package irc

import (
	"fmt"
	"strings"
	"time"
)

const (
	MAX_REPLY_LEN = 510 // 512 - CRLF
)

func joinedLen(names []string) int {
	var l = len(names) - 1 // " " between names
	for _, name := range names {
		l += len(name)
	}
	return l
}

type Identifier interface {
	Id() string
	Nick() string
}

type Replier interface {
	Replies() chan<- Reply
}

type Reply interface {
	Format(*Client, chan<- string)
	Source() Identifier
}

type BaseReply struct {
	source  Identifier
	message string
}

func (reply *BaseReply) Source() Identifier {
	return reply.source
}

type StringReply struct {
	*BaseReply
	code string
}

func NewStringReply(source Identifier, code string,
	format string, args ...interface{}) *StringReply {
	message := fmt.Sprintf(format, args...)
	fullMessage := fmt.Sprintf(":%s %s %s", source.Id(), code, message)
	return &StringReply{
		BaseReply: &BaseReply{source, fullMessage},
		code:      code,
	}
}

func (reply *StringReply) Format(client *Client, write chan<- string) {
	write <- reply.message
}

func (reply *StringReply) String() string {
	return fmt.Sprintf("Reply(source=%s, code=%s, message=%s)",
		reply.source, reply.code, reply.message)
}

type NumericReply struct {
	*BaseReply
	code int
}

func NewNumericReply(source Identifier, code int, format string,
	args ...interface{}) *NumericReply {
	return &NumericReply{
		BaseReply: &BaseReply{source, fmt.Sprintf(format, args...)},
		code:      code,
	}
}

func (reply *NumericReply) Format(client *Client, write chan<- string) {
	write <- reply.FormatString(client)
}

func (reply *NumericReply) FormatString(client *Client) string {
	return fmt.Sprintf(":%s %03d %s %s", reply.Source().Id(), reply.code,
		client.Nick(), reply.message)
}

func (reply *NumericReply) String() string {
	return fmt.Sprintf("Reply(source=%s, code=%d, message=%s)",
		reply.source, reply.code, reply.message)
}

// names reply

type NamesReply struct {
	*BaseReply
	channel *Channel
}

func NewNamesReply(channel *Channel) Reply {
	return &NamesReply{
		BaseReply: &BaseReply{
			source: channel,
		},
		channel: channel,
	}
}

func (reply *NamesReply) Format(client *Client, write chan<- string) {
	base := RplNamReply(reply.channel, []string{})
	baseLen := len(base.FormatString(client))
	tooLong := func(names []string) bool {
		return (baseLen + joinedLen(names)) > MAX_REPLY_LEN
	}
	from, to := 0, 1
	nicks := reply.channel.Nicks()
	for to < len(nicks) {
		if (from < (to - 1)) && tooLong(nicks[from:to]) {
			RplNamReply(reply.channel, nicks[from:to-1]).Format(client, write)
			from, to = to-1, to
		} else {
			to += 1
		}
	}
	if from < len(nicks) {
		RplNamReply(reply.channel, nicks[from:]).Format(client, write)
	}
	RplEndOfNames(reply.channel).Format(client, write)
}

func (reply *NamesReply) String() string {
	return fmt.Sprintf("NamesReply(channel=%s, names=%s)",
		reply.channel, reply.channel.Nicks())
}

// messaging replies

func RplPrivMsg(source Identifier, target Identifier, message string) Reply {
	return NewStringReply(source, RPL_PRIVMSG, "%s :%s", target.Nick(), message)
}

func RplNick(source Identifier, newNick string) Reply {
	return NewStringReply(source, RPL_NICK, newNick)
}

func RplJoin(channel *Channel, client *Client) Reply {
	return NewStringReply(client, RPL_JOIN, channel.name)
}

func RplPart(channel *Channel, client *Client, message string) Reply {
	return NewStringReply(client, RPL_PART, "%s :%s", channel.name, message)
}

func RplPong(server *Server, client *Client) Reply {
	return NewStringReply(server, RPL_PONG, client.Nick())
}

func RplQuit(client *Client, message string) Reply {
	return NewStringReply(client, RPL_QUIT, ":%s", message)
}

func RplError(server *Server, target Identifier) Reply {
	return NewStringReply(server, RPL_ERROR, target.Nick())
}

func RplInviteMsg(channel *Channel, inviter *Client) Reply {
	return NewStringReply(inviter, RPL_INVITE, channel.name)
}

// numeric replies

func RplWelcome(source Identifier, client *Client) Reply {
	return NewNumericReply(source, RPL_WELCOME,
		"Welcome to the Internet Relay Network %s", client.Id())
}

func RplYourHost(server *Server) Reply {
	return NewNumericReply(server, RPL_YOURHOST,
		"Your host is %s, running version %s", server.name, VERSION)
}

func RplCreated(server *Server) Reply {
	return NewNumericReply(server, RPL_CREATED,
		"This server was created %s", server.ctime.Format(time.RFC1123))
}

func RplMyInfo(server *Server) Reply {
	return NewNumericReply(server, RPL_MYINFO,
		"%s %s aiwroOs kn", server.name, VERSION)
}

func RplUModeIs(server *Server, client *Client) Reply {
	return NewNumericReply(server, RPL_UMODEIS, client.UModeString())
}

func RplNoTopic(channel *Channel) Reply {
	return NewNumericReply(channel.server, RPL_NOTOPIC,
		"%s :No topic is set", channel.name)
}

func RplTopic(channel *Channel) Reply {
	return NewNumericReply(channel.server, RPL_TOPIC,
		"%s :%s", channel.name, channel.topic)
}

func RplInvitingMsg(channel *Channel, invitee *Client) Reply {
	return NewNumericReply(channel.server, RPL_INVITING,
		"%s %s", channel.name, invitee.Nick())
}

func RplNamReply(channel *Channel, names []string) *NumericReply {
	return NewNumericReply(channel.server, RPL_NAMREPLY, "= %s :%s",
		channel.name, strings.Join(names, " "))
}

func RplEndOfNames(channel *Channel) Reply {
	return NewNumericReply(channel, RPL_ENDOFNAMES,
		"%s :End of NAMES list", channel.name)
}

func RplYoureOper(server *Server) Reply {
	return NewNumericReply(server, RPL_YOUREOPER,
		":You are now an IRC operator")
}

func RplWhoisUser(server *Server, client *Client) Reply {
	return NewNumericReply(server, RPL_WHOISUSER, "%s %s %s * :%s",
		client.nick, client.username, client.hostname, client.realname)
}

func RplEndOfWhois(server *Server) Reply {
	return NewNumericReply(server, RPL_ENDOFWHOIS, ":End of WHOIS list")
}

// errors (also numeric)

func ErrAlreadyRegistered(source Identifier) Reply {
	return NewNumericReply(source, ERR_ALREADYREGISTRED,
		":You may not reregister")
}

func ErrNickNameInUse(source Identifier, nick string) Reply {
	return NewNumericReply(source, ERR_NICKNAMEINUSE,
		"%s :Nickname is already in use", nick)
}

func ErrUnknownCommand(source Identifier, command string) Reply {
	return NewNumericReply(source, ERR_UNKNOWNCOMMAND,
		"%s :Unknown command", command)
}

func ErrUsersDontMatch(source Identifier) Reply {
	return NewNumericReply(source, ERR_USERSDONTMATCH,
		":Cannot change mode for other users")
}

func ErrNeedMoreParams(source Identifier, command string) Reply {
	return NewNumericReply(source, ERR_NEEDMOREPARAMS,
		"%s :Not enough parameters", command)
}

func ErrNoSuchChannel(source Identifier, channel string) Reply {
	return NewNumericReply(source, ERR_NOSUCHCHANNEL,
		"%s :No such channel", channel)
}

func ErrUserOnChannel(channel *Channel, member *Client) Reply {
	return NewNumericReply(channel.server, ERR_USERONCHANNEL,
		"%s %s :is already on channel", member.nick, channel.name)
}

func ErrNotOnChannel(channel *Channel) Reply {
	return NewNumericReply(channel.server, ERR_NOTONCHANNEL,
		"%s :You're not on that channel", channel.name)
}

func ErrInviteOnlyChannel(channel *Channel) Reply {
	return NewNumericReply(channel.server, ERR_INVITEONLYCHAN,
		"%s :Cannot join channel (+i)", channel.name)
}

func ErrBadChannelKey(channel *Channel) Reply {
	return NewNumericReply(channel.server, ERR_BADCHANNELKEY,
		"%s :Cannot join channel (+k)", channel.name)
}

func ErrNoSuchNick(source Identifier, nick string) Reply {
	return NewNumericReply(source, ERR_NOSUCHNICK,
		"%s :No such nick/channel", nick)
}

func ErrPasswdMismatch(server *Server) Reply {
	return NewNumericReply(server, ERR_PASSWDMISMATCH, ":Password incorrect")
}

func ErrNoChanModes(channel *Channel) Reply {
	return NewNumericReply(channel.server, ERR_NOCHANMODES,
		"%s :Channel doesn't support modes", channel.name)
}

func ErrNoPrivileges(server *Server) Reply {
	return NewNumericReply(server, ERR_NOPRIVILEGES, ":Permission Denied")
}

func ErrRestricted(server *Server) Reply {
	return NewNumericReply(server, ERR_RESTRICTED, ":Your connection is restricted!")
}

func ErrNoSuchServer(server *Server, target string) Reply {
	return NewNumericReply(server, ERR_NOSUCHSERVER, "%s :No such server", target)
}