"""
This is a Python hack to change a global variable into something more
dynamic, looking to an environment variable, if any.

This is needed to allow PyPS to be moved around at other locations than
envisioned without having to patch this file.
"""

import os

# The name of the variable used to specify where to find the PyPS runtime:
PIPS_PYPS_RUNTIME_DIR_VARNAME = "PIPS_PYPS_RUNTIME_DIR"

def PypsRuntimeDir(default_dir):
    """
    Override the string value access with a possible environment variable
    """
    if PIPS_PYPS_RUNTIME_DIR_VARNAME in os.environ:
        # If the PIPS_PYPS_RUNTIME_DIR_VARNAME environment variable is set, use it:
        return os.environ[PIPS_PYPS_RUNTIME_DIR_VARNAME]
    else:
        # Use the compile-time value:
        return default_dir

# Some test cases:
# Use to be: pypsruntime="/usr/local/par4all%/share/runtime"

# Now the use case is:
# pypsruntime = PypsRuntimeDir("/usr/local/par4all%/share/runtime")
# print(pypsruntime)