#!/usr/bin/env python2

VERSION = 0.2

# origin_dir - Get directory where this program is located. 
# 
# Copyright (C) 2001  Peter Åstrand <astrand@lysator.liu.se>
# 
# 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; version 2 of the License. 
# 
# 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.

# Usage 1: Import in Python application and run get_origin_dir() to fetch
# origin directory.
#
# Usage 2: Use as an wrapper for a binary that needs to now its own location.
# Rename <binary> to <binary.bin>.
# Copy this program to <binary> (must be in same directory as <binary.bin>).
# Change PROGRAM_BINARY below to <binary.bin>.
# <binary.bin> can now look at environment variable PROGRAM_ORIGIN_DIR to
# get its location. It can also look at argv[0], which is an absolute path.
#
# Usage3: Use origin_dir.py in a shellscript, to get the scripts location.
# Make sure origin_dir.py is installed somewhere where Python can find it.
# Include the following line at top of the shell script:
# ORIGIN_DIR=`python -c "import origin_dir; print origin_dir.get_origin_dir(\"$0\")"`
#
# The scripts location is now in the environment variable ORIGIN_DIR. 


PROGRAM_BINARY = "myapp.bin"


import os
import sys
import string

def realpath(filename):
    """Return the canonical path of the specified filename, eliminating any
symbolic links encountered in the path."""

    filename = os.path.abspath(filename)

    bits = ['/'] + string.split(filename, '/')[1:]
    for i in range(2, len(bits)+1):
        component = apply(os.path.join, bits[0:i])
        if os.path.islink(component):
            resolved = os.readlink(component)
            (dir, file) = os.path.split(component)
            resolved = os.path.normpath(os.path.join(dir, resolved))
            newpath = apply(os.path.join, [resolved] + bits[i:])
            return realpath(newpath)

    return filename


def get_origin_dir(argv0=sys.argv[0]):
    """Get program origin directory"""
    
    abs_path = realpath(os.path.abspath(argv0))

    return os.path.dirname(abs_path)


if __name__ == "__main__":
    origin_dir = get_origin_dir()
    os.putenv("PROGRAM_ORIGIN_DIR", origin_dir)
    sys.argv[0] = os.path.join(origin_dir, PROGRAM_BINARY)
    os.execv(sys.argv[0], sys.argv)