/*
   Copyright 2022 Erigon-Lightclient contributors
   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 sentinel

import (
	"crypto/ecdsa"
	"fmt"
	"net"
	"strings"

	"github.com/ledgerwatch/erigon/p2p/discover"
	"github.com/ledgerwatch/log/v3"
	"github.com/libp2p/go-libp2p"
	"github.com/libp2p/go-libp2p-core/crypto"
	"github.com/libp2p/go-libp2p/config"
	"github.com/libp2p/go-libp2p/p2p/muxer/mplex"
	"github.com/libp2p/go-libp2p/p2p/security/noise"
	"github.com/libp2p/go-libp2p/p2p/transport/tcp"
	"github.com/multiformats/go-multiaddr"
	"github.com/pkg/errors"
)

type SentinelConfig struct {
	DiscoverConfig discover.Config
	IpAddr         string
	Port           int
	TCPPort        uint
	// Optional
	LocalIP       string
	EnableUPnP    bool
	RelayNodeAddr string
	HostAddress   string
	HostDNS       string
}

func convertToCryptoPrivkey(privkey *ecdsa.PrivateKey) (crypto.PrivKey, error) {
	privBytes := privkey.D.Bytes()
	// In the event the number of bytes outputted by the big-int are less than 32,
	// we append bytes to the start of the sequence for the missing most significant
	// bytes.
	if len(privBytes) < 32 {
		privBytes = append(make([]byte, 32-len(privBytes)), privBytes...)
	}
	return crypto.UnmarshalSecp256k1PrivateKey(privBytes)
}

// Adds a private key to the libp2p option if the option was provided.
// If the private key file is missing or cannot be read, or if the
// private key contents cannot be marshaled, an exception is thrown.
func privKeyOption(privkey *ecdsa.PrivateKey) libp2p.Option {
	return func(cfg *libp2p.Config) error {
		ifaceKey, err := convertToCryptoPrivkey(privkey)
		if err != nil {
			return err
		}
		log.Debug("ECDSA private key generated")
		return cfg.Apply(libp2p.Identity(ifaceKey))
	}
}

func withRelayAddrs(relay string) config.AddrsFactory {
	return func(addrs []multiaddr.Multiaddr) []multiaddr.Multiaddr {
		if relay == "" {
			return addrs
		}

		var relayAddrs []multiaddr.Multiaddr

		for _, a := range addrs {
			if strings.Contains(a.String(), "/p2p-circuit") {
				continue
			}
			relayAddr, err := multiaddr.NewMultiaddr(relay + "/p2p-circuit" + a.String())
			if err != nil {
				log.Debug("Failed to create multiaddress for relay node")
			} else {
				relayAddrs = append(relayAddrs, relayAddr)
			}
		}

		if len(relayAddrs) == 0 {
			log.Warn("Addresses via relay node are zero - using non-relay addresses")
			return addrs
		}
		return append(addrs, relayAddrs...)
	}
}

// multiAddressBuilder takes in an ip address string and port to produce a go multiaddr format.
func multiAddressBuilder(ipAddr string, port uint) (multiaddr.Multiaddr, error) {
	parsedIP := net.ParseIP(ipAddr)
	if parsedIP.To4() == nil && parsedIP.To16() == nil {
		return nil, errors.Errorf("invalid ip address provided: %s", ipAddr)
	}
	if parsedIP.To4() != nil {
		return multiaddr.NewMultiaddr(fmt.Sprintf("/ip4/%s/tcp/%d", ipAddr, port))
	}
	return multiaddr.NewMultiaddr(fmt.Sprintf("/ip6/%s/tcp/%d", ipAddr, port))
}

// buildOptions for the libp2p host.
func buildOptions(cfg SentinelConfig, s *Sentinel) ([]libp2p.Option, error) {
	var (
		//ip     = net.IP(cfg.IpAddr)
		priKey = cfg.DiscoverConfig.PrivateKey
	)

	listen, err := multiAddressBuilder(cfg.IpAddr, cfg.TCPPort)
	if err != nil {
		return nil, err
	}
	if cfg.LocalIP != "" {
		if net.ParseIP(cfg.LocalIP) == nil {
			return nil, fmt.Errorf("Invalid local ip provided: %s", cfg.LocalIP)
		}
		listen, err = multiAddressBuilder(cfg.LocalIP, cfg.TCPPort)
		if err != nil {
			return nil, err
		}
	}

	options := []libp2p.Option{
		privKeyOption(priKey),
		libp2p.ListenAddrs(listen),
		libp2p.UserAgent("erigon/lightclient"),
		libp2p.ConnectionGater(s),
		libp2p.Transport(tcp.NewTCPTransport),
		libp2p.Muxer("/mplex/6.7.0", mplex.DefaultTransport),
		libp2p.DefaultMuxers,
	}

	options = append(options, libp2p.Security(noise.ID, noise.New))

	if cfg.EnableUPnP {
		options = append(options, libp2p.NATPortMap()) // Allow to use UPnP
	}
	if cfg.RelayNodeAddr != "" {
		options = append(options, libp2p.AddrsFactory(withRelayAddrs(cfg.RelayNodeAddr)))
	} else {
		// Disable relay if it has not been set.
		options = append(options, libp2p.DisableRelay())
	}
	if cfg.HostAddress != "" {
		options = append(options, libp2p.AddrsFactory(func(addrs []multiaddr.Multiaddr) []multiaddr.Multiaddr {
			external, err := multiAddressBuilder(cfg.HostAddress, cfg.TCPPort)
			if err != nil {
				return nil
			} else {
				addrs = append(addrs, external)
			}
			return addrs
		}))
	}
	if cfg.HostDNS != "" {
		options = append(options, libp2p.AddrsFactory(func(addrs []multiaddr.Multiaddr) []multiaddr.Multiaddr {
			external, err := multiaddr.NewMultiaddr(fmt.Sprintf("/dns4/%s/tcp/%d", cfg.HostDNS, cfg.TCPPort))
			if err != nil {
				return nil
			} else {
				addrs = append(addrs, external)
			}
			return addrs
		}))
	}
	// Disable Ping Service.
	options = append(options, libp2p.Ping(false))
	return options, nil
}