/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   Written 2022 by Adrián Arroyo Calle (adrian.arroyocalle@gmail.com)
   Part of Scryer Prolog.

   http_open(+Address, -Stream, +Options)
   ======================================

   Yields Stream to read the body of an HTTP reply from Address.
   Address is a list of characters, and includes the method. Both HTTP
   and HTTPS are supported.

   Options supported:

     * method(+Method): Sets the HTTP method of the call. Method can be get (default), head, delete, post, put or patch.
     * data(+Data): Data to be sent in the request. Useful for POST, PUT and PATCH operations.
     * size(-Size): Unifies with the value of the Content-Length header
     * request_headers(+RequestHeaders): Headers to be used in the request
     * headers(-ListHeaders): Unifies with a list with all headers returned in the response
     * status_code(-Code): Unifies with the status code of the request (200, 201, 404, ...)

   Example:

       ?- http_open("https://github.com/mthom/scryer-prolog", S, []).
       %@    S = '$stream'(0x7fcfc9e00f00).

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

:- module(http_open, [http_open/3]).

:- use_module(library(lists)).

http_open(Address, Response, Options) :-
    parse_http_options(Options, OptionValues),
    ( member(method(Method), OptionValues) -> true; Method = get),
    ( member(data(Data), OptionValues) -> true; Data = []),
    ( member(request_headers(RequestHeaders), OptionValues) -> true; RequestHeaders = ['user-agent'("Scryer Prolog")]),
    ( member(status_code(Code), OptionValues) -> true; true),
    ( member(headers(Headers), OptionValues) -> true; true),
    ( member(size(Size), OptionValues) -> member('content-length'(Size), Headers); true),
    '$http_open'(Address, Response, Method, Code, Data, Headers, RequestHeaders).

parse_http_options(Options, OptionValues) :-
    maplist(parse_http_options_, Options, OptionValues).

parse_http_options_(method(Method), method(Method)) :-
    (  var(Method) ->
       throw(error(instantiation_error, http_open/3))
    ;
       member(Method, [get, post, put, delete, patch, head]) -> true
    ;
       throw(error(domain_error(http_option, method(Method)), _))
    ).

parse_http_options_(data(Data), data(Data)) :-
    (  var(Data) ->
       throw(error(instantiation_error, http_open/3))
    ;  true
    ).

parse_http_options_(request_headers(Headers), request_headers(Headers)) :-
    (  var(Headers) ->
       throw(error(instantiation_error, http_open/3))
    ;  true
    ).

parse_http_options_(size(Size), size(Size)).
parse_http_options_(status_code(Code), status_code(Code)).
parse_http_options_(headers(Headers), headers(Headers)).