#!/usr/bin/env python

# used in a script with shebang in 1 of 2 ways
# #!/path/to/rel relative_interpreter
# #!/usr/bin/env rel relative_interpreter
# the latter requires support for more than 1 parameter to the intpreter (not on linux)
#
# will set SCRIPT_FILE and SCRIPT_PATH
# example:
# #!/usr/local/bin/rel python
# or, going with the form that just requires rel be in the path
# #!/usr/bin/env rel python
#
# these assume the script is in the same folder as the python interpreter. other deeper locations are also valid, like:
# #!/usr/bin/env rel ../Resources/Python.app/Contents/MacOS/Python
#
# Many systems only allow 1 parameter with Shebang. On these systems, rel
# must be installed in a standard location, then the following syntax can be used
# and it will use the interpreter relative to the script's path
# #!/usr/bin/rel python
#

import os,sys
import logging
LOG = logging.debug

def main():
    interpreter=sys.argv[1]
    scriptfile=sys.argv[2]
    args=[None]+sys.argv[2:]
    LOG('%s %s' % (interpreter,scriptfile))
    scriptpath=os.path.dirname(os.path.realpath(scriptfile))
    interpreter=os.path.normpath(os.path.join(scriptpath,interpreter))
    LOG('%s %s' % (scriptpath,interpreter))
    args[0]=interpreter
    #print replacements
    LOG('running interpreter '+interpreter+' with parameters '+repr(args))
    LOG('script_path=%s' % (scriptpath))
    assert(os.path.exists(interpreter) and not os.path.isdir(interpreter))
    assert(os.path.exists(scriptfile) and not os.path.isdir(scriptfile))
    assert(os.path.exists(scriptpath) and os.path.isdir(scriptpath))
    env=os.environ.copy()
    env['SCRIPT_FILE']=scriptfile
    env['SCRIPT_PATH']=scriptpath
    os.execve(interpreter,args,env)
    raise RuntimeError('Exec Failed')

if __name__ == '__main__':
    main()