import re data border 1px base-color fff include another_file css incl

import re

data = """
@border: 1px;
@base-color: #fff;

@include(another_file.css);
@include(another_file.css);
@new_function(value);

#header {
    color: @base-color;
    border-left: @border-width @border-width @border-width @border-width;
    border-right: 3px;
}

.footer {
    color: #1999998;
}
"""

REGEX_FUNCTION = re.compile(r'@(.[0-9a-z-_ ]+)\((.[a-z-_\.\/\\]+)\);', re.S);
REGEX_VARIABLE = re.compile(r'@(.[0-9a-z-_]+)', re.S)

STORE_VARIABLES = {}
STORE_FUNCTIONS = {}

def function(f):
    STORE_FUNCTIONS[f.__name__] = f

@function
def include(filename):
    file = open(filename, 'r')
    try:
        data = file.read()
    finally:
        file.close()
    return parse_css(data)

def parse_css(data):
    for line in data.splitlines():
        if line.startswith('@'):
            if ':' in line:
                var_name, value = line.split(':', 1)
                STORE_VARIABLES[var_name] = value[:-1]
                data = data.replace(line, '')
            elif '(' in line and\
                 ')' in line:
                result = REGEX_FUNCTION.search(line)

                func_name = ''

                if result:
                    func_name, arg = list(result.groups())
                
                func = STORE_FUNCTIONS.get(func_name, None)
                if func:
                    result = func(arg)
                    data = data.replace(line, result)
                else:
                    data = data.replace(line, '')

        elif not line.startswith('@') and '@' in line:
            result = REGEX_VARIABLE.search(line).groups()
            
            for var_name in result:
                var_name = '@'+var_name
                value = STORE_VARIABLES.get(var_name, None)
                
                if value:
                    result = line.replace(var_name, value)
                    data = data.replace(line, result)

    return data