/*
   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"

	"github.com/ledgerwatch/erigon/cl/clparams"
	"github.com/ledgerwatch/log/v3"
	"github.com/libp2p/go-libp2p"
	mplex "github.com/libp2p/go-libp2p-mplex"
	"github.com/libp2p/go-libp2p/core/crypto"
	"github.com/libp2p/go-libp2p/p2p/security/noise"
	"github.com/libp2p/go-libp2p/p2p/transport/tcp"
	"github.com/multiformats/go-multiaddr"
)

type SentinelConfig struct {
	NetworkConfig *clparams.NetworkConfig
	GenesisConfig *clparams.GenesisConfig
	BeaconConfig  *clparams.BeaconChainConfig
	IpAddr        string
	Port          int
	TCPPort       uint
	// Optional
	LocalIP        string
	EnableUPnP     bool
	RelayNodeAddr  string
	HostAddress    string
	HostDNS        string
	NoDiscovery    bool
	TmpDir         string
	LocalDiscovery bool
}

func convertToCryptoPrivkey(privkey *ecdsa.PrivateKey) (crypto.PrivKey, error) {
	privBytes := privkey.D.Bytes()
	if len(privBytes) < 32 {
		privBytes = append(make([]byte, 32-len(privBytes)), privBytes...)
	}
	return crypto.UnmarshalSecp256k1PrivateKey(privBytes)
}

func privKeyOption(privkey *ecdsa.PrivateKey) libp2p.Option {
	return func(cfg *libp2p.Config) error {
		ifaceKey, err := convertToCryptoPrivkey(privkey)
		if err != nil {
			return err
		}
		log.Debug("[Sentinel] ECDSA private key generated")
		return cfg.Apply(libp2p.Identity(ifaceKey))
	}
}

// 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, fmt.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))
}

func buildOptions(cfg *SentinelConfig, s *Sentinel) ([]libp2p.Option, error) {
	var priKey = s.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/caplin"),
		libp2p.Transport(tcp.NewTCPTransport),
		libp2p.Muxer("/mplex/6.7.0", mplex.DefaultTransport),
		libp2p.DefaultMuxers,
	}

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

	if cfg.EnableUPnP {
		options = append(options, libp2p.NATPortMap()) // Allow to use UPnP
	}

	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
}