package latest

import (
	"context"
	"errors"
	"fmt"
)

// seriesRead carries the two facts the poll and the acquirer both extract
// from a series page. Persistence, stamps and scheduling stay with the
// callers, so the policies that keep the two flows distinct (stamp order,
// cooldowns) are not swallowed by the module.
type seriesRead struct {
	Latest    latestChapter
	HasLatest bool
	Cover     string
	HasCover  bool
	// BodyLen is the fetched body's length, surfaced because the no-chapter
	// log uses it to tell a markup change from a body the size cap cut short.
	BodyLen int
}

// errNotFetchable and errNoFetcher separate the gate and the route from fetch
// failures so each caller keeps its own distinct log line for all three.
var (
	errNotFetchable = errors.New("series url not fetchable")
	errNoFetcher    = errors.New("no fetcher for site")
)

// readSeriesPage performs the series-page read the poll and the acquirer have
// in common: gate the address, choose the route, fetch the page, extract the
// Latest Chapter and the Cover address. It persists nothing and stamps
// nothing.
//
// series_url arrives in a client-supplied PUT body (PUT /bookmarks/{key}
// accepts any string), so the gate is not an optimisation against burning a
// request on an unknown site: without it, the server would issue a GET from
// its own network position to whatever URL a token-holder writes, including
// link-local/internal addresses or non-https schemes.
func readSeriesPage(ctx context.Context, site, seriesURL string, browser, tls Fetcher) (seriesRead, error) {
	if !fetchableSeriesURL(site, seriesURL) {
		return seriesRead{}, fmt.Errorf("%w: site=%q url=%q", errNotFetchable, site, seriesURL)
	}
	f := fetcherFor(site, browser, tls)
	if f == nil {
		return seriesRead{}, fmt.Errorf("%w: site %q", errNoFetcher, site)
	}
	body, status, err := f.Get(ctx, seriesURL)
	if err != nil {
		return seriesRead{}, fmt.Errorf("fetch %s: %w", seriesURL, err)
	}
	if status != 200 {
		return seriesRead{}, fmt.Errorf("fetch %s: status %d", seriesURL, status)
	}
	latest, hasLatest := latestChapterFrom(site, seriesURL, body)
	cover, hasCover := coverFrom(site, seriesURL, body)
	return seriesRead{Latest: latest, HasLatest: hasLatest, Cover: cover, HasCover: hasCover, BodyLen: len(body)}, nil
}