"""

Glob-based, order-based rules matcher that can answer "maybe"

where the inputs make clear that something is unknown.

"""

import sys

import re

import os

import os.path

def globmatcher(pattern):

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

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

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

# Returns True for a definite match

# False for a definite non-match

# None where we can't be sure because a key is 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:

                return False

            kkw = kw[k]

            if kkw is None:

                return False

    return c

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 matchrules(self, kw):

        d = self.preset.copy()

        d.update(kw)

        res = set()

        for a, c in self.rules:

            m = c(d)

            if m is None:

                # "Maybe match" - add it and carry on

                res.add(a)

            elif m:

                # Definite match - add it and stop

                res.add(a)

                break

        return res

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

        for a in self.matchrules(kw):

            if a in self.levels:

                if self.levels.index(a) <= self.levels.index(level):

                    return True

        return False

    def readfile(self, fn):

        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()

rules = Ruleset()