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Merge pull request #59 from recoilme/43-all_posts
pagination
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,138 @@ | ||
| package pagination | ||
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| import ( | ||
| "math" | ||
| ) | ||
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| // Pagination is a general purpose pagination type, it knows how to calculate | ||
| // offset and number of pages. It also contains some utility functions | ||
| // that helps common tasks. One special utility is the PagesStream method | ||
| // that returns a channel to range over for presenting a list of all pages | ||
| // without adding them all to a slice. | ||
| type Pagination struct { | ||
| itemsPerPage int | ||
| numberOfItems int | ||
| currentPage int | ||
| } | ||
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| // New returns a new Pagination with the provided values. | ||
| // The current page is normalized to be inside the bounds | ||
| // of the available pages. So if the current page supplied | ||
| // is less than 1 the current page is normalized as 1, and if | ||
| // it is larger than the number of pages needed its normalized | ||
| // as the last available page. | ||
| func New(numberOfItems, itemsPerPage, currentPage int) *Pagination { | ||
| if currentPage == 0 { | ||
| currentPage = 1 | ||
| } | ||
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| n := int(math.Ceil(float64(numberOfItems) / float64(itemsPerPage))) | ||
| if currentPage > n { | ||
| currentPage = n | ||
| } | ||
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| return &Pagination{ | ||
| itemsPerPage: itemsPerPage, | ||
| numberOfItems: numberOfItems, | ||
| currentPage: currentPage, | ||
| } | ||
| } | ||
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| // PagesStream returns a channel that will be incremented to | ||
| // the available number of pages. Useful to range over when | ||
| // building a list of pages. | ||
| func (p *Pagination) PagesStream() chan int { | ||
| stream := make(chan int) | ||
| go func() { | ||
| for i := 1; i <= p.NumberOfPages(); i++ { | ||
| stream <- i | ||
| } | ||
| close(stream) | ||
| }() | ||
| return stream | ||
| } | ||
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| // Offset calculates the offset into the collection the current page represents. | ||
| func (p *Pagination) Offset() int { | ||
| return (p.CurrentPage() - 1) * p.ItemsPerPage() | ||
| } | ||
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| // NumberOfPages calculates the number of pages needed | ||
| // based on number of items and items per page. | ||
| func (p *Pagination) NumberOfPages() int { | ||
| return int(math.Ceil(float64(p.NumberOfItems()) / float64(p.ItemsPerPage()))) | ||
| } | ||
|
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| // PreviousPage returns the page number of the page before current page. | ||
| // If current page is the first in the list of pages, 1 is returned. | ||
| func (p *Pagination) PreviousPage() int { | ||
| if p.CurrentPage() <= 1 { | ||
| return 1 | ||
| } | ||
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| return p.CurrentPage() - 1 | ||
| } | ||
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| func (p *Pagination) IsFirstPage() bool { | ||
| if p.CurrentPage() <= 1 { | ||
| return true | ||
| } | ||
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| return false | ||
| } | ||
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| func (p *Pagination) IsLastPage() bool { | ||
| if p.CurrentPage() >= p.NumberOfPages() { | ||
| return true | ||
| } | ||
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| return false | ||
| } | ||
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| // NextPage returns the page number of the page after current page. | ||
| // If current page is the last in the list of pages, the last page number is returned. | ||
| func (p *Pagination) NextPage() int { | ||
| if p.CurrentPage() >= p.NumberOfPages() { | ||
| return p.NumberOfPages() | ||
| } | ||
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| return p.CurrentPage() + 1 | ||
| } | ||
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| // IsCurrentPage checks a number to see if it matches the current page. | ||
| func (p *Pagination) IsCurrentPage(page int) bool { | ||
| return p.CurrentPage() == page | ||
| } | ||
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| // Pages returns a list with all page numbers. | ||
| // Eg. [1 2 3 4 5] | ||
| func (p *Pagination) Pages() []int { | ||
| s := make([]int, 0, p.NumberOfPages()) | ||
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| for i := 1; i <= p.NumberOfPages(); i++ { | ||
| s = append(s, i) | ||
| } | ||
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| return s | ||
| } | ||
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| // Show returns true if the pagination should be used. | ||
| // Ie. if there is more than one page. | ||
| func (p *Pagination) Show() bool { | ||
| return p.NumberOfPages() > 1 | ||
| } | ||
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| // CurrentPage returns the current page. | ||
| func (p *Pagination) CurrentPage() int { | ||
| return p.currentPage | ||
| } | ||
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| // NumberOfItems returns the number of items. | ||
| func (p *Pagination) NumberOfItems() int { | ||
| return p.numberOfItems | ||
| } | ||
|
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| // ItemsPerPage returns the number of items to show per page. | ||
| func (p *Pagination) ItemsPerPage() int { | ||
| return p.itemsPerPage | ||
| } |
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