page <= 0 {
		page = 1
	}
	if size <= 0 {
		// 默认查10条
		size = 10
	}
	offset = (page - 1) * size
	limit = size
	return
}

// 计算响应分页
// size 小于等于 0 时不做除法，避免出现负数总页数
func GetPage(page, size, totalCount int64) Pagination {
	pa := Pagination{}
	var totalPage int64
	if size > 0 {
		totalPage = int64(math.Ceil(float64(totalCount) / float64(size)))
	}
	pa.Page = page
	pa.Size = size
	pa.TotalPage = totalPage
	pa.TotalCount = totalCount
	return pa
}