oslstats/internal/db/paginate.go

package db

import (
	"net/http"
	"strings"

	"git.haelnorr.com/h/golib/hws"
	"git.haelnorr.com/h/oslstats/internal/validation"
	"github.com/uptrace/bun"
)

type PageOpts struct {
	Page    int
	PerPage int
	Order   bun.Order
	OrderBy string
}

type OrderOpts struct {
	Order   bun.Order
	OrderBy string
	Label   string
}

func GetPageOpts(s *hws.Server, w http.ResponseWriter, r *http.Request) (*PageOpts, bool) {
	var getter validation.Getter
	switch r.Method {
	case "GET":
		getter = validation.NewQueryGetter(r)
	case "POST":
		var ok bool
		getter, ok = validation.ParseFormOrError(s, w, r)
		if !ok {
			return nil, false
		}
	default:
		return nil, false
	}
	return getPageOpts(s, w, r, getter), true
}

func getPageOpts(s *hws.Server, w http.ResponseWriter, r *http.Request, g validation.Getter) *PageOpts {
	page := g.Int("page").Optional().Min(1).Value
	perPage := g.Int("per_page").Optional().Min(1).Max(100).Value
	order := g.String("order").TrimSpace().ToUpper().Optional().AllowedValues([]string{"ASC", "DESC"}).Value
	orderBy := g.String("order_by").TrimSpace().Optional().ToLower().Value
	valid := g.ValidateAndError(s, w, r)
	if !valid {
		return nil
	}
	pageOpts := &PageOpts{
		Page:    page,
		PerPage: perPage,
		Order:   bun.Order(order),
		OrderBy: orderBy,
	}
	return pageOpts
}

func setPageOpts(q *bun.SelectQuery, p, d *PageOpts, totalitems int) (*bun.SelectQuery, *PageOpts) {
	if p == nil {
		p = new(PageOpts)
	}
	if p.Page <= 0 {
		p.Page = d.Page
	}
	if p.PerPage == 0 {
		p.PerPage = d.PerPage
	}
	maxpage := p.TotalPages(totalitems)
	if p.Page > maxpage && maxpage > 0 {
		p.Page = maxpage
	}
	if p.Order == "" {
		p.Order = d.Order
	}
	if p.OrderBy == "" {
		p.OrderBy = d.OrderBy
	}
	p.OrderBy = sanitiseOrderBy(p.OrderBy)
	q = q.OrderBy(p.OrderBy, p.Order).
		Limit(p.PerPage).
		Offset(p.PerPage * (p.Page - 1))
	return q, p
}

func sanitiseOrderBy(orderby string) string {
	result := strings.ToLower(orderby)
	var builder strings.Builder
	for _, r := range result {
		if isValidChar(r) {
			builder.WriteRune(r)
		}
	}
	sanitized := builder.String()

	if sanitized == "" {
		return "_"
	}

	if !isValidFirstChar(rune(sanitized[0])) {
		sanitized = "_" + sanitized
	}

	if len(sanitized) > 63 {
		sanitized = sanitized[:63]
	}

	return sanitized
}

func isValidChar(r rune) bool {
	return (r >= 'a' && r <= 'z') ||
		(r >= '0' && r <= '9') ||
		r == '_'
}

func isValidFirstChar(r rune) bool {
	return (r >= 'a' && r <= 'z') || r == '_'
}

// TotalPages calculates the total number of pages
func (p *PageOpts) TotalPages(total int) int {
	if p.PerPage == 0 {
		return 0
	}
	pages := total / p.PerPage
	if total%p.PerPage > 0 {
		pages++
	}
	return pages
}

// HasPrevPage checks if there is a previous page
func (p *PageOpts) HasPrevPage() bool {
	return p.Page > 1
}

// HasNextPage checks if there is a next page
func (p *PageOpts) HasNextPage(total int) bool {
	return p.Page < p.TotalPages(total)
}

// GetPageRange returns an array of page numbers to display
// maxButtons controls how many page buttons to show
func (p *PageOpts) GetPageRange(total int, maxButtons int) []int {
	totalPages := p.TotalPages(total)
	if totalPages == 0 {
		return []int{}
	}

	// If total pages is less than max buttons, show all pages
	if totalPages <= maxButtons {
		pages := make([]int, totalPages)
		for i := range totalPages {
			pages[i] = i + 1
		}
		return pages
	}

	// Calculate range around current page
	halfButtons := maxButtons / 2
	start := p.Page - halfButtons
	end := p.Page + halfButtons

	// Adjust if at beginning
	if start < 1 {
		start = 1
		end = maxButtons
	}

	// Adjust if at end
	if end > totalPages {
		end = totalPages
		start = totalPages - maxButtons + 1
	}

	pages := make([]int, 0, maxButtons)
	for i := start; i <= end; i++ {
		pages = append(pages, i)
	}
	return pages
}

// StartItem returns the number of the first item on the current page
func (p *PageOpts) StartItem() int {
	if p.Page < 1 {
		return 0
	}
	return (p.Page-1)*p.PerPage + 1
}

// EndItem returns the number of the last item on the current page
func (p *PageOpts) EndItem(total int) int {
	end := p.Page * p.PerPage
	if end > total {
		return total
	}
	return end
}