package templ

import (
	"errors"
	"strings"
)

// FailedSanitizationURL is returned if a URL fails sanitization checks.
const FailedSanitizationURL = SafeURL("about:invalid#TemplFailedSanitizationURL")

// URL sanitizes the input string s and returns a SafeURL.
func URL(s string) SafeURL {
	if i := strings.IndexRune(s, ':'); i >= 0 && !strings.ContainsRune(s[:i], '/') {
		protocol := s[:i]
		if !strings.EqualFold(protocol, "http") && !strings.EqualFold(protocol, "https") && !strings.EqualFold(protocol, "mailto") && !strings.EqualFold(protocol, "tel") && !strings.EqualFold(protocol, "ftp") && !strings.EqualFold(protocol, "ftps") {
			return FailedSanitizationURL
		}
	}
	return SafeURL(s)
}

// SafeURL is a URL that has been sanitized.
type SafeURL string

// JoinURLErrs joins an optional list of errors and returns a sanitized SafeURL.
func JoinURLErrs[T ~string](s T, errs ...error) (SafeURL, error) {
	if safeURL, ok := any(s).(SafeURL); ok {
		return safeURL, errors.Join(errs...)
	}
	return URL(string(s)), errors.Join(errs...)
}