package main

import (
	"fmt"
	"io/ioutil"
	"net"
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strconv"
	"strings"
	"time"

	flags "github.com/btcsuite/go-flags"
	"github.com/lightningnetwork/lnd/brontide"
	"github.com/lightningnetwork/lnd/lnwire"
	"github.com/roasbeef/btcd/btcec"
	"github.com/roasbeef/btcutil"
)

const (
	defaultConfigFilename     = "lnd.conf"
	defaultDataDirname        = "data"
	defaultTLSCertFilename    = "tls.cert"
	defaultTLSKeyFilename     = "tls.key"
	defaultLogLevel           = "info"
	defaultLogDirname         = "logs"
	defaultLogFilename        = "lnd.log"
	defaultRPCPort            = 10009
	defaultRESTPort           = 8080
	defaultPeerPort           = 5656
	defaultRPCHost            = "localhost"
	defaultMaxPendingChannels = 1
	defaultNumChanConfs       = 1
)

var (
	lndHomeDir         = btcutil.AppDataDir("lnd", false)
	defaultConfigFile  = filepath.Join(lndHomeDir, defaultConfigFilename)
	defaultDataDir     = filepath.Join(lndHomeDir, defaultDataDirname)
	defaultTLSCertPath = filepath.Join(lndHomeDir, defaultTLSCertFilename)
	defaultTLSKeyPath  = filepath.Join(lndHomeDir, defaultTLSKeyFilename)
	defaultLogDir      = filepath.Join(lndHomeDir, defaultLogDirname)

	btcdHomeDir            = btcutil.AppDataDir("btcd", false)
	defaultBtcdRPCCertFile = filepath.Join(btcdHomeDir, "rpc.cert")

	ltcdHomeDir            = btcutil.AppDataDir("ltcd", false)
	defaultLtcdRPCCertFile = filepath.Join(ltcdHomeDir, "rpc.cert")
)

type chainConfig struct {
	Active   bool   `long:"active" description:"If the chain should be active or not."`
	ChainDir string `long:"chaindir" description:"The directory to store the chains's data within."`

	RPCHost    string `long:"rpchost" description:"The daemon's rpc listening address. If a port is omitted, then the default port for the selected chain parameters will be used."`
	RPCUser    string `long:"rpcuser" description:"Username for RPC connections"`
	RPCPass    string `long:"rpcpass" default-mask:"-" description:"Password for RPC connections"`
	RPCCert    string `long:"rpccert" description:"File containing the daemon's certificate file"`
	RawRPCCert string `long:"rawrpccert" description:"The raw bytes of the daemon's PEM-encoded certificate chain which will be used to authenticate the RPC connection."`

	TestNet3 bool `long:"testnet" description:"Use the test network"`
	SimNet   bool `long:"simnet" description:"Use the simulation test network"`
	RegTest  bool `long:"regtest" description:"Use the regression test network"`
}

type neutrinoConfig struct {
	Active       bool          `long:"active" description:"If SPV mode should be active or not."`
	AddPeers     []string      `short:"a" long:"addpeer" description:"Add a peer to connect with at startup"`
	ConnectPeers []string      `long:"connect" description:"Connect only to the specified peers at startup"`
	MaxPeers     int           `long:"maxpeers" description:"Max number of inbound and outbound peers"`
	BanDuration  time.Duration `long:"banduration" description:"How long to ban misbehaving peers.  Valid time units are {s, m, h}.  Minimum 1 second"`
	BanThreshold uint32        `long:"banthreshold" description:"Maximum allowed ban score before disconnecting and banning misbehaving peers."`
}

type autoPilotConfig struct {
	// TODO(roasbeef): add
	Active      bool    `long:"active" description:"If the autopilot agent should be active or not."`
	MaxChannels int     `long:"maxchannels" description:"The maximum number of channels that should be created"`
	Allocation  float64 `long:"allocation" description:"The percentage of total funds that should be committed to automatic channel establishment"`
}

// config defines the configuration options for lnd.
//
// See loadConfig for further details regarding the configuration
// loading+parsing process.
type config struct {
	ShowVersion bool `short:"V" long:"version" description:"Display version information and exit"`

	ConfigFile  string `long:"C" long:"configfile" description:"Path to configuration file"`
	DataDir     string `short:"b" long:"datadir" description:"The directory to store lnd's data within"`
	TLSCertPath string `long:"tlscertpath" description:"Path to TLS certificate for lnd's RPC and REST services"`
	TLSKeyPath  string `long:"tlskeypath" description:"Path to TLS private key for lnd's RPC and REST services"`
	LogDir      string `long:"logdir" description:"Directory to log output."`

	Listeners   []string `long:"listen" description:"Add an interface/port to listen for connections (default all interfaces port: 5656)"`
	ExternalIPs []string `long:"externalip" description:"Add an ip to the list of local addresses we claim to listen on to peers"`

	DebugLevel string `short:"d" long:"debuglevel" description:"Logging level for all subsystems {trace, debug, info, warn, error, critical} -- You may also specify <subsystem>=<level>,<subsystem2>=<level>,... to set the log level for individual subsystems -- Use show to list available subsystems"`

	Profile string `long:"profile" description:"Enable HTTP profiling on given port -- NOTE port must be between 1024 and 65536"`

	PeerPort           int  `long:"peerport" description:"The port to listen on for incoming p2p connections"`
	RPCPort            int  `long:"rpcport" description:"The port for the rpc server"`
	RESTPort           int  `long:"restport" description:"The port for the REST server"`
	DebugHTLC          bool `long:"debughtlc" description:"Activate the debug htlc mode. With the debug HTLC mode, all payments sent use a pre-determined R-Hash. Additionally, all HTLCs sent to a node with the debug HTLC R-Hash are immediately settled in the next available state transition."`
	MaxPendingChannels int  `long:"maxpendingchannels" description:"The maximum number of incoming pending channels permitted per peer."`

	Litecoin *chainConfig `group:"Litecoin" namespace:"litecoin"`
	Bitcoin  *chainConfig `group:"Bitcoin" namespace:"bitcoin"`

	DefaultNumChanConfs int `long:"defaultchanconfs" description:"The default number of confirmations a channel must have before it's considered open."`

	NeutrinoMode *neutrinoConfig `group:"neutrino" namespace:"neutrino"`

	Autopilot *autoPilotConfig `group:"autopilot" namespace:"autopilot"`
}

// loadConfig initializes and parses the config using a config file and command
// line options.
//
// The configuration proceeds as follows:
// 	1) Start with a default config with sane settings
// 	2) Pre-parse the command line to check for an alternative config file
// 	3) Load configuration file overwriting defaults with any specified options
// 	4) Parse CLI options and overwrite/add any specified options
func loadConfig() (*config, error) {
	defaultCfg := config{
		ConfigFile:          defaultConfigFile,
		DataDir:             defaultDataDir,
		DebugLevel:          defaultLogLevel,
		TLSCertPath:         defaultTLSCertPath,
		TLSKeyPath:          defaultTLSKeyPath,
		LogDir:              defaultLogDir,
		PeerPort:            defaultPeerPort,
		RPCPort:             defaultRPCPort,
		RESTPort:            defaultRESTPort,
		MaxPendingChannels:  defaultMaxPendingChannels,
		DefaultNumChanConfs: defaultNumChanConfs,
		Bitcoin: &chainConfig{
			RPCHost: defaultRPCHost,
			RPCCert: defaultBtcdRPCCertFile,
		},
		Litecoin: &chainConfig{
			RPCHost: defaultRPCHost,
			RPCCert: defaultLtcdRPCCertFile,
		},
		Autopilot: &autoPilotConfig{
			MaxChannels: 5,
			Allocation:  0.6,
		},
	}

	// Pre-parse the command line options to pick up an alternative config
	// file.
	preCfg := defaultCfg
	if _, err := flags.Parse(&preCfg); err != nil {
		return nil, err
	}

	// Show the version and exit if the version flag was specified.
	appName := filepath.Base(os.Args[0])
	appName = strings.TrimSuffix(appName, filepath.Ext(appName))
	usageMessage := fmt.Sprintf("Use %s -h to show usage", appName)
	if preCfg.ShowVersion {
		fmt.Println(appName, "version", version())
		os.Exit(0)
	}

	// Create the home directory if it doesn't already exist.
	funcName := "loadConfig"
	if err := os.MkdirAll(lndHomeDir, 0700); err != nil {
		// Show a nicer error message if it's because a symlink is
		// linked to a directory that does not exist (probably because
		// it's not mounted).
		if e, ok := err.(*os.PathError); ok && os.IsExist(err) {
			if link, lerr := os.Readlink(e.Path); lerr == nil {
				str := "is symlink %s -> %s mounted?"
				err = fmt.Errorf(str, e.Path, link)
			}
		}

		str := "%s: Failed to create home directory: %v"
		err := fmt.Errorf(str, funcName, err)
		fmt.Fprintln(os.Stderr, err)
		return nil, err
	}

	// Next, load any additional configuration options from the file.
	var configFileError error
	cfg := defaultCfg
	if err := flags.IniParse(preCfg.ConfigFile, &cfg); err != nil {
		configFileError = err
	}

	// Finally, parse the remaining command line options again to ensure
	// they take precedence.
	if _, err := flags.Parse(&cfg); err != nil {
		return nil, err
	}

	// At this moment, multiple active chains are not supported.
	if cfg.Litecoin.Active && cfg.Bitcoin.Active {
		str := "%s: Currently both Bitcoin and Litecoin cannot be " +
			"active together"
		err := fmt.Errorf(str, funcName)
		return nil, err
	}

	// The SPV mode implemented currently doesn't support Litecoin, so the
	// two modes are incompatible.
	if cfg.NeutrinoMode.Active && cfg.Litecoin.Active {
		str := "%s: The light client mode currently supported does " +
			"not yet support execution on the Litecoin network"
		err := fmt.Errorf(str, funcName)
		return nil, err
	}

	if cfg.Litecoin.Active {
		if cfg.Litecoin.SimNet {
			str := "%s: simnet mode for litecoin not currently supported"
			return nil, fmt.Errorf(str, funcName)
		}

		// The litecoin chain is the current active chain. However
		// throuhgout the codebase we required chiancfg.Params. So as a
		// temporary hack, we'll mutate the default net params for
		// bitcoin with the litecoin specific informat.ion
		paramCopy := bitcoinTestNetParams
		applyLitecoinParams(&paramCopy)
		activeNetParams = paramCopy

		if !cfg.NeutrinoMode.Active {
			// Attempt to parse out the RPC credentials for the
			// litecoin chain if the information wasn't specified
			err := parseRPCParams(cfg.Litecoin, litecoinChain, funcName)
			if err != nil {
				err := fmt.Errorf("unable to load RPC credentials for "+
					"ltcd: %v", err)
				return nil, err
			}
		}

		cfg.Litecoin.ChainDir = filepath.Join(cfg.DataDir, litecoinChain.String())

		// Finally we'll register the litecoin chain as our current
		// primary chain.
		registeredChains.RegisterPrimaryChain(litecoinChain)
	}
	if cfg.Bitcoin.Active {
		// Multiple networks can't be selected simultaneously.  Count
		// number of network flags passed; assign active network params
		// while we're at it.
		numNets := 0
		if cfg.Bitcoin.TestNet3 {
			numNets++
			activeNetParams = bitcoinTestNetParams
		}
		if cfg.Bitcoin.RegTest {
			numNets++
			activeNetParams = regTestNetParams
		}
		if cfg.Bitcoin.SimNet {
			activeNetParams = bitcoinSimNetParams
		}
		if numNets > 1 {
			str := "%s: The testnet, segnet, and simnet params can't be " +
				"used together -- choose one of the three"
			err := fmt.Errorf(str, funcName)
			return nil, err
		}

		if !cfg.NeutrinoMode.Active {
			// If needed, we'll attempt to automatically configure
			// the RPC control plan for the target btcd node.
			err := parseRPCParams(cfg.Bitcoin, bitcoinChain, funcName)
			if err != nil {
				err := fmt.Errorf("unable to load RPC credentials for "+
					"btcd: %v", err)
				return nil, err
			}
		}

		cfg.Bitcoin.ChainDir = filepath.Join(cfg.DataDir, bitcoinChain.String())

		// Finally we'll register the bitcoin chain as our current
		// primary chain.
		registeredChains.RegisterPrimaryChain(bitcoinChain)
	}

	// Validate profile port number.
	if cfg.Profile != "" {
		profilePort, err := strconv.Atoi(cfg.Profile)
		if err != nil || profilePort < 1024 || profilePort > 65535 {
			str := "%s: The profile port must be between 1024 and 65535"
			err := fmt.Errorf(str, funcName)
			fmt.Fprintln(os.Stderr, err)
			fmt.Fprintln(os.Stderr, usageMessage)
			return nil, err
		}
	}

	// Append the network type to the data directory so it is "namespaced"
	// per network. In addition to the block database, there are other
	// pieces of data that are saved to disk such as address manager state.
	// All data is specific to a network, so namespacing the data directory
	// means each individual piece of serialized data does not have to
	// worry about changing names per network and such.
	// TODO(roasbeef): when we go full multi-chain remove the additional
	// namespacing on the target chain.
	cfg.DataDir = cleanAndExpandPath(cfg.DataDir)
	cfg.DataDir = filepath.Join(cfg.DataDir, activeNetParams.Name)
	cfg.DataDir = filepath.Join(cfg.DataDir,
		registeredChains.primaryChain.String())

	// Append the network type to the log directory so it is "namespaced"
	// per network in the same fashion as the data directory.
	cfg.LogDir = cleanAndExpandPath(cfg.LogDir)
	cfg.LogDir = filepath.Join(cfg.LogDir, activeNetParams.Name)
	cfg.LogDir = filepath.Join(cfg.LogDir,
		registeredChains.primaryChain.String())

	// Ensure that the paths to the TLS key and certificate files are
	// expanded and cleaned.
	cfg.TLSCertPath = cleanAndExpandPath(cfg.TLSCertPath)
	cfg.TLSKeyPath = cleanAndExpandPath(cfg.TLSKeyPath)

	// Initialize logging at the default logging level.
	initLogRotator(filepath.Join(cfg.LogDir, defaultLogFilename))

	// Parse, validate, and set debug log level(s).
	if err := parseAndSetDebugLevels(cfg.DebugLevel); err != nil {
		err := fmt.Errorf("%s: %v", funcName, err.Error())
		fmt.Fprintln(os.Stderr, err)
		fmt.Fprintln(os.Stderr, usageMessage)
		return nil, err
	}

	// Warn about missing config file only after all other configuration is
	// done.  This prevents the warning on help messages and invalid
	// options.  Note this should go directly before the return.
	if configFileError != nil {
		ltndLog.Warnf("%v", configFileError)
	}

	return &cfg, nil
}

// cleanAndExpandPath expands environment variables and leading ~ in the
// passed path, cleans the result, and returns it.
// This function is taken from https://github.com/btcsuite/btcd
func cleanAndExpandPath(path string) string {
	// Expand initial ~ to OS specific home directory.
	if strings.HasPrefix(path, "~") {
		homeDir := filepath.Dir(lndHomeDir)
		path = strings.Replace(path, "~", homeDir, 1)
	}

	// NOTE: The os.ExpandEnv doesn't work with Windows-style %VARIABLE%,
	// but the variables can still be expanded via POSIX-style $VARIABLE.
	return filepath.Clean(os.ExpandEnv(path))
}

// parseAndSetDebugLevels attempts to parse the specified debug level and set
// the levels accordingly. An appropriate error is returned if anything is
// invalid.
func parseAndSetDebugLevels(debugLevel string) error {
	// When the specified string doesn't have any delimters, treat it as
	// the log level for all subsystems.
	if !strings.Contains(debugLevel, ",") && !strings.Contains(debugLevel, "=") {
		// Validate debug log level.
		if !validLogLevel(debugLevel) {
			str := "The specified debug level [%v] is invalid"
			return fmt.Errorf(str, debugLevel)
		}

		// Change the logging level for all subsystems.
		setLogLevels(debugLevel)

		return nil
	}

	// Split the specified string into subsystem/level pairs while detecting
	// issues and update the log levels accordingly.
	for _, logLevelPair := range strings.Split(debugLevel, ",") {
		if !strings.Contains(logLevelPair, "=") {
			str := "The specified debug level contains an invalid " +
				"subsystem/level pair [%v]"
			return fmt.Errorf(str, logLevelPair)
		}

		// Extract the specified subsystem and log level.
		fields := strings.Split(logLevelPair, "=")
		subsysID, logLevel := fields[0], fields[1]

		// Validate subsystem.
		if _, exists := subsystemLoggers[subsysID]; !exists {
			str := "The specified subsystem [%v] is invalid -- " +
				"supported subsytems %v"
			return fmt.Errorf(str, subsysID, supportedSubsystems())
		}

		// Validate log level.
		if !validLogLevel(logLevel) {
			str := "The specified debug level [%v] is invalid"
			return fmt.Errorf(str, logLevel)
		}

		setLogLevel(subsysID, logLevel)
	}

	return nil
}

// validLogLevel returns whether or not logLevel is a valid debug log level.
func validLogLevel(logLevel string) bool {
	switch logLevel {
	case "trace":
		fallthrough
	case "debug":
		fallthrough
	case "info":
		fallthrough
	case "warn":
		fallthrough
	case "error":
		fallthrough
	case "critical":
		return true
	}
	return false
}

// supportedSubsystems returns a sorted slice of the supported subsystems for
// logging purposes.
func supportedSubsystems() []string {
	// Convert the subsystemLoggers map keys to a slice.
	subsystems := make([]string, 0, len(subsystemLoggers))
	for subsysID := range subsystemLoggers {
		subsystems = append(subsystems, subsysID)
	}

	// Sort the subsystems for stable display.
	sort.Strings(subsystems)
	return subsystems
}

// noiseDial is a factory function which creates a connmgr compliant dialing
// function by returning a closure which includes the server's identity key.
func noiseDial(idPriv *btcec.PrivateKey) func(net.Addr) (net.Conn, error) {
	return func(a net.Addr) (net.Conn, error) {
		lnAddr := a.(*lnwire.NetAddress)
		return brontide.Dial(idPriv, lnAddr)
	}
}

func parseRPCParams(cConfig *chainConfig, net chainCode, funcName string) error {
	// If the rpcuser and rpcpass paramters aren't set, then we'll attempt
	// to automatically obtain the properm mcredentials for btcd and set
	// them within the configuration.
	if cConfig.RPCUser != "" || cConfig.RPCPass != "" {
		return nil
	}

	// If we're in simnet mode, then the running btcd instance won't read
	// the RPC credentials from the configuration. So if lnd wasn't
	// specified the paramters, then we won't be able to start.
	if cConfig.SimNet {
		str := "%v: rpcuser and rpcpass must be set to your btcd " +
			"node's RPC paramters"
		return fmt.Errorf(str, funcName)
	}

	daemonName := "btcd"
	if net == litecoinChain {
		daemonName = "ltcd"
	}
	fmt.Println("Attempting automatic RPC configuration to " + daemonName)

	homeDir := btcdHomeDir
	if net == litecoinChain {
		homeDir = ltcdHomeDir
	}
	confFile := filepath.Join(homeDir, fmt.Sprintf("%v.conf", daemonName))
	rpcUser, rpcPass, err := extractRPCParams(confFile)
	if err != nil {
		return fmt.Errorf("unable to extract RPC "+
			"credentials: %v, cannot start w/o RPC connection",
			err)
	}

	fmt.Printf("Automatically obtained %v's RPC credentials\n", daemonName)
	cConfig.RPCUser, cConfig.RPCPass = rpcUser, rpcPass
	return nil
}

// extractRPCParams attempts to extract the RPC credentials for an existing
// btcd instance. The passed path is expected to be the location of btcd's
// application data directory on the target system.
func extractRPCParams(btcdConfigPath string) (string, string, error) {
	// First, we'll open up the btcd configuration file found at the target
	// destination.
	btcdConfigFile, err := os.Open(btcdConfigPath)
	if err != nil {
		return "", "", err
	}
	defer btcdConfigFile.Close()

	// With the file open extract the contents of the configuration file so
	// we can attempt o locate the RPC credentials.
	configContents, err := ioutil.ReadAll(btcdConfigFile)
	if err != nil {
		return "", "", err
	}

	// Attempt to locate the RPC user using a regular expression. If we
	// don't have a match for our regular expression then we'll exit with
	// an error.
	rpcUserRegexp, err := regexp.Compile(`(?m)^\s*rpcuser=([^\s]+)`)
	if err != nil {
		return "", "", err
	}
	userSubmatches := rpcUserRegexp.FindSubmatch(configContents)
	if userSubmatches == nil {
		return "", "", fmt.Errorf("unable to find rpcuser in config")
	}

	// Similarly, we'll use another regular expression to find the set
	// rpcpass (if any). If we can't find the pass, then we'll exit with an
	// error.
	rpcPassRegexp, err := regexp.Compile(`(?m)^\s*rpcpass=([^\s]+)`)
	if err != nil {
		return "", "", err
	}
	passSubmatches := rpcPassRegexp.FindSubmatch(configContents)
	if passSubmatches == nil {
		return "", "", fmt.Errorf("unable to find rpcuser in config")
	}

	return string(userSubmatches[1]), string(passSubmatches[1]), nil
}