// Copyright (c) 2013-2014 Conformal Systems LLC.
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.

package main

import (
	"errors"
	"fmt"
	"github.com/conformal/btcdb"
	_ "github.com/conformal/btcdb/ldb"
	_ "github.com/conformal/btcdb/memdb"
	"github.com/conformal/btcutil"
	"github.com/conformal/btcwire"
	"github.com/conformal/go-flags"
	"github.com/conformal/go-socks"
	"net"
	"os"
	"path/filepath"
	"runtime"
	"sort"
	"strconv"
	"strings"
	"time"
)

const (
	defaultConfigFilename = "btcd.conf"
	defaultDataDirname    = "data"
	defaultLogLevel       = "info"
	defaultBtcnet         = btcwire.MainNet
	defaultMaxPeers       = 125
	defaultBanDuration    = time.Hour * 24
	defaultVerifyEnabled  = false
	defaultDbType         = "leveldb"
)

var (
	btcdHomeDir        = btcutil.AppDataDir("btcd", false)
	defaultConfigFile  = filepath.Join(btcdHomeDir, defaultConfigFilename)
	defaultDataDir     = filepath.Join(btcdHomeDir, defaultDataDirname)
	defaultListener    = net.JoinHostPort("", netParams(defaultBtcnet).listenPort)
	knownDbTypes       = btcdb.SupportedDBs()
	defaultRPCKeyFile  = filepath.Join(btcdHomeDir, "rpc.key")
	defaultRPCCertFile = filepath.Join(btcdHomeDir, "rpc.cert")
	defaultLogFile     = filepath.Join(btcdHomeDir, "logs", "btcd.log")
)

// runServiceCommand is only set to a real function on Windows.  It is used
// to parse and execute service commands specified via the -s flag.
var runServiceCommand func(string) error

// config defines the configuration options for btcd.
//
// See loadConfig for details on the configuration load process.
type config struct {
	ShowVersion        bool          `short:"V" long:"version" description:"Display version information and exit"`
	ConfigFile         string        `short:"C" long:"configfile" description:"Path to configuration file"`
	DataDir            string        `short:"b" long:"datadir" description:"Directory to store data"`
	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"`
	DisableListen      bool          `long:"nolisten" description:"Disable listening for incoming connections -- NOTE: Listening is automatically disabled if the --connect or --proxy options are used without also specifying listen interfaces via --listen"`
	Listeners          []string      `long:"listen" description:"Add an interface/port to listen for connections (default all interfaces port: 8333, testnet: 18333)"`
	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"`
	RPCUser            string        `short:"u" long:"rpcuser" description:"Username for RPC connections"`
	RPCPass            string        `short:"P" long:"rpcpass" default-mask:"-" description:"Password for RPC connections"`
	RPCListeners       []string      `long:"rpclisten" description:"Add an interface/port to listen for RPC connections (default port: 8334, testnet: 18334)"`
	RPCCert            string        `long:"rpccert" description:"File containing the certificate file"`
	RPCKey             string        `long:"rpckey" description:"File containing the certificate key"`
	DisableRPC         bool          `long:"norpc" description:"Disable built-in RPC server -- NOTE: The RPC server is disabled by default if no rpcuser/rpcpass is specified"`
	DisableDNSSeed     bool          `long:"nodnsseed" description:"Disable DNS seeding for peers"`
	ExternalIPs        []string      `long:"externalip" description:"Add an ip to the list of local addresses we claim to listen on to peers"`
	Proxy              string        `long:"proxy" description:"Connect via SOCKS5 proxy (eg. 127.0.0.1:9050)"`
	ProxyUser          string        `long:"proxyuser" description:"Username for proxy server"`
	ProxyPass          string        `long:"proxypass" default-mask:"-" description:"Password for proxy server"`
	OnionProxy         string        `long:"onion" description:"Connect to tor hidden services via SOCKS5 proxy (eg. 127.0.0.1:9050)"`
	OnionProxyUser     string        `long:"onionuser" description:"Username for onion proxy server"`
	OnionProxyPass     string        `long:"onionpass" default-mask:"-" description:"Password for onion proxy server"`
	NoOnion            bool          `long:"noonion" description:"Disable connecting to tor hidden services"`
	TestNet3           bool          `long:"testnet" description:"Use the test network"`
	RegressionTest     bool          `long:"regtest" description:"Use the regression test network"`
	DisableCheckpoints bool          `long:"nocheckpoints" description:"Disable built-in checkpoints.  Don't do this unless you know what you're doing."`
	DbType             string        `long:"dbtype" description:"Database backend to use for the Block Chain"`
	Profile            string        `long:"profile" description:"Enable HTTP profiling on given port -- NOTE port must be between 1024 and 65536"`
	CpuProfile         string        `long:"cpuprofile" description:"Write CPU profile to the specified file"`
	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"`
	Upnp               bool          `long:"upnp" description:"Use UPnP to map our listening port outside of NAT"`
	onionlookup        func(string) ([]net.IP, error)
	lookup             func(string) ([]net.IP, error)
	oniondial          func(string, string) (net.Conn, error)
	dial               func(string, string) (net.Conn, error)
}

// serviceOptions defines the configuration options for btcd as a service on
// Windows.
type serviceOptions struct {
	ServiceCommand string `short:"s" long:"service" description:"Service command {install, remove, start, stop}"`
}

// cleanAndExpandPath expands environement variables and leading ~ in the
// passed path, cleans the result, and returns it.
func cleanAndExpandPath(path string) string {
	// Expand initial ~ to OS specific home directory.
	if strings.HasPrefix(path, "~") {
		homeDir := filepath.Dir(btcdHomeDir)
		path = strings.Replace(path, "~", homeDir, 1)
	}

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

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

// 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
}

// validDbType returns whether or not dbType is a supported database type.
func validDbType(dbType string) bool {
	for _, knownType := range knownDbTypes {
		if dbType == knownType {
			return true
		}
	}

	return false
}

// removeDuplicateAddresses returns a new slice with all duplicate entries in
// addrs removed.
func removeDuplicateAddresses(addrs []string) []string {
	result := make([]string, 0)
	seen := map[string]bool{}
	for _, val := range addrs {
		if _, ok := seen[val]; !ok {
			result = append(result, val)
			seen[val] = true
		}
	}
	return result
}

// normalizeAddress returns addr with the passed default port appended if
// there is not already a port specified.
func normalizeAddress(addr, defaultPort string) string {
	_, _, err := net.SplitHostPort(addr)
	if err != nil {
		return net.JoinHostPort(addr, defaultPort)
	}
	return addr
}

// normalizeAddresses returns a new slice with all the passed peer addresses
// normalized with the given default port, and all duplicates removed.
func normalizeAddresses(addrs []string, defaultPort string) []string {
	for i, addr := range addrs {
		addrs[i] = normalizeAddress(addr, defaultPort)
	}

	return removeDuplicateAddresses(addrs)
}

// filesExists reports whether the named file or directory exists.
func fileExists(name string) bool {
	if _, err := os.Stat(name); err != nil {
		if os.IsNotExist(err) {
			return false
		}
	}
	return true
}

// newConfigParser returns a new command line flags parser.
func newConfigParser(cfg *config, so *serviceOptions, options flags.Options) *flags.Parser {
	parser := flags.NewParser(cfg, options)
	if runtime.GOOS == "windows" {
		parser.AddGroup("Service Options", "Service Options", so)
	}
	return parser
}

// 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
//
// The above results in btcd functioning properly without any config settings
// while still allowing the user to override settings with config files and
// command line options.  Command line options always take precedence.
func loadConfig() (*config, []string, error) {
	// Default config.
	cfg := config{
		DebugLevel:  defaultLogLevel,
		MaxPeers:    defaultMaxPeers,
		BanDuration: defaultBanDuration,
		ConfigFile:  defaultConfigFile,
		DataDir:     defaultDataDir,
		DbType:      defaultDbType,
		RPCKey:      defaultRPCKeyFile,
		RPCCert:     defaultRPCCertFile,
	}

	// Service options which are only added on Windows.
	serviceOpts := serviceOptions{}

	// Create the home directory if it doesn't already exist.
	err := os.MkdirAll(btcdHomeDir, 0700)
	if err != nil {
		btcdLog.Errorf("%v", err)
		return nil, nil, err
	}

	// Pre-parse the command line options to see if an alternative config
	// file or the version flag was specified.  Any errors can be ignored
	// here since they will be caught be the final parse below.
	preCfg := cfg
	preParser := newConfigParser(&preCfg, &serviceOpts, flags.None)
	preParser.Parse()

	// Show the version and exit if the version flag was specified.
	if preCfg.ShowVersion {
		appName := filepath.Base(os.Args[0])
		appName = strings.TrimSuffix(appName, filepath.Ext(appName))
		fmt.Println(appName, "version", version())
		os.Exit(0)
	}

	// Perform service command and exit if specified.  Invalid service
	// commands show an appropriate error.  Only runs on Windows since
	// the runServiceCommand function will be nil when not on Windows.
	if serviceOpts.ServiceCommand != "" && runServiceCommand != nil {
		err := runServiceCommand(serviceOpts.ServiceCommand)
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
		}
		os.Exit(0)
	}

	// Load additional config from file.
	var configFileError error
	parser := newConfigParser(&cfg, &serviceOpts, flags.Default)
	if !preCfg.RegressionTest || preCfg.ConfigFile != defaultConfigFile {
		err := flags.NewIniParser(parser).ParseFile(preCfg.ConfigFile)
		if err != nil {
			if _, ok := err.(*os.PathError); !ok {
				fmt.Fprintln(os.Stderr, err)
				parser.WriteHelp(os.Stderr)
				return nil, nil, err
			}
			configFileError = err
		}
	}

	// Don't add peers from the config file when in regression test mode.
	if preCfg.RegressionTest && len(cfg.AddPeers) > 0 {
		cfg.AddPeers = nil
	}

	// Parse command line options again to ensure they take precedence.
	remainingArgs, err := parser.Parse()
	if err != nil {
		if e, ok := err.(*flags.Error); !ok || e.Type != flags.ErrHelp {
			parser.WriteHelp(os.Stderr)
		}
		return nil, nil, err
	}

	// The two test networks can't be selected simultaneously.
	if cfg.TestNet3 && cfg.RegressionTest {
		str := "%s: The testnet and regtest params can't be used " +
			"together -- choose one of the two"
		err := fmt.Errorf(str, "loadConfig")
		fmt.Fprintln(os.Stderr, err)
		parser.WriteHelp(os.Stderr)
		return nil, nil, err
	}

	// Choose the active network params based on the testnet and regression
	// test net flags.
	if cfg.TestNet3 {
		activeNetParams = netParams(btcwire.TestNet3)
	} else if cfg.RegressionTest {
		activeNetParams = netParams(btcwire.TestNet)
	}

	// Special show command to list supported subsystems and exit.
	if cfg.DebugLevel == "show" {
		fmt.Println("Supported subsystems", supportedSubsystems())
		os.Exit(0)
	}

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

	// Validate database type.
	if !validDbType(cfg.DbType) {
		str := "%s: The specified database type [%v] is invalid -- " +
			"supported types %v"
		err := fmt.Errorf(str, "loadConfig", cfg.DbType, knownDbTypes)
		fmt.Fprintln(os.Stderr, err)
		parser.WriteHelp(os.Stderr)
		return nil, nil, err
	}

	// 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, "loadConfig")
			fmt.Fprintln(os.Stderr, err)
			parser.WriteHelp(os.Stderr)
			return nil, 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.
	cfg.DataDir = cleanAndExpandPath(cfg.DataDir)
	cfg.DataDir = filepath.Join(cfg.DataDir, activeNetParams.netName)

	// Don't allow ban durations that are too short.
	if cfg.BanDuration < time.Duration(time.Second) {
		str := "%s: The banduration option may not be less than 1s -- parsed [%v]"
		err := fmt.Errorf(str, "loadConfig", cfg.BanDuration)
		fmt.Fprintln(os.Stderr, err)
		parser.WriteHelp(os.Stderr)
		return nil, nil, err
	}

	// --addPeer and --connect do not mix.
	if len(cfg.AddPeers) > 0 && len(cfg.ConnectPeers) > 0 {
		str := "%s: the --addpeer and --connect options can not be " +
			"mixed"
		err := fmt.Errorf(str, "loadConfig")
		fmt.Fprintln(os.Stderr, err)
		parser.WriteHelp(os.Stderr)
		return nil, nil, err
	}

	// --proxy or --connect without --listen disables listening.
	if (cfg.Proxy != "" || len(cfg.ConnectPeers) > 0) &&
		len(cfg.Listeners) == 0 {
		cfg.DisableListen = true
	}

	// Connect means no DNS seeding.
	if len(cfg.ConnectPeers) > 0 {
		cfg.DisableDNSSeed = true
	}

	// Add the default listener if none were specified. The default
	// listener is all addresses on the listen port for the network
	// we are to connect to.
	if len(cfg.Listeners) == 0 {
		cfg.Listeners = []string{
			net.JoinHostPort("", activeNetParams.listenPort),
		}
	}

	// The RPC server is disabled if no username or password is provided.
	if cfg.RPCUser == "" || cfg.RPCPass == "" {
		cfg.DisableRPC = true
	}

	// Default RPC to listen on localhost only.
	if !cfg.DisableRPC && len(cfg.RPCListeners) == 0 {
		addrs, err := net.LookupHost("localhost")
		if err != nil {
			return nil, nil, err
		}
		cfg.RPCListeners = make([]string, 0, len(addrs))
		for _, addr := range addrs {
			addr = net.JoinHostPort(addr, activeNetParams.rpcPort)
			cfg.RPCListeners = append(cfg.RPCListeners, addr)
		}

	}

	// Add default port to all listener addresses if needed and remove
	// duplicate addresses.
	cfg.Listeners = normalizeAddresses(cfg.Listeners,
		activeNetParams.listenPort)

	// Add default port to all rpc listener addresses if needed and remove
	// duplicate addresses.
	cfg.RPCListeners = normalizeAddresses(cfg.RPCListeners,
		activeNetParams.rpcPort)

	// Add default port to all added peer addresses if needed and remove
	// duplicate addresses.
	cfg.AddPeers = normalizeAddresses(cfg.AddPeers,
		activeNetParams.peerPort)
	cfg.ConnectPeers = normalizeAddresses(cfg.ConnectPeers,
		activeNetParams.peerPort)

	// Setup dial and DNS resolution (lookup) functions depending on the
	// specified options.  The default is to use the standard net.Dial
	// function as well as the system DNS resolver.  When a proxy is
	// specified, the dial function is set to the proxy specific dial
	// function and the lookup is set to use tor (unless --noonion is
	// specified in which case the system DNS resolver is used).
	cfg.dial = net.Dial
	cfg.lookup = net.LookupIP
	if cfg.Proxy != "" {
		proxy := &socks.Proxy{
			Addr:     cfg.Proxy,
			Username: cfg.ProxyUser,
			Password: cfg.ProxyPass,
		}
		cfg.dial = proxy.Dial
		if !cfg.NoOnion {
			cfg.lookup = func(host string) ([]net.IP, error) {
				return torLookupIP(host, cfg.Proxy)
			}
		}
	}

	// Setup onion address dial and DNS resolution (lookup) functions
	// depending on the specified options.  The default is to use the
	// same dial and lookup functions selected above.  However, when an
	// onion-specific proxy is specified, the onion address dial and
	// lookup functions are set to use the onion-specific proxy while
	// leaving the normal dial and lookup functions as selected above.
	// This allows .onion address traffic to be routed through a different
	// proxy than normal traffic.
	if cfg.OnionProxy != "" {
		cfg.oniondial = func(a, b string) (net.Conn, error) {
			proxy := &socks.Proxy{
				Addr:     cfg.OnionProxy,
				Username: cfg.OnionProxyUser,
				Password: cfg.OnionProxyPass,
			}
			return proxy.Dial(a, b)
		}
		cfg.onionlookup = func(host string) ([]net.IP, error) {
			return torLookupIP(host, cfg.OnionProxy)
		}
	} else {
		cfg.oniondial = cfg.dial
		cfg.onionlookup = cfg.lookup
	}

	// Specifying --noonion means the onion address dial and DNS resolution
	// (lookup) functions result in an error.
	if cfg.NoOnion {
		cfg.oniondial = func(a, b string) (net.Conn, error) {
			return nil, errors.New("tor has been disabled")
		}
		cfg.onionlookup = func(a string) ([]net.IP, error) {
			return nil, errors.New("tor has been disabled")
		}
	}

	// 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 {
		btcdLog.Warnf("%v", configFileError)
	}

	return &cfg, remainingArgs, nil
}

// btcdDial connects to the address on the named network using the appropriate
// dial function depending on the address and configuration options.  For
// example, .onion addresses will be dialed using the onion specific proxy if
// one was specified, but will otherwise use the normal dial function (which
// could itself use a proxy or not).
func btcdDial(network, address string) (net.Conn, error) {
	if strings.HasSuffix(address, ".onion") {
		return cfg.oniondial(network, address)
	}
	return cfg.dial(network, address)
}

// btcdLookup returns the correct DNS lookup function to use depending on the
// passed host and configuration options.  For example, .onion addresses will be
// resolved using the onion specific proxy if one was specified, but will
// otherwise treat the normal proxy as tor unless --noonion was specified in
// which case the lookup will fail.  Meanwhile, normal IP addresses will be
// resolved using tor if a proxy was specified unless --noonion was also
// specified in which case the normal system DNS resolver will be used.
func btcdLookup(host string) ([]net.IP, error) {
	if strings.HasSuffix(host, ".onion") {
		return cfg.onionlookup(host)
	}
	return cfg.lookup(host)
}