74 lines
2.9 KiB
Prolog
74 lines
2.9 KiB
Prolog
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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Written 2022 by Adrián Arroyo Calle (adrian.arroyocalle@gmail.com)
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Part of Scryer Prolog.
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*/
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/** Make HTTP requests.
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This library contains the predicate `http_open/3` which allows you to perform HTTP(S) calls.
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Useful for making API calls, or parsing websites. It uses Hyper underneath.
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*/
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:- module(http_open, [http_open/3]).
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:- use_module(library(lists)).
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%% http_open(+Address, -Stream, +Options).
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%
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% Yields Stream to read the body of an HTTP reply from Address.
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% Address is a list of characters, and includes the method. Both HTTP
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% and HTTPS are supported.
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%
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% Options supported:
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%
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% * `method(+Method)`: Sets the HTTP method of the call. Method can be `get` (default), `head`, `delete`, `post`, `put` or `patch`.
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% * `data(+Data)`: Data to be sent in the request. Useful for POST, PUT and PATCH operations.
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% * `size(-Size)`: Unifies with the value of the Content-Length header
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% * `request_headers(+RequestHeaders)`: Headers to be used in the request
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% * `headers(-ListHeaders)`: Unifies with a list with all headers returned in the response
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% * `status_code(-Code)`: Unifies with the status code of the request (200, 201, 404, ...)
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%
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% Example:
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%
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% ```
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% ?- http_open("https://www.example.com", S, []), get_n_chars(S, N, HTML).
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% S = '$stream'(0x7fb548001be8), N = 1256, HTML = "<!doctype html>\n<ht ...".
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% ```
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http_open(Address, Response, Options) :-
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parse_http_options(Options, OptionValues),
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( member(method(Method), OptionValues) -> true; Method = get),
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( member(data(Data), OptionValues) -> true; Data = []),
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( member(request_headers(RequestHeaders), OptionValues) -> true; RequestHeaders = ['user-agent'("Scryer Prolog")]),
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( member(status_code(Code), OptionValues) -> true; true),
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( member(headers(Headers), OptionValues) -> true; true),
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( member(size(Size), OptionValues) -> member('content-length'(Size), Headers); true),
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'$http_open'(Address, Response, Method, Code, Data, Headers, RequestHeaders).
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parse_http_options(Options, OptionValues) :-
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maplist(parse_http_options_, Options, OptionValues).
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parse_http_options_(method(Method), method(Method)) :-
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( var(Method) ->
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throw(error(instantiation_error, http_open/3))
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;
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member(Method, [get, post, put, delete, patch, head]) -> true
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;
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throw(error(domain_error(http_option, method(Method)), _))
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).
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parse_http_options_(data(Data), data(Data)) :-
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( var(Data) ->
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throw(error(instantiation_error, http_open/3))
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; true
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).
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parse_http_options_(request_headers(Headers), request_headers(Headers)) :-
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( var(Headers) ->
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throw(error(instantiation_error, http_open/3))
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; true
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).
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parse_http_options_(size(Size), size(Size)).
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parse_http_options_(status_code(Code), status_code(Code)).
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parse_http_options_(headers(Headers), headers(Headers)).
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