package node

import (
	"context"
	"crypto/ecdsa"
	"encoding/binary"
	"errors"
	"fmt"
	"math"
	"net"
	"strconv"

	"github.com/ethereum/go-ethereum/p2p/enode"
	"github.com/ethereum/go-ethereum/p2p/enr"
	ma "github.com/multiformats/go-multiaddr"
	"github.com/waku-org/go-waku/logging"
	"github.com/waku-org/go-waku/waku/v2/utils"
	"go.uber.org/zap"
)

func (w *WakuNode) newLocalnode(priv *ecdsa.PrivateKey) (*enode.LocalNode, error) {
	db, err := enode.OpenDB("")
	if err != nil {
		return nil, err
	}
	return enode.NewLocalNode(db, priv), nil
}

func (w *WakuNode) updateLocalNode(localnode *enode.LocalNode, priv *ecdsa.PrivateKey, wsAddr []ma.Multiaddr, ipAddr *net.TCPAddr, udpPort int, wakuFlags utils.WakuEnrBitfield, advertiseAddr *net.IP, log *zap.Logger) error {
	localnode.SetFallbackUDP(udpPort)
	localnode.Set(enr.WithEntry(utils.WakuENRField, wakuFlags))
	localnode.SetFallbackIP(net.IP{127, 0, 0, 1})
	localnode.SetStaticIP(ipAddr.IP)

	if udpPort > 0 && udpPort <= math.MaxUint16 {
		localnode.Set(enr.UDP(uint16(udpPort))) // lgtm [go/incorrect-integer-conversion]
	}

	if ipAddr.Port > 0 && ipAddr.Port <= math.MaxUint16 {
		localnode.Set(enr.TCP(uint16(ipAddr.Port))) // lgtm [go/incorrect-integer-conversion]
	} else {
		log.Error("setting tcpPort", zap.Int("port", ipAddr.Port))
	}

	if advertiseAddr != nil {
		localnode.SetStaticIP(*advertiseAddr)
	}

	// Adding websocket multiaddresses
	var fieldRaw []byte

	for _, addr := range wsAddr {
		p2p, err := addr.ValueForProtocol(ma.P_P2P)
		if err != nil {
			return err
		}

		p2pAddr, err := ma.NewMultiaddr("/p2p/" + p2p)
		if err != nil {
			return fmt.Errorf("could not create p2p addr: %w", err)
		}

		maRaw := addr.Decapsulate(p2pAddr).Bytes()
		maSize := make([]byte, 2)
		binary.BigEndian.PutUint16(maSize, uint16(len(maRaw)))

		fieldRaw = append(fieldRaw, maSize...)
		fieldRaw = append(fieldRaw, maRaw...)
	}

	if len(fieldRaw) != 0 {
		localnode.Set(enr.WithEntry(utils.MultiaddrENRField, fieldRaw))
	}

	return nil
}

func isPrivate(addr candidateAddr) bool {
	return addr.ip.IP.IsPrivate()
}

func isExternal(addr candidateAddr) bool {
	return !isPrivate(addr) && !addr.ip.IP.IsLoopback() && !addr.ip.IP.IsUnspecified()
}

func isLoopback(addr candidateAddr) bool {
	return addr.ip.IP.IsLoopback()
}

func filterIP(ss []candidateAddr, fn func(candidateAddr) bool) (ret []candidateAddr) {
	for _, s := range ss {
		if fn(s) {
			ret = append(ret, s)
		}
	}
	return
}

type candidateAddr struct {
	ip    *net.TCPAddr
	maddr ma.Multiaddr
}

func extractIP(addr ma.Multiaddr) (*net.TCPAddr, error) {
	var ipStr string
	dns4, err := addr.ValueForProtocol(ma.P_DNS4)
	if err != nil {
		ipStr, err = addr.ValueForProtocol(ma.P_IP4)
		if err != nil {
			return nil, err
		}
	} else {
		netIP, err := net.ResolveIPAddr("ip4", dns4)
		if err != nil {
			return nil, err
		}
		ipStr = netIP.String()
	}

	portStr, err := addr.ValueForProtocol(ma.P_TCP)
	if err != nil {
		return nil, err
	}
	port, err := strconv.Atoi(portStr)
	if err != nil {
		return nil, err
	}
	return &net.TCPAddr{
		IP:   net.ParseIP(ipStr),
		Port: port,
	}, nil
}

func selectMostExternalAddress(addresses []ma.Multiaddr) (ma.Multiaddr, *net.TCPAddr, error) {
	var ipAddrs []candidateAddr

	for _, addr := range addresses {
		ipAddr, err := extractIP(addr)
		if err != nil {
			continue
		}

		ipAddrs = append(ipAddrs, candidateAddr{
			ip:    ipAddr,
			maddr: addr,
		})
	}

	externalIPs := filterIP(ipAddrs, isExternal)
	if len(externalIPs) > 0 {
		return externalIPs[0].maddr, externalIPs[0].ip, nil
	}

	privateIPs := filterIP(ipAddrs, isPrivate)
	if len(privateIPs) > 0 {
		return privateIPs[0].maddr, privateIPs[0].ip, nil
	}

	loopback := filterIP(ipAddrs, isLoopback)
	if len(loopback) > 0 {
		return loopback[0].maddr, loopback[0].ip, nil
	}

	return nil, nil, errors.New("could not obtain ip address")
}

func selectWSListenAddress(addresses []ma.Multiaddr, extAddr ma.Multiaddr) ([]ma.Multiaddr, error) {
	extAddrDNS, err := extAddr.ValueForProtocol(ma.P_DNS4)
	var extAddrIP string
	if err != nil {
		extAddrIP, err = extAddr.ValueForProtocol(ma.P_IP4)
		if err != nil {
			return nil, err
		}
	}

	var result []ma.Multiaddr
	for _, addr := range addresses {
		// Filter addresses that match the extAddr
		if extAddrDNS != "" {
			dns4, err := addr.ValueForProtocol(ma.P_DNS4)
			if err != nil {
				continue
			}
			if dns4 != extAddrDNS {
				continue
			}
		} else {
			ip4, err := addr.ValueForProtocol(ma.P_IP4)
			if err != nil {
				continue
			}
			if ip4 != extAddrIP {
				continue
			}
		}

		_, err := addr.ValueForProtocol(ma.P_WS)
		if err == nil {
			result = append(result, addr)
		}

		_, err = addr.ValueForProtocol(ma.P_WSS)
		if err == nil {
			result = append(result, addr)
		}
	}

	return result, nil
}

func (w *WakuNode) setupENR(ctx context.Context, addrs []ma.Multiaddr) error {
	extAddr, ipAddr, err := selectMostExternalAddress(addrs)
	if err != nil {
		w.log.Error("obtaining external address", zap.Error(err))
		return err
	}

	wsAddresses, err := selectWSListenAddress(addrs, extAddr)
	if err != nil {
		w.log.Error("obtaining websocket addresses", zap.Error(err))
		return err
	}

	// TODO: make this optional depending on DNS Disc being enabled
	if w.opts.privKey != nil && w.localNode != nil {
		err := w.updateLocalNode(w.localNode, w.opts.privKey, wsAddresses, ipAddr, w.opts.udpPort, w.wakuFlag, w.opts.advertiseAddr, w.log)
		if err != nil {
			w.log.Error("obtaining ENR record from multiaddress", logging.MultiAddrs("multiaddr", extAddr), zap.Error(err))
			return err
		} else {
			w.log.Info("enr record", logging.ENode("enr", w.localNode.Node()))
			// Restarting DiscV5
			discV5 := w.DiscV5()
			if discV5 != nil && discV5.IsStarted() {
				w.log.Info("restarting discv5")
				w.discoveryV5.Stop()
				err = w.discoveryV5.Start(ctx)
				if err != nil {
					w.log.Error("could not restart discv5", zap.Error(err))
					return err
				}
			}
		}
	}

	return nil
}