package fa

import (
	"strings"

	"github.com/PuerkitoBio/goquery"
)

// ListingPage is one page of a listing endpoint (Gallery / Scraps /
// Favorites). It carries everything an external caller needs to drive
// pagination by hand: the items, the 1-based page number that produced
// them, and whether FA exposed a "next page" link.
//
// External scrapers that want to manage their own loop (resume from a
// checkpoint, run pages in parallel, throttle differently) should call
// the per-page methods ([Client.GalleryPage], [Client.ScrapsPage],
// [Client.FavoritesPage]) and stop when HasNext is false. Callers that
// just want every item in order should keep using the iter.Seq2-shaped
// methods ([Client.Gallery] et al.), which use the same primitive
// internally.
type ListingPage struct {
	Items   []*Submission
	HasNext bool
	Page    int // 1-based page number this result corresponds to
}

// ListOptions configures the pagination of a simple iterator method like
// [Client.Gallery] or [Client.Notes]. Filtered iterators ([Client.Search],
// [Client.Browse]) use their own option structs that fold the same fields
// in alongside their filter parameters.
//
// Zero values mean "use the SDK defaults": start at page 1, no upper bound
// on pages. Pass [ListOptions{MaxPages: 3}] to bound a crawl.
type ListOptions struct {
	// StartPage is the 1-based page to begin iteration on. Zero or 1 = first
	// page. Useful for resuming after a known-good page.
	StartPage int

	// MaxPages bounds the number of pages the iterator will request before
	// stopping. Zero (the default) = unbounded; iteration stops when FA
	// serves an empty page or omits the "next" link.
	MaxPages int
}

// firstPage returns the effective starting page (≥ 1).
func (o ListOptions) firstPage() int {
	if o.StartPage < 1 {
		return 1
	}
	return o.StartPage
}

// reachedLimit reports whether the iterator has fetched MaxPages pages and
// should stop. Always false when MaxPages is 0 (unbounded).
func (o ListOptions) reachedLimit(pagesFetched int) bool {
	return o.MaxPages > 0 && pagesFetched >= o.MaxPages
}

// detectNextPage returns true if doc shows there is a next page available.
// FA's beta theme renders pagination as either a Next form button or a
// hyperlink with a recognisable label.
func detectNextPage(doc *goquery.Document) bool {
	if doc.Find("form button.button.standard:contains('Next')").Length() > 0 {
		return true
	}
	hit := false
	doc.Find("a.button.standard, a.button-link, a.pagination-next").EachWithBreak(func(_ int, sel *goquery.Selection) bool {
		text := strings.ToLower(trimText(sel))
		if strings.Contains(text, "next") || strings.Contains(text, "older") {
			hit = true
			return false
		}
		return true
	})
	return hit
}