:- module(custom_404,
          [ run/1
          ]).
:- use_module(library(http/thread_httpd)).
:- use_module(library(http/http_dispatch)).
:- use_module(library(http/http_header)).
:- use_module(library(http/html_write)).

:- http_handler(/, home, []).

/** <module> Customise the 404 page

Run this demo. Click the missing link.
*/

run(Port) :-
    http_server(http_dispatch, [port(Port)]).

home(_Request) :-
    reply_html_page(title('Custom 404 demo'),
                    ul(li(a(href(i_do_not_exists),
                            'Non existing page')))).

:- multifile http:status_page/3.

http:status_page(not_found(URL), _Context, HTML) :-
    phrase(page([ title('Sorry, no such page')
                ],
                {|html(URL)||
<h1>Sorry, no such page</h1>
<p>I'm afraid you asked for a page we do not have.  Please try the
search box to locate the page you are looking for.
                    |}),
           HTML).