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// Copyright 2015 Unknwon
//
// Licensed under the Apache License, Version 2.0 (the "License"): you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations
// under the License.
// Package paginater is a helper module for custom pagination calculation.
package paginater
// Paginater represents a set of results of pagination calculations.
type Paginater struct {
total int
pagingNum int
current int
numPages int
}
// New initialize a new pagination calculation and returns a Paginater as result.
func New(total, pagingNum, current, numPages int) *Paginater {
if pagingNum <= 0 {
pagingNum = 1
}
if current <= 0 {
current = 1
}
p := &Paginater{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 *Paginater) IsFirst() bool {
return p.current == 1
}
// HasPrevious returns true if there is a previous page relative to current page.
func (p *Paginater) HasPrevious() bool {
return p.current > 1
}
func (p *Paginater) 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 *Paginater) HasNext() bool {
return p.total > p.current*p.pagingNum
}
func (p *Paginater) Next() int {
if !p.HasNext() {
return p.current
}
return p.current + 1
}
// IsLast returns true if current page is the last page.
func (p *Paginater) 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 *Paginater) Total() int {
return p.total
}
// TotalPage returns number of total pages.
func (p *Paginater) TotalPages() int {
if p.total == 0 {
return 1
}
if p.total%p.pagingNum == 0 {
return p.total / p.pagingNum
}
return p.total/p.pagingNum + 1
}
// Current returns current page number.
func (p *Paginater) Current() int {
return p.current
}
// Page presents a page in the paginater.
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 {
if numPages%2 == 0 {
return numPages / 2
}
return numPages/2 + 1
}
// 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 *Paginater) 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
maxIdx := numPages - 1
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++
maxIdx++
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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