Example Hello

Jan Burse, created Feb 24. 2019
* Prolog code for the multimedia hello HTTP server.
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:- package(library(example04)).
:- module(hello, []).
:- reexport(library(misc/http)).
* dispatch(O, P, R, S):
* The predicate succeeds in dispatching the request for object
* O, with path P, with request R and the socket S.
% dispatch(+Object, +Spec, +Request, +Socket)
:- override dispatch/4.
:- public dispatch/4.
dispatch(_, '/example04/piglet.gif', Request, Session) :- !,
dispatch_binary(library(example04/piglet), Request, Session).
dispatch(_, '/example04/hello.jsp', Request, Session) :- !,
dispatch_hello(Request, Session).
dispatch(Object, Spec, Request, Session) :-
misc/http:dispatch(Object, Spec, Request, Session).
% dispatch_hello(+Request, +Socket)
:- private dispatch_hello/2.
dispatch_hello(Request, Session) :-
http_parameter(Request, name, Name), !,
catch(handle_hello(Name, Session), _, true).
dispatch_hello(_, Session) :-
dispatch_error(415, Session).
% handle_hello(+Atom, +Socket)
:- private handle_hello/2.
handle_hello(Name, Session) :-
open(Session, write, Response),
send_hello(Name, Response),
% send_hello(+Atom, +Socket)
:- private send_hello/2.
send_hello(Name, Response) :-
response_text(200, ['Content-Type'-'text/html; charset=UTF-8'], Response),
atom_split(Title, ' ', ['Hello',Name]),
html_begin(Response, Title),
write(Response, ' <center><img src="piglet.gif">\r\n'),
write(Response, '<h1>Happy New Year 2019, '),
html_escape(Response, Name),
write(Response, '</h1></center>\r\n'),
% html_begin(+Stream, +Atom)
:- private html_begin/2.
html_begin(Response, Title) :-
write(Response, '<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">\r\n'),
write(Response, '<html>\r\n'),
write(Response, ' <head>\r\n'),
write(Response, ' <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">\r\n'),
write(Response, ' <meta name="viewport" content="width=device-width, initial-scale=1.0">\r\n'),
write(Response, ' <title>'),
html_escape(Response, Title),
write(Response, '</title>\r\n'),
write(Response, ' </head>\r\n'),
write(Response, ' <body>\r\n').
% html_end(+Stream)
:- private html_end/1.
html_end(Response) :-
write(Response, ' </body>\r\n'),
write(Response, '</html>\r\n').
% ?- run_http(example04/hello, 8085), write('.'), flush_output, fail; true.
% Point browser to: http://localhost:8085/example04/hello.jsp?name=Fritz