package irc

import (
	"errors"
	"strings"
)

var commands = map[string]func([]string) (Message, error){
	"JOIN":    NewJoinMessage,
	"MODE":    NewModeMessage,
	"NICK":    NewNickMessage,
	"PART":    NewPartMessage,
	"PING":    NewPingMessage,
	"PONG":    NewPongMessage,
	"PRIVMSG": NewPrivMsgMessage,
	"QUIT":    NewQuitMessage,
	"TOPIC":   NewTopicMessage,
	"USER":    NewUserMessage,
}

var (
	ErrParseMessage = errors.New("failed to parse message")
)

func ParseMessage(line string) (msg Message, err error) {
	command, args := parseLine(line)
	constructor, ok := commands[command]
	if !ok {
		msg = &UnknownMessage{command}
		return
	}
	msg, err = constructor(args)
	return
}

func parseArg(line string) (arg string, rest string) {
	if line == "" {
		return
	}

	if strings.HasPrefix(line, ":") {
		arg = line[1:]
	} else {
		parts := strings.SplitN(line, " ", 2)
		arg = parts[0]
		if len(parts) > 1 {
			rest = parts[1]
		}
	}
	return
}

func parseLine(line string) (command string, args []string) {
	args = make([]string, 0)
	for arg, rest := parseArg(line); arg != ""; arg, rest = parseArg(rest) {
		args = append(args, arg)
	}
	command, args = args[0], args[1:]
	return
}