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    1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2002-2023, University of Amsterdam,
    7                              VU University Amsterdam
    8			      SWI-Prolog Solutions b.v.
    9    All rights reserved.
   10
   11    Redistribution and use in source and binary forms, with or without
   12    modification, are permitted provided that the following conditions
   13    are met:
   14
   15    1. Redistributions of source code must retain the above copyright
   16       notice, this list of conditions and the following disclaimer.
   17
   18    2. Redistributions in binary form must reproduce the above copyright
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   20       the documentation and/or other materials provided with the
   21       distribution.
   22
   23    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   24    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   25    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   26    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   27    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   28    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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   31    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   33    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   34    POSSIBILITY OF SUCH DAMAGE.
   35*/
   36
   37:- module(http_client,
   38          [ http_get/3,                 % +URL, -Reply, +Options
   39            http_delete/3,              % +URL, -Reply, +Options
   40            http_post/4,                % +URL, +In, -Reply, +Options
   41            http_put/4,                 % +URL, +In, -Reply, +Options
   42            http_patch/4,               % +URL, +In, -Reply, +Options
   43            http_read_data/3,           % +Header, -Data, :Options
   44            http_disconnect/1           % +What
   45          ]).   46:- autoload(http_header,[http_post_data/3]).   47:- autoload(http_stream,[http_chunked_open/3,stream_range_open/3]).   48:- autoload(library(error),[must_be/2]).   49:- autoload(library(lists),[delete/3,select/3]).   50:- autoload(library(memfile),
   51	    [ new_memory_file/1, open_memory_file/4, free_memory_file/1,
   52	      memory_file_to_atom/3, memory_file_to_string/3,
   53	      memory_file_to_codes/3, open_memory_file/3
   54	    ]).   55:- autoload(library(option),
   56	    [option/3,option/2,meta_options/3,select_option/3]).   57:- autoload(library(uri),[uri_query_components/2]).   58:- autoload(library(http/http_open),
   59	    [http_open/3,http_close_keep_alive/1]).   60
   61:- meta_predicate
   62    http_read_data(+, -, :).   63
   64:- multifile
   65    http_convert_data/4,            % http_read_data plugin-hook
   66    http:post_data_hook/3.   67
   68:- predicate_options(http_get/3, 3,
   69                     [ pass_to(http_open:http_open/3, 3),
   70                       pass_to(http_open:http_read_data/3, 3),
   71                       pass_to(http_json:http_read_json/3, 3)
   72                     ]).   73:- predicate_options(http_delete/3, 3, [pass_to(http_get/3, 3)]).   74:- predicate_options(http_post/4, 4, [pass_to(http_get/3, 3)]).   75:- predicate_options(http_put/4, 4, [pass_to(http_post/4, 4)]).   76:- predicate_options(http_read_data/3, 3,
   77                     [ to(any),
   78                       content_type(any),
   79                       form_data(oneof([form,mime])),
   80                       input_encoding(encoding),        % multipart messages
   81                       on_filename(callable),
   82                       module(atom),			% x-prolog data
   83                       variable_names(-list)
   84                     ]).

HTTP client library

This library provides the four basic HTTP client actions: GET, DELETE, POST and PUT. In addition, it provides http_read_data/3, which is used by library(http/http_parameters) to decode POST data in server applications.

This library is based on http_open/3, which opens a URL as a Prolog stream. The reply is processed by http_read_data/3. The following content-types are supported. Options passed to http_get/3 and friends are passed to http_read_data/3, which in turn passes them to the conversion predicates. Support for additional content types can be added by extending the multifile predicate http_client:http_convert_data/4.

'application/x-www-form-urlencoded'
Built in. Converts form-data into a list of Name=Value terms.
'application/x-prolog'
Built in. Reads a single Prolog term.
'multipart/form-data'
Processed if library(http/http_multipart_plugin) is loaded. This format should be used to handle web forms that upload a file.
text/html|text/xml
Processed if library(http/http_sgml_plugin) is loaded. See load_html/3 for details and load_xml/3 for details. The output is often processed using xpath/3.
application/json|application/jsonrequest
Processed if library(http/http_json) is loaded. The option json_object(As) can be used to return a term json(Attributes) (As is term) or a dict (As is dict). */
  118                 /*******************************
  119                 *              GET             *
  120                 *******************************/
 http_get(+URL, -Data, +Options) is det
Get data from a URL server and convert it to a suitable Prolog representation based on the Content-Type header and plugins. This predicate is the common implementation of the HTTP client operations. The predicates http_delete/3, http_post/4 and http_put/4 call this predicate with an appropriate method(+Method) option and ---for http_post/4 and http_put/4--- a post(+Data) option.

Options are passed to http_open/3 and http_read_data/3. Other options:

reply_header(-Fields)
Synonym for headers(Fields) from http_open/3. Provided for backward compatibility. Note that http_version(Major-Minor) is missing in the new version.
  140http_get(URL, Data, Options) :-
  141    headers_option(Options, Options1, Headers),
  142    option(reply_header(Headers), Options, _),
  143    http_open(URL, In, Options1),
  144    delete(Headers, transfer_encoding(_), Headers1),
  145    call_cleanup(
  146        http_read_data(In, Headers1, Data, Options),
  147        close(In)).
  148
  149headers_option(Options, Options1, Headers) :-
  150    option(headers(Headers), Options),
  151    !,
  152    Options1 = Options.
  153headers_option(Options, [headers(Headers)|Options], Headers).
 http_delete(+URL, -Data, +Options) is det
Execute a DELETE method on the server. Arguments are the same as for http_get/3. Typically one should pass the option status_code(-Code) to assess and evaluate the returned status code. Without, codes other than 200 are interpreted as an error.
See also
- Implemented on top of http_get/3.
To be done
- Properly map the 201, 202 and 204 replies.
  166http_delete(URL, Data, Options) :-
  167    http_get(URL, Data, [method(delete)|Options]).
 http_post(+URL, +Data, -Reply, +Options) is det
Issue an HTTP POST request. Data is posted using http_post_data/3. The HTTP server reply is returned in Reply, using the same rules as for http_get/3.
See also
- Implemented on top of http_get/3.
  178http_post(URL, Data, Reply, Options) :-
  179    http_get(URL, Reply,
  180             [ post(Data)
  181             | Options
  182             ]).
 http_put(+URL, +Data, -Reply, +Options)
Issue an HTTP PUT request. Arguments are the same as for http_post/4.
See also
- Implemented on top of http_post/4.
  191http_put(URL, In, Out, Options) :-
  192    http_post(URL, In, Out, [method(put)|Options]).
 http_patch(+URL, +Data, -Reply, +Options)
Issue an HTTP PATCH request. Arguments are the same as for http_post/4.
See also
- Implemented on top of http_post/4.
  201http_patch(URL, In, Out, Options) :-
  202    http_post(URL, In, Out, [method(patch)|Options]).
 http_read_data(+Request, -Data, +Options) is det
Read data from an HTTP connection and convert it according to the supplied to(Format) option or based on the Content-type in the Request. The following options are supported:
to(Format)
Convert data into Format. Values are:
  • stream(+WriteStream)) Append the content of the message to Stream
  • atom Return the reply as an atom
  • string Return the reply as a string
  • codes Return the reply as a list of codes
form_data(AsForm)
input_encoding(+Encoding)
on_filename(:CallBack)
These options are implemented by the plugin library(http/http_multipart_plugin) and apply to processing multipart/form-data content.
content_type(+Type)
Overrule the content-type that is part of Request as a work-around for wrongly configured servers.

Without plugins, this predicate handles

'application/x-www-form-urlencoded'
Converts form-data into a list of Name=Value terms.
'application/x-prolog'
Converts data into a Prolog term.
Arguments:
Request- is a parsed HTTP request as returned by http_read_request/2 or available from the HTTP server's request dispatcher. Request must contain a term input(In) that provides the input stream from the HTTP server.
  242http_read_data(Fields, Data, QOptions) :-
  243    meta_options(is_meta, QOptions, Options),
  244    memberchk(input(In), Fields),
  245    (   catch(http_read_data(In, Fields, Data, Options),
  246              error(Formal,_),
  247              throw(error(Formal, context(_, in_http_request))))
  248    ->  true
  249    ;   throw(error(failed(http_read_data), _))
  250    ).
  251
  252is_meta(on_filename).
  253
  254http_read_data(_In, Fields, Data, _Options) :-
  255    option(status_code(Code), Fields),
  256    no_content_status(Code),
  257    \+ ( option(content_length(Len), Fields),
  258	 Len > 0
  259       ),
  260    !,
  261    Data = ''.
  262http_read_data(In, Fields, Data, Options) :-    % Transfer-encoding: chunked
  263    select(transfer_encoding(chunked), Fields, RestFields),
  264    !,
  265    setup_call_cleanup(
  266        http_chunked_open(In, DataStream, []),
  267        http_read_data(DataStream, RestFields, Data, Options),
  268        close(DataStream)).
  269http_read_data(In, Fields, Data, Options) :-
  270    option(to(X), Options),
  271    !,
  272    (   X = stream(Stream)
  273    ->  (   memberchk(content_length(Bytes), Fields)
  274        ->  copy_stream_data(In, Stream, Bytes)
  275        ;   copy_stream_data(In, Stream)
  276        )
  277    ;   must_be(oneof([atom,string,codes]), X),
  278        setup_call_cleanup(
  279            new_memory_file(MemFile),
  280            ( setup_call_cleanup(
  281                  open_memory_file(MemFile, write, Stream,
  282                                   [encoding(octet)]),
  283                  (   memberchk(content_length(Bytes), Fields)
  284                  ->  copy_stream_data(In, Stream, Bytes)
  285                  ;   copy_stream_data(In, Stream)
  286                  ),
  287                  close(Stream)),
  288              encoding(Fields, Encoding, Options),
  289              memory_file_to(X, MemFile, Encoding, Data0)
  290            ),
  291            free_memory_file(MemFile)),
  292        Data = Data0
  293    ).
  294http_read_data(In, Fields, Data, _) :-
  295    option(content_type(ContentType), Fields),
  296    is_content_type(ContentType, 'application/x-www-form-urlencoded'),
  297    !,
  298    http_read_data(In, Fields, Codes, [to(string)]),
  299    uri_query_components(Codes, Data).
  300http_read_data(In, Fields, Data, Options) :-                    % call hook
  301    (   select_option(content_type(Type), Options, Options1)
  302    ->  delete(Fields, content_type(_), Fields1),
  303        http_convert_data(In, [content_type(Type)|Fields1], Data, Options1)
  304    ;   http_convert_data(In, Fields, Data, Options)
  305    ),
  306    !.
  307http_read_data(In, Fields, Data, Options) :-
  308    http_read_data(In, Fields, Data, [to(atom)|Options]).
  309
  310memory_file_to(atom, MemFile, Encoding, Data) :-
  311    memory_file_to_atom(MemFile, Data, Encoding).
  312memory_file_to(string, MemFile, Encoding, Data) :-
  313    memory_file_to_string(MemFile, Data, Encoding).
  314memory_file_to(codes, MemFile, Encoding, Data) :-
  315    memory_file_to_codes(MemFile, Data, Encoding).
  316
  317
  318encoding(_Fields, Encoding, Options) :-
  319    option(input_encoding(Encoding), Options),
  320    !.
  321encoding(Fields, utf8, _) :-
  322    memberchk(content_type(Type), Fields),
  323    (   sub_atom(Type, _, _, _, 'UTF-8')
  324    ->  true
  325    ;   sub_atom(Type, _, _, _, 'utf-8')
  326    ),
  327    !.
  328encoding(_, octet, _).
  329
  330is_content_type(ContentType, Check) :-
  331    sub_atom(ContentType, 0, Len, After, Check),
  332    (   After == 0
  333    ->  true
  334    ;   sub_atom(ContentType, Len, 1, _, ';')
  335    ).
 no_content_status(+Code) is semidet
True when Code is an HTTP status code that carries no content.
See also
- Issue#157
  343no_content_status(Code) :-
  344    between(100, 199, Code),
  345    !.
  346no_content_status(204).
 http_convert_data(+In, +Fields, -Data, +Options) is semidet
Multi-file hook to convert a HTTP payload according to the Content-Type header. The default implementation deals with application/x-prolog. The HTTP framework provides implementations for JSON (library(http/http_json)), HTML/XML (library(http/http_sgml_plugin))
  356http_convert_data(In, Fields, Data, Options) :-
  357    memberchk(content_type(Type), Fields),
  358    is_content_type(Type, 'application/x-prolog'),
  359    !,
  360    (   memberchk(content_length(Bytes), Fields)
  361    ->  setup_call_cleanup(
  362            ( stream_range_open(In, Range, [size(Bytes)]),
  363              set_stream(Range, encoding(utf8)),
  364              set_stream(Range, file_name('HTTP:DATA'))
  365            ),
  366            read_term(Range, Data, Options),
  367            close(Range))
  368    ;   set_stream(In, encoding(utf8)),
  369        read_term(In, Data, Options)
  370    ).
 http_disconnect(+Connections) is det
Close down some connections. Currently Connections must have the value all, closing all connections.
deprecated
- New code should use http_close_keep_alive/1 from library(http/http_open).
  380http_disconnect(all) :-
  381    http_close_keep_alive(_).
 http:post_data_hook(+Term, +Out, +Options) is semidet
Hook to extend the datatypes supported by the post(Data) option of http_open/3. The default implementation supports prolog(Term), sending a Prolog term as application/x-prolog.
  389http:post_data_hook(prolog(Term), Out, HdrExtra) :-
  390    setup_call_cleanup(
  391        ( new_memory_file(MemFile),
  392          open_memory_file(MemFile, write, Handle)
  393        ),
  394        ( format(Handle,
  395                 'Content-Type: application/x-prolog; charset=UTF-8~n~n',
  396                 []),
  397          write_term(Handle, Term,
  398                     [ quoted(true),
  399                       ignore_ops(true),
  400                       fullstop(true),
  401                       nl(true)
  402                     ])
  403        ),
  404        close(Handle)),
  405    setup_call_cleanup(
  406        open_memory_file(MemFile, read, RdHandle,
  407                         [ free_on_close(true)
  408                         ]),
  409        http_post_data(cgi_stream(RdHandle), Out, HdrExtra),
  410        close(RdHandle))