# Copyright 2008 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

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

goodpathre = re.compile("([%s]+/)*[%s]+$" % (allowedchars, allowedchars))

def goodpath(path):

    return goodpathre.match(path) is not None

goodglobre = re.compile("[*/%s]+$" % allowedchars)

def goodglob(pattern):

    return goodglobre.match(pattern) is not None

# Don't put anything except *A-Za-z0-9_- in rule globs or   

# it will match nothing.  No regexp metachars, not even .

# We may fix this later.

def globmatcher(pattern):

    if not goodglob(pattern):

        #fail("Bad glob pattern in auth config: %s" % pattern)

        # FIXME: report it somehow

        return lambda x: False

    # Substitution cunning so ** can be different from *

    pattern = pattern.replace("*", "[]")

    pattern = pattern.replace("[][]", "[/%s]*" % allowedchars)

    pattern = pattern.replace("[]", "[%s]*" % allowedchars)

    rex = re.compile(pattern + "$")

    # 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 Ruleset(object):

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

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

    def __init__(self):

        # The user called "root" automatically has the highest

        # privilege

        self.rules = [(self.levels[0], rule([('user', 'root')]))]

        self.preset = {}

    def add(self, action, conditions):

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

    def set(self, **kw):

        self.preset.update(kw)

    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)

    @classmethod

    def readfile(cls, fn):

        res = cls()

        try:

            f = open(fn)

            try:

                for l in f:

                    l = l.strip()

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

                        continue

                    l = l.split()

                    res.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

            return cls()

        return res