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// Copyright 2022 The Gitea Authors.
// Copyright 2015 https://github.com/unknwon. Licensed under the Apache License, Version 2.0
package paginator
/*
In template:
```html
{{if not .Page.IsFirst}}[First](1){{end}}
{{if .Page.HasPrevious}}[Previous]({{.Page.Previous}}){{end}}
{{range .Page.Pages}}
{{if eq .Num -1}}
...
{{else}}
{{.Num}}{{if .IsCurrent}}(current){{end}}
{{end}}
{{end}}
{{if .Page.HasNext}}[Next]({{.Page.Next}}){{end}}
{{if not .Page.IsLast}}[Last]({{.Page.TotalPages}}){{end}}
```
Output:
```
[First](1) [Previous](2) ... 2 3(current) 4 ... [Next](4) [Last](5)
```
*/
// Paginator represents a set of results of pagination calculations.
type Paginator struct {
total int // total rows count
pagingNum int // how many rows in one page
current int // current page number
numPages int // how many pages to show on the UI
}
// New initialize a new pagination calculation and returns a Paginator as result.
func New(total, pagingNum, current, numPages int) *Paginator {
if pagingNum <= 0 {
pagingNum = 1
}
if current <= 0 {
current = 1
}
p := &Paginator{total, pagingNum, current, numPages}
if p.current > p.TotalPages() {
p.current = p.TotalPages()
}
return p
}
// IsFirst returns true if current page is the first page.
func (p *Paginator) IsFirst() bool {
return p.current == 1
}
// HasPrevious returns true if there is a previous page relative to current page.
func (p *Paginator) HasPrevious() bool {
return p.current > 1
}
func (p *Paginator) Previous() int {
if !p.HasPrevious() {
return p.current
}
return p.current - 1
}
// HasNext returns true if there is a next page relative to current page.
func (p *Paginator) HasNext() bool {
return p.total > p.current*p.pagingNum
}
func (p *Paginator) Next() int {
if !p.HasNext() {
return p.current
}
return p.current + 1
}
// IsLast returns true if current page is the last page.
func (p *Paginator) IsLast() bool {
if p.total == 0 {
return true
}
return p.total > (p.current-1)*p.pagingNum && !p.HasNext()
}
// Total returns number of total rows.
func (p *Paginator) Total() int {
return p.total
}
// TotalPages returns number of total pages.
func (p *Paginator) TotalPages() int {
if p.total == 0 {
return 1
}
return (p.total + p.pagingNum - 1) / p.pagingNum
}
// Current returns current page number.
func (p *Paginator) Current() int {
return p.current
}
// PagingNum returns number of page size.
func (p *Paginator) PagingNum() int {
return p.pagingNum
}
// Page presents a page in the paginator.
type Page struct {
num int
isCurrent bool
}
func (p *Page) Num() int {
return p.num
}
func (p *Page) IsCurrent() bool {
return p.isCurrent
}
func getMiddleIdx(numPages int) int {
return (numPages + 1) / 2
}
// Pages returns a list of nearby page numbers relative to current page.
// If value is -1 means "..." that more pages are not showing.
func (p *Paginator) Pages() []*Page {
if p.numPages == 0 {
return []*Page{}
} else if p.numPages == 1 && p.TotalPages() == 1 {
// Only show current page.
return []*Page{{1, true}}
}
// Total page number is less or equal.
if p.TotalPages() <= p.numPages {
pages := make([]*Page, p.TotalPages())
for i := range pages {
pages[i] = &Page{i + 1, i+1 == p.current}
}
return pages
}
numPages := p.numPages
offsetIdx := 0
hasMoreNext := false
// Check more previous and next pages.
previousNum := getMiddleIdx(p.numPages) - 1
if previousNum > p.current-1 {
previousNum -= previousNum - (p.current - 1)
}
nextNum := p.numPages - previousNum - 1
if p.current+nextNum > p.TotalPages() {
delta := nextNum - (p.TotalPages() - p.current)
nextNum -= delta
previousNum += delta
}
offsetVal := p.current - previousNum
if offsetVal > 1 {
numPages++
offsetIdx = 1
}
if p.current+nextNum < p.TotalPages() {
numPages++
hasMoreNext = true
}
pages := make([]*Page, numPages)
// There are more previous pages.
if offsetIdx == 1 {
pages[0] = &Page{-1, false}
}
// There are more next pages.
if hasMoreNext {
pages[len(pages)-1] = &Page{-1, false}
}
// Check previous pages.
for i := 0; i < previousNum; i++ {
pages[offsetIdx+i] = &Page{i + offsetVal, false}
}
pages[offsetIdx+previousNum] = &Page{p.current, true}
// Check next pages.
for i := 1; i <= nextNum; i++ {
pages[offsetIdx+previousNum+i] = &Page{p.current + i, false}
}
return pages
}
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