/*
  Searchpath  -  helpers for searching directory lists and locating modules

  Copyright (C)         Lumiera.org
    2011,               Hermann Vosseler <Ichthyostega@web.de>

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public License as
  published by the Free Software Foundation; either version 2 of
  the License, or (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

* *****************************************************/


#include "lib/error.hpp"
#include "lib/searchpath.hpp"
#include "lib/symbol.hpp"


/** how to retrieve the absolute path of the currently running executable
 *  on a Linux system: read the link provided by the kernel through /proc
 */
#define GET_PATH_TO_EXECUTABLE "/proc/self/exe"



namespace lib {
  
  LUMIERA_ERROR_DEFINE (FILE_NOT_DIRECTORY, "path element points at a file instead of a directory");
  
  
  
  regex SearchPathSplitter::EXTRACT_PATHSPEC ("(\\$?ORIGIN/)?([^:]+)");
  
  
  /** @internal helper to figure out the installation directory,
   *  as given by the absolute path of the currently executing program
   *  @warning this is Linux specific code */
  string
  findExePath()
  {
    static string buff(lib::STRING_MAX_RELEVANT+1, '\0' );
    if (!buff[0])
      {
        ssize_t chars_read = readlink (GET_PATH_TO_EXECUTABLE, &buff[0], lib::STRING_MAX_RELEVANT);
        
        if (0 > chars_read || chars_read == ssize_t(lib::STRING_MAX_RELEVANT))
          throw error::Fatal ("unable to discover path of running executable");
        
        buff.resize(chars_read);
      }
    return buff;
  }
  
  
  
  
  string
  resolveModulePath (string moduleName, string searchPath)
  {
    fsys::path modulePathName (moduleName);
    SearchPathSplitter searchLocation(searchPath);
    
    while (true)
      {
        if (fsys::exists (modulePathName))
          {
            INFO (config, "found module %s", modulePathName.string().c_str());
            return modulePathName.string();
          }
        
        // try / continue search path
        if (searchLocation.isValid())
          modulePathName = fsys::path() / searchLocation.next() / moduleName;
        else
          throw error::Config ("Module \""+moduleName+"\" not found"
                              + (searchPath.empty()? ".":" in search path: "+searchPath));
  }   }

  
  
} // namespace lib