# -*- Mode:python; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
#
# Copyright (C) 2015-2019, The University of Memphis,
#                          Arizona Board of Regents,
#                          Regents of the University of California.
#
# This file is part of Mini-NDN.
# See AUTHORS.md for a complete list of Mini-NDN authors and contributors.
#
# Mini-NDN 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.
#
# Mini-NDN 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 Mini-NDN, e.g., in COPYING.md file.
# If not, see <http://www.gnu.org/licenses/>.

from igraph import Graph
from mininet.log import info

class LinkInfo(object):
    """
    This class is used to encapsule link information (IP and interface names).
    """

    def __init__(self, start_intf_name, start_ip, end_intf_name, end_ip):
        self.start_intf_name = start_intf_name
        self.start_intf_ip = start_ip
        self.end_intf_name = end_intf_name
        self.end_ip = end_ip

class IPRoutingHelper(object):
    """The routing helper allows to run IP-based evaluations with Mini-NDN. It configures static IP
    routes to all nodes, which means that all nodes can reach all other nodes in the network
    reachable, even when relaying is required.

     Usage from Experiment folder: `IPRoutingHelper.calcAllRoutes(self.net)`
    """

    @staticmethod
    def findLinkInformation(links, first_node, second_node):
        """ This method returns link information of a link connecting two nodes.

        :param links: All links in the emulation topology
        :param first_node: Current node which is looked at
        :param second_node: Target node (neighbour  of first_node)
        :return: Link information as LinkInfo object, or returns null None if the
            nodes are not directly connected
        """
        for link in links:
            if link.intf1.node.name == first_node and link.intf2.node.name == second_node:
                return LinkInfo(link.intf1.name, link.intf1.ip, link.intf2.name, link.intf2.ip)
            elif link.intf2.node.name == first_node and link.intf1.node.name == second_node:
                return LinkInfo(link.intf2.name, link.intf2.ip, link.intf1.name, link.intf1.ip)

        return None

    @staticmethod
    def calcAllRoutes(net):
        """ Configures IP routes between all nodes in the emulation topology. This is done in three
         steps:

        1) IP forwarding is enabled on all nodes
        2) The igraph lib is used to calculate all shortest paths between the nodes
        3) Route add commands are used to actually configure the ip routes

        :param net:
        """

        mini_nodes = net.hosts
        mini_links = net.links

        # Enabling IP forwaring on all nodes
        info('Configure IP forwarding on all nodes\n')
        for node in mini_nodes:
            node.cmd('sysctl -w net.ipv4.ip_forward=1')

        # Calculate igraph to calculate all shortest paths between nodes
        node_names = [node.name for node in mini_nodes]
        links = []
        for link in mini_links:
            links.append((link.intf1.node.name, link.intf2.node.name))
            links.append((link.intf2.node.name, link.intf1.node.name))

        networkGraph = Graph()
        networkGraph = networkGraph.as_directed()
        for node in node_names:
            networkGraph.add_vertex(node)
        for (a, b) in links:
            networkGraph.add_edges([(a, b), (b, a)])

        named_paths = []
        for from_node in node_names:
            for to_node in node_names:
                if from_node != to_node:
                    paths = networkGraph.get_all_shortest_paths(from_node, to_node)
                    if len(paths) == 0:
                        continue
                    shortest_path = paths[0]
                    shortest_path_with_nodenames = []
                    for node in shortest_path:
                        shortest_path_with_nodenames.append(networkGraph.vs['name'][node])
                    named_paths.append(shortest_path_with_nodenames)

        # Iterate over all paths and configure the routes using the 'route add'
        info('Configure routes on all nodes\n')
        for path in named_paths:
            start_node = path[0]
            end_node = path[-1]
            mini_start = net.get(start_node)
            mini_end = net.get(end_node)

            link_info = IPRoutingHelper.findLinkInformation(mini_links, path[0], path[1])
            start_intf = link_info.start_intf_name

            for intf in mini_end.intfs:
                addr = mini_end.intfs[intf].ip
                if len(path) == 2:
                    # For direct connection, configure exit interface
                    info('[{}] route add -host {} dev {}\n'.format(start_node, addr, start_intf))
                    mini_start.cmd('route add -host {} dev {}'.format(addr, start_intf))
                elif len(path) > 2:
                    # For longer paths, configure next hop as gateway
                    gateway_ip = link_info.end_ip
                    info('[{}] route add -host {} dev {} gw {}\n'
                         .format(start_node, addr, start_intf, gateway_ip))
                    mini_start.cmd('route add -host {} dev {} gw {}'
                                   .format(addr, start_intf, gateway_ip))