package jounce

import (
	"crypto/tls"
	"fmt"
	"io"
	"net"
	"strconv"
	"strings"
	"time"

	"gopkg.in/irc.v3"
)

type upstreamChannel struct {
	Name      string
	Topic     string
	TopicWho  string
	TopicTime time.Time
	Status    channelStatus
	modes     modeSet
	Members   map[string]membership
	complete  bool
}

type upstreamConn struct {
	upstream *Upstream
	logger   Logger
	net      net.Conn
	irc      *irc.Conn
	srv      *Server
	user     *user
	messages chan<- *irc.Message

	serverName            string
	availableUserModes    string
	availableChannelModes string
	channelModesWithParam string

	registered bool
	closed     bool
	modes      modeSet
	channels   map[string]*upstreamChannel
}

func connectToUpstream(u *user, upstream *Upstream) (*upstreamConn, error) {
	logger := &prefixLogger{u.srv.Logger, fmt.Sprintf("upstream %q: ", upstream.Addr)}
	logger.Printf("connecting to server")

	netConn, err := tls.Dial("tcp", upstream.Addr, nil)
	if err != nil {
		return nil, fmt.Errorf("failed to dial %q: %v", upstream.Addr, err)
	}

	msgs := make(chan *irc.Message, 64)
	conn := &upstreamConn{
		upstream: upstream,
		logger:   logger,
		net:      netConn,
		irc:      irc.NewConn(netConn),
		srv:      u.srv,
		user:     u,
		messages: msgs,
		channels: make(map[string]*upstreamChannel),
	}

	go func() {
		for msg := range msgs {
			if err := conn.irc.WriteMessage(msg); err != nil {
				conn.logger.Printf("failed to write message: %v", err)
			}
		}
	}()

	return conn, nil
}

func (c *upstreamConn) Close() error {
	if c.closed {
		return fmt.Errorf("upstream connection already closed")
	}
	if err := c.net.Close(); err != nil {
		return err
	}
	close(c.messages)
	c.closed = true
	return nil
}

func (c *upstreamConn) getChannel(name string) (*upstreamChannel, error) {
	ch, ok := c.channels[name]
	if !ok {
		return nil, fmt.Errorf("unknown channel %q", name)
	}
	return ch, nil
}

func (c *upstreamConn) handleMessage(msg *irc.Message) error {
	switch msg.Command {
	case "PING":
		// TODO: handle params
		c.messages <- &irc.Message{
			Command: "PONG",
			Params:  []string{c.srv.Hostname},
		}
		return nil
	case "MODE":
		if len(msg.Params) < 2 {
			return newNeedMoreParamsError(msg.Command)
		}
		name := msg.Params[0]
		modeStr := msg.Params[1]

		if name == msg.Prefix.Name { // user mode change
			if name != c.upstream.Nick {
				return fmt.Errorf("received MODE message for unknow nick %q", name)
			}
			return c.modes.Apply(modeStr)
		} else { // channel mode change
			ch, err := c.getChannel(name)
			if err != nil {
				return err
			}
			if err := ch.modes.Apply(modeStr); err != nil {
				return err
			}

			c.user.forEachDownstream(func(dc *downstreamConn) {
				dc.messages <- msg
			})
		}
	case "NOTICE":
		c.logger.Print(msg)
	case irc.RPL_WELCOME:
		c.registered = true
		c.logger.Printf("connection registered")

		for _, ch := range c.upstream.Channels {
			c.messages <- &irc.Message{
				Command: "JOIN",
				Params:  []string{ch},
			}
		}
	case irc.RPL_MYINFO:
		if len(msg.Params) < 5 {
			return newNeedMoreParamsError(msg.Command)
		}
		c.serverName = msg.Params[1]
		c.availableUserModes = msg.Params[3]
		c.availableChannelModes = msg.Params[4]
		if len(msg.Params) > 5 {
			c.channelModesWithParam = msg.Params[5]
		}
	case "JOIN":
		if len(msg.Params) < 1 {
			return newNeedMoreParamsError(msg.Command)
		}

		for _, ch := range strings.Split(msg.Params[0], ",") {
			if msg.Prefix.Name == c.upstream.Nick {
				c.logger.Printf("joined channel %q", ch)
				c.channels[ch] = &upstreamChannel{
					Name:    ch,
					Members: make(map[string]membership),
				}
			} else {
				ch, err := c.getChannel(ch)
				if err != nil {
					return err
				}
				ch.Members[msg.Prefix.Name] = 0
			}
		}

		c.user.forEachDownstream(func(dc *downstreamConn) {
			dc.messages <- msg
		})
	case "PART":
		if len(msg.Params) < 1 {
			return newNeedMoreParamsError(msg.Command)
		}

		for _, ch := range strings.Split(msg.Params[0], ",") {
			if msg.Prefix.Name == c.upstream.Nick {
				c.logger.Printf("parted channel %q", ch)
				delete(c.channels, ch)
			} else {
				ch, err := c.getChannel(ch)
				if err != nil {
					return err
				}
				delete(ch.Members, msg.Prefix.Name)
			}
		}

		c.user.forEachDownstream(func(dc *downstreamConn) {
			dc.messages <- msg
		})
	case irc.RPL_TOPIC, irc.RPL_NOTOPIC:
		if len(msg.Params) < 3 {
			return newNeedMoreParamsError(msg.Command)
		}
		ch, err := c.getChannel(msg.Params[1])
		if err != nil {
			return err
		}
		if msg.Command == irc.RPL_TOPIC {
			ch.Topic = msg.Params[2]
		} else {
			ch.Topic = ""
		}
	case "TOPIC":
		if len(msg.Params) < 1 {
			return newNeedMoreParamsError(msg.Command)
		}
		ch, err := c.getChannel(msg.Params[0])
		if err != nil {
			return err
		}
		if len(msg.Params) > 1 {
			ch.Topic = msg.Params[1]
		} else {
			ch.Topic = ""
		}
	case rpl_topicwhotime:
		if len(msg.Params) < 4 {
			return newNeedMoreParamsError(msg.Command)
		}
		ch, err := c.getChannel(msg.Params[1])
		if err != nil {
			return err
		}
		ch.TopicWho = msg.Params[2]
		sec, err := strconv.ParseInt(msg.Params[3], 10, 64)
		if err != nil {
			return fmt.Errorf("failed to parse topic time: %v", err)
		}
		ch.TopicTime = time.Unix(sec, 0)
	case irc.RPL_NAMREPLY:
		if len(msg.Params) < 4 {
			return newNeedMoreParamsError(msg.Command)
		}
		ch, err := c.getChannel(msg.Params[2])
		if err != nil {
			return err
		}

		status, err := parseChannelStatus(msg.Params[1])
		if err != nil {
			return err
		}
		ch.Status = status

		for _, s := range strings.Split(msg.Params[3], " ") {
			membership, nick := parseMembershipPrefix(s)
			ch.Members[nick] = membership
		}
	case irc.RPL_ENDOFNAMES:
		if len(msg.Params) < 2 {
			return newNeedMoreParamsError(msg.Command)
		}
		ch, err := c.getChannel(msg.Params[1])
		if err != nil {
			return err
		}

		if ch.complete {
			return fmt.Errorf("received unexpected RPL_ENDOFNAMES")
		}
		ch.complete = true

		c.user.forEachDownstream(func(dc *downstreamConn) {
			forwardChannel(dc, ch)
		})
	case "PRIVMSG":
		c.user.forEachDownstream(func(dc *downstreamConn) {
			dc.messages <- msg
		})
	case irc.RPL_YOURHOST, irc.RPL_CREATED:
		// Ignore
	case irc.RPL_LUSERCLIENT, irc.RPL_LUSEROP, irc.RPL_LUSERUNKNOWN, irc.RPL_LUSERCHANNELS, irc.RPL_LUSERME:
		// Ignore
	case irc.RPL_MOTDSTART, irc.RPL_MOTD, irc.RPL_ENDOFMOTD:
		// Ignore
	case rpl_localusers, rpl_globalusers:
		// Ignore
	case irc.RPL_STATSVLINE, irc.RPL_STATSPING, irc.RPL_STATSBLINE, irc.RPL_STATSDLINE:
		// Ignore
	default:
		c.logger.Printf("unhandled upstream message: %v", msg)
	}
	return nil
}

func (c *upstreamConn) readMessages() error {
	defer c.Close()

	c.messages <- &irc.Message{
		Command: "NICK",
		Params:  []string{c.upstream.Nick},
	}

	c.messages <- &irc.Message{
		Command: "USER",
		Params:  []string{c.upstream.Username, "0", "*", c.upstream.Realname},
	}

	for {
		msg, err := c.irc.ReadMessage()
		if err == io.EOF {
			break
		} else if err != nil {
			return fmt.Errorf("failed to read IRC command: %v", err)
		}

		if err := c.handleMessage(msg); err != nil {
			c.logger.Printf("failed to handle message %q: %v", msg, err)
		}
	}

	return c.Close()
}