%%% BEGIN openflax/handler/autocomplete.erl %%%
%%%
%%% openflax - Open Source web server for Erlang/OTP
%%% Copyright (c)2003 Cat's Eye Technologies.  All rights reserved.
%%%
%%% Redistribution and use in source and binary forms, with or without
%%% modification, are permitted provided that the following conditions
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%%%
%%%   Redistributions of source code must retain the above copyright
%%%   notice, this list of conditions and the following disclaimer.
%%%
%%%   Redistributions in binary form must reproduce the above copyright
%%%   notice, this list of conditions and the following disclaimer in
%%%   the documentation and/or other materials provided with the
%%%   distribution.
%%%
%%%   Neither the name of Cat's Eye Technologies nor the names of its
%%%   contributors may be used to endorse or promote products derived
%%%   from this software without specific prior written permission.
%%%
%%% THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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%% @doc Filename auto-completion handler for OpenFlax.
%%
%% <p>This handler should be invoked from <code>cfg_openflax_dispatch</code>
%% when the URI matches a pattern of <code>"* "</code> or similar.
%% The trailing space (shown as a plus sign in the URL) indicates the
%% filename is not complete.  This handler will complete that filename,
%% if possible, and redirect the user agent to that resource.</p>
%%
%% <p>This handler requires <code>openflax.handler.file</code>.</p>
%%
%% @end

-module(openflax.handler.autocomplete).
-vsn('$Id: autocomplete.erl 31 2004-04-23 07:00:11Z catseye $').
-author('cpressey@catseye.mine.nu').
-copyright('Copyright (c)2003 Cat`s Eye Technologies. All rights reserved.').

-behaviour(openflax.handler).

-export([start/1, stop/1, serve/1]). % behaviour

-import(lists).
-import(string).
-import(filename).
-import(file).

%% @spec start(conf()) -> conf()
%% @doc Initializes the filename auto-completion handler.

start(Conf) ->
  openflax.conf:new().

%% @spec stop(conf()) -> conf()
%% @doc Shuts down the auto-completion handler.

stop(Conf) ->
  Conf.

%% @spec serve(conf()) -> ok | {error, Reason}
%% @doc Redirects the user agent from a partial filename
%% to a full filename matching the partial filename, if any.

serve(Conf) ->
  FileName = openflax.handler.file:document(Conf),
  % Perform filename completion
  case complete(openflax.string:truncate(FileName), Conf) of
    [NewFileName | _] ->
      % Found a prefix, so redirect them to it
      redirect_completed(NewFileName, Conf);
    [] ->
      % No match at all - still not found
      {not_found, Conf}
  end.

%% @spec redirect_completed(filename(), conf()) -> ok
%% @doc Redirects the user agent to the completed filename.
%% Called only when filename completion is successful.

redirect_completed(NewFileName, Conf) ->
  StartChar = length(openflax.conf:get_string(cfg_document_root, Conf)) + 1,
  NewFileName0 = "/" ++ string:substr(NewFileName, StartChar),
  {{moved_permanently, NewFileName0}, Conf}.

%% @spec complete(string(), conf()) -> [filename()]
%% @doc Given a partial name of a file with a full path, returns a list of
%% files in that directory that the prefix matches.  The list may be empty
%% (if no files match,) it may have one entry (if there was a unique match,)
%% or it may have many entries (if the prefix was ambiguous.)

complete(PartialFileName, Conf) ->
  DirName = filename:dirname(PartialFileName),
  BaseName = filename:basename(PartialFileName),
  {ok, Dir} = file:list_dir(DirName),
  Dir0 = lists:filter(fun(X) ->
    openflax.handler.file:is_accessible(filename:join([DirName, X]), Conf)
  end, Dir),
  Dir1 = lists:reverse(lists:sort(Dir0)),
  complete(DirName, Dir1, BaseName, length(BaseName), []).

complete(DirName, [], PartialFileName, Length, Acc) -> Acc;
complete(DirName, [FileName | Tail], PartialFileName, Length, Acc) ->
  Test = string:left(FileName, Length),
  case string:left(FileName, Length) of
    PartialFileName ->
      FullFileName = filename:join([DirName, FileName]),
      complete(DirName, Tail, PartialFileName, Length, [FullFileName | Acc]);
    _ ->
      complete(DirName, Tail, PartialFileName, Length, Acc)
  end.

%%% END of openflax/handler/autocomplete.erl %%%