package irc

import (
	"bufio"
	"crypto/tls"
	"net"
	"strings"
	"sync"
	"time"

	"github.com/jpillora/backoff"
)

type Config struct {
	Host           string
	Port           string
	TLS            bool
	TLSConfig      *tls.Config
	ServerPassword string
	Nick           string
	Username       string
	Realname       string

	SASLMechanisms []string
	Account        string
	Password       string

	// Version is the reply to VERSION and FINGER CTCP messages
	Version string
	// Source is the reply to SOURCE CTCP messages
	Source string

	HandleNickInUse func(string) string
}

type Client struct {
	Config *Config

	Messages          chan *Message
	ConnectionChanged chan ConnectionState
	Features          *Features

	state    *state
	nick     string
	channels []string

	wantedCapabilities    []string
	requestedCapabilities map[string][]string
	enabledCapabilities   map[string][]string
	negotiating           bool
	saslMechanisms        []SASL
	currentSASLIndex      int

	conn       net.Conn
	connected  bool
	registered bool
	dialer     *net.Dialer
	recvBuf    []byte
	scan       *bufio.Scanner
	backoff    *backoff.Backoff
	out        chan string

	quit      chan struct{}
	reconnect chan struct{}
	sendRecv  sync.WaitGroup
	lock      sync.Mutex
}

func NewClient(config *Config) *Client {
	if config.Port == "" {
		if config.TLS {
			config.Port = "6697"
		} else {
			config.Port = "6667"
		}
	}

	if config.Username == "" {
		config.Username = config.Nick
	}

	if config.Realname == "" {
		config.Realname = config.Nick
	}

	if config.SASLMechanisms == nil {
		config.SASLMechanisms = DefaultSASLMechanisms
	}

	client := &Client{
		Config:                config,
		Messages:              make(chan *Message, 32),
		ConnectionChanged:     make(chan ConnectionState, 4),
		Features:              NewFeatures(),
		nick:                  config.Nick,
		requestedCapabilities: map[string][]string{},
		enabledCapabilities:   map[string][]string{},
		dialer:                &net.Dialer{Timeout: 10 * time.Second},
		recvBuf:               make([]byte, 0, 4096),
		backoff: &backoff.Backoff{
			Min:    500 * time.Millisecond,
			Max:    30 * time.Second,
			Jitter: true,
		},
		out:       make(chan string, 32),
		quit:      make(chan struct{}),
		reconnect: make(chan struct{}),
	}
	client.state = newState(client)
	client.initSASL()

	return client
}

func (c *Client) initSASL() {
	saslMechanisms := []SASL{}

	for _, mech := range c.Config.SASLMechanisms {
		if mech == "EXTERNAL" {
			if c.Config.TLSConfig != nil && len(c.Config.TLSConfig.Certificates) > 0 {
				saslMechanisms = append(saslMechanisms, &SASLExternal{})
			}
		} else if c.Config.Account != "" && c.Config.Password != "" {
			if mech == "PLAIN" {
				saslMechanisms = append(saslMechanisms, &SASLPlain{
					Username: c.Config.Account,
					Password: c.Config.Password,
				})
			} else if strings.HasPrefix(mech, "SCRAM-") {
				saslMechanisms = append(saslMechanisms, &SASLScram{
					Username: c.Config.Account,
					Password: c.Config.Password,
					Hash:     mech[6:],
				})
			}
		}
	}

	c.wantedCapabilities = append([]string{}, clientWantedCaps...)

	if len(saslMechanisms) > 0 {
		c.wantedCapabilities = append(c.wantedCapabilities, "sasl")
		c.saslMechanisms = saslMechanisms
		c.currentSASLIndex = 0
	}
}

func (c *Client) GetNick() string {
	c.lock.Lock()
	nick := c.nick
	c.lock.Unlock()
	return nick
}

func (c *Client) Is(nick string) bool {
	return c.EqualFold(nick, c.GetNick())
}

func (c *Client) setNick(nick string) {
	c.lock.Lock()
	c.nick = nick
	c.lock.Unlock()
}

func (c *Client) Connected() bool {
	c.lock.Lock()
	connected := c.connected
	c.lock.Unlock()
	return connected
}

func (c *Client) Registered() bool {
	c.lock.Lock()
	reg := c.registered
	c.lock.Unlock()
	return reg
}

func (c *Client) setRegistered(reg bool) {
	c.lock.Lock()
	c.registered = reg
	c.lock.Unlock()
}

func (c *Client) Host() string {
	return c.Config.Host
}

func (c *Client) MOTD() []string {
	return c.state.getMOTD()
}

func (c *Client) ChannelUsers(channel string) []string {
	return c.state.getUsers(channel)
}

func (c *Client) ChannelTopic(channel string) string {
	return c.state.getTopic(channel)
}

func (c *Client) Nick(nick string) {
	c.Write("NICK " + nick)
}

func (c *Client) Oper(name, password string) {
	c.Write("OPER " + name + " " + password)
}

func (c *Client) Mode(target, modes, params string) {
	c.Write(strings.TrimRight("MODE "+target+" "+modes+" "+params, " "))
}

func (c *Client) Quit() {
	go func() {
		if c.Connected() {
			c.write("QUIT")
		}
		close(c.quit)
	}()
}

func (c *Client) Join(channels ...string) {
	c.Write("JOIN " + strings.Join(channels, ","))
}

func (c *Client) Part(channels ...string) {
	c.Write("PART " + strings.Join(channels, ","))
	c.removeChannels(channels...)
}

func (c *Client) Topic(channel string, topic ...string) {
	msg := "TOPIC " + channel
	if len(topic) > 0 {
		msg += " :" + topic[0]
	}
	c.Write(msg)
}

func (c *Client) Invite(nick, channel string) {
	c.Write("INVITE " + nick + " " + channel)
}

func (c *Client) Kick(channel string, users ...string) {
	c.Write("KICK " + channel + " " + strings.Join(users, ","))
}

func (c *Client) Privmsg(target, msg string) {
	c.Writef("PRIVMSG %s :%s", target, msg)
}

func (c *Client) Notice(target, msg string) {
	c.Writef("NOTICE %s :%s", target, msg)
}

func (c *Client) ReplyCTCP(target, command, params string) {
	c.Notice(target, EncodeCTCP(&CTCP{
		Command: command,
		Params:  params,
	}))
}

func (c *Client) Whois(nick string) {
	c.Write("WHOIS " + nick)
}

func (c *Client) Away(message string) {
	c.Write("AWAY :" + message)
}

func (c *Client) List() {
	c.Write("LIST")
}

func (c *Client) writePass(password string) {
	c.write("PASS " + password)
}

func (c *Client) writeNick(nick string) {
	c.write("NICK " + nick)
}

func (c *Client) writeUser(username, realname string) {
	c.writef("USER %s 0 * :%s", username, realname)
}

func (c *Client) authenticate(response string) {
	c.write("AUTHENTICATE " + response)
}

func (c *Client) register() {
	c.beginCAP()
	if c.Config.ServerPassword != "" {
		c.writePass(c.Config.ServerPassword)
	}
	c.writeNick(c.Config.Nick)
	c.writeUser(c.Config.Username, c.Config.Realname)
}

func (c *Client) addChannel(channel string) {
	c.lock.Lock()
	c.channels = append(c.channels, channel)
	c.lock.Unlock()
}

func (c *Client) removeChannels(channels ...string) {
	c.lock.Lock()
	for _, removeCh := range channels {
		for i, ch := range c.channels {
			if c.EqualFold(removeCh, ch) {
				c.channels = append(c.channels[:i], c.channels[i+1:]...)
			}
		}
	}
	c.lock.Unlock()
}

func (c *Client) flushChannels() {
	c.lock.Lock()
	if len(c.channels) > 0 {
		c.Join(c.channels...)
		c.channels = []string{}
	}
	c.lock.Unlock()
}