% import.sty  Ver 5.1  23-Mar-2009  Donald Arseneau  (asnd@triumf.ca)
%
% This software is in the public domain; free of any restrictions.
%
% Two new \LaTeX\ commands, "\import {full_path} {file}" and 
% "\subimport {path_extension} {file}" are defined to input a file 
% from another directory, allowing that file to find its own inputs
% (using "\input", "\includegraphics" etc.) in that directory.
% 
% Alias command names are "\inputfrom" and "\subinputfrom".
%
% Also provided are "\includefrom" and "\subincludefrom", which are
% based on the "\include" command, rather than "\input".  There are
% also "*" variants described below.
%
% For example, if a remote file "/usr5/friend/work/report.tex" has contents:
%
%      My graph: \includegraphics{picture}
%      \input{explanation}
%
% then you can safely input that file in your own document with the command
% "\import{/usr5/friend/work/}{report}"; the explanation and picture will 
% be taken from the "/usr5/friend/work/" directory.
%
% The "\subimport" command takes a relative path instead of a full absolute
% file path, and it allows imported files to import files themselves, using
% their own directory as the root of another "path_extension". Do not use
% both "\import" and "\subimport" in the same file.
%
% For example, if a file is imported (using either command) from directory
% "abc/" and that file contains the command "\subimport{lmn/}{xyz}" then
% file "abc/lmn/xyz.tex" is input, and any "\input" commands in that file
% will read files from directory "abc/lmn/". 
%
% Note that the sub-import path is merely appended to the current import
% path.  Mistakes from this method must be rectified by "\import@path@fix".
%
% Depending on on how your \TeX\ system is configured, if a file with the 
% same name as the import file exists in the current directory or in the 
% TEXINPUTS path, that other file will be read in preference to one in the 
% import directory.  So here is the real behavior of the previous example:
% Given the sequence "\import{abc/}{one}", "\subimport{lmn/uvw/}{two}" (in
% file one), "\input{three}" (in file two), \LaTeX\ first looks for three.tex
% in the TEXINPUTS search path; if not found, it tries "abc/lmn/uvw/three";
% if that doesn't exist, it tries "abc/three"; if still not found, it tries
% the defined "\input@path", if there is one.
%
% To avoid searching the TEXINPUTS path when importing files, use the `star'
% versions of the commands: "\import*" and "\subimport*".
%
% A hook "\import@path@fix" is provided to reformat the import path
% to fit the syntax of a particular operating system.  It *could* be
% defined to convert unix-style path names to the local format, but 
% all it does now is remove "][" from VMS sub-import directories.
%
% Presently, the paths are defined ``locally'' so input files must have 
% balanced grouping.
%====================== END INSTRUCTIONS ===========================

\ProvidesPackage{import}[2009/03/23 \space  v 5.1]
\ProcessOptions

\@ifundefined{import}{%
 \newcommand{\import}{\global\let\import@path\@empty \@doimport\input}
}{
 \PackageWarning{import}{\string\import\space command is already defined!^^J%
   Defining only its \string\inputfrom\space alias.}
}
\newcommand{\inputfrom}{\global\let\import@path\@empty \@doimport\input}
\newcommand{\subimport}{\@doimport\input}
\newcommand{\subinputfrom}{\@doimport\input}
\newcommand{\includefrom}{\global\let\import@path\@empty \@doimport\include}
\newcommand{\subincludefrom}{\@doimport\include}

\def\@doimport#1{\@ifstar
  {\@sub@import#1\@iffileonpath}{\@sub@import#1\IfFileExists}}

% #1 = import command,  #2 = switch for *,  #3 = import path extension
\def\@sub@import#1#2#3{%
  \begingroup
  \protected@edef\@tempa{\endgroup
    \let\noexpand\IfFileExists\noexpand#2%
    \noexpand\@import  \noexpand#1%  param 1
      {\@ifundefined{input@path}{}{\input@path}}% 2
      {\@ifundefined{Ginput@path}{}{\Ginput@path}}% 3
      {\import@path#3}{\import@path}% 4,5
      {\ifx\IfFileExists\im@@IfFileExists \noexpand\im@@IfFileExists 
       \else \noexpand\IfFileExists \fi}}% 6
  \@tempa}
%
% #1 = import command (\input or \include)
% #2 = previous input path list. #3 = previous graphics input path list.
% #4 = full path added to each.  #5 = previous import path.  
% #6 = previous \IfFileExists.   #7 = file name.
%
\def\@import#1#2#3#4#5#6#7{%
  \gdef\import@path{#4}%
  \protected@edef\input@path{{\import@path@fix{#4}}#2}%
  \protected@edef\Ginput@path{{\import@path@fix{#4}}#3}%
  #1{#7}%
  \let\IfFileExists#6% restore after \import*
  \gdef\import@path{#5}%
  \def\input@path{#2}\ifx\input@path\@empty \let\input@path\@undefined \fi
  \def\Ginput@path{#3}\ifx\Ginput@path\@empty \let\Ginput@path\@undefined \fi
}

\let\im@@IfFileExists\IfFileExists
\gdef\import@path{}

\let\import@path@fix\@firstofone % default

% Check for vms file names and set \import@path@fix appropriately
\gdef\@gtempa{[]}
\ifx\@gtempa\@currdir % VMS directory syntax
 \gdef\import@path@fix#1{\@gobbleVMSbrack#1][>}
 \gdef\@gobbleVMSbrack#1][#2{#1\ifx>#2\@empty
    \expandafter \strip@prefix \fi % Gobble up to >
    \@gobbleVMSbrack #2}
\fi
