client.go

package twitch

import (
	"bufio"
	"crypto/tls"
	"errors"
	"fmt"
	"io"
	"net"
	"net/textproto"
	"strings"
	"sync"
	"time"
)

const (
	// ircTwitch constant for twitch irc chat address
	ircTwitchTLS = "irc.chat.twitch.tv:6697"
	ircTwitch    = "irc.chat.twitch.tv:6667"

	pingSignature = "go-twitch-irc"
	pingMessage   = "PING :" + pingSignature

	// TagsCapability for Twitch's Tags capabilities, see https://dev.twitch.tv/docs/irc/tags
	TagsCapability = "twitch.tv/tags"

	// CommandsCapability for Twitch's Commands capabilities, see https://dev.twitch.tv/docs/irc/commands
	CommandsCapability = "twitch.tv/commands"

	// MembershipCapability for Twitch's Membership capabilities, see https://dev.twitch.tv/docs/irc/membership
	MembershipCapability = "twitch.tv/membership"
)

var (
	// ErrClientDisconnected returned from Connect() when a Disconnect() was called
	ErrClientDisconnected = errors.New("client called Disconnect()")

	// ErrLoginAuthenticationFailed returned from Connect() when either the wrong or a malformed oauth token is used
	ErrLoginAuthenticationFailed = errors.New("login authentication failed")

	// ErrConnectionIsNotOpen is returned by Disconnect in case you call it without being connected
	ErrConnectionIsNotOpen = errors.New("connection is not open")

	// WriteBufferSize can be modified to change the write channel buffer size.
	// Must be configured before NewClient is called to take effect
	WriteBufferSize = 512

	// ReadBufferSize can be modified to change the read channel buffer size.
	// Must be configured before NewClient is called to take effect
	ReadBufferSize = 64

	// DefaultCapabilities is the default caps when creating a new Client
	DefaultCapabilities = []string{TagsCapability, CommandsCapability}
)

// Internal errors
var (
	errReconnect = errors.New("reconnect")
)

// User data you receive from TMI
type User struct {
	ID          string
	Name        string
	DisplayName string
	Color       string
	Badges      map[string]int
}

// Message interface that all messages implement
type Message interface {
	GetType() MessageType
}

// RawMessage data you receive from TMI
type RawMessage struct {
	Raw     string
	Type    MessageType
	RawType string
	Tags    map[string]string
	Message string
}

// GetType implements the Message interface, and returns this message's type
func (msg *RawMessage) GetType() MessageType {
	return msg.Type
}

// WhisperMessage data you receive from WHISPER message type
type WhisperMessage struct {
	User User

	Raw       string
	Type      MessageType
	RawType   string
	Tags      map[string]string
	Message   string
	Target    string
	MessageID string
	ThreadID  string
	Emotes    []*Emote
	Action    bool
}

// GetType implements the Message interface, and returns this message's type
func (msg *WhisperMessage) GetType() MessageType {
	return msg.Type
}

// PrivateMessage data you receive from PRIVMSG message type
type PrivateMessage struct {
	User User

	Raw          string
	Type         MessageType
	RawType      string
	Tags         map[string]string
	Message      string
	Channel      string
	RoomID       string
	ID           string
	Time         time.Time
	Emotes       []*Emote
	Bits         int
	Action       bool
	FirstMessage bool
	Reply        *Reply
}

type Reply struct {
	ParentMsgID       string
	ParentUserID      string
	ParentUserLogin   string
	ParentDisplayName string
	ParentMsgBody     string
}

// GetType implements the Message interface, and returns this message's type
func (msg *PrivateMessage) GetType() MessageType {
	return msg.Type
}

// ClearChatMessage data you receive from CLEARCHAT message type
type ClearChatMessage struct {
	Raw            string
	Type           MessageType
	RawType        string
	Tags           map[string]string
	Message        string
	Channel        string
	RoomID         string
	Time           time.Time
	BanDuration    int
	TargetUserID   string
	TargetUsername string
}

// GetType implements the Message interface, and returns this message's type
func (msg *ClearChatMessage) GetType() MessageType {
	return msg.Type
}

// ClearMessage data you receive from CLEARMSG message type
type ClearMessage struct {
	Raw         string
	Type        MessageType
	RawType     string
	Tags        map[string]string
	Message     string
	Channel     string
	Login       string
	TargetMsgID string
}

// GetType implements the Message interface, and returns this message's type
func (msg *ClearMessage) GetType() MessageType {
	return msg.Type
}

// RoomStateMessage data you receive from ROOMSTATE message type
type RoomStateMessage struct {
	Raw     string
	Type    MessageType
	RawType string
	Tags    map[string]string
	Message string
	Channel string
	RoomID  string
	State   map[string]int
}

// GetType implements the Message interface, and returns this message's type
func (msg *RoomStateMessage) GetType() MessageType {
	return msg.Type
}

// UserNoticeMessage  data you receive from USERNOTICE message type
type UserNoticeMessage struct {
	User User

	Raw       string
	Type      MessageType
	RawType   string
	Tags      map[string]string
	Message   string
	Channel   string
	RoomID    string
	ID        string
	Time      time.Time
	Emotes    []*Emote
	MsgID     string
	MsgParams map[string]string
	SystemMsg string
}

// GetType implements the Message interface, and returns this message's type
func (msg *UserNoticeMessage) GetType() MessageType {
	return msg.Type
}

// UserStateMessage data you receive from the USERSTATE message type
type UserStateMessage struct {
	User User

	Raw       string
	Type      MessageType
	RawType   string
	Tags      map[string]string
	Message   string
	Channel   string
	EmoteSets []string
}

// GetType implements the Message interface, and returns this message's type
func (msg *UserStateMessage) GetType() MessageType {
	return msg.Type
}

// NoticeMessage data you receive from the NOTICE message type
type NoticeMessage struct {
	Raw     string
	Type    MessageType
	RawType string
	Tags    map[string]string
	Message string
	Channel string
	MsgID   string
}

// GetType implements the Message interface, and returns this message's type
func (msg *NoticeMessage) GetType() MessageType {
	return msg.Type
}

// UserJoinMessage desJoines the message that is sent whenever a user joins a channel we're connected to
// See https://dev.twitch.tv/docs/irc/membership/#join-twitch-membership
type UserJoinMessage struct {
	Raw     string
	Type    MessageType
	RawType string

	// Channel name
	Channel string

	// User name
	User string
}

// GetType implements the Message interface, and returns this message's type
func (msg *UserJoinMessage) GetType() MessageType {
	return msg.Type
}

// UserPartMessage describes the message that is sent whenever a user leaves a channel we're connected to
// See https://dev.twitch.tv/docs/irc/membership/#part-twitch-membership
type UserPartMessage struct {
	Raw     string
	Type    MessageType
	RawType string

	// Channel name
	Channel string

	// User name
	User string
}

// GetType implements the Message interface, and returns this message's type
func (msg *UserPartMessage) GetType() MessageType {
	return msg.Type
}

// GlobalUserStateMessage On successful login, provides data about the current logged-in user through IRC tags
// See https://dev.twitch.tv/docs/irc/tags/#globaluserstate-twitch-tags
type GlobalUserStateMessage struct {
	User User

	Raw       string
	Type      MessageType
	RawType   string
	Tags      map[string]string
	EmoteSets []string
}

// GetType implements the Message interface, and returns this message's type
func (msg *GlobalUserStateMessage) GetType() MessageType {
	return msg.Type
}

// ReconnectMessage describes the
type ReconnectMessage struct {
	Raw     string
	Type    MessageType
	RawType string
}

// GetType implements the Message interface, and returns this message's type
func (msg *ReconnectMessage) GetType() MessageType {
	return msg.Type
}

// NamesMessage describes the data posted in response to a /names command
// See https://www.alien.net.au/irc/irc2numerics.html#353
type NamesMessage struct {
	Raw     string
	Type    MessageType
	RawType string

	// Channel name
	Channel string

	// List of user names
	Users []string
}

// GetType implements the Message interface, and returns this message's type
func (msg *NamesMessage) GetType() MessageType {
	return msg.Type
}

// PingMessage describes an IRC PING message
type PingMessage struct {
	Raw     string
	Type    MessageType
	RawType string

	Message string
}

// GetType implements the Message interface, and returns this message's type
func (msg *PingMessage) GetType() MessageType {
	return msg.Type
}

// PongMessage describes an IRC PONG message
type PongMessage struct {
	Raw     string
	Type    MessageType
	RawType string

	Message string
}

// GetType implements the Message interface, and returns this message's type
func (msg *PongMessage) GetType() MessageType {
	return msg.Type
}

// Client client to control your connection and attach callbacks
type Client struct {
	IrcAddress               string
	ircUser                  string
	ircToken                 string
	TLS                      bool
	connActive               tAtomBool
	channels                 map[string]bool
	channelUserlistMutex     *sync.RWMutex
	channelUserlist          map[string]map[string]bool
	channelsMtx              *sync.RWMutex
	onConnect                func()
	onWhisperMessage         func(message WhisperMessage)
	onPrivateMessage         func(message PrivateMessage)
	onClearChatMessage       func(message ClearChatMessage)
	onRoomStateMessage       func(message RoomStateMessage)
	onClearMessage           func(message ClearMessage)
	onUserNoticeMessage      func(message UserNoticeMessage)
	onUserStateMessage       func(message UserStateMessage)
	onGlobalUserStateMessage func(message GlobalUserStateMessage)
	onNoticeMessage          func(message NoticeMessage)
	onUserJoinMessage        func(message UserJoinMessage)
	onUserPartMessage        func(message UserPartMessage)
	onReconnectMessage       func(message ReconnectMessage)
	onNamesMessage           func(message NamesMessage)
	onPingMessage            func(message PingMessage)
	onPongMessage            func(message PongMessage)
	onUnsetMessage           func(message RawMessage)

	onPingSent func()

	// read is the incoming messages channel, normally buffered with ReadBufferSize
	read chan string

	// write is the outgoing messages channel, normally buffered with WriteBufferSize
	write chan string

	// clientReconnect is closed whenever the client needs to reconnect for connection issue reasons
	clientReconnect chanCloser

	// userDisconnect is closed when the user calls Disconnect
	userDisconnect chanCloser

	// pongReceived is listened to by the pinger go-routine after it has sent off a ping. will be triggered by handleLine
	pongReceived chan bool

	// messageReceived is listened to by the pinger go-routine to interrupt the idle ping interval
	messageReceived chan bool

	// Option whether to send pings every `IdlePingInterval`. The IdlePingInterval is interrupted every time a message is received from the irc server
	// The variable may only be modified before calling Connect
	SendPings bool

	// IdlePingInterval is the interval at which to send a ping to the irc server to ensure the connection is alive.
	// The variable may only be modified before calling Connect
	IdlePingInterval time.Duration

	// PongTimeout is the time go-twitch-irc waits after sending a ping before issuing a reconnect
	// The variable may only be modified before calling Connect
	PongTimeout time.Duration

	// SetupCmd is the command that is ran on successful connection to Twitch. Useful if you are proxying or something to run a custom command on connect.
	// The variable must be modified before calling Connect or the command will not run.
	SetupCmd string

	// Capabilities is the list of capabilities that should be sent as part of the connection setup
	// By default, this is all caps (Tags, Commands, Membership)
	// If this is an empty list or nil, no CAP REQ message is sent at all
	Capabilities []string

	// The ratelimits the client will respect when sending messages
	joinRateLimiter RateLimiter
}

// NewClient to create a new client
func NewClient(username, oauth string) *Client {
	return &Client{
		ircUser:         username,
		ircToken:        oauth,
		TLS:             true,
		channels:        map[string]bool{},
		channelUserlist: map[string]map[string]bool{},
		channelsMtx:     &sync.RWMutex{},
		messageReceived: make(chan bool),

		read:  make(chan string, ReadBufferSize),
		write: make(chan string, WriteBufferSize),

		// NOTE: IdlePingInterval must be higher than PongTimeout
		SendPings:        true,
		IdlePingInterval: time.Second * 15,
		PongTimeout:      time.Second * 5,

		channelUserlistMutex: &sync.RWMutex{},

		Capabilities: DefaultCapabilities,

		joinRateLimiter: CreateDefaultRateLimiter(),
	}
}

// NewAnonymousClient to create a new client without login requirements (anonymous user)
// Do note that the Say and Whisper functions will be ineffectual when using this constructor
func NewAnonymousClient() *Client {
	return NewClient("justinfan123123", "oauth:59301")
}

// OnConnect attach callback to when a connection has been established
func (c *Client) OnConnect(callback func()) {
	c.onConnect = callback
}

// OnWhisperMessage attach callback to new whisper
func (c *Client) OnWhisperMessage(callback func(message WhisperMessage)) {
	c.onWhisperMessage = callback
}

// OnPrivateMessage attach callback to new standard chat messages
func (c *Client) OnPrivateMessage(callback func(message PrivateMessage)) {
	c.onPrivateMessage = callback
}

// OnClearChatMessage attach callback to new messages such as timeouts
func (c *Client) OnClearChatMessage(callback func(message ClearChatMessage)) {
	c.onClearChatMessage = callback
}

// OnClearMessage attach callback when a single message is deleted
func (c *Client) OnClearMessage(callback func(message ClearMessage)) {
	c.onClearMessage = callback
}

// OnRoomStateMessage attach callback to new messages such as submode enabled
func (c *Client) OnRoomStateMessage(callback func(message RoomStateMessage)) {
	c.onRoomStateMessage = callback
}

// OnUserNoticeMessage attach callback to new usernotice message such as sub, resub, and raids
func (c *Client) OnUserNoticeMessage(callback func(message UserNoticeMessage)) {
	c.onUserNoticeMessage = callback
}

// OnUserStateMessage attach callback to new userstate
func (c *Client) OnUserStateMessage(callback func(message UserStateMessage)) {
	c.onUserStateMessage = callback
}

// OnGlobalUserStateMessage attach callback to new global user state
func (c *Client) OnGlobalUserStateMessage(callback func(message GlobalUserStateMessage)) {
	c.onGlobalUserStateMessage = callback
}

// OnNoticeMessage attach callback to new notice message such as hosts
func (c *Client) OnNoticeMessage(callback func(message NoticeMessage)) {
	c.onNoticeMessage = callback
}

// OnUserJoinMessage attaches callback to user joins
func (c *Client) OnUserJoinMessage(callback func(message UserJoinMessage)) {
	c.onUserJoinMessage = callback
}

// OnUserPartMessage attaches callback to user parts
func (c *Client) OnUserPartMessage(callback func(message UserPartMessage)) {
	c.onUserPartMessage = callback
}

// OnReconnectMessage attaches callback that is triggered whenever the twitch servers tell us to reconnect
func (c *Client) OnReconnectMessage(callback func(message ReconnectMessage)) {
	c.onReconnectMessage = callback
}

// OnNamesMessage attaches callback to /names response
func (c *Client) OnNamesMessage(callback func(message NamesMessage)) {
	c.onNamesMessage = callback
}

// OnPingMessage attaches callback to PING message
func (c *Client) OnPingMessage(callback func(message PingMessage)) {
	c.onPingMessage = callback
}

// OnPongMessage attaches callback to PONG message
func (c *Client) OnPongMessage(callback func(message PongMessage)) {
	c.onPongMessage = callback
}

// OnUnsetMessage attaches callback to message types we currently don't support
func (c *Client) OnUnsetMessage(callback func(message RawMessage)) {
	c.onUnsetMessage = callback
}

// OnPingSent attaches callback that's called whenever the client sends out a ping message
func (c *Client) OnPingSent(callback func()) {
	c.onPingSent = callback
}

// Say write something in a chat
func (c *Client) Say(channel, text string) {
	channel = strings.ToLower(channel)

	c.send(fmt.Sprintf("PRIVMSG #%s :%s", channel, text))
}

// Reply to a message previously sent in the same channel using the twitch reply feature
func (c *Client) Reply(channel, parentMsgId string, text string) {
	channel = strings.ToLower(channel)

	c.send(fmt.Sprintf("@reply-parent-msg-id=%s PRIVMSG #%s :%s", parentMsgId, channel, text))
}

// Whisper write something in private to someone on twitch
// whispers are heavily spam protected
// so your message might get blocked because of this
// verify your bot to prevent this
func (c *Client) Whisper(username, text string) {
	c.send(fmt.Sprintf("PRIVMSG #%s :/w %s %s", c.ircUser, username, text))
}

// Join enter a twitch channel to read more messages.
// It will respect the given ratelimits.
// This is not a blocking operation.
func (c *Client) Join(channels ...string) {
	messages, joined := c.createJoinMessages(channels...)

	// If we have an active connection, explicitly join
	// before we add the joined channels to our map
	c.channelsMtx.Lock()
	for _, message := range messages {
		if c.connActive.get() {
			c.send(message)
		}
	}

	for _, channel := range joined {
		c.channels[channel] = c.connActive.get()
		c.channelUserlistMutex.Lock()
		c.channelUserlist[channel] = map[string]bool{}
		c.channelUserlistMutex.Unlock()
	}
	c.channelsMtx.Unlock()
}

// FollowersOn run twitch command `/followers` with the given channel and duration in argument
func (c *Client) FollowersOn(channel, duration string) {
	c.Say(channel, "/followers "+duration)
}

// FollowersOn run twitch command `/followersoff` with the given channel in argument
func (c *Client) FollowersOff(channel string) {
	c.Say(channel, "/followersoff")
}

// Ban run twitch command `/ban username reason` with the given channel and reason in argument
func (c *Client) Ban(channel, username, reason string) {
	c.Say(channel, "/ban "+username+" "+reason)
}

// Creates an irc join message to join the given channels.
//
// Returns the join message, any channels included in the join message,
// and any remaining channels. Channels which have already been joined
// are not included in the remaining channels that are returned.
func (c *Client) createJoinMessages(channels ...string) ([]string, []string) {
	baseMessage := "JOIN"
	joinMessages := []string{}
	joined := []string{}

	if channels == nil || len(channels) < 1 {
		return joinMessages, joined
	}

	sb := strings.Builder{}
	sb.WriteString(baseMessage)
	channelsWritten := 0

	for _, channel := range channels {
		channel = strings.ToLower(channel)
		// If the channel already exists in the map we don't need to re-join it
		c.channelsMtx.Lock()
		if c.channels[channel] {
			c.channelsMtx.Unlock()
			continue
		}
		c.channelsMtx.Unlock()
		if sb.Len()+len(channel)+2 > maxMessageLength || (!c.joinRateLimiter.IsUnlimited() && channelsWritten >= c.joinRateLimiter.GetLimit()) {
			joinMessages = append(joinMessages, sb.String())
			sb.Reset()
			sb.WriteString(baseMessage)
			channelsWritten = 0
		}
		if channelsWritten == 0 {
			sb.WriteString(" #" + channel)
			channelsWritten++
		} else {
			sb.WriteString(",#" + channel)
			channelsWritten++
		}
		joined = append(joined, channel)
	}

	joinMessages = append(joinMessages, sb.String())

	return joinMessages, joined
}

// Depart leave a twitch channel
func (c *Client) Depart(channel string) {
	if c.connActive.get() {
		c.send(fmt.Sprintf("PART #%s", channel))
	}

	c.channelsMtx.Lock()
	delete(c.channels, channel)
	c.channelUserlistMutex.Lock()
	delete(c.channelUserlist, channel)
	c.channelUserlistMutex.Unlock()
	c.channelsMtx.Unlock()
}

// Disconnect close current connection
func (c *Client) Disconnect() error {
	if !c.connActive.get() {
		return ErrConnectionIsNotOpen
	}

	c.userDisconnect.Close()

	return nil
}

// Connect connect the client to the irc server
func (c *Client) Connect() error {
	if c.IrcAddress == "" && c.TLS {
		c.IrcAddress = ircTwitchTLS
	} else if c.IrcAddress == "" && !c.TLS {
		c.IrcAddress = ircTwitch
	}

	dialer := &net.Dialer{
		KeepAlive: time.Second * 10,
	}

	var conf *tls.Config
	if strings.HasPrefix(c.IrcAddress, "127.0.0.1:") {
		conf = &tls.Config{
			MinVersion: tls.VersionTLS12,
			//nolint:gosec // disable certificate chain check locally
			InsecureSkipVerify: true,
		}
	} else {
		conf = &tls.Config{
			MinVersion: tls.VersionTLS12,
		}
	}

	for {
		err := c.makeConnection(dialer, conf)

		switch err {
		case errReconnect:
			continue

		default:
			return err
		}
	}
}

func (c *Client) makeConnection(dialer *net.Dialer, conf *tls.Config) (err error) {
	c.connActive.set(false)
	var conn net.Conn
	if c.TLS {
		conn, err = tls.DialWithDialer(dialer, "tcp", c.IrcAddress, conf)
	} else {
		conn, err = dialer.Dial("tcp", c.IrcAddress)
	}
	if err != nil {
		return
	}

	wg := sync.WaitGroup{}
	c.clientReconnect.Reset()
	c.userDisconnect.Reset()

	// Start the connection reader in a separate go-routine
	wg.Add(1)
	go c.startReader(conn, &wg)

	if c.SendPings {
		// If SendPings is true (which it is by default), start the thread
		// responsible for managing sending pings and reading pongs
		// in a separate go-routine
		wg.Add(1)
		c.startPinger(conn, &wg)
	}

	// Send the initial connection messages (like logging in, getting the CAP REQ stuff)
	c.setupConnection(conn)

	// Start the connection writer in a separate go-routine
	wg.Add(1)
	go c.startWriter(conn, &wg)

	// start the parser in the same go-routine as makeConnection was called from
	// the error returned from parser will be forwarded to the caller of makeConnection
	// and that error will decide whether or not to reconnect
	err = c.startParser()

	conn.Close()
	c.clientReconnect.Close()

	// Wait for the reader, pinger, and writer to close
	wg.Wait()

	return
}

// Userlist returns the userlist for a given channel
func (c *Client) Userlist(channel string) ([]string, error) {
	c.channelUserlistMutex.RLock()
	defer c.channelUserlistMutex.RUnlock()
	usermap, ok := c.channelUserlist[channel]
	if !ok || usermap == nil {
		return nil, fmt.Errorf("could not find userlist for channel '%s' in client", channel)
	}
	userlist := make([]string, len(usermap))

	i := 0
	for key := range usermap {
		userlist[i] = key
		i++
	}

	return userlist, nil
}

// SetIRCToken updates the oauth token for this client used for authentication
// This will not cause a reconnect, but is meant more for "on next connect, use this new token" in case the old token has expired
func (c *Client) SetIRCToken(ircToken string) {
	c.ircToken = ircToken
}

// SetJoinRateLimiter will set the rate limits for the client.
// Use the factory methods CreateDefaultRateLimiter, CreateVerifiedRateLimiter or CreateUnlimitedRateLimiter to create the rate limits
// or make your own RateLimiter based on the interface
func (c *Client) SetJoinRateLimiter(rateLimiter RateLimiter) {
	c.joinRateLimiter = rateLimiter
}

func (c *Client) startReader(reader io.Reader, wg *sync.WaitGroup) {
	defer func() {
		c.clientReconnect.Close()

		wg.Done()
	}()

	tp := textproto.NewReader(bufio.NewReader(reader))

	for {
		line, err := tp.ReadLine()
		if err != nil {
			return
		}
		messages := strings.Split(line, "\r\n")
		for _, msg := range messages {
			if !c.connActive.get() && strings.Contains(msg, ":tmi.twitch.tv 001") {
				c.connActive.set(true)
				c.initialJoins()
				if c.onConnect != nil {
					c.onConnect()
				}
			}
			c.read <- msg
		}
	}
}

func (c *Client) startPinger(closer io.Closer, wg *sync.WaitGroup) {
	c.pongReceived = make(chan bool, 1)

	go func() {
		defer func() {
			wg.Done()
		}()

		for {
			select {
			case <-c.clientReconnect.channel:
				return

			case <-c.userDisconnect.channel:
				return

			case <-c.messageReceived:
				// Interrupt idle ping interval
				continue

			case <-time.After(c.IdlePingInterval):
				if c.onPingSent != nil {
					c.onPingSent()
				}
				c.send(pingMessage)

				select {
				case <-c.pongReceived:
					// Received pong message within the time limit, we're good
					continue

				case <-time.After(c.PongTimeout):
					// No pong message was received within the pong timeout, disconnect
					c.clientReconnect.Close()
					closer.Close()
				}
			}
		}
	}()
}

func (c *Client) setupConnection(conn net.Conn) {
	if c.SetupCmd != "" {
		conn.Write([]byte(c.SetupCmd + "\r\n"))
	}
	if len(c.Capabilities) > 0 {
		_, _ = conn.Write([]byte("CAP REQ :" + strings.Join(c.Capabilities, " ") + "\r\n"))
	}
	conn.Write([]byte("PASS " + c.ircToken + "\r\n"))
	conn.Write([]byte("NICK " + c.ircUser + "\r\n"))
}

func (c *Client) startWriter(writer io.WriteCloser, wg *sync.WaitGroup) {
	defer func() {
		wg.Done()
	}()
	for {
		select {
		case <-c.clientReconnect.channel:
			return
		case <-c.userDisconnect.channel:
			return
		case msg := <-c.write:
			c.writeMessage(writer, msg)
		}
	}
}

func (c *Client) writeMessage(writer io.WriteCloser, msg string) {
	if strings.HasPrefix(msg, "JOIN") {
		splits := strings.Split(msg, ",")
		c.joinRateLimiter.Throttle(len(splits))
	}

	_, err := writer.Write([]byte(msg + "\r\n"))
	if err != nil {
		// Attempt to re-send failed messages
		c.write <- msg

		writer.Close()
		c.clientReconnect.Close()
	}
}

func (c *Client) startParser() error {
	for {
		// reader
		select {
		case msg := <-c.read:
			if err := c.handleLine(msg); err != nil {
				return err
			}

		case <-c.clientReconnect.channel:
			return errReconnect

		case <-c.userDisconnect.channel:
			return ErrClientDisconnected
		}
	}
}

func (c *Client) initialJoins() {
	// join or rejoin channels on connection
	channels := []string{}
	for channel := range c.channels {
		channels = append(channels, channel)
		c.channels[channel] = false
	}
	c.Join(channels...)
}

func (c *Client) send(line string) {
	select {
	case c.write <- line:
	default:
		// The buffer of c.write is full, queue up the message to be sent later.
		// We have no guarantee of order anymore if the buffer is full
		go func() {
			c.write <- line
		}()
	}
}

// Errors returned from handleLine break out of readConnections, which starts a reconnect
// This means that we should only return fatal errors as errors here
func (c *Client) handleLine(line string) error {
	go func() {
		// Send a message on the `messageReceived` channel, but do not block in case no one is receiving on the other end
		select {
		case c.messageReceived <- true:
		default:
		}
	}()

	message := ParseMessage(line)

	switch msg := message.(type) {
	case *WhisperMessage:
		if c.onWhisperMessage != nil {
			c.onWhisperMessage(*msg)
		}
		return nil

	case *PrivateMessage:
		if c.onPrivateMessage != nil {
			c.onPrivateMessage(*msg)
		}
		return nil

	case *ClearChatMessage:
		if c.onClearChatMessage != nil {
			c.onClearChatMessage(*msg)
		}
		return nil

	case *ClearMessage:
		if c.onClearMessage != nil {
			c.onClearMessage(*msg)
		}
		return nil

	case *RoomStateMessage:
		if c.onRoomStateMessage != nil {
			c.onRoomStateMessage(*msg)
		}
		return nil

	case *UserNoticeMessage:
		if c.onUserNoticeMessage != nil {
			c.onUserNoticeMessage(*msg)
		}
		return nil

	case *UserStateMessage:
		if c.onUserStateMessage != nil {
			c.onUserStateMessage(*msg)
		}
		return nil

	case *GlobalUserStateMessage:
		if c.onGlobalUserStateMessage != nil {
			c.onGlobalUserStateMessage(*msg)
		}
		return nil

	case *NoticeMessage:
		if c.onNoticeMessage != nil {
			c.onNoticeMessage(*msg)
		}
		return c.handleNoticeMessage(*msg)

	case *UserJoinMessage:
		if c.handleUserJoinMessage(*msg) {
			if c.onUserJoinMessage != nil {
				c.onUserJoinMessage(*msg)
			}
		}
		return nil

	case *UserPartMessage:
		if c.handleUserPartMessage(*msg) {
			if c.onUserPartMessage != nil {
				c.onUserPartMessage(*msg)
			}
		}
		return nil

	case *ReconnectMessage:
		// https://dev.twitch.tv/docs/irc/commands/#reconnect-twitch-commands
		if c.onReconnectMessage != nil {
			c.onReconnectMessage(*msg)
		}
		return errReconnect

	case *NamesMessage:
		if c.onNamesMessage != nil {
			c.onNamesMessage(*msg)
		}
		c.handleNamesMessage(*msg)
		return nil

	case *PingMessage:
		if c.onPingMessage != nil {
			c.onPingMessage(*msg)
		}
		c.handlePingMessage(*msg)
		return nil

	case *PongMessage:
		if c.onPongMessage != nil {
			c.onPongMessage(*msg)
		}
		c.handlePongMessage(*msg)
		return nil

	case *RawMessage:
		if c.onUnsetMessage != nil {
			c.onUnsetMessage(*msg)
		}
	}

	return nil
}

func (c *Client) handleNoticeMessage(msg NoticeMessage) error {
	if msg.Channel == "*" {
		if msg.Message == "Login authentication failed" || msg.Message == "Improperly formatted auth" || msg.Message == "Invalid NICK" {
			return ErrLoginAuthenticationFailed
		}
	}

	return nil
}

func (c *Client) handleUserJoinMessage(msg UserJoinMessage) bool {
	// Ignore own joins
	if msg.User == c.ircUser {
		return false
	}

	c.channelUserlistMutex.Lock()
	defer c.channelUserlistMutex.Unlock()

	if c.channelUserlist[msg.Channel] == nil {
		c.channelUserlist[msg.Channel] = map[string]bool{}
	}

	if _, ok := c.channelUserlist[msg.Channel][msg.User]; !ok {
		c.channelUserlist[msg.Channel][msg.User] = true
	}

	return true
}

func (c *Client) handleUserPartMessage(msg UserPartMessage) bool {
	// Ignore own parts
	if msg.User == c.ircUser {
		return false
	}

	c.channelUserlistMutex.Lock()
	defer c.channelUserlistMutex.Unlock()

	delete(c.channelUserlist[msg.Channel], msg.User)

	return true
}

func (c *Client) handleNamesMessage(msg NamesMessage) {
	c.channelUserlistMutex.Lock()
	defer c.channelUserlistMutex.Unlock()

	if c.channelUserlist[msg.Channel] == nil {
		c.channelUserlist[msg.Channel] = map[string]bool{}
	}

	for _, user := range msg.Users {
		c.channelUserlist[msg.Channel][user] = true
	}
}

func (c *Client) handlePingMessage(msg PingMessage) {
	if msg.Message == "" {
		c.send("PONG")
	} else {
		c.send("PONG :" + msg.Message)
	}
}

func (c *Client) handlePongMessage(msg PongMessage) {
	if msg.Message == pingSignature {
		// Received a pong that was sent by us
		select {
		case c.pongReceived <- true:
		default:
		}
	}
}

// chanCloser is a helper function for abusing channels for notifications
// this is an easy "notify many" channel
type chanCloser struct {
	mutex sync.Mutex

	o       *sync.Once
	channel chan struct{}
}

func (c *chanCloser) Reset() {
	c.mutex.Lock()
	defer c.mutex.Unlock()
	c.o = &sync.Once{}
	c.channel = make(chan struct{})
}

func (c *chanCloser) Close() {
	c.mutex.Lock()
	defer c.mutex.Unlock()
	c.o.Do(func() {
		close(c.channel)
	})
}