package p2p

import (
	"blockchain-go/common/gopool"
	"blockchain-go/p2p/discover"
	"blockchain-go/p2p/enode"
	"blockchain-go/p2p/enr"
	"blockchain-go/p2p/nat"
	"blockchain-go/p2p/rlpx"
	"blockchain-go/params"
	"crypto/ecdsa"
	"errors"
	"fmt"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/ethereum/go-ethereum/p2p/netutil"
	"net"
	"os"
	"os/signal"
	"sort"
	"sync"
	"syscall"
	"time"
)

var (
	ErrServerStopped = errors.New("server stopped")
)

// Server manages all peer connections.
type Server struct {
	Config

	//newTransport func(net.Conn, *ecdsa.PublicKey) transport
	//newPeerHook  func(*Peer)
	//listenFunc func(network, addr string) (net.Listener, error)

	lock    sync.Mutex // protects running
	running bool

	listener     net.Listener
	ourHandshake *protoHandshake
	loopWG       sync.WaitGroup // loop, listenLoop
	//peerFeed event.Feed
	//log log.Logger

	//nodedb    *enode.DB
	localnode *enode.LocalNode
	ntab      *discover.UDPv4
	//DiscV5    *discover.UDPv5
	discmix   *enode.FairMix
	dialsched *dialScheduler

	quit chan struct{}
	//addtrusted    chan *enode.Node
	//removetrusted chan *enode.Node
	//peerOp                  chan peerOpFunc
	//peerOpDone              chan struct{}
	//delpeer                 chan peerDrop
	checkpointPostHandshake chan *conn
	checkpointAddPeer       chan *conn
	sigs                    chan os.Signal

	//inboundHistory expHeap
}

func (server *Server) Start() (err error) {
	server.sigs = make(chan os.Signal, 1)
	signal.Notify(server.sigs, syscall.SIGINT, syscall.SIGTERM)

	server.quit = make(chan struct{})
	server.checkpointPostHandshake = make(chan *conn)
	server.checkpointAddPeer = make(chan *conn)

	// 配置远端引导节点
	if err := server.setupBootstrapNodes(); err != nil {
		return err
	}

	// 配置本地协议
	if err := server.setupCaps(); err != nil {
		return nil
	}

	// 配置本地节点
	if err := server.setupLocalNode(); err != nil {
		return err
	}

	// 配置节点连接监听器
	if err := server.setupListening(); err != nil {
		return err
	}

	// 配置节点发现器
	if err := server.setupDiscovery(); err != nil {
		return err
	}

	// 配置拨号调度
	server.setupDialScheduler()

	// server核心运行
	go server.StopListener()
	server.run()

	return nil
}

func (server *Server) run() {
	server.loopWG.Add(1)

	fmt.Printf("Started P2P networking, self: %v.\n", server.localnode.Node().URLv4())

	var (
		peers        = make(map[enode.ID]*Peer)
		inboundCount = 0
	)

running:
	for {
		select {
		case <-server.quit:
			fmt.Printf("exit signal by user.\n")

			break running
		case c := <-server.checkpointPostHandshake:
			//p := server.launchPeer(c)
			//fmt.Printf("Check peer in local: %v\n", p.rw.node.IP())

			c.cont <- server.postHandshakeChecks(peers, inboundCount, c)
		case c := <-server.checkpointAddPeer:
			p := server.launchPeer(c)
			peers[c.node.ID()] = p
			server.dialsched.peerAdded(c)

			if p.Inbound() {
				inboundCount++
			}

			fmt.Printf("Adding p2p peer: %v, peer count: %v.\n", p.rw.node.IP(), len(peers))
		}
	}
}

func (server *Server) postHandshakeChecks(peers map[enode.ID]*Peer, inboundCount int, c *conn) error {
	switch {
	case !c.is(trustedConn) && len(peers) >= server.MaxPeers:
		return DiscTooManyPeers
	// TODO 暂时不做入站出站限制
	//case !c.is(trustedConn) && c.is(inboundConn) && inboundCount >= server.maxInboundConns():
	//	return DiscTooManyPeers
	case peers[c.node.ID()] != nil:
		return DiscAlreadyConnected
	case c.node.ID() == server.localnode.ID():
		return DiscSelf
	default:
		return nil
	}
}

func (server *Server) launchPeer(c *conn) *Peer {
	p := newPeer(c, server.Protocols)

	gopool.Submit(func() {
		server.runPeer(p)
	})

	return p
}

func (server *Server) runPeer(p *Peer) {
	// TODO 实现peer的细节
}

func (server *Server) StopListener() {
	<-server.sigs

	close(server.quit)
	server.loopWG.Done()
	server.discmix.Close()
	server.dialsched.stop()
}

// 本地协议
func (server *Server) setupCaps() (err error) {
	// 创建握手器
	publicKey := crypto.FromECDSAPub(&server.PrivateKey.PublicKey)
	server.ourHandshake = &protoHandshake{
		Version: baseProtocolVersion,
		Name:    server.Name,
		ID:      publicKey[1:],
	}

	// 配置握手器
	for _, capability := range OurCaps {
		server.ourHandshake.Caps = append(server.ourHandshake.Caps, capability)
	}
	sort.Sort(capsByNameAndVersion(server.ourHandshake.Caps))

	return nil
}

// 配置节点发现逻辑
func (server *Server) setupDiscovery() (err error) {
	server.discmix = enode.NewFairMix(discmixTimeout)

	// TODO 添加特定协议的发现源。
	//dnsclient := dnsdisc.NewClient(dnsdisc.Config{})
	//dialCandidates, err := dnsclient.NewIterator()
	//server.discmix.AddSource(dialCandidates)

	addr, err := net.ResolveUDPAddr("udp", server.ListenAddr)
	if err != nil {
		return err
	}
	conn, err := net.ListenUDP("udp", addr)
	if err != nil {
		return err
	}

	realAddr := conn.LocalAddr().(*net.UDPAddr)
	fmt.Printf("UDP listener up, addr: %v.\n", realAddr)

	if server.NAT != nil {
		if !realAddr.IP.IsLoopback() {
			server.loopWG.Add(1)

			gopool.Submit(func() {
				nat.Map(server.NAT, server.quit, "udp", realAddr.Port, realAddr.Port, "blockchain-p2p discovery")
				server.loopWG.Done()
			})
		}
	}
	server.localnode.SetFallbackUDP(realAddr.Port)

	// 设置V4的发现协议
	var unhandled chan discover.ReadPacket
	//var sconn *sharedUDPConn
	//if server.DiscoveryV5 {
	//	unhandled = make(chan discover.ReadPacket, 100)
	//	sconn = &sharedUDPConn{conn, unhandled}
	//}
	cfg := discover.Config{
		PrivateKey:  server.PrivateKey,
		NetRestrict: server.NetRestrict,
		Bootnodes:   server.BootstrapNodes,
		Unhandled:   unhandled,
		//Log:         server.log,
	}
	ntab, err := discover.ListenV4(conn, server.localnode, cfg)
	if err != nil {
		return err
	}
	server.ntab = ntab
	server.discmix.AddSource(ntab.RandomNodes())

	return nil
}

// 设置引导节点，更快发现指定网络
func (server *Server) setupBootstrapNodes() (err error) {
	urls := params.MainnetBootNodes

	server.BootstrapNodes = make([]*enode.Node, 0, len(urls))
	for _, url := range urls {
		if url != "" {
			node, err := enode.Parse(enode.ValidSchemes, url)
			if err != nil {
				return err
			}
			server.BootstrapNodes = append(server.BootstrapNodes, node)
		}
	}

	return nil
}

// 设置拨号调度器
func (server *Server) setupDialScheduler() {
	server.MaxPeers = params.MaxPeers
	server.MaxPendingPeers = params.MaxPendingPeers

	config := dialConfig{
		self:           server.localnode.ID(),
		maxDialPeers:   server.maxDialedConns(),
		maxActiveDials: server.MaxPendingPeers,
		log:            server.Logger,
		netRestrict:    server.NetRestrict,
		dialer:         server.Dialer,
		clock:          server.clock,
	}

	if server.ntab != nil {
		config.resolver = server.ntab
	}
	if config.dialer == nil {
		config.dialer = tcpDialer{&net.Dialer{Timeout: defaultDialTimeout}}
	}
	server.dialsched = newDialScheduler(config, server.discmix, server.SetupConn)
}

func (server *Server) maxDialedConns() (limit int) {
	if server.NoDial || server.MaxPeers == 0 {
		return 0
	}
	if server.DialRatio == 0 {
		limit = server.MaxPeers / defaultDialRatio
	} else {
		limit = server.MaxPeers / server.DialRatio
	}
	if limit == 0 {
		limit = 1
	}
	return limit
}

// 配置本地节点
func (server *Server) setupLocalNode() (err error) {
	// 创建本地节点
	server.localnode = enode.NewLocalNode(server.PrivateKey)
	server.localnode.SetFallbackIP(net.IP{127, 0, 0, 1})

	// 配置本地静态IP
	ip, _ := server.NAT.ExternalIP()
	server.localnode.SetStaticIP(ip)

	return nil
}

// 设置新节点连接监听器
func (server *Server) setupListening() (err error) {
	listener, err := net.Listen("tcp", params.ListenerPort)
	if err != nil {
		return err
	}

	server.listener = listener
	server.ListenAddr = listener.Addr().String()

	if tcp, ok := listener.Addr().(*net.TCPAddr); ok {
		server.localnode.Set(enr.TCP(tcp.Port))

		if !tcp.IP.IsLoopback() && server.NAT != nil {
			server.loopWG.Add(1)

			gopool.Submit(func() {
				nat.Map(server.NAT, server.quit, "tcp", tcp.Port, tcp.Port, "blockchain-p2p")

				server.loopWG.Done()
			})
		}
	}

	server.loopWG.Add(1)
	go server.listenLoop()

	return nil
}

func (server *Server) listenLoop() {
	fmt.Printf("TCP Listener up, addr: %v.\n", server.listener.Addr())

	tokens := defaultMaxPendingPeers
	slots := make(chan struct{}, tokens)
	for i := 0; i < tokens; i++ {
		slots <- struct{}{}
	}

	defer server.loopWG.Done()
	defer func() {
		for i := 0; i < cap(slots); i++ {
			<-slots
		}
	}()

	for {
		<-slots

		var (
			fd          net.Conn
			err         error
			lastLogTime time.Time
		)

		// accept处理
		for {
			fd, err = server.listener.Accept()
			if netutil.IsTemporaryError(err) {
				if time.Since(lastLogTime) > 1*time.Second {
					fmt.Errorf("temporary read error, err: %v", err)

					lastLogTime = time.Now()
				}
				time.Sleep(time.Millisecond * 200)
				continue
			} else if err != nil {
				fmt.Errorf("read error, err: %v", err)
				slots <- struct{}{}
				return
			}
			break
		}

		// accept成功的处理
		remoteIP := netutil.AddrIP(fd.RemoteAddr())
		// TODO 检查此IP是是否能加入本地节点的链接
		//if err := server.checkInboundConn(remoteIP); err != nil {
		//	srv.log.Debug("Rejected inbound connection", "addr", fd.RemoteAddr(), "err", err)
		//	fd.Close()
		//	slots <- struct{}{}
		//	continue
		//}
		if remoteIP != nil {
			var addr *net.TCPAddr
			if tcp, ok := fd.RemoteAddr().(*net.TCPAddr); ok {
				addr = tcp
			}
			fd = newMeteredConn(fd, true, addr)
			fmt.Printf("Accepted connection, addr: %v.", fd.RemoteAddr())
		}
		gopool.Submit(func() {
			server.SetupConn(fd, inboundConn, nil)
			slots <- struct{}{}
		})
	}
}

func (server *Server) newRLPX(conn net.Conn, dialDest *ecdsa.PublicKey) transport {
	return &rlpxTransport{conn: rlpx.NewConn(conn, dialDest)}
}

func (server *Server) SetupConn(fd net.Conn, flags connFlag, dialDest *enode.Node) error {
	//fmt.Printf("Setup conn %v.\n", fd.RemoteAddr())

	c := &conn{fd: fd, flags: flags, cont: make(chan error)}
	if dialDest == nil {
		c.transport = server.newRLPX(fd, nil)
	} else {
		c.transport = server.newRLPX(fd, dialDest.Pubkey())
	}

	err := server.setupConn(c, dialDest)
	if err != nil {
		c.close(err)
	}
	return err
}

func (server *Server) setupConn(c *conn, dialDest *enode.Node) error {
	remotePubkey, err := c.doEncHandshake(server.PrivateKey)
	if err != nil {
		return err
	}

	// 将connection转换成node
	c.node = enode.NodeFromConn(remotePubkey, c.fd)
	//fmt.Printf("Parse node: id: %v, addr: %v\n", c.node.ID(), c.fd.RemoteAddr())

	// 检查是否需要握手
	err = server.checkpoint(c, server.checkpointPostHandshake)
	if err != nil {
		return err
	}

	// 进行握手
	phs, err := c.doProtoHandshake(server.ourHandshake)
	if err != nil {
		return err
	}
	c.caps, c.name = phs.Caps, phs.Name
	//fmt.Printf("Handshake ok, id: %v, addr: %v.\n", c.node.ID(), c.fd.RemoteAddr())

	// 握手成功后将此链接放入addPeer的检查点
	err = server.checkpoint(c, server.checkpointAddPeer)
	if err != nil {
		return err
	}

	return nil
}

func (server *Server) checkpoint(c *conn, stage chan<- *conn) error {
	select {
	case stage <- c:
	case <-server.quit:
		return ErrServerStopped
	}
	return <-c.cont
}