# -*- coding: utf-8 -*-
#
# Copyright (C) 2004-2009 Edgewall Software
# Copyright (C) 2004 Francois Harvey <fharvey@securiweb.net>
# Copyright (C) 2005 Matthew Good <trac@matt-good.net>
# All rights reserved.
#
# This software is licensed as described in the file COPYING, which
# you should have received as part of this distribution. The terms
# are also available at http://trac.edgewall.org/wiki/TracLicense.
#
# This software consists of voluntary contributions made by many
# individuals. For the exact contribution history, see the revision
# history and logs, available at http://trac.edgewall.org/log/.
#
# Author: Francois Harvey <fharvey@securiweb.net>
#         Matthew Good <trac@matt-good.net>

import os.path

from trac.config import Option
from trac.core import *
from trac.versioncontrol import Authorizer


class SvnAuthzOptions(Component):

    authz_file = Option('trac', 'authz_file', '',
        """Path to Subversion
        [http://svnbook.red-bean.com/en/1.1/ch06s04.html#svn-ch-6-sect-4.4.2 authorization (authz) file]
        """)

    authz_module_name = Option('trac', 'authz_module_name', '',
        """The module prefix used in the authz_file.""")


def SubversionAuthorizer(env, repos, authname):
    authz_file = env.config.get('trac', 'authz_file')
    if not authz_file:
        return Authorizer()
    if not os.path.isabs(authz_file):
        authz_file = os.path.join(env.path, authz_file)
    if not os.path.exists(authz_file):
        env.log.error('[trac] authz_file (%s) does not exist.' % authz_file)

    module_name = env.config.get('trac', 'authz_module_name')
    return RealSubversionAuthorizer(repos, authname, module_name, authz_file)

def parent_iter(path):
    path = path.strip('/')
    if path:
        path = '/' + path + '/'
    else:
        path = '/'

    while 1:
        yield path
        if path == '/':
            raise StopIteration()
        path = path[:-1]
        yield path
        idx = path.rfind('/')
        path = path[:idx + 1]


class RealSubversionAuthorizer(Authorizer):
    """FIXME: this should become a IPermissionPolicy, of course.

    `check_permission(username, action, resource)` should be able to
    replace `has_permission(path)` when resource is a `('source', path)`
    and `has_permission_for_changeset` when resource is a `('changeset', rev)`.
    """

    auth_name = ''
    module_name = ''
    conf_authz = None

    def __init__(self, repos, auth_name, module_name, cfg_file, cfg_fp=None):
        self.repos = repos
        self.auth_name = auth_name
        self.module_name = module_name
                                
        from ConfigParser import ConfigParser
        self.conf_authz = ConfigParser()
        if cfg_fp:
            self.conf_authz.readfp(cfg_fp, cfg_file)
        elif cfg_file:
            self.conf_authz.read(cfg_file)

        self.groups = self._groups()

    def has_permission(self, path):
        if path is None:
            return 1

        for p in parent_iter(path):
            if self.module_name:
                for perm in self._get_section(self.module_name + ':' + p):
                    if perm is not None:
                        return perm
            for perm in self._get_section(p):
                if perm is not None:
                    return perm

        return 0

    def has_permission_for_changeset(self, rev):
        changeset = self.repos.get_changeset(rev)
        for change in changeset.get_changes():
            # the repository checks permissions for each change, so just check
            # if any changes can be accessed
            return 1
        return 0

    # Internal API

    def _groups(self):
        if not self.conf_authz.has_section('groups'):
            return []

        grp_parents = {}
        usr_grps = []

        for group in self.conf_authz.options('groups'):
            for member in self.conf_authz.get('groups', group).split(','):
                member = member.strip()
                if member == self.auth_name:
                    usr_grps.append(group)
                elif member.startswith('@'):
                    grp_parents.setdefault(member[1:], []).append(group)

        expanded = {}

        def expand_group(group):
            if group in expanded:
                return
            expanded[group] = True
            for parent in grp_parents.get(group, []):
                expand_group(parent)

        for g in usr_grps:
            expand_group(g)

        # expand groups
        return expanded.keys()

    def _get_section(self, section):
        if not self.conf_authz.has_section(section):
            return

        yield self._get_permission(section, self.auth_name)

        group_perm = None
        for g in self.groups:
            p = self._get_permission(section, '@' + g)
            if p is not None:
                group_perm = p

            if group_perm:
                yield 1

        yield group_perm

        yield self._get_permission(section, '*')

    def _get_permission(self, section, subject):
        if self.conf_authz.has_option(section, subject):
            return 'r' in self.conf_authz.get(section, subject)
        return None