package crawl

import (
	"net/url"
	"strconv"
	"strings"
)

// The thresholds of the rendered comparison (P33-55): text counts as
// added by JavaScript when the rendered page has at least growthWords more
// words and growthShare more than the raw HTML.
const (
	growthWords   = 50
	growthShare   = 0.2
	maxJSOnlyURLs = 5
)

// compareRendered compares a page's raw HTML with its JavaScript-rendered
// DOM (D-70, P33-55; pure): same-host links, an H1 or a substantial amount
// of text that appear only after JavaScript are one content_js finding
// with details.check rendered and details.what naming them. hosts are the
// site host and its www twin. An identical rendering finds nothing.
func compareRendered(raw, rendered *PageFacts, hosts []string) []Finding {
	if raw == nil || rendered == nil {
		return nil
	}
	same := func(u *url.URL) (string, bool) {
		if u == nil {
			return "", false
		}
		host := strings.ToLower(u.Hostname())
		for _, h := range hosts {
			if host == h {
				p := u.EscapedPath()
				if p == "" {
					p = "/"
				}
				if u.RawQuery != "" {
					p += "?" + u.RawQuery
				}
				return p, true
			}
		}
		return "", false
	}
	before := map[string]bool{}
	for _, l := range raw.Links {
		if k, ok := same(l.URL); ok {
			before[k] = true
		}
	}
	var added []string
	seen := map[string]bool{}
	for _, l := range rendered.Links {
		k, ok := same(l.URL)
		if !ok || before[k] || seen[k] {
			continue
		}
		seen[k] = true
		added = append(added, k)
	}
	details := map[string]any{}
	var what []string
	if len(added) > 0 {
		shown := added
		if len(shown) > maxJSOnlyURLs {
			shown = shown[:maxJSOnlyURLs]
		}
		details["links"] = shown
		what = append(what, "links "+strings.Join(shown, ", "))
	}
	if len(raw.H1()) == 0 {
		if h1 := rendered.H1(); len(h1) > 0 {
			details["h1"] = h1[0]
			what = append(what, "H1 “"+h1[0]+"”")
		}
	}
	if grow := rendered.Words - raw.Words; grow >= growthWords && float64(grow) >= growthShare*float64(raw.Words) {
		details["words_raw"] = raw.Words
		details["words_rendered"] = rendered.Words
		what = append(what, strconv.Itoa(grow)+" words of text")
	}
	if len(what) == 0 {
		return nil
	}
	return []Finding{{Kind: KindContentJS, Check: checkRendered, Details: details, What: strings.Join(what, "; ")}}
}

// The two content_js checks: the raw HTML against the CMS record, and the
// raw HTML against the JavaScript-rendered DOM.
const (
	checkCMS      = "cms"
	checkRendered = "rendered"
)

// parseURL parses an absolute or site-relative address.
func parseURL(raw string) (*url.URL, error) { return url.Parse(strings.TrimSpace(raw)) }