package config

import (
	"encoding/hex"
	"fmt"
	"net"
	"strconv"
	"strings"

	"github.com/juju/errors"
	statsd "gopkg.in/alexcesaro/statsd.v2"
)

// Buffer sizes define internal socket buffer sizes.
const (
	BufferWriteSize = 32 * 1024
	BufferReadSize  = 32 * 1024
)

// Config represents common configuration of mtg.
type Config struct {
	Debug      bool
	Verbose    bool
	SecureMode bool

	BindPort       uint16
	PublicIPv4Port uint16
	PublicIPv6Port uint16
	StatsPort      uint16

	BindIP     net.IP
	PublicIPv4 net.IP
	PublicIPv6 net.IP
	StatsIP    net.IP

	StatsD struct {
		Addr       net.Addr
		Prefix     string
		Tags       map[string]string
		TagsFormat statsd.TagFormat
		Enabled    bool
	}

	Secret []byte
	AdTag  []byte
}

// URLs contains links to the proxy (tg://, t.me) and their QR codes.
type URLs struct {
	TG        string `json:"tg_url"`
	TMe       string `json:"tme_url"`
	TGQRCode  string `json:"tg_qrcode"`
	TMeQRCode string `json:"tme_qrcode"`
}

// IPURLs contains links to both ipv4 and ipv6 of the proxy.
type IPURLs struct {
	IPv4      URLs   `json:"ipv4"`
	IPv6      URLs   `json:"ipv6"`
	BotSecret string `json:"secret_for_mtproxybot"`
}

// BindAddr returns connection for this server to bind to.
func (c *Config) BindAddr() string {
	return getAddr(c.BindIP, c.BindPort)
}

// StatAddr returns connection string to the stats API.
func (c *Config) StatAddr() string {
	return getAddr(c.StatsIP, c.StatsPort)
}

// UseMiddleProxy defines if this proxy has to connect middle proxies
// which supports promoted channels or directly access Telegram.
func (c *Config) UseMiddleProxy() bool {
	return len(c.AdTag) > 0
}

// BotSecretString returns secret string which should work with MTProxybot.
func (c *Config) BotSecretString() string {
	return hex.EncodeToString(c.Secret)
}

// SecretString returns a secret in a form entered on the start of the
// application.
func (c *Config) SecretString() string {
	secret := c.BotSecretString()
	if c.SecureMode {
		return "dd" + secret
	}
	return secret
}

// GetURLs returns configured IPURLs instance with links to this server.
func (c *Config) GetURLs() IPURLs {
	urls := IPURLs{}
	secret := c.SecretString()
	if c.PublicIPv4 != nil {
		urls.IPv4 = getURLs(c.PublicIPv4, c.PublicIPv4Port, secret)
	}
	if c.PublicIPv6 != nil {
		urls.IPv6 = getURLs(c.PublicIPv6, c.PublicIPv6Port, secret)
	}
	urls.BotSecret = c.BotSecretString()

	return urls
}

func getAddr(host fmt.Stringer, port uint16) string {
	return net.JoinHostPort(host.String(), strconv.Itoa(int(port)))
}

// NewConfig returns new configuration. If required, it manages and
// fetches data from external sources. Parameters passed to this
// function, should come from command line arguments.
func NewConfig(debug, verbose bool, // nolint: gocyclo
	bindIP net.IP, bindPort uint16,
	publicIPv4 net.IP, PublicIPv4Port uint16,
	publicIPv6 net.IP, publicIPv6Port uint16,
	statsIP net.IP, statsPort uint16,
	secret, adtag string,
	statsdIP string, statsdPort uint16, statsdNetwork string, statsdPrefix string,
	statsdTagsFormat string, statsdTags map[string]string) (*Config, error) {
	secureMode := false
	if strings.HasPrefix(secret, "dd") && len(secret) == 34 {
		secureMode = true
		secret = strings.TrimPrefix(secret, "dd")
	} else if len(secret) != 32 {
		return nil, errors.New("Telegram demands secret of length 32")
	}
	secretBytes, err := hex.DecodeString(secret)
	if err != nil {
		return nil, errors.Annotate(err, "Cannot create config")
	}

	var adTagBytes []byte
	if len(adtag) != 0 {
		adTagBytes, err = hex.DecodeString(adtag)
		if err != nil {
			return nil, errors.Annotate(err, "Cannot create config")
		}
	}

	if publicIPv4 == nil {
		publicIPv4, err = getGlobalIPv4()
		if err != nil {
			publicIPv4 = nil
		} else if publicIPv4.To4() == nil {
			return nil, errors.Errorf("IP %s is not IPv4", publicIPv4.String())
		}
	}
	if PublicIPv4Port == 0 {
		PublicIPv4Port = bindPort
	}

	if publicIPv6 == nil {
		publicIPv6, err = getGlobalIPv6()
		if err != nil {
			publicIPv6 = nil
		} else if publicIPv6.To4() != nil {
			return nil, errors.Errorf("IP %s is not IPv6", publicIPv6.String())
		}
	}
	if publicIPv6Port == 0 {
		publicIPv6Port = bindPort
	}

	if statsIP == nil {
		statsIP = publicIPv4
	}

	conf := &Config{
		Debug:          debug,
		Verbose:        verbose,
		BindIP:         bindIP,
		BindPort:       bindPort,
		PublicIPv4:     publicIPv4,
		PublicIPv4Port: PublicIPv4Port,
		PublicIPv6:     publicIPv6,
		PublicIPv6Port: publicIPv6Port,
		StatsIP:        statsIP,
		StatsPort:      statsPort,
		Secret:         secretBytes,
		AdTag:          adTagBytes,
		SecureMode:     secureMode,
	}

	if statsdIP != "" {
		conf.StatsD.Enabled = true
		conf.StatsD.Prefix = statsdPrefix
		conf.StatsD.Tags = statsdTags

		var addr net.Addr
		hostPort := net.JoinHostPort(statsdIP, strconv.Itoa(int(statsdPort)))
		switch statsdNetwork {
		case "tcp":
			addr, err = net.ResolveTCPAddr("tcp", hostPort)
		case "udp":
			addr, err = net.ResolveUDPAddr("udp", hostPort)
		default:
			err = errors.Errorf("Unknown network %s", statsdNetwork)
		}
		if err != nil {
			return nil, errors.Annotate(err, "Cannot resolve statsd address")
		}
		conf.StatsD.Addr = addr

		switch statsdTagsFormat {
		case "datadog":
			conf.StatsD.TagsFormat = statsd.Datadog
		case "influxdb":
			conf.StatsD.TagsFormat = statsd.InfluxDB
		case "":
		default:
			return nil, errors.Errorf("Unknown tags format %s", statsdTagsFormat)
		}
	}

	return conf, nil
}