// Copyright (C) 2015-2016 Nippon Telegraph and Telephone Corporation.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package server

import (
	"fmt"
	log "github.com/Sirupsen/logrus"
	"github.com/osrg/gobgp/config"
	"github.com/osrg/gobgp/packet/bgp"
	"github.com/osrg/gobgp/packet/bmp"
	"github.com/osrg/gobgp/table"
	"net"
	"strconv"
	"time"
)

func (b *bmpClient) tryConnect() *net.TCPConn {
	interval := 1
	for {
		log.Debug("connecting bmp server: ", b.host)
		conn, err := net.Dial("tcp", b.host)
		if err != nil {
			select {
			case <-b.dead:
				return nil
			default:
			}
			time.Sleep(time.Duration(interval) * time.Second)
			if interval < 30 {
				interval *= 2
			}
		} else {
			log.Info("bmp server is connected, ", b.host)
			return conn.(*net.TCPConn)
		}
	}
}

func (b *bmpClient) Stop() {
	close(b.dead)
}

func (b *bmpClient) loop() {
	for {
		conn := b.tryConnect()
		if conn == nil {
			break
		}

		if func() bool {
			ops := []WatchOption{WatchPeerState(true)}
			if b.typ != config.BMP_ROUTE_MONITORING_POLICY_TYPE_POST_POLICY {
				ops = append(ops, WatchUpdate(true))
			} else if b.typ != config.BMP_ROUTE_MONITORING_POLICY_TYPE_PRE_POLICY {
				ops = append(ops, WatchPostUpdate(true))
			}
			w := b.s.Watch(ops...)
			defer w.Stop()

			write := func(msg *bmp.BMPMessage) error {
				buf, _ := msg.Serialize()
				_, err := conn.Write(buf)
				if err != nil {
					log.Warnf("failed to write to bmp server %s", b.host)
				}
				return err
			}

			if err := write(bmp.NewBMPInitiation([]bmp.BMPTLV{})); err != nil {
				return false
			}

			for {
				select {
				case ev := <-w.Event():
					switch msg := ev.(type) {
					case *watcherEventUpdateMsg:
						info := &table.PeerInfo{
							Address: msg.peerAddress,
							AS:      msg.peerAS,
							ID:      msg.peerID,
						}
						if err := write(bmpPeerRoute(bmp.BMP_PEER_TYPE_GLOBAL, msg.postPolicy, 0, info, msg.timestamp.Unix(), msg.payload)); err != nil {
							return false
						}
					case *watcherEventStateChangedMsg:
						info := &table.PeerInfo{
							Address: msg.peerAddress,
							AS:      msg.peerAS,
							ID:      msg.peerID,
						}
						if msg.state == bgp.BGP_FSM_ESTABLISHED {
							if err := write(bmpPeerUp(msg.localAddress.String(), msg.localPort, msg.peerPort, msg.sentOpen, msg.recvOpen, bmp.BMP_PEER_TYPE_GLOBAL, false, 0, info, msg.timestamp.Unix())); err != nil {
								return false
							}
						} else {
							if err := write(bmpPeerDown(bmp.BMP_PEER_DOWN_REASON_UNKNOWN, bmp.BMP_PEER_TYPE_GLOBAL, false, 0, info, msg.timestamp.Unix())); err != nil {
								return false
							}
						}
					}
				case <-b.dead:
					conn.Close()
					return true
				}
			}
		}() {
			return
		}
	}
}

type bmpClient struct {
	s    *BgpServer
	dead chan struct{}
	host string
	typ  config.BmpRouteMonitoringPolicyType
}

func bmpPeerUp(laddr string, lport, rport uint16, sent, recv *bgp.BGPMessage, t uint8, policy bool, pd uint64, peeri *table.PeerInfo, timestamp int64) *bmp.BMPMessage {
	ph := bmp.NewBMPPeerHeader(t, policy, pd, peeri.Address.String(), peeri.AS, peeri.ID.String(), float64(timestamp))
	return bmp.NewBMPPeerUpNotification(*ph, laddr, lport, rport, sent, recv)
}

func bmpPeerDown(reason uint8, t uint8, policy bool, pd uint64, peeri *table.PeerInfo, timestamp int64) *bmp.BMPMessage {
	ph := bmp.NewBMPPeerHeader(t, policy, pd, peeri.Address.String(), peeri.AS, peeri.ID.String(), float64(timestamp))
	return bmp.NewBMPPeerDownNotification(*ph, reason, nil, []byte{})
}

func bmpPeerRoute(t uint8, policy bool, pd uint64, peeri *table.PeerInfo, timestamp int64, payload []byte) *bmp.BMPMessage {
	ph := bmp.NewBMPPeerHeader(t, policy, pd, peeri.Address.String(), peeri.AS, peeri.ID.String(), float64(timestamp))
	m := bmp.NewBMPRouteMonitoring(*ph, nil)
	body := m.Body.(*bmp.BMPRouteMonitoring)
	body.BGPUpdatePayload = payload
	return m
}

func (b *bmpClientManager) addServer(c *config.BmpServerConfig) error {
	host := net.JoinHostPort(c.Address, strconv.Itoa(int(c.Port)))
	if _, y := b.clientMap[host]; y {
		return fmt.Errorf("bmp client %s is already configured", host)
	}
	b.clientMap[host] = &bmpClient{
		s:    b.s,
		dead: make(chan struct{}),
		host: host,
		typ:  c.RouteMonitoringPolicy,
	}
	go b.clientMap[host].loop()
	return nil
}

func (b *bmpClientManager) deleteServer(c *config.BmpServerConfig) error {
	host := net.JoinHostPort(c.Address, strconv.Itoa(int(c.Port)))
	if c, y := b.clientMap[host]; !y {
		return fmt.Errorf("bmp client %s isn't found", host)
	} else {
		c.Stop()
		delete(b.clientMap, host)
	}
	return nil
}

type bmpClientManager struct {
	s         *BgpServer
	clientMap map[string]*bmpClient
}

func newBmpClientManager(s *BgpServer) *bmpClientManager {
	return &bmpClientManager{
		s:         s,
		clientMap: make(map[string]*bmpClient),
	}
}