package main

import (
	"context"
	"crypto/tls"
	"encoding/hex"
	"fmt"
	"log"
	"net"
	"strings"

	"github.com/breez/lspd/btceclegacy"
	lspdrpc "github.com/breez/lspd/rpc"
	ecies "github.com/ecies/go/v2"
	"github.com/golang/protobuf/proto"
	grpc_middleware "github.com/grpc-ecosystem/go-grpc-middleware"
	"golang.org/x/sync/singleflight"
	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/metadata"
	"google.golang.org/grpc/status"

	"github.com/btcsuite/btcd/btcec/v2"
	"github.com/btcsuite/btcd/chaincfg/chainhash"
	"github.com/btcsuite/btcd/wire"
	"github.com/caddyserver/certmagic"
	"github.com/lightningnetwork/lnd/lnwire"
)

type server struct {
	address         string
	certmagicDomain string
	lis             net.Listener
	s               *grpc.Server
	nodes           map[string]*node
}

type node struct {
	client              LightningClient
	nodeConfig          *NodeConfig
	privateKey          *btcec.PrivateKey
	publicKey           *btcec.PublicKey
	eciesPrivateKey     *ecies.PrivateKey
	eciesPublicKey      *ecies.PublicKey
	openChannelReqGroup singleflight.Group
}

func (s *server) ChannelInformation(ctx context.Context, in *lspdrpc.ChannelInformationRequest) (*lspdrpc.ChannelInformationReply, error) {
	node, err := getNode(ctx)
	if err != nil {
		return nil, err
	}

	return &lspdrpc.ChannelInformationReply{
		Name:                  node.nodeConfig.Name,
		Pubkey:                node.nodeConfig.NodePubkey,
		Host:                  node.nodeConfig.Host,
		ChannelCapacity:       int64(node.nodeConfig.PublicChannelAmount),
		TargetConf:            int32(node.nodeConfig.TargetConf),
		MinHtlcMsat:           int64(node.nodeConfig.MinHtlcMsat),
		BaseFeeMsat:           int64(node.nodeConfig.BaseFeeMsat),
		FeeRate:               node.nodeConfig.FeeRate,
		TimeLockDelta:         node.nodeConfig.TimeLockDelta,
		ChannelFeePermyriad:   int64(node.nodeConfig.ChannelFeePermyriad),
		ChannelMinimumFeeMsat: int64(node.nodeConfig.ChannelMinimumFeeMsat),
		LspPubkey:             node.publicKey.SerializeCompressed(), // TODO: Is the publicKey different from the ecies public key?
		MaxInactiveDuration:   int64(node.nodeConfig.MaxInactiveDuration),
	}, nil
}

func (s *server) RegisterPayment(ctx context.Context, in *lspdrpc.RegisterPaymentRequest) (*lspdrpc.RegisterPaymentReply, error) {
	node, err := getNode(ctx)
	if err != nil {
		return nil, err
	}

	data, err := ecies.Decrypt(node.eciesPrivateKey, in.Blob)
	if err != nil {
		log.Printf("ecies.Decrypt(%x) error: %v", in.Blob, err)
		data, err = btceclegacy.Decrypt(node.privateKey, in.Blob)
		if err != nil {
			log.Printf("btcec.Decrypt(%x) error: %v", in.Blob, err)
			return nil, fmt.Errorf("btcec.Decrypt(%x) error: %w", in.Blob, err)
		}
	}

	var pi lspdrpc.PaymentInformation
	err = proto.Unmarshal(data, &pi)
	if err != nil {
		log.Printf("proto.Unmarshal(%x) error: %v", data, err)
		return nil, fmt.Errorf("proto.Unmarshal(%x) error: %w", data, err)
	}
	log.Printf("RegisterPayment - Destination: %x, pi.PaymentHash: %x, pi.PaymentSecret: %x, pi.IncomingAmountMsat: %v, pi.OutgoingAmountMsat: %v",
		pi.Destination, pi.PaymentHash, pi.PaymentSecret, pi.IncomingAmountMsat, pi.OutgoingAmountMsat)
	err = checkPayment(node.nodeConfig, pi.IncomingAmountMsat, pi.OutgoingAmountMsat)
	if err != nil {
		log.Printf("checkPayment(%v, %v) error: %v", pi.IncomingAmountMsat, pi.OutgoingAmountMsat, err)
		return nil, fmt.Errorf("checkPayment(%v, %v) error: %v", pi.IncomingAmountMsat, pi.OutgoingAmountMsat, err)
	}
	err = registerPayment(pi.Destination, pi.PaymentHash, pi.PaymentSecret, pi.IncomingAmountMsat, pi.OutgoingAmountMsat)
	if err != nil {
		log.Printf("RegisterPayment() error: %v", err)
		return nil, fmt.Errorf("RegisterPayment() error: %w", err)
	}
	return &lspdrpc.RegisterPaymentReply{}, nil
}

func (s *server) OpenChannel(ctx context.Context, in *lspdrpc.OpenChannelRequest) (*lspdrpc.OpenChannelReply, error) {
	node, err := getNode(ctx)
	if err != nil {
		return nil, err
	}

	r, err, _ := node.openChannelReqGroup.Do(in.Pubkey, func() (interface{}, error) {
		pubkey, err := hex.DecodeString(in.Pubkey)
		if err != nil {
			return nil, err
		}

		channelCount, err := node.client.GetNodeChannelCount(pubkey)
		if err != nil {
			return nil, err
		}

		var outPoint *wire.OutPoint
		if channelCount == 0 {
			outPoint, err = node.client.OpenChannel(&OpenChannelRequest{
				CapacitySat: node.nodeConfig.ChannelAmount,
				Destination: pubkey,
				TargetConf:  node.nodeConfig.TargetConf,
				MinHtlcMsat: node.nodeConfig.MinHtlcMsat,
				IsPrivate:   node.nodeConfig.ChannelPrivate,
			})

			if err != nil {
				log.Printf("Error in OpenChannel: %v", err)
				return nil, err
			}

			log.Printf("Response from OpenChannel: (TX: %v)", outPoint.String())
		}

		return &lspdrpc.OpenChannelReply{TxHash: outPoint.Hash.String(), OutputIndex: outPoint.Index}, nil
	})

	if err != nil {
		return nil, err
	}
	return r.(*lspdrpc.OpenChannelReply), err
}

func (n *node) getSignedEncryptedData(in *lspdrpc.Encrypted) (string, []byte, bool, error) {
	usedEcies := true
	signedBlob, err := ecies.Decrypt(n.eciesPrivateKey, in.Data)
	if err != nil {
		log.Printf("ecies.Decrypt(%x) error: %v", in.Data, err)
		usedEcies = false
		signedBlob, err = btceclegacy.Decrypt(n.privateKey, in.Data)
		if err != nil {
			log.Printf("btcec.Decrypt(%x) error: %v", in.Data, err)
			return "", nil, usedEcies, fmt.Errorf("btcec.Decrypt(%x) error: %w", in.Data, err)
		}
	}
	var signed lspdrpc.Signed
	err = proto.Unmarshal(signedBlob, &signed)
	if err != nil {
		log.Printf("proto.Unmarshal(%x) error: %v", signedBlob, err)
		return "", nil, usedEcies, fmt.Errorf("proto.Unmarshal(%x) error: %w", signedBlob, err)
	}
	pubkey, err := btcec.ParsePubKey(signed.Pubkey)
	if err != nil {
		log.Printf("unable to parse pubkey: %v", err)
		return "", nil, usedEcies, fmt.Errorf("unable to parse pubkey: %w", err)
	}
	wireSig, err := lnwire.NewSigFromRawSignature(signed.Signature)
	if err != nil {
		return "", nil, usedEcies, fmt.Errorf("failed to decode signature: %v", err)
	}
	sig, err := wireSig.ToSignature()
	if err != nil {
		return "", nil, usedEcies, fmt.Errorf("failed to convert from wire format: %v",
			err)
	}
	// The signature is over the sha256 hash of the message.
	digest := chainhash.HashB(signed.Data)
	if !sig.Verify(digest, pubkey) {
		return "", nil, usedEcies, fmt.Errorf("invalid signature")
	}
	return hex.EncodeToString(signed.Pubkey), signed.Data, usedEcies, nil
}

func (s *server) CheckChannels(ctx context.Context, in *lspdrpc.Encrypted) (*lspdrpc.Encrypted, error) {
	node, err := getNode(ctx)
	if err != nil {
		return nil, err
	}

	nodeID, data, usedEcies, err := node.getSignedEncryptedData(in)
	if err != nil {
		log.Printf("getSignedEncryptedData error: %v", err)
		return nil, fmt.Errorf("getSignedEncryptedData error: %v", err)
	}
	var checkChannelsRequest lspdrpc.CheckChannelsRequest
	err = proto.Unmarshal(data, &checkChannelsRequest)
	if err != nil {
		log.Printf("proto.Unmarshal(%x) error: %v", data, err)
		return nil, fmt.Errorf("proto.Unmarshal(%x) error: %w", data, err)
	}
	notFakeChannels, err := getNotFakeChannels(nodeID, checkChannelsRequest.FakeChannels)
	if err != nil {
		log.Printf("getNotFakeChannels(%v) error: %v", checkChannelsRequest.FakeChannels, err)
		return nil, fmt.Errorf("getNotFakeChannels(%v) error: %w", checkChannelsRequest.FakeChannels, err)
	}
	closedChannels, err := node.client.GetClosedChannels(nodeID, checkChannelsRequest.WaitingCloseChannels)
	if err != nil {
		log.Printf("GetClosedChannels(%v) error: %v", checkChannelsRequest.FakeChannels, err)
		return nil, fmt.Errorf("GetClosedChannels(%v) error: %w", checkChannelsRequest.FakeChannels, err)
	}
	checkChannelsReply := lspdrpc.CheckChannelsReply{
		NotFakeChannels: notFakeChannels,
		ClosedChannels:  closedChannels,
	}
	dataReply, err := proto.Marshal(&checkChannelsReply)
	if err != nil {
		log.Printf("proto.Marshall() error: %v", err)
		return nil, fmt.Errorf("proto.Marshal() error: %w", err)
	}
	pubkey, err := btcec.ParsePubKey(checkChannelsRequest.EncryptPubkey)
	if err != nil {
		log.Printf("unable to parse pubkey: %v", err)
		return nil, fmt.Errorf("unable to parse pubkey: %w", err)
	}

	var encrypted []byte
	if usedEcies {
		encrypted, err = ecies.Encrypt(node.eciesPublicKey, dataReply)
		if err != nil {
			log.Printf("ecies.Encrypt() error: %v", err)
			return nil, fmt.Errorf("ecies.Encrypt() error: %w", err)
		}
	} else {
		encrypted, err = btceclegacy.Encrypt(pubkey, dataReply)
		if err != nil {
			log.Printf("btcec.Encrypt() error: %v", err)
			return nil, fmt.Errorf("btcec.Encrypt() error: %w", err)
		}
	}

	return &lspdrpc.Encrypted{Data: encrypted}, nil
}

func getNotFakeChannels(nodeID string, channelPoints map[string]uint64) (map[string]uint64, error) {
	r := make(map[string]uint64)
	if len(channelPoints) == 0 {
		return r, nil
	}
	channels, err := confirmedChannels(nodeID)
	if err != nil {
		return nil, err
	}
	for channelPoint, chanID := range channels {
		if _, ok := channelPoints[channelPoint]; ok {
			r[channelPoint] = chanID
		}
	}
	return r, nil
}

func NewGrpcServer(configs []*NodeConfig, address string, certmagicDomain string) (*server, error) {
	if len(configs) == 0 {
		return nil, fmt.Errorf("no nodes supplied")
	}

	nodes := make(map[string]*node)
	for _, config := range configs {
		pk, err := hex.DecodeString(config.LspdPrivateKey)
		if err != nil {
			return nil, fmt.Errorf("hex.DecodeString(config.lspdPrivateKey=%v) error: %v", config.LspdPrivateKey, err)
		}

		eciesPrivateKey := ecies.NewPrivateKeyFromBytes(pk)
		eciesPublicKey := eciesPrivateKey.PublicKey
		privateKey, publicKey := btcec.PrivKeyFromBytes(pk)

		node := &node{
			nodeConfig:      config,
			privateKey:      privateKey,
			publicKey:       publicKey,
			eciesPrivateKey: eciesPrivateKey,
			eciesPublicKey:  eciesPublicKey,
		}

		if config.Lnd == nil && config.Cln == nil {
			return nil, fmt.Errorf("node has to be either cln or lnd")
		}

		if config.Lnd != nil && config.Cln != nil {
			return nil, fmt.Errorf("node cannot be both cln and lnd")
		}

		if config.Lnd != nil {
			node.client, err = NewLndClient(config.Lnd)
			if err != nil {
				return nil, err
			}
		}

		if config.Cln != nil {
			node.client, err = NewClnClient(config.Cln.SocketPath)
			if err != nil {
				return nil, err
			}
		}

		_, exists := nodes[config.Token]
		if exists {
			return nil, fmt.Errorf("cannot have multiple nodes with the same token")
		}

		nodes[config.Token] = node
	}

	return &server{
		address:         address,
		certmagicDomain: certmagicDomain,
		nodes:           nodes,
	}, nil
}

func (s *server) Start() error {
	// Make sure all nodes are available and set name and pubkey if not set
	// in config.
	for _, n := range s.nodes {
		info, err := n.client.GetInfo()
		if err != nil {
			return fmt.Errorf("failed to get info from host %s", n.nodeConfig.Host)
		}

		if n.nodeConfig.Name == "" {
			n.nodeConfig.Name = info.Alias
		}

		if n.nodeConfig.NodePubkey == "" {
			n.nodeConfig.NodePubkey = info.Pubkey
		}
	}

	var lis net.Listener
	if s.certmagicDomain == "" {
		var err error
		lis, err = net.Listen("tcp", s.address)
		if err != nil {
			log.Fatalf("failed to listen: %v", err)
		}
	} else {
		tlsConfig, err := certmagic.TLS([]string{s.certmagicDomain})
		if err != nil {
			log.Fatalf("failed to run certmagic: %v", err)
		}
		lis, err = tls.Listen("tcp", s.address, tlsConfig)
		if err != nil {
			log.Fatalf("failed to listen: %v", err)
		}
	}

	srv := grpc.NewServer(
		grpc_middleware.WithUnaryServerChain(func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
			if md, ok := metadata.FromIncomingContext(ctx); ok {
				for _, auth := range md.Get("authorization") {
					if !strings.HasPrefix(auth, "Bearer ") {
						continue
					}

					token := strings.Replace(auth, "Bearer ", "", 1)
					node, ok := s.nodes[token]
					if !ok {
						continue
					}

					return handler(context.WithValue(ctx, "node", node), req)
				}
			}
			return nil, status.Errorf(codes.PermissionDenied, "Not authorized")
		}),
	)
	lspdrpc.RegisterChannelOpenerServer(srv, &server{})

	s.s = srv
	s.lis = lis
	if err := srv.Serve(lis); err != nil {
		return fmt.Errorf("failed to serve: %v", err)
	}

	return nil
}

func (s *server) Stop() {
	srv := s.s
	if srv != nil {
		srv.GracefulStop()
	}
}

func getNode(ctx context.Context) (*node, error) {
	n := ctx.Value("node")
	if n == nil {
		return nil, status.Errorf(codes.PermissionDenied, "Not authorized")
	}

	node, ok := n.(*node)
	if !ok || node == nil {
		return nil, status.Errorf(codes.PermissionDenied, "Not authorized")
	}

	return node, nil
}