/*
goircd -- minimalistic simple Internet Relay Chat (IRC) server
Copyright (C) 2014-2020 Sergey Matveev <stargrave@stargrave.org>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, version 3 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

package main

import (
	"fmt"
	"log"
	"regexp"
	"sort"
	"strings"
	"sync"
)

type Room struct {
	name    string
	topic   string
	key     string
	members map[*Client]struct{}
	events  chan ClientEvent
	sync.RWMutex
}

var (
	RERoom = regexp.MustCompile("^#[^\x00\x07\x0a\x0d ,:/]{1,200}$")

	rooms     map[string]*Room = make(map[string]*Room)
	roomsLock sync.RWMutex
	roomsWG   sync.WaitGroup
)

func (r *Room) SendTopic(c *Client) {
	t := r.topic
	if t == "" {
		c.ReplyNicknamed("331", r.name, "No topic is set")
	} else {
		c.ReplyNicknamed("332", r.name, t)
	}
}

func (r *Room) SendNames(c *Client) {
	allowed := false
	if r.key == "" {
		allowed = true
	} else if _, isMember := r.members[c]; isMember {
		allowed = true
	}
	if !allowed {
		c.ReplyNicknamed("475", r.name, "Cannot join channel (+k)")
		return
	}
	r.RLock()
	nicknames := make([]string, 0, len(r.members))
	for member := range r.members {
		nicknames = append(nicknames, member.nickname)
	}
	r.RUnlock()
	sort.Strings(nicknames)
	maxLen := 512 - len(*hostname) - 2 - 2

MoreNicknames:
	lenAll := 0
	lenName := 0
	for i, n := range nicknames {
		lenName = len(n) + 1
		if lenAll+lenName >= maxLen {
			c.ReplyNicknamed("353", "=", r.name, strings.Join(nicknames[:i-1], " "))
			nicknames = nicknames[i:]
			goto MoreNicknames
		}
		lenAll += lenName
	}
	if len(nicknames) > 0 {
		c.ReplyNicknamed("353", "=", r.name, strings.Join(nicknames, " "))
	}
	c.ReplyNicknamed("366", r.name, "End of NAMES list")
}

func (r *Room) Broadcast(msg string, excludes ...*Client) {
	var exclude *Client
	if len(excludes) > 0 {
		exclude = excludes[0]
	}
	r.RLock()
	for member := range r.members {
		if member == exclude {
			continue
		}
		member.Msg(msg)
	}
	r.RUnlock()
}

func (r *Room) StateSave() {
	stateSink <- StateEvent{r.name, r.topic, r.key}
}

func (r *Room) Processor(events <-chan ClientEvent) {
	for e := range events {
		c := e.client
		switch e.eventType {
		case EventTerm:
			roomsWG.Done()
			return
		case EventNew:
			r.Lock()
			r.members[c] = struct{}{}
			r.Unlock()
			if *verbose {
				log.Println(c, "joined", r.name)
			}
			r.SendTopic(c)
			r.Broadcast(fmt.Sprintf(":%s JOIN %s", c, r.name))
			logSink <- LogEvent{r.name, c.nickname, "joined", true}
			r.SendNames(c)
		case EventDel:
			if _, subscribed := r.members[c]; !subscribed {
				c.ReplyNicknamed("442", r.name, "You are not on that channel")
				continue
			}
			msg := fmt.Sprintf(":%s PART %s :%s", c, r.name, c.nickname)
			r.Broadcast(msg)
			r.Lock()
			delete(r.members, c)
			r.Unlock()
			logSink <- LogEvent{r.name, c.nickname, "left", true}
			if *verbose {
				log.Println(c, "left", r.name)
			}
		case EventTopic:
			if _, subscribed := r.members[c]; !subscribed {
				c.ReplyParts("442", r.name, "You are not on that channel")
				continue
			}
			if e.text == "" {
				r.SendTopic(c)
				continue
			}
			topic := strings.TrimLeft(e.text, ":")
			r.topic = topic
			msg := fmt.Sprintf(":%s TOPIC %s :%s", c, r.name, r.topic)
			r.Broadcast(msg)
			logSink <- LogEvent{r.name, c.nickname, "set topic to " + r.topic, true}
			r.StateSave()
		case EventWho:
			r.RLock()
			for m := range r.members {
				c.ReplyNicknamed(
					"352",
					r.name,
					m.username,
					m.Host(),
					*hostname,
					m.nickname,
					"H",
					"0 "+m.realname,
				)
			}
			c.ReplyNicknamed("315", r.name, "End of /WHO list")
			r.RUnlock()
		case EventMode:
			if e.text == "" {
				mode := "+n"
				if r.key != "" {
					mode = mode + "k"
				}
				c.Msg(fmt.Sprintf("324 %s %s %s", c.nickname, r.name, mode))
				continue
			}
			if strings.HasPrefix(e.text, "b") {
				c.ReplyNicknamed("368", r.name, "End of channel ban list")
				continue
			}
			if strings.HasPrefix(e.text, "-k") || strings.HasPrefix(e.text, "+k") {
				if _, subscribed := r.members[c]; !subscribed {
					c.ReplyParts("442", r.name, "You are not on that channel")
					continue
				}
			} else {
				c.ReplyNicknamed("472", e.text, "Unknown MODE flag")
				continue
			}
			var msg string
			var msgLog string
			if strings.HasPrefix(e.text, "+k") {
				cols := strings.Split(e.text, " ")
				if len(cols) == 1 {
					c.ReplyNotEnoughParameters("MODE")
					continue
				}
				r.key = cols[1]
				msg = fmt.Sprintf(":%s MODE %s +k %s", c, r.name, r.key)
				msgLog = "set channel key"
			} else {
				r.key = ""
				msg = fmt.Sprintf(":%s MODE %s -k", c, r.name)
				msgLog = "removed channel key"
			}
			r.Broadcast(msg)
			logSink <- LogEvent{r.name, c.nickname, msgLog, true}
			r.StateSave()
		case EventMsg:
			sep := strings.Index(e.text, " ")
			r.Broadcast(fmt.Sprintf(
				":%s %s %s :%s", c, e.text[:sep], r.name, e.text[sep+1:],
			), c)
			logSink <- LogEvent{r.name, c.nickname, e.text[sep+1:], false}
		}
	}
}

func RoomRegister(name string) *Room {
	r := &Room{
		name:    name,
		members: make(map[*Client]struct{}),
		events:  make(chan ClientEvent),
	}
	roomsLock.Lock()
	roomsWG.Add(1)
	rooms[name] = r
	roomsLock.Unlock()
	go r.Processor(r.events)
	return r
}