From dbc193ab2a478489067b6871949ce7657f945d48 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Adri=C3=A1n=20Arroyo=20Calle?= <adrian.arroyocalle@gmail.com>
Date: Wed, 9 Dec 2020 23:40:00 +0100
Subject: [PATCH] WIP http_server

---
 src/lib/http/http_server.pl | 98 +++++++++++++++++++++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 src/lib/http/http_server.pl

diff --git a/src/lib/http/http_server.pl b/src/lib/http/http_server.pl
new file mode 100644
index 00000000..c1889cff
--- /dev/null
+++ b/src/lib/http/http_server.pl
@@ -0,0 +1,98 @@
+:- module(http_server, [http_listen/2, sample_handler/1]).
+
+:- use_module(library(sockets)).
+:- use_module(library(dcgs)).
+:- use_module(library(format)).
+:- use_module(library(error)).
+:- use_module(library(charsio)).
+:- use_module(library(lists)).
+
+% TODO
+% - Parse request Headers
+% - Output response Headers
+% - Improve route matching
+% - Long-running socket_server_accept
+% - Cookies?
+% - HTTP Error Codes
+% - Redirections
+% - Improve code quality
+
+http_listen(Port, Handlers) :-
+    must_be(integer, Port),
+    must_be(list, Handlers),
+    once(socket_server_open(Port, Socket)),
+    socket_server_accept(Socket, Client, Stream, [type(text)]),
+    read_header_lines(Stream, Lines),
+    [Request|Headers] = Lines,
+    (
+        phrase(parse_request(Version, Method, Path), Request) -> ( 
+                call_handler(Path, Headers, Handlers, Response),
+                http_response(StatusCode, Body) = Response,
+                format(Stream, "HTTP/1.0 ~d\r\n\r\n~s", [StatusCode, Body])
+            );(
+                format(Stream, "HTTP/1.0 400 Bad Request\r\n\r\n", []) % bad format
+            )
+    ),
+    close(Stream).
+
+call_handler(Path, Headers, Handlers, Response) :-
+    member(http_route(Dcg, Handler), Handlers),
+    phrase(Dcg, Path),!,
+    call(Handler, Response).
+
+call_handler(_, _, _, http_response(404, "Not found")).
+
+parse_request(http_version(Major, Minor), Method, Path) -->
+    method(Method),
+    " ",
+    string_without(" ", Path),
+    " ",
+    "HTTP/",
+    natural(Major),
+    ".",
+    natural(Minor),
+    "\r\n".
+
+method(options) --> "OPTIONS".
+method(get) --> "GET".
+method(head) --> "HEAD".
+method(post) --> "POST".
+method(put) --> "PUT".
+method(delete) --> "DELETE".
+
+string_without(Not, [Char|String]) -->
+    [Char],
+    {
+        \+ member(Char, Not)
+    },
+    string_without(Not, String).
+
+string_without(_, []) -->
+    [].
+
+natural(Nat) -->
+    natural_(NatChars),
+    {
+        number_chars(Nat, NatChars)
+    }.
+
+natural_([Nat|Nats]) -->
+    [Nat],
+    {
+        char_type(Nat, decimal_digit)
+    },
+    natural_(Nats).
+
+natural_([]) -->
+    [].
+
+read_header_lines(Stream, Hs) :-
+        read_line_to_chars(Stream, Cs, []),
+        (   Cs == "" -> Hs = []
+        ;   Cs == "\r\n" -> Hs = []
+        ;   Hs = [Cs|Rest],
+            read_header_lines(Stream, Rest)
+        ).
+
+sample_handler(Response) :-
+    Response = http_response(200, "Hello Prolog friends!").
\ No newline at end of file
-- 
2.54.0