# Copyright 2008-2009 LShift Ltd

# Author(s):

# Paul Crowley <paul@lshift.net>

#

# This software may be used and distributed according to the terms

# of the GNU General Public License, incorporated herein by reference.

import sys

import re

import os

import os.path

allowedchars = "A-Za-z0-9_-"

def globmatcher(pattern):

    p = "[^/]*".join(re.escape(c) for c in pattern.split("*"))

    # ** means "match recursively" ie "ignore directories"

    rex = re.compile(p.replace("[^/]*[^/]*", ".*") + "$")

    # None matches everything

    return lambda x: x is None or rex.match(x) is not None

def rule(pairs):

    matchers = [(k, globmatcher(v)) for k, v in pairs]

    def c(kw):

        for k, m in matchers:

            if k not in kw or not m(kw[k]):

                return False

        return True

    return c

class AccessException(Exception):

    pass

class Ruleset(object):

    '''Class representing the rules in a rule file'''

    levels = ["init", "write", "read", "deny"]

    def __init__(self):

        self.rules = []

        self.preset = {}

    def add(self, action, conditions):

        self.rules.append((action, conditions))

    def set(self, **kw):

        self.preset.update(kw)

    def get(self, k):

        return self.preset.get(k, None)

    def matchrule(self, kw):

        d = self.preset.copy()

        d.update(kw)

        for a, c in self.rules:

            if c(d):

                return a

        return None

    def allow(self, level, **kw):

        a = self.matchrule(kw)

        return a in self.levels and self.levels.index(a) <= self.levels.index(level)

    def check(self, level, **kw):

        if not self.allow(level, **kw):

            raise AccessException()

    def readfile(self, fn):

        try:

            f = open(fn)

            try:

                for l in f:

                    l = l.strip()

                    if len(l) == 0 or l.startswith("#"):

                        continue

                    l = l.split()

                    self.add(l[0], rule([c.split("=", 1) for c in l[1:]]))

            finally:

                f.close()

        except Exception, e:

            print >> sys.stderr, "Failure reading rules file:", e

rules = Ruleset()