# Copyright (C) 2007-2010 by the Free Software Foundation, Inc.
#
# This file is part of GNU Mailman.
#
# GNU Mailman is free software: you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free
# Software Foundation, either version 3 of the License, or (at your option)
# any later version.
#
# GNU Mailman is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
# more details.
#
# You should have received a copy of the GNU General Public License along with
# GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.

"""Application support for chain processing."""

from __future__ import absolute_import, unicode_literals

__metaclass__ = type
__all__ = [
    'initialize',
    'process',
    ]


from mailman.chains.accept import AcceptChain
from mailman.chains.builtin import BuiltInChain
from mailman.chains.discard import DiscardChain
from mailman.chains.headers import HeaderMatchChain
from mailman.chains.hold import HoldChain
from mailman.chains.reject import RejectChain
from mailman.config import config
from mailman.interfaces.chain import LinkAction



def process(mlist, msg, msgdata, start_chain='built-in'):
    """Process the message through a chain.

    :param mlist: the IMailingList for this message.
    :param msg: The Message object.
    :param msgdata: The message metadata dictionary.
    :param start_chain: The name of the chain to start the processing with.
    """
    # Set up some bookkeeping.
    chain_stack = []
    msgdata['rule_hits'] = hits = []
    msgdata['rule_misses'] = misses = []
    # Find the starting chain and begin iterating through its links.
    chain = config.chains[start_chain]
    chain_iter = chain.get_links(mlist, msg, msgdata)
    # Loop until we've reached the end of all processing chains.
    while chain:
        # Iterate over all links in the chain.  Do this outside a for-loop so
        # we can capture a chain's link iterator in mid-flight.  This supports
        # the 'detour' link action.
        try:
            link = next(chain_iter)
        except StopIteration:
            # This chain is exhausted.  Pop the last chain on the stack and
            # continue iterating through it.  If there's nothing left on the
            # chain stack then we're completely finished processing.
            if len(chain_stack) == 0:
                return
            chain, chain_iter = chain_stack.pop()
            continue
        # Process this link.
        if link.rule.check(mlist, msg, msgdata):
            if link.rule.record:
                hits.append(link.rule.name)
            # The rule matched so run its action.
            if link.action is LinkAction.jump:
                chain = link.chain
                chain_iter = chain.get_links(mlist, msg, msgdata)
                continue
            elif link.action is LinkAction.detour:
                # Push the current chain so that we can return to it when
                # the next chain is finished.
                chain_stack.append((chain, chain_iter))
                chain = link.chain
                chain_iter = chain.get_links(mlist, msg, msgdata)
                continue
            elif link.action is LinkAction.stop:
                # Stop all processing.
                return
            elif link.action is LinkAction.defer:
                # Just process the next link in the chain.
                pass
            elif link.action is LinkAction.run:
                link.function(mlist, msg, msgdata)
            else:
                raise AssertionError(
                    'Bad link action: {0}'.format(link.action))
        else:
            # The rule did not match; keep going.
            if link.rule.record:
                misses.append(link.rule.name)



def initialize():
    """Set up chains, both built-in and from the database."""
    for chain_class in (DiscardChain, HoldChain, RejectChain, AcceptChain):
        chain = chain_class()
        assert chain.name not in config.chains, (
            'Duplicate chain name: {0}'.format(chain.name))
        config.chains[chain.name] = chain
    # Set up a couple of other default chains.
    chain = BuiltInChain()
    config.chains[chain.name] = chain
    # Create and initialize the header matching chain.
    chain = HeaderMatchChain()
    config.chains[chain.name] = chain
    # XXX Read chains from the database and initialize them.
    pass