package main

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"net"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"time"

	"github.com/btcsuite/btcd/chaincfg/chainhash"
	"github.com/btcsuite/btcd/wire"
	"github.com/lightninglabs/faraday"
	"github.com/lightninglabs/faraday/fiat"
	"github.com/lightninglabs/faraday/frdrpc"
	"github.com/lightninglabs/faraday/utils"
	"github.com/lightninglabs/lndclient"
	"github.com/lightningnetwork/lnd/lncfg"
	"github.com/lightningnetwork/lnd/lnrpc"
	"github.com/lightningnetwork/lnd/macaroons"
	"github.com/urfave/cli"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
	"google.golang.org/protobuf/proto"
	"gopkg.in/macaroon.v2"
)

var (
	// maxMsgRecvSize is the largest message our client will receive. We
	// set this to 200MiB atm.
	maxMsgRecvSize = grpc.MaxCallRecvMsgSize(1 * 1024 * 1024 * 200)

	// defaultMacaroonTimeout is the default macaroon timeout in seconds
	// that we set when sending it over the line.
	defaultMacaroonTimeout int64 = 60
)

// fatal logs and error and exits.
func fatal(err error) {
	_, _ = fmt.Fprintf(os.Stderr, "[frcli] %v\n", err)
	os.Exit(1)
}

// printRespJSON prints a proto message as json.
func printRespJSON(resp proto.Message) {
	jsonBytes, err := lnrpc.ProtoJSONMarshalOpts.Marshal(resp)
	if err != nil {
		fmt.Println("unable to decode response: ", err)
		return
	}

	fmt.Println(string(jsonBytes))
}

func printJSON(resp interface{}) {
	b, err := json.Marshal(resp)
	if err != nil {
		fatal(err)
	}

	var out bytes.Buffer
	_ = json.Indent(&out, b, "", "\t")
	out.WriteString("\n")
	_, _ = out.WriteTo(os.Stdout)
}

// getClient returns a faraday client.
func getClient(ctx *cli.Context) (frdrpc.FaradayServerClient, func()) {
	conn := getClientConn(ctx)

	cleanUp := func() {
		if err := conn.Close(); err != nil {
			fatal(err)
		}
	}

	return frdrpc.NewFaradayServerClient(conn), cleanUp
}

// getClientConn gets a client connection to the address provided by the
// rpcserver flag.
func getClientConn(ctx *cli.Context) *grpc.ClientConn {
	// Extract the paths that we need for loading the TLS and macaroon
	// files.
	tlsCertPath, macaroonPath, err := extractPathArgs(ctx)
	if err != nil {
		fatal(err)
	}

	// We always need to send a macaroon.
	macOption, err := readMacaroon(macaroonPath)
	if err != nil {
		fatal(err)
	}

	// We need to use a custom dialer so we can also connect to unix sockets
	// and not just TCP addresses.
	genericDialer := clientAddressDialer(defaultRPCPort)

	opts := []grpc.DialOption{
		grpc.WithContextDialer(genericDialer),
		grpc.WithDefaultCallOptions(maxMsgRecvSize),
		macOption,
	}

	// TLS cannot be disabled, we'll always have a cert file to read.
	creds, err := credentials.NewClientTLSFromFile(tlsCertPath, "")
	if err != nil {
		fatal(fmt.Errorf("unable to read tls cert (path: %v): %v",
			tlsCertPath, err))
	}

	opts = append(opts, grpc.WithTransportCredentials(creds))

	conn, err := grpc.Dial(ctx.GlobalString("rpcserver"), opts...)
	if err != nil {
		fatal(fmt.Errorf("unable to connect to RPC server: %v", err))
	}

	return conn
}

// extractPathArgs parses the TLS certificate and macaroon paths from the
// command.
func extractPathArgs(ctx *cli.Context) (string, string, error) {
	// We'll start off by parsing the network. This is needed to determine
	// the correct path to the TLS certificate and macaroon when not
	// specified.
	networkStr := strings.ToLower(ctx.GlobalString("network"))
	_, err := lndclient.Network(networkStr).ChainParams()
	if err != nil {
		return "", "", err
	}

	// We'll now fetch the faradaydir so we can make a decision on how to
	// properly read the macaroon and cert files. This will either be the
	// default, or will have been overwritten by the end user.
	faradayDir := lncfg.CleanAndExpandPath(ctx.GlobalString(
		faradayDirFlag.Name,
	))
	tlsCertPath := lncfg.CleanAndExpandPath(ctx.GlobalString(
		tlsCertFlag.Name,
	))
	macPath := lncfg.CleanAndExpandPath(ctx.GlobalString(
		macaroonPathFlag.Name,
	))

	// If a custom faraday directory was set, we'll also check if a custom
	// path for the TLS cert and macaroon file was set as well. If not,
	// we'll override the path so they can be found within the custom
	// faraday directory.
	if faradayDir != faraday.FaradayDirBase ||
		networkStr != faraday.DefaultNetwork {

		// Only overwrite the tls cert path if the user has not
		// explicitly defined it.
		if !ctx.GlobalIsSet(tlsCertFlag.Name) {
			tlsCertPath = filepath.Join(
				faradayDir, networkStr,
				faraday.DefaultTLSCertFilename,
			)
		}

		// Only overwrite the macaroon path if the user has not
		// explicitly defined it.
		if !ctx.GlobalIsSet(macaroonPathFlag.Name) {
			macPath = filepath.Join(
				faradayDir, networkStr,
				faraday.DefaultMacaroonFilename,
			)
		}
	}

	return tlsCertPath, macPath, nil
}

// ClientAddressDialer parsed client address and returns a dialer.
func clientAddressDialer(defaultPort string) func(context.Context,
	string) (net.Conn, error) {

	return func(ctx context.Context, addr string) (net.Conn, error) {
		parsedAddr, err := lncfg.ParseAddressString(
			addr, defaultPort, net.ResolveTCPAddr,
		)
		if err != nil {
			return nil, err
		}

		d := net.Dialer{}
		return d.DialContext(
			ctx, parsedAddr.Network(), parsedAddr.String(),
		)
	}
}

// readMacaroon tries to read the macaroon file at the specified path and create
// gRPC dial options from it.
//
// TODO(guggero): Provide this function in lnd's macaroon package and use it
// from there.
func readMacaroon(macPath string) (grpc.DialOption, error) {
	// Load the specified macaroon file.
	macBytes, err := ioutil.ReadFile(macPath)
	if err != nil {
		return nil, fmt.Errorf("unable to read macaroon path : %v", err)
	}

	mac := &macaroon.Macaroon{}
	if err = mac.UnmarshalBinary(macBytes); err != nil {
		return nil, fmt.Errorf("unable to decode macaroon: %v", err)
	}

	macConstraints := []macaroons.Constraint{
		// We add a time-based constraint to prevent replay of the
		// macaroon. It's good for 60 seconds by default to make up for
		// any discrepancy between client and server clocks, but leaking
		// the macaroon before it becomes invalid makes it possible for
		// an attacker to reuse the macaroon. In addition, the validity
		// time of the macaroon is extended by the time the server clock
		// is behind the client clock, or shortened by the time the
		// server clock is ahead of the client clock (or invalid
		// altogether if, in the latter case, this time is more than 60
		// seconds).
		macaroons.TimeoutConstraint(defaultMacaroonTimeout),
	}

	// Apply constraints to the macaroon.
	constrainedMac, err := macaroons.AddConstraints(mac, macConstraints...)
	if err != nil {
		return nil, err
	}

	// Now we append the macaroon credentials to the dial options.
	cred, err := macaroons.NewMacaroonCredential(constrainedMac)
	if err != nil {
		return nil, fmt.Errorf("error creating macaroon credential: %v",
			err)
	}
	return grpc.WithPerRPCCredentials(cred), nil
}

// parseChannelPoint parses a funding txid and output index from the command
// line. Both named options as well as unnamed parameters are supported.
func parseChannelPoint(ctx *cli.Context) (*wire.OutPoint, error) {
	args := ctx.Args()

	var txid string
	switch {
	case ctx.IsSet("funding_txid"):
		txid = ctx.String("funding_txid")

	case args.Present():
		txid = args.First()
		args = args.Tail()
	default:
		return nil, fmt.Errorf("funding txid argument missing")
	}

	hash, err := chainhash.NewHashFromStr(txid)
	if err != nil {
		return nil, err
	}

	channelPoint := &wire.OutPoint{
		Hash: *hash,
	}

	switch {
	case ctx.IsSet("output_index"):
		channelPoint.Index = uint32(ctx.Int("output_index"))

	case args.Present():
		index, err := strconv.ParseUint(args.First(), 10, 32)
		if err != nil {
			return nil, fmt.Errorf("unable to decode output "+
				"index: %v", err)
		}
		channelPoint.Index = uint32(index)
	}

	return channelPoint, nil
}

// fiatBackendBitfinex is the rpc enum value for BITFINEX.
// TODO: Replace with frdrpc.FiatBackend_BITFINEX once the frdrpc module is
// tagged and the dependency is bumped.
const fiatBackendBitfinex = frdrpc.FiatBackend(5)

// parseFiatBackend parses the user chosen fiat backend into a FiatBackend type.
func parseFiatBackend(fiatBackend string) (frdrpc.FiatBackend, error) {
	switch fiatBackend {
	case "":
		return frdrpc.FiatBackend_UNKNOWN_FIATBACKEND, nil

	case fiat.CoinCapPriceBackend.String():
		return frdrpc.FiatBackend_COINCAP, nil

	case fiat.CoinDeskPriceBackend.String():
		return frdrpc.FiatBackend_COINDESK, nil

	case fiat.CustomPriceBackend.String():
		return frdrpc.FiatBackend_CUSTOM, nil

	case fiat.CoinGeckoPriceBackend.String():
		return frdrpc.FiatBackend_COINGECKO, nil

	case fiat.BitfinexPriceBackend.String():
		return fiatBackendBitfinex, nil

	default:
		return frdrpc.FiatBackend_UNKNOWN_FIATBACKEND, fmt.Errorf(
			"unknown fiat backend",
		)
	}
}

// filterPrices filters a slice of prices based on given start and end
// timestamps.
func filterPrices(prices []*frdrpc.BitcoinPrice, startTime, endTime int64) (
	[]*frdrpc.BitcoinPrice, error) {

	// Ensure that startTime is before endTime.
	if err := utils.ValidateTimeRange(
		time.Unix(startTime, 0), time.Unix(endTime, 0),
		utils.DisallowFutureRange,
	); err != nil {
		return nil, err
	}

	// Sort the prices by timestamp.
	sort.SliceStable(prices, func(i, j int) bool {
		return prices[i].PriceTimestamp < prices[j].PriceTimestamp
	})

	// Filter out timestamps that are not within the start time to
	// end time range but ensure that the timestamp right before
	// or equal to the start timestamp is kept.
	//
	// nolint: prealloc
	var (
		filteredPrices    []*frdrpc.BitcoinPrice
		earliestTimeStamp *frdrpc.BitcoinPrice
	)
	for _, p := range prices {
		if p.PriceTimestamp <= uint64(startTime) {
			if earliestTimeStamp == nil ||
				earliestTimeStamp.PriceTimestamp <
					p.PriceTimestamp {

				earliestTimeStamp = p
			}
			continue
		}

		if p.PriceTimestamp >= uint64(endTime) {
			continue
		}

		filteredPrices = append(filteredPrices, p)
	}

	if earliestTimeStamp == nil {
		return nil, errors.New("a price point with a timestamp " +
			"earlier than the given start timestamp is required")
	}

	return append([]*frdrpc.BitcoinPrice{earliestTimeStamp},
		filteredPrices...), nil
}