package page

import (
	"math"
)

// 服务端用

const (
	DefaultPage     = 1
	MinPageSize     = 1
	DefaultPageSize = 10
	MaxPageSize     = 1000
)

type Pagination struct {
	Page      int32 `json:"page"`
	PageSize  int32 `json:"page_size"`
	TotalPage int32 `json:"total_page"`
	Total     int32 `json:"total"`
}

type Integer interface {
	~int | ~int32
}

// 用于对一个切片分页
func PageToSlice[T Integer](page, pageSize, total T) (begin, end T) {
	if page < DefaultPage {
		page = DefaultPage
	}

	if pageSize <= 0 {
		pageSize = DefaultPageSize
	}

	if pageSize <= MinPageSize {
		pageSize = MinPageSize
	}

	if pageSize >= MaxPageSize {
		pageSize = MaxPageSize
	}

	// 计算总页数
	totalPage := (total / pageSize) + 1
	if page > totalPage {
		page = totalPage
	}

	begin = (page - 1) * pageSize
	if total-begin <= pageSize {
		end = total
	} else {
		end = begin + pageSize
	}
	return
}

// 用于分页查询
func PageToOffset[T Integer](page, pageSize T) (offset, limit T) {
	if page < DefaultPage {
		page = DefaultPage
	}

	if pageSize <= 0 {
		pageSize = DefaultPageSize
	}

	if pageSize <= MinPageSize {
		pageSize = MinPageSize
	}

	if pageSize >= MaxPageSize {
		pageSize = MaxPageSize
	}

	offset = (page - 1) * pageSize
	limit = pageSize
	return
}

func CalcPagination[T Integer, E Integer](page, pageSize T, total E) (res Pagination) {
	if page < DefaultPage {
		page = DefaultPage
	}

	if pageSize <= MinPageSize {
		pageSize = MinPageSize
	}

	if pageSize >= MaxPageSize {
		pageSize = MaxPageSize
	}
	res.Page = int32(page)
	res.PageSize = int32(pageSize)
	res.Total = int32(total)

	res.TotalPage = int32(math.Ceil(float64(res.Total) / float64(res.PageSize)))

	return
}