#!/usr/bin/env python

import sys
import copy
import Queue
import redis
import subprocess
import syslog
import os
from swsscommon import swsscommon


def run_command(command):
    syslog.syslog(syslog.LOG_DEBUG, "execute command {}.".format(command))
    p = subprocess.Popen(command, shell=True, stdout=subprocess.PIPE)
    stdout = p.communicate()[0]
    p.wait()
    if p.returncode != 0:
        syslog.syslog(syslog.LOG_ERR, 'command execution returned {}. Command: "{}", stdout: "{}"'.format(p.returncode, command, stdout))


class BGPConfigManager(object):
    def __init__(self, daemon):
        self.daemon = daemon
        self.bgp_asn = None
        self.bgp_message = Queue.Queue(0)
        daemon.add_manager(swsscommon.CONFIG_DB, swsscommon.CFG_DEVICE_METADATA_TABLE_NAME, self.__metadata_handler)
        daemon.add_manager(swsscommon.CONFIG_DB, swsscommon.CFG_BGP_NEIGHBOR_TABLE_NAME, self.__bgp_handler)

    def __metadata_handler(self, key, op, data):
        if key != "localhost" \
            or "bgp_asn" not in data \
                or self.bgp_asn == data["bgp_asn"]:
            return

        # TODO add ASN update commands 

        self.bgp_asn = data["bgp_asn"]
        self.__update_bgp()

    def __update_bgp(self):
        while not self.bgp_message.empty():
            key, op, data = self.bgp_message.get()
            syslog.syslog(syslog.LOG_INFO, 'value for {} changed to {}'.format(key, data))
            if op == swsscommon.SET_COMMAND:
                command = "vtysh -c 'configure terminal' -c 'router bgp {}' -c 'neighbor {} remote-as {}'".format(self.bgp_asn, key, data['asn'])
                run_command(command)
                if "name" in data:
                    command = "vtysh -c 'configure terminal' -c 'router bgp {}' -c 'neighbor {} description {}'".format(self.bgp_asn, key, data['name'])
                    run_command(command)
                if "admin_status" in data:
                    command_mod = "no " if data["admin_status"] == "up" else ""
                    command = "vtysh -c 'configure terminal' -c 'router bgp {}' -c '{}neighbor {} shutdown'".format(self.bgp_asn, command_mod, key)
                    run_command(command)                
            elif op == swsscommon.DEL_COMMAND:
                # Neighbor is deleted
                command = "vtysh -c 'configure terminal' -c 'router bgp {}' -c 'no neighbor {}'".format(self.bgp_asn, key)
                run_command(command)

    def __bgp_handler(self, key, op, data):
        self.bgp_message.put((key, op, data))
        # If ASN is not set, we just cache this message until the ASN is set.
        if self.bgp_asn == None:
            return
        self.__update_bgp()


class Daemon(object):
   
    SELECT_TIMEOUT = 1000
    SUPPORT_DATABASE_LIST = (swsscommon.APPL_DB, swsscommon.CONFIG_DB)

    def __init__(self):
        self.appl_db = swsscommon.DBConnector(swsscommon.APPL_DB, swsscommon.DBConnector.DEFAULT_UNIXSOCKET, 0)
        self.conf_db = swsscommon.DBConnector(swsscommon.CONFIG_DB, swsscommon.DBConnector.DEFAULT_UNIXSOCKET, 0)
        self.selector = swsscommon.Select()
        self.db_connectors = {}
        self.callbacks = {}
        self.subscribers = set()

    def get_db_connector(self, db):
        if db not in Daemon.SUPPORT_DATABASE_LIST:
            raise ValueError("database {} not Daemon support list {}.".format(db, SUPPORT_DATABASE_LIST))
        # if this database connector has been initialized
        if db not in self.db_connectors:
            self.db_connectors[db] = swsscommon.DBConnector(db, swsscommon.DBConnector.DEFAULT_UNIXSOCKET, 0)
        return self.db_connectors[db]

    def add_manager(self, db, table_name, callback):
        if db not in self.callbacks:
            self.callbacks[db] = {}
        if table_name not in self.callbacks[db]:
            self.callbacks[db][table_name] = []
            conn = self.get_db_connector(db)
            subscriber = swsscommon.SubscriberStateTable(conn, table_name)
            self.subscribers.add(subscriber)
            self.selector.addSelectable(subscriber)
        self.callbacks[db][table_name].append(callback)

    def start(self):
        while True:
            state, selectable = self.selector.select(Daemon.SELECT_TIMEOUT)
            if not selectable:
                continue
            for subscriber in self.subscribers:
                key, op, fvs = subscriber.pop()
                # if no new message
                if not key:
                    continue
                data = dict(fvs)
                syslog.syslog(syslog.LOG_DEBUG, "Receive message : {}".format((key, op, fvs)))
                for callback in self.callbacks[subscriber.getDbConnector().getDbId()][subscriber.getTableName()]:
                    callback(key, op, data)


def main():
    syslog.openlog("bgpcfgd")
    daemon = Daemon()
    bgp_manager = BGPConfigManager(daemon)
    daemon.start()
    syslog.closelog()

if __name__ == "__main__":
    main()