%D \module
%D   [       file=file-mod, % was supp-fil,
%D        version=20110701, % 1995.10.10,
%D          title=\CONTEXT\ File Macros,
%D       subtitle=Resolvers,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.

%D We could move some more to the lua end (implementors).

\writestatus{loading}{ConTeXt File Macros / Resolvers}

\unprotect

\registerctxluafile{file-res}{}

%D \macros
%D   {readfile,ReadFile}
%D
%D One cannot be sure if a file exists. When no file can be found, the \type
%D {\input} primitive gives an error message and switches to interactive mode. The
%D macro \type {\readfile} takes care of non||existing files. This macro has two
%D faces.
%D
%D \starttyping
%D \ReadFile {filename}
%D \readfile {filename} {before loading} {not found}
%D \stoptyping
%D
%D Many \TEX\ implementations have laid out some strategy for locating files. This
%D can lead to unexpected results, especially when one loads files that are not
%D found in the current directory. Let's give an example of this. In \CONTEXT\
%D illustrations can be defined in an external file. The resizing macro first looks
%D if an illustration is defined in the local definitions file. When no such file is
%D found, it searches for a global file and when this file is not found either, the
%D illustration itself is scanned for dimensions. One can imagine what happens if an
%D adapted, localy stored illustration, is scaled according to dimensions stored
%D somewhere else.
%D
%D When some \TEX\ implementation starts looking for a file, it normally first looks
%D in the current directory. When no file is found, \TEX\ starts searching on the
%D path where format and|/|or style files are stored. Depending on the
%D implementation this can considerably slow down processing speed.
%D
%D In \CONTEXT, we support a project||wise ordening of files. In such an approach it
%D seems feasible to store common files in a lower directory. When for instance
%D searching for a general layout file, we therefore have to backtrack.
%D
%D These three considerations have lead to a more advanced approach for loading
%D files.
%D
%D We first present an earlier implementation of \type {\readfile}. This command
%D backtracks parent directories, upto a predefined level. Users can change this
%D level (on the commandline using a directive); we default to~3.
%D
%D We use \type {\normalinput} instead of \type {\input} because we want to be able
%D to redefine the original \type {\input} when needed, for instance when loading
%D third party libraries.

\mutable\lettonothing\readfilename

\def\syst_files_read_file#protocol#path#name% #true #false
  {\edef\readfilename{\clf_getreadfilename{#protocol}{#path}{#name}}%
   \ifempty\readfilename
     \expandafter\secondoftwoarguments
   \else
     \expandafter\syst_files_read_file_indeed
   \fi}

\def\syst_files_read_file_indeed#true#false%
  {#true%
   \relax
   \normalinput{\readfilename}%
   \relax}

%D \macros
%D   {readjobfile,readlocfile,readsysfile,
%D    readfixfile,readsetfile}
%D
%D This implementation honnors the third situation, but we still can get unwanted
%D files loaded and/or can get involved in extensive searching.
%D
%D Due to different needs, we decided to offer four alternative loading commands.
%D With \type {\readjobfile} we load a local file and do no backtracking, while
%D \type {\readlocfile} backtracks~\number \maxreadlevel\ directories, including the
%D current one.
%D
%D System files can be anywhere and therefore \type {\readsysfile} is not bound to
%D the current directory and obeys the \TEX\ implementation.
%D
%D Of the last two, \type {\readfixfile} searches on the directory specified and
%D backtracks too, while \type {\readsetfile} does only search on the specified
%D path.
%D
%D The most liberal is \type {\readfile}.

\permanent\protected\def\readjobfile     #name{\syst_files_read_file{job}    {.}{#name}} % current path, no backtracking
\permanent\protected\def\readlocfile     #name{\syst_files_read_file{loc}    {.}{#name}} % current path, backtracking
\permanent\protected\def\readsysfile     #name{\syst_files_read_file{sys}    {.}{#name}} % current path, obeys tex search
\permanent\protected\def\readfixfile#path#name{\syst_files_read_file{fix}{#path}{#name}} % specified path, backtracking
\permanent\protected\def\readsetfile#path#name{\syst_files_read_file{set}{#path}{#name}} % specified path, no backtracking
\permanent\protected\def\readfile        #name{\syst_files_read_file{any}    {.}{#name}}
\permanent\protected\def\ReadFile        #name{\syst_files_read_file{any}    {.}{#name}\donothing\donothing}

%D So now we've got ourselves five file loading commands:
%D
%D \starttyping
%D \readfile                {filename} {before loading} {not found}
%D
%D \readjobfile             {filename} {before loading} {not found}
%D \readlocfile             {filename} {before loading} {not found}
%D \readfixfile             {filename} {before loading} {not found}
%D \readsysfile {directory} {filename} {before loading} {not found}
%D \stoptyping

\permanent\protected\def\readtexfile#name#true#false%
  {\pushcatcodetable
   \catcodetable\ctxcatcodes
   \readfile{#name}{#true}{#false}%
   \popcatcodetable}

% \permanent\protected\def\readxmlfile#name#true#false%
%   {\pushcatcodetable
%    \catcodetable\xmlcatcodes
%    \readfile{#name}{#true}{#false}%
%    \popcatcodetable}

%D \macros
%D   {doiflocfileelse,locfilename}
%D
%D \starttyping
%D \doiflocfileelse {filename} {before loading} {not found}
%D \stoptyping

\permanent\protected\def\doifelselocfile#name{\clf_doifelselocfile{#name}}
\permanent          \def\locfilename    #name{\clf_locfilename    {#name}}

\aliased\let\doiflocfileelse\doifelselocfile

\protect \endinput
