#!/usr/bin/env python

import os
env = os.environ 

# upon import, we record the enviroment
from copy import deepcopy
old_env = deepcopy( env )

sep = " ; "


def quote( s ):
    if (s[0]!='"' and s[-1]!='"') : return '"'+s+'"'
    return s

def diff ( mode = "bash" ) :
 
    r = ""
    for k,v in os.environ.items() :
        
        if not k in old_env or v != old_env[ k ] :
            
            if mode == "bash" :
                r += "export "+k+"="+quote(v)+sep
            if mode == "tcsh" or mode == "csh" :
                r += "setenv "+k+" "+v+sep

    return r


def remove_from_path( env_var_name, r ):

    if env_var_name not in env : return
    v = env [ env_var_name ].split(':')
    env[env_var_name]=  ':'.join( p for p in v if p != r )


def insert_in_path ( env_var_name, r ):    
    
    if env_var_name not in env :
        env[ env_var_name ] = r
        return

    v = env [ env_var_name ].split(':')
    
    if v[0] == '.' :        # keep . at the front, insert r after
        v.insert( 1, r )
    else :
        v.insert( 0, r )    # insert r at the front

    env[ env_var_name ] = ':'.join( v )