package config

import (
	"bytes"
	"encoding/hex"
	"fmt"
	"net"
	"strconv"
	"time"

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

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

	ReadBufferSize  int
	WriteBufferSize int

	BindPort       uint16
	PublicIPv4Port uint16
	PublicIPv6Port uint16
	StatsPort      uint16

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

	AntiReplayMaxSize      int
	AntiReplayEvictionTime time.Duration

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

	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
	writeBufferSize, readBufferSize uint32,
	bindIP, publicIPv4, publicIPv6, statsIP net.IP,
	bindPort, publicIPv4Port, publicIPv6Port, statsPort, statsdPort uint16,
	statsdIP, statsdNetwork, statsdPrefix, statsdTagsFormat string,
	statsdTags map[string]string, prometheusPrefix string,
	secureOnly bool,
	antiReplayMaxSize int, antiReplayEvictionTime time.Duration,
	secret, adtag []byte) (*Config, error) {
	secureMode := secureOnly
	if bytes.HasPrefix(secret, []byte{0xdd}) && len(secret) == 17 {
		secureMode = true
		secret = bytes.TrimPrefix(secret, []byte{0xdd})
	} else if len(secret) != 16 {
		return nil, errors.New("Telegram demands secret of length 32")
	}

	var err error
	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,
		SecureOnly:             secureOnly,
		BindIP:                 bindIP,
		BindPort:               bindPort,
		PublicIPv4:             publicIPv4,
		PublicIPv4Port:         publicIPv4Port,
		PublicIPv6:             publicIPv6,
		PublicIPv6Port:         publicIPv6Port,
		StatsIP:                statsIP,
		StatsPort:              statsPort,
		Secret:                 secret,
		AdTag:                  adtag,
		SecureMode:             secureMode,
		ReadBufferSize:         int(readBufferSize),
		WriteBufferSize:        int(writeBufferSize),
		AntiReplayMaxSize:      antiReplayMaxSize,
		AntiReplayEvictionTime: antiReplayEvictionTime,
	}
	conf.Prometheus.Prefix = prometheusPrefix

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

		var (
			addr net.Addr
			err  error
		)
		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
}