package main

import (
	"fmt"
	"net/textproto"
	"regexp"
	"strings"
	"os"
)


type PrivMsg struct {
	nick, channel, text string
}


var (
	conn *textproto.Conn
	err  os.Error

	ping    = regexp.MustCompile("^PING :([a-zA-Z0-9\\.]+)$")
	motd    = regexp.MustCompile(":End of /MOTD command\\.$")
	privmsg = regexp.MustCompile("^:([a-zA-Z0-9`_\\-]+)![a-zA-Z0-9/\\\\\\.\\-]+@[a-zA-Z0-9/\\\\\\.\\-]+ PRIVMSG (#[a-zA-Z0-9]+) :(.*)$")
)


func talk(channel, msg string) {
	conn.Cmd("PRIVMSG " + channel + " :" + msg)
}


func handlePing(auth string) {
	conn.Cmd("PONG :" + auth)
	fmt.Printf("PONG :%s\n", auth)
}


func handlePrivmsg(pm *PrivMsg) {
	if strings.Contains(pm.text, "MrGoBot") {
		talk(pm.channel, "Hello, " + pm.nick + "!")
	}
}


func handleMotd() {
	conn.Cmd("JOIN #GoBot")
	fmt.Println("JOIN #GoBot")
}


func parseLine(line string) {
	// Channel activity
	if match := privmsg.FindStringSubmatch(line); match != nil {
		pm := new(PrivMsg)
		pm.nick, pm.channel, pm.text = match[1], match[2], match[3]
		handlePrivmsg(pm)
		return
	}

	// Server PING
	if match := ping.FindStringSubmatch(line); match != nil {
		handlePing(match[1])
		return
	}

	// End of MOTD (successful login to IRC server)
	if match := motd.FindString(line); match != "" {
		handleMotd()
		return
	}
}


func main() {
	conn, err = textproto.Dial("tcp", "chat.freenode.net:6667")
	if err != nil {
		fmt.Printf("%s", err)
		return
	}

	conn.Cmd("NICK MrGoBot\n\rUSER mrgobot 8 * :MrGoBot")

	for {
		text, err := conn.ReadLine()
		if err != nil {
			fmt.Printf("%s", err)
			return
		}

		go parseLine(text)

		fmt.Println(text)
	}
}