# -*- python -*-
from __future__ import print_function
from subprocess import PIPE, Popen
import os, sys


def module(command, *arguments, **kwargs):
    """
    Execute a regular Lmod command and apply environment changes to
    the current Python environment (i.e. os.environ).
    
    In case len(arguments) == 1 the string will be split on whitespace into 
    separate arguments. Pass a list of strings to avoid this.
    
    Raises an exception in case Lmod execution returned a non-zero
    exit code.
    
    Use with keyword argument show_environ_updates=True to show the actual
    changes made to os.environ (mostly for debugging).
    
    Examples:
    module('list')
    module('load', 'gcc')
    module('load', 'gcc cmake')
    module('load', 'gcc cmake', show_environ_updates=True)
    """
    numArgs = len(arguments)
    A = ['/usr/share/lmod/lmod/libexec/lmod', 'python', '--protected_vars', command]
    if (numArgs == 1):
        A += arguments[0].split()
    else:
        A += list(arguments)

    proc           = Popen(A, stdout=PIPE, stderr=PIPE)
    status         = proc.returncode 
    stdout, stderr = proc.communicate()
    err_out        = sys.stderr
    
    if (os.environ.get('LMOD_REDIRECT','no') != 'no'):
        err_out=sys.stdout

    os.environ['__LMOD_PROTECTED_LD_LIBRARY_PATH'] = os.environ.get('LD_LIBRARY_PATH','')
    os.environ['__LMOD_PROTECTED_LD_PRELOAD']      = os.environ.get('LD_PRELOAD','')
    os.environ['LD_LIBRARY_PATH']                  = ''
    os.environ['LD_PRELOAD']                       = ''
    print(stderr.decode(),file=err_out)
    
    if ('show_environ_updates' in kwargs):
        print(stdout.decode())
    exec(stdout.decode())
    return status, stderr.decode()
