"""

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 1 for a definite match

# -1 for a definite non-match

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

def rmatch(k, m, kw):

    if k not in kw:

        return -1

    kkw = kw[k]

    if kkw is None:

        return 0

    elif m.match(kkw) is None:

        return -1

    else:

        return 1

def rule(pairs):

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

    def c(kw):

        return min(rmatch(k, m, kw) for k, m in matchers)

    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 set(self, **kw):

        self.preset.update(kw)

    def get(self, k):

        return self.preset.get(k, None)

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

        levelindex = self.levels.index(level)

        d = self.preset.copy()

        d.update(kw)

        for a, c in self.rules:

            m = c(d)

            if m == 1:

                # Definite match - what it says goes

                return a <= levelindex

            elif m == 0:

                # "Maybe match" - allow if it says yes, ignore if no

                if a <= levelindex:

                    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()

                # Unrecognized actions are off the high end

                if l[0] in self.levels:

                    ix = self.levels.index(l[0])

                else:

                    ix = len(self.levels)

                self.rules.append((ix, 

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

        finally:

            f.close()

rules = Ruleset()