/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Written 2022 by Adrián Arroyo Calle (adrian.arroyocalle@gmail.com) Part of Scryer Prolog. */ /** Make HTTP requests. This library contains the predicate `http_open/3` which allows you to perform HTTP(S) calls. Useful for making API calls, or parsing websites. It uses Hyper underneath. */ :- module(http_open, [http_open/3]). :- use_module(library(lists)). %% 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://www.example.com", S, []), get_n_chars(S, N, HTML). % S = '$stream'(0x7fb548001be8), N = 1256, HTML = "\n true; Method = get), ( member(data(Data), OptionValues) -> true; Data = []), ( member(request_headers(RequestHeaders), OptionValues) -> true; RequestHeaders = ['user-agent'("Scryer Prolog")]), ( member(status_code(Code), OptionValues) -> true; true), ( member(headers(Headers), OptionValues) -> true; true), ( member(size(Size), OptionValues) -> member('content-length'(Size), Headers); true), '$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)).