roese-utils/rspagination/rspagination.go

package rspagination

import (
	"math"

	"gorm.io/gorm"
)

// GetTotalPages returns total pages for pagination
// Example whereQuery = "stock_item_id = ?" and args = stockItemId is Where("stock_item_id = ?", stockItemId)
func GetTotalPages(database *gorm.DB, paginationLimit int, any interface{}, whereQuery interface{}, args ...interface{}) int {
	var totalPages int64

	if whereQuery == nil {
		database.Model(any).
			Count(&totalPages)
	} else if len(args) == 0 { // here used with db.Where(&User{Name: "jinzhu", Age: 20}).First(&user)
		database.Model(any).
			Where(whereQuery).
			Count(&totalPages)
	} else { // here used with "name = ?", "jinzhu"
		database.Model(any).
			Where(whereQuery, args).
			Count(&totalPages)
	}

	return CalculateTotalPages(int(totalPages), paginationLimit)
}

func CalculateTotalPages(totalItems int, paginationLimit int) int {
	return int(math.Ceil(float64(totalItems) / float64(paginationLimit)))
}

func GetPageOffset(page int, paginationLimit int) int {
	return (page - 1) * paginationLimit
}

type PageQuery struct {
	Page int
}

func DbPageQuery(database *gorm.DB, query PageQuery, paginationLimit int, result any, orderBy string, whereQuery interface{}, args ...interface{}) *gorm.DB {
	if whereQuery == nil {
		return database.Limit(paginationLimit).
			Offset(GetPageOffset(query.Page, paginationLimit)).
			Order(orderBy).
			Find(result)
	}

	return database.Limit(paginationLimit).
		Offset(GetPageOffset(query.Page, paginationLimit)).
		Where(whereQuery, args).
		Order(orderBy).
		Find(result)
}

// GetPage returns start and end for pagination
// can be used like this: robots[start:end]
func GetPage(lenList int, page int, limit int) (start int, end int) {
	if page <= 0 {
		page = 1
	}

	start = (page - 1) * limit
	end = page * limit

	if start > lenList {
		start = lenList
	}

	if end > lenList {
		end = lenList
	}

	return start, end
}