# Copyright 2017 RedHat, inc
#
# This file is part of Ansible
#
# Ansible 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.
#
# Ansible 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 Ansible.  If not, see <http://www.gnu.org/licenses/>.
#############################################
'''
DOCUMENTATION:
    name: constructed
    plugin_type: inventory
    version_added: "2.4"
    short_description: Uses Jinja2 to construct vars and groups based on existing inventory.
    description:
        - Uses a YAML configuration file to define var expresisions and group conditionals
        - The Jinja2 conditionals that qualify a host for membership.
        - The JInja2 exprpessions are calculated and assigned to the variables
        - Only variables already available from previous inventories can be used for templating.
        - Failed expressions will be ignored (assumes vars were missing).
    compose:
        description: create vars from jinja2 expressions
        type: dictionary
        default: {}
    groups:
        description: add hosts to group based on Jinja2 conditionals
        type: dictionary
        default: {}
EXAMPLES: | # inventory.config file in YAML format
    plugin: comstructed
    compose:
        var_sum: var1 + var2
    groups:
        # simple name matching
        webservers: inventory_hostname.startswith('web')

        # using ec2 'tags' (assumes aws inventory)
        development: "'devel' in (ec2_tags|list)"

        # using other host properties populated in inventory
        private_only: not (public_dns_name is defined or ip_address is defined)

        # complex group membership
        multi_group: (group_names|intersection(['alpha', 'beta', 'omega']))|length >= 2
'''

from __future__ import (absolute_import, division, print_function)
__metaclass__ = type

import os

from ansible.errors import AnsibleParserError
from ansible.plugins.inventory import BaseInventoryPlugin
from ansible.module_utils._text import to_native
from ansible.utils.vars import combine_vars


class InventoryModule(BaseInventoryPlugin):
    """ constructs groups and vars using Jinaj2 template expressions """

    NAME = 'constructed'

    def __init__(self):

        super(InventoryModule, self).__init__()

    def verify_file(self, path):

        valid = False
        if super(InventoryModule, self).verify_file(path):
            file_name, ext = os.path.splitext(path)

            if not ext or ext == '.config':
                valid = True

        return valid

    def parse(self, inventory, loader, path, cache=False):
        ''' parses the inventory file '''

        super(InventoryModule, self).parse(inventory, loader, path, cache=True)

        try:
            data = self.loader.load_from_file(path)
        except Exception as e:
            raise AnsibleParserError("Unable to parse %s: %s" % (to_native(path), to_native(e)))

        if not data or data.get('plugin') != self.NAME:
            raise AnsibleParserError("%s is empty or not a constructed groups config file" % (to_native(path)))

        try:
            # Go over hosts (less var copies)
            for host in inventory.hosts:

                # get available variables to templar
                hostvars = inventory.hosts[host].get_vars()
                if host in inventory.cache:  # adds facts if cache is active
                    hostvars = combine_vars(hostvars, inventory.cache[host])

                # create composite vars
                self._set_composite_vars(data.get('compose'), hostvars, host)

                # constructed groups based on conditionals
                self._add_host_to_composed_groups(data.get('groups'), hostvars, host)

        except Exception as e:
            raise AnsibleParserError("failed to parse %s: %s " % (to_native(path), to_native(e)))