# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright (c) 2012 Openstack, LLC.
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.


import ConfigParser
import os
import string

# this import has the effect of defining global var "filters",
# referenced by build_filter(), below.  It gets set up by
# quantum-rootwrap, when we load_filters().
from quantum.rootwrap import filters


def build_filter(class_name, *args):
    """Returns a filter object of class class_name"""
    if not hasattr(filters, class_name):
        # TODO(jrd): Log the error (whenever quantum-rootwrap has a log file)
        return None
    filterclass = getattr(filters, class_name)
    return filterclass(*args)


def load_filters(filters_path):
    """Load filters from a list of directories"""
    filterlist = []
    for filterdir in filters_path:
        if not os.path.isdir(filterdir):
            continue
        for filterfile in os.listdir(filterdir):
            filterconfig = ConfigParser.RawConfigParser()
            filterconfig.read(os.path.join(filterdir, filterfile))
            for (name, value) in filterconfig.items("Filters"):
                filterdefinition = [string.strip(s) for s in value.split(',')]
                newfilter = build_filter(*filterdefinition)
                if newfilter is None:
                    continue
                filterlist.append(newfilter)
    return filterlist


def match_filter(filter_list, userargs):
    """
    Checks user command and arguments through command filters and
    returns the first matching filter, or None is none matched.
    """

    found_filter = None

    for f in filter_list:
        if f.match(userargs):
            if isinstance(f, filters.ExecCommandFilter):
                # This command calls exec verify that remaining args
                # matches another filter.
                leaf_filters = [fltr for fltr in filter_list
                                if not isinstance(fltr,
                                                  filters.ExecCommandFilter)]
                args = f.exec_args(userargs)
                if not args or not match_filter(leaf_filters, args):
                    continue

            # Try other filters if executable is absent
            if not os.access(f.exec_path, os.X_OK):
                if not found_filter:
                    found_filter = f
                continue
            # Otherwise return matching filter for execution
            return f

    # No filter matched or first missing executable
    return found_filter