from mininet.topo import Topo
from mininet.net import Mininet
from mininet.link import TCLink
from mininet.node import OVSBridge
from mininet.cli import CLI
from subprocess import Popen, PIPE

import logging

class MininetBuilder(Topo):
    def __init__(self):
        Topo.__init__( self )
        self.net = None

    def command_to(self, who, cmd):
        """
        Launch command `cmd` to the specific name space of `who`
        """
        return who.cmd(cmd)

    def command_global(self, cmd):
        """
        Launch command `cmd` over the global system, i.e., not specific to a name space
        """
        p = Popen(cmd, shell=True, stdout=PIPE, stderr=PIPE)
        stdout, stderr = p.communicate()
        if stderr:
            logging.error("Got error when running cmd: {}".format(cmd))
            return "Error"
        return stdout

    def start_network(self):
        """
        Start the network using Mininet

        Note that the use of OVSBridge avoid facing issues with OVS controllers.
        """
        self.net = Mininet(topo=self,link=TCLink,switch=OVSBridge)
        self.net.start()

    def get_cli(self):
        """
        Get the Mininet command line interface
        """
        if self.net is None:
            logging.error("Cannot get the CLI")
        else:
            CLI(self.net)

    def get_host(self, who):
        if self.net is None:
            logging.error("Network not available...")
            raise Exception("Network not ready")
        else:
            return self.net.getNodeByName(who)

    def stop_network(self):
        if self.net is None:
            logging.warning("Unable to stop the network: net is None")
        else:
            self.net.stop()