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)  2002-2016, University of Amsterdam,
    7                              VU University Amsterdam
    8    All rights reserved.
    9
   10    Redistribution and use in source and binary forms, with or without
   11    modification, are permitted provided that the following conditions
   12    are met:
   13
   14    1. Redistributions of source code must retain the above copyright
   15       notice, this list of conditions and the following disclaimer.
   16
   17    2. Redistributions in binary form must reproduce the above copyright
   18       notice, this list of conditions and the following disclaimer in
   19       the documentation and/or other materials provided with the
   20       distribution.
   21
   22    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   23    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   24    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   25    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   26    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   27    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   28    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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   30    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   31    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   32    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   33    POSSIBILITY OF SUCH DAMAGE.
   34*/
   35
   36:- module(http_client,
   37          [ http_get/3,                 % +URL, -Reply, +Options
   38            http_delete/3,              % +URL, -Reply, +Options
   39            http_post/4,                % +URL, +In, -Reply, +Options
   40            http_put/4,                 % +URL, +In, -Reply, +Options
   41            http_patch/4,               % +URL, +In, -Reply, +Options
   42            http_read_data/3,           % +Header, -Data, :Options
   43            http_disconnect/1           % +What
   44          ]).   45:- use_module(library(http/http_open)).   46:- use_module(library(uri)).   47:- use_module(http_header).   48:- use_module(http_stream).   49:- use_module(library(memfile)).   50:- use_module(library(lists)).   51:- use_module(library(error)).   52:- use_module(library(option)).   53
   54:- meta_predicate
   55    http_read_data(+, -, :).   56
   57:- multifile
   58    http_convert_data/4,            % http_read_data plugin-hook
   59    http:post_data_hook/3.   60
   61:- predicate_options(http_get/3, 3,
   62                     [ pass_to(http_open/3, 3),
   63                       pass_to(http_read_data/3, 3)
   64                     ]).   65:- predicate_options(http_delete/3, 3, [pass_to(http_get/3, 3)]).   66:- predicate_options(http_post/4, 4, [pass_to(http_get/3, 3)]).   67:- predicate_options(http_put/4, 4, [pass_to(http_post/4, 4)]).   68:- predicate_options(http_read_data/3, 3,
   69                     [ to(any),
   70                       content_type(any),
   71                       form_data(oneof([form,mime])),
   72                       input_encoding(encoding),
   73                       on_filename(callable)
   74                     ]).

  108                 /*******************************
  109                 *              GET             *
  110                 *******************************/

 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.

  130http_get(URL, Data, Options) :-
  131    headers_option(Options, Options1, Headers),
  132    option(reply_header(Headers), Options, _),
  133    http_open(URL, In, Options1),
  134    delete(Headers, transfer_encoding(_), Headers1),
  135    call_cleanup(
  136        http_read_data(In, Headers1, Data, Options),
  137        close(In)).
  138
  139headers_option(Options, Options1, Headers) :-
  140    option(headers(Headers), Options),
  141    !,
  142    Options1 = Options.
  143headers_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.

  156http_delete(URL, Data, Options) :-
  157    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.

  168http_post(URL, Data, Reply, Options) :-
  169    http_get(URL, Reply,
  170             [ post(Data)
  171             | Options
  172             ]).

 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.

  181http_put(URL, In, Out, Options) :-
  182    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.

  191http_patch(URL, In, Out, Options) :-
  192    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.

  232http_read_data(Fields, Data, QOptions) :-
  233    meta_options(is_meta, QOptions, Options),
  234    memberchk(input(In), Fields),
  235    (   http_read_data(In, Fields, Data, Options)
  236    ->  true
  237    ;   throw(error(failed(http_read_data), _))
  238    ).
  239
  240is_meta(on_filename).
  241
  242http_read_data(In, Fields, Data, Options) :-    % Transfer-encoding: chunked
  243    select(transfer_encoding(chunked), Fields, RestFields),
  244    !,
  245    setup_call_cleanup(
  246        http_chunked_open(In, DataStream, []),
  247        http_read_data(DataStream, RestFields, Data, Options),
  248        close(DataStream)).
  249http_read_data(In, Fields, Data, Options) :-
  250    option(to(X), Options),
  251    !,
  252    (   X = stream(Stream)
  253    ->  (   memberchk(content_length(Bytes), Fields)
  254        ->  copy_stream_data(In, Stream, Bytes)
  255        ;   copy_stream_data(In, Stream)
  256        )
  257    ;   must_be(oneof([atom,string,codes]), X),
  258        setup_call_cleanup(
  259            new_memory_file(MemFile),
  260            ( setup_call_cleanup(
  261                  open_memory_file(MemFile, write, Stream,
  262                                   [encoding(octet)]),
  263                  (   memberchk(content_length(Bytes), Fields)
  264                  ->  copy_stream_data(In, Stream, Bytes)
  265                  ;   copy_stream_data(In, Stream)
  266                  ),
  267                  close(Stream)),
  268              encoding(Fields, Encoding),
  269              memory_file_to(X, MemFile, Encoding, Data0)
  270            ),
  271            free_memory_file(MemFile)),
  272        Data = Data0
  273    ).
  274http_read_data(In, Fields, Data, _) :-
  275    option(content_type(ContentType), Fields),
  276    is_content_type(ContentType, 'application/x-www-form-urlencoded'),
  277    !,
  278    http_read_data(In, Fields, Codes, [to(string)]),
  279    uri_query_components(Codes, Data).
  280http_read_data(In, Fields, Data, Options) :-                    % call hook
  281    (   select_option(content_type(Type), Options, Options1)
  282    ->  delete(Fields, content_type(_), Fields1),
  283        http_convert_data(In, [content_type(Type)|Fields1], Data, Options1)
  284    ;   http_convert_data(In, Fields, Data, Options)
  285    ),
  286    !.
  287http_read_data(In, Fields, Data, Options) :-
  288    http_read_data(In, Fields, Data, [to(atom)|Options]).
  289
  290memory_file_to(atom, MemFile, Encoding, Data) :-
  291    memory_file_to_atom(MemFile, Data, Encoding).
  292memory_file_to(string, MemFile, Encoding, Data) :-
  293    memory_file_to_string(MemFile, Data, Encoding).
  294memory_file_to(codes, MemFile, Encoding, Data) :-
  295    memory_file_to_codes(MemFile, Data, Encoding).
  296
  297
  298encoding(Fields, utf8) :-
  299    memberchk(content_type(Type), Fields),
  300    (   sub_atom(Type, _, _, _, 'UTF-8')
  301    ->  true
  302    ;   sub_atom(Type, _, _, _, 'utf-8')
  303    ),
  304    !.
  305encoding(_, octet).
  306
  307is_content_type(ContentType, Check) :-
  308    sub_atom(ContentType, 0, Len, After, Check),
  309    (   After == 0
  310    ->  true
  311    ;   sub_atom(ContentType, Len, 1, _, ';')
  312    ).

 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))

  322http_convert_data(In, Fields, Data, Options) :-
  323    memberchk(content_type(Type), Fields),
  324    is_content_type(Type, 'application/x-prolog'),
  325    !,
  326    (   memberchk(content_length(Bytes), Fields)
  327    ->  setup_call_cleanup(
  328            ( stream_range_open(In, Range, [size(Bytes)]),
  329              set_stream(Range, encoding(utf8)),
  330              set_stream(Range, file_name('HTTP:DATA'))
  331            ),
  332            read_term(Range, Data, Options),
  333            close(Range))
  334    ;   set_stream(In, encoding(utf8)),
  335        read_term(In, Data, Options)
  336    ).

 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).

  346http_disconnect(all) :-
  347    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.

  355http:post_data_hook(prolog(Term), Out, HdrExtra) :-
  356    setup_call_cleanup(
  357        ( new_memory_file(MemFile),
  358          open_memory_file(MemFile, write, Handle)
  359        ),
  360        ( format(Handle,
  361                 'Content-Type: application/x-prolog; charset=UTF-8~n~n',
  362                 []),
  363          write_term(Handle, Term,
  364                     [ quoted(true),
  365                       ignore_ops(true),
  366                       fullstop(true),
  367                       nl(true)
  368                     ])
  369        ),
  370        close(Handle)),
  371    setup_call_cleanup(
  372        open_memory_file(MemFile, read, RdHandle,
  373                         [ free_on_close(true)
  374                         ]),
  375        http_post_data(cgi_stream(RdHandle), Out, HdrExtra),
  376        close(RdHandle))