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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)  2011-2020, VU University Amsterdam
    7    All rights reserved.
    8
    9    Redistribution and use in source and binary forms, with or without
   10    modification, are permitted provided that the following conditions
   11    are met:
   12
   13    1. Redistributions of source code must retain the above copyright
   14       notice, this list of conditions and the following disclaimer.
   15
   16    2. Redistributions in binary form must reproduce the above copyright
   17       notice, this list of conditions and the following disclaimer in
   18       the documentation and/or other materials provided with the
   19       distribution.
   20
   21    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   22    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   23    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   24    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   25    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   26    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   27    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   28    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   29    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   31    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   32    POSSIBILITY OF SUCH DAMAGE.
   33*/
   34
   35:- module(http_files,
   36          [ http_reply_from_files/3     % +Dir, +Options, +Request
   37          ]).   38:- use_module(library(http/http_dispatch)).   39:- use_module(library(http/http_dirindex)).   40:- use_module(library(filesex)).   41:- use_module(library(lists)).   42:- use_module(library(option)).   43
   44:- predicate_options(http_reply_from_files/3, 2, [indexes(list(atom))]).

Serve plain files from a hierarchy

Although the SWI-Prolog Web Server is intended to serve documents that are computed dynamically, serving plain files is sometimes necessary. This small module combines the functionality of http_reply_file/3 and http_reply_dirindex/3 to act as a simple web-server. Such a server can be created using the following code sample, which starts a server at port 8080 that serves files from the current directory ('.'). Note that the handler needs a prefix option to specify that it must handle all paths that begin with the registed location of the handler.

:- use_module(library(http/http_server)).
:- use_module(library(http/http_files)).

:- http_handler(root(.), http_reply_from_files('.', []), [prefix]).

:- initialization(http_server([port(8080)]), main).
See also
- pwp_handler/2 provides similar facilities, where .pwp files can be used to add dynamic behaviour. */
 http_reply_from_files(+Dir, +Options, +Request)
HTTP handler that serves files from the directory Dir. This handler uses http_reply_file/3 to reply plain files. If the request resolves to a directory, it uses the option indexes to locate an index file (see below) or uses http_reply_dirindex/3 to create a listing of the directory.

Options:

indexes(+List)
List of files tried to find an index for a directory. The default is ['index.html'].

Note that this handler must be tagged as a prefix handler (see http_handler/3 and module introduction). This also implies that it is possible to override more specific locations in the hierarchy using http_handler/3 with a longer path-specifier.

Arguments:
Dir- is either a directory or an path-specification as used by absolute_file_name/3. This option provides great flexibility in (re-)locating the physical files and allows merging the files of multiple physical locations into one web-hierarchy by using multiple file_search_path/2 clauses that define the same alias.
See also
- The hookable predicate file_mime_type/2 is used to determine the Content-type from the file name.
  100http_reply_from_files(Dir, Options, Request) :-
  101    (   memberchk(path_info(PathInfo), Request)
  102    ->  true
  103    ;   PathInfo = ''
  104    ),
  105    http_safe_file(PathInfo, []),
  106    locate_file(Dir, PathInfo, Result, ResultType, Options),
  107    !,
  108    reply(ResultType, Result, Request).
  109
  110reply(file, Path, Request) :-
  111    http_reply_file(Path, [unsafe(true)], Request).
  112reply(index, Path, Request) :-
  113    http_reply_dirindex(Path, [unsafe(true)], Request).
  114reply(redirect, _, Request) :-
  115    memberchk(path(Path), Request),
  116    atom_concat(Path, /, NewLocation),
  117    http_redirect(moved_temporary, NewLocation, Request).
  118
  119locate_file(Dir, PathInfo, Result, ResultType, Options) :-
  120    absolute_file_name(Dir, DirPath,
  121                       [ file_type(directory),
  122                         access(read),
  123                         solutions(all)
  124                       ]),
  125    directory_file_path(DirPath, PathInfo, Path),
  126    (   exists_file(Path)
  127    ->  ResultType = file,
  128        Result = Path
  129    ;   exists_directory(Path),
  130        (   sub_atom(Path, _, _, 0, /)
  131        ->  (   option(indexes(Indexes), Options, ['index.html']),
  132                member(Index, Indexes),
  133                directory_file_path(Path, Index, IndexFile),
  134                exists_file(IndexFile)
  135            ->  Result = IndexFile,
  136                ResultType = file
  137            ;   Result = Path,
  138                ResultType = index
  139            )
  140        ;   ResultType = redirect
  141        )
  142    )