gochat/backend/pkg/pagination/pagination.go

package pagination

import (
	"strconv"

	"github.com/gin-gonic/gin"
)

// DefaultPerPage is the default page size.
// Reference: Chatwoot API default pagination (25 items per page)
const DefaultPerPage = 25
const MaxPerPage = 100

// Params holds pagination parameters extracted from request
type Params struct {
	Page    int
	PerPage int
	Offset  int
}

// Parse extracts pagination params from Gin context query.
// Pattern: Chatwoot controllers use params[:page] and params[:per_page]
func Parse(c *gin.Context) Params {
	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
	perPage, _ := strconv.Atoi(c.DefaultQuery("per_page", strconv.Itoa(DefaultPerPage)))

	if page < 1 {
		page = 1
	}
	if perPage < 1 {
		perPage = DefaultPerPage
	}
	if perPage > MaxPerPage {
		perPage = MaxPerPage
	}

	return Params{
		Page:    page,
		PerPage: perPage,
		Offset:  (page - 1) * perPage,
	}
}

// OffsetToPage converts offset back to page number
func OffsetToPage(offset, perPage int) int {
	if perPage <= 0 {
		return 1
	}
	return (offset / perPage) + 1
}