package page import ( "math" "strconv" "github.com/labstack/echo/v4" ) const ( // DefaultItemsPerPage stores the default amount of items per page DefaultItemsPerPage = 20 // PageQueryKey stores the query key used to indicate the current page PageQueryKey = "page" ) // Pager provides a mechanism to allow a user to page results via a query parameter type Pager struct { // Items stores the total amount of items in the result set Items int // Page stores the current page number Page int // ItemsPerPage stores the amount of items to display per page ItemsPerPage int // Pages stores the total amount of pages in the result set Pages int } // NewPager creates a new Pager func NewPager(ctx echo.Context, itemsPerPage int) Pager { p := Pager{ ItemsPerPage: itemsPerPage, Page: 1, } if page := ctx.QueryParam(PageQueryKey); page != "" { if pageInt, err := strconv.Atoi(page); err == nil { if pageInt > 0 { p.Page = pageInt } } } return p } // SetItems sets the amount of items in total for the pager and calculate the amount // of total pages based off on the item per page. // This should be used rather than setting either items or pages directly. func (p *Pager) SetItems(items int) { p.Items = items p.Pages = int(math.Ceil(float64(items) / float64(p.ItemsPerPage))) if p.Page > p.Pages { p.Page = p.Pages } } // IsBeginning determines if the pager is at the beginning of the pages func (p Pager) IsBeginning() bool { return p.Page == 1 } // IsEnd determines if the pager is at the end of the pages func (p Pager) IsEnd() bool { return p.Page >= p.Pages } // GetOffset determines the offset of the results in order to get the items for // the current page func (p Pager) GetOffset() int { if p.Page == 0 { p.Page = 1 } return (p.Page - 1) * p.ItemsPerPage }