package corelib

type PaginationData struct {
	LeftPages    []int `json:"left_pages"`     // 当前页左边显示
	RightPages   []int `json:"right_pages"`    // 当前页右边
	CurrentPage  int   `json:"current_page"`   // 当前页
	NumPages     int   `json:"num_pages"`      // 总页数
	LeftHasMore  bool  `json:"left_has_more"`  // 左边显示更多
	RightHasMore bool  `json:"right_has_more"` // 右边显示更多
}

// GetPaginationData 分页数据
// numPages 总页数
// currentPage 当前页
// aroundCount 当前页左右两边显示多少个分页按钮
func GetPaginationData(numPages int, currentPage int, aroundCount int) PaginationData {
	// 边缘条件判断
	if currentPage > numPages {
		currentPage = numPages
	}
	if currentPage < 1 {
		currentPage = 1
	}
	// 当前页向左减去around_count后剩下的页数
	leftAroundPages := currentPage - aroundCount
	// 当前页向右减去around_count后剩下的页数
	rightAroundPages := numPages - currentPage - aroundCount + 1
	// 左边还有更多页
	leftHasMore := false
	// 右边还有更多页
	rightHasMore := false
	// 当前页左边显示页码
	var leftPages []int
	// 当前页右边显示页码
	var rightPages []int

	if leftAroundPages <= 1 || currentPage-aroundCount-1 == 1 {
		leftPages = rangeList(1, currentPage-1)
	} else {
		leftHasMore = true
		leftPages = rangeList(leftAroundPages, currentPage-1)
	}

	if rightAroundPages <= 1 || currentPage+aroundCount+1 == numPages {
		rightPages = rangeList(currentPage+1, numPages)
	} else {
		rightHasMore = true
		rightPages = rangeList(currentPage+1, currentPage+aroundCount)
	}
	return PaginationData{
		LeftPages: leftPages, RightPages: rightPages, CurrentPage: currentPage,
		NumPages: numPages, LeftHasMore: leftHasMore, RightHasMore: rightHasMore}
}

// LeftPages RightPages
func rangeList(start int, end int) []int {
	var list []int
	for i := start; i <= end; i++ {
		list = append(list, i)
	}
	if list == nil {
		return []int{}
	}
	return list
}