package classes

import (
	"regexp"
	"strings"
)

// The PHP routes.php patterns of the frontend rewrite.
var (
	locElement   = regexp.MustCompile(`<loc>(.*?)</loc>`)
	xhtmlLinkRef = regexp.MustCompile(`(<xhtml:link[^>]*href=")([^"]*)(")`)
)

// Rewrite is the frontend_url rewrite of PHP routes.php: with frontendURL
// set, backendURL is replaced literally (str_replace) inside every loc
// element, inside every xhtml:link href and in the exact stylesheet href.
// Both URLs are right-trimmed of slashes first. An empty frontendURL (or
// "0", which PHP reads as false) leaves xml unchanged.
func Rewrite(xml, backendURL, frontendURL string) string {
	if frontendURL == "" || frontendURL == "0" {
		return xml
	}
	frontend := strings.TrimRight(frontendURL, "/")
	backend := strings.TrimRight(backendURL, "/")
	replace := func(s string) string {
		if backend == "" {
			return s
		}
		return strings.ReplaceAll(s, backend, frontend)
	}
	xml = locElement.ReplaceAllStringFunc(xml, func(m string) string {
		inner := m[len("<loc>") : len(m)-len("</loc>")]
		return "<loc>" + replace(inner) + "</loc>"
	})
	xml = xhtmlLinkRef.ReplaceAllStringFunc(xml, func(m string) string {
		sub := xhtmlLinkRef.FindStringSubmatch(m)
		return sub[1] + replace(sub[2]) + sub[3]
	})
	if backend != "" {
		xml = strings.ReplaceAll(xml, `href="`+backend+`/sitemap.xsl"`, `href="`+frontend+`/sitemap.xsl"`)
	}
	return xml
}

// BackendURL is PHP rtrim(url('/'), '/') for a request whose root URL is
// root: the URL the rewrite replaces.
func BackendURL(root string) string {
	return strings.TrimRight(URLTo(root, "/"), "/")
}