// gomuks - A terminal Matrix client written in Go.
// Copyright (C) 2018 Tulir Asokan
//
// 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, either version 3 of the License, or
// (at your option) any later version.
//
// 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 rooms

import (
	"fmt"
	"sort"
	"sync"
	"time"

	"maunium.net/go/gomatrix"
	"maunium.net/go/gomuks/debug"
)

type RoomNameSource int

const (
	ExplicitRoomName RoomNameSource = iota
	CanonicalAliasRoomName
	AliasRoomName
	MemberRoomName
)

// RoomTag is a tag given to a specific room.
type RoomTag struct {
	// The name of the tag.
	Tag string
	// The order of the tag. Smaller values are ordered higher.
	Order float64
}

// Room represents a single Matrix room.
type Room struct {
	*gomatrix.Room

	// The first batch of events that has been fetched for this room.
	// Used for fetching additional history.
	PrevBatch string
	// The MXID of the user whose session this room was created for.
	SessionUserID string

	// The number of unread messages that were notified about.
	UnreadMessages int
	// Whether or not any of the unread messages were highlights.
	Highlighted bool
	// Whether or not the room contains any new messages.
	// This can be true even when UnreadMessages is zero if there's
	// a notificationless message like bot notices.
	HasNewMessages bool

	// List of tags given to this room
	RawTags []RoomTag
	// Timestamp of previously received actual message.
	LastReceivedMessage time.Time

	// MXID -> Member cache calculated from membership events.
	memberCache map[string]*Member
	// The first non-SessionUserID member in the room. Calculated at
	// the same time as memberCache.
	firstMemberCache *Member
	// The name of the room. Calculated from the state event name,
	// canonical_alias or alias or the member cache.
	nameCache string
	// The event type from which the name cache was calculated from.
	nameCacheSource RoomNameSource
	// The topic of the room. Directly fetched from the m.room.topic state event.
	topicCache string
	// The canonical alias of the room. Directly fetched from the m.room.canonical_alias state event.
	canonicalAliasCache string
	// The list of aliases. Directly fetched from the m.room.aliases state event.
	aliasesCache []string

	// fetchHistoryLock is used to make sure multiple goroutines don't fetch
	// history for this room at the same time.
	fetchHistoryLock *sync.Mutex
}

// LockHistory locks the history fetching mutex.
// If the mutex is nil, it will be created.
func (room *Room) LockHistory() {
	if room.fetchHistoryLock == nil {
		room.fetchHistoryLock = &sync.Mutex{}
	}
	room.fetchHistoryLock.Lock()
}

// UnlockHistory unlocks the history fetching mutex.
// If the mutex is nil, this does nothing.
func (room *Room) UnlockHistory() {
	if room.fetchHistoryLock != nil {
		room.fetchHistoryLock.Unlock()
	}
}

// MarkRead clears the new message statuses on this room.
func (room *Room) MarkRead() {
	room.UnreadMessages = 0
	room.Highlighted = false
	room.HasNewMessages = false
}

func (room *Room) Tags() []RoomTag {
	if len(room.RawTags) == 0 {
		return []RoomTag{{"", 0.5}}
	}
	return room.RawTags
}

// UpdateState updates the room's current state with the given Event. This will clobber events based
// on the type/state_key combination.
func (room *Room) UpdateState(event *gomatrix.Event) {
	_, exists := room.State[event.Type]
	if !exists {
		room.State[event.Type] = make(map[string]*gomatrix.Event)
	}
	switch event.Type {
	case "m.room.name":
		room.nameCache = ""
	case "m.room.canonical_alias":
		if room.nameCacheSource >= CanonicalAliasRoomName {
			room.nameCache = ""
		}
		room.canonicalAliasCache = ""
	case "m.room.aliases":
		if room.nameCacheSource >= AliasRoomName {
			room.nameCache = ""
		}
		room.aliasesCache = nil
	case "m.room.member":
		room.memberCache = nil
		room.firstMemberCache = nil
		if room.nameCacheSource >= MemberRoomName {
			room.nameCache = ""
		}
	case "m.room.topic":
		room.topicCache = ""
	}

	stateKey := ""
	if event.StateKey != nil {
		stateKey = *event.StateKey
	}
	if event.Type != "m.room.member" {
		debug.Printf("[ROOM] Updating state %s#%s for %s", event.Type, stateKey, room.ID)
	}

	if event.StateKey == nil {
		room.State[event.Type][""] = event
	} else {
		room.State[event.Type][*event.StateKey] = event
	}
}

// GetStateEvent returns the state event for the given type/state_key combo, or nil.
func (room *Room) GetStateEvent(eventType string, stateKey string) *gomatrix.Event {
	stateEventMap, _ := room.State[eventType]
	event, _ := stateEventMap[stateKey]
	return event
}

// GetStateEvents returns the state events for the given type.
func (room *Room) GetStateEvents(eventType string) map[string]*gomatrix.Event {
	stateEventMap, _ := room.State[eventType]
	return stateEventMap
}

// GetTopic returns the topic of the room.
func (room *Room) GetTopic() string {
	if len(room.topicCache) == 0 {
		topicEvt := room.GetStateEvent("m.room.topic", "")
		if topicEvt != nil {
			room.topicCache, _ = topicEvt.Content["topic"].(string)
		}
	}
	return room.topicCache
}

func (room *Room) GetCanonicalAlias() string {
	if len(room.canonicalAliasCache) == 0 {
		canonicalAliasEvt := room.GetStateEvent("m.room.canonical_alias", "")
		if canonicalAliasEvt != nil {
			room.canonicalAliasCache, _ = canonicalAliasEvt.Content["alias"].(string)
		} else {
			room.canonicalAliasCache = "-"
		}
	}
	if room.canonicalAliasCache == "-" {
		return ""
	}
	return room.canonicalAliasCache
}

// GetAliases returns the list of aliases that point to this room.
func (room *Room) GetAliases() []string {
	if room.aliasesCache == nil {
		aliasEvents := room.GetStateEvents("m.room.aliases")
		room.aliasesCache = []string{}
		for _, event := range aliasEvents {
			aliases, _ := event.Content["aliases"].([]interface{})

			newAliases := make([]string, len(room.aliasesCache)+len(aliases))
			copy(newAliases, room.aliasesCache)
			for index, alias := range aliases {
				newAliases[len(room.aliasesCache)+index], _ = alias.(string)
			}
			room.aliasesCache = newAliases
		}
	}
	return room.aliasesCache
}

// updateNameFromNameEvent updates the room display name to be the name set in the name event.
func (room *Room) updateNameFromNameEvent() {
	nameEvt := room.GetStateEvent("m.room.name", "")
	if nameEvt != nil {
		room.nameCache, _ = nameEvt.Content["name"].(string)
	}
}

// updateNameFromAliases updates the room display name to be the first room alias it finds.
//
// Deprecated: the Client-Server API recommends against using non-canonical aliases as display name.
func (room *Room) updateNameFromAliases() {
	// TODO the spec says clients should not use m.room.aliases for room names.
	//      However, Riot also uses m.room.aliases, so this is here now.
	aliases := room.GetAliases()
	if len(aliases) > 0 {
		sort.Sort(sort.StringSlice(aliases))
		room.nameCache = aliases[0]
	}
}

// updateNameFromMembers updates the room display name based on the members in this room.
//
// The room name depends on the number of users:
//  Less than two users -> "Empty room"
//  Exactly two users   -> The display name of the other user.
//  More than two users -> The display name of one of the other users, followed
//                         by "and X others", where X is the number of users
//                         excluding the local user and the named user.
func (room *Room) updateNameFromMembers() {
	members := room.GetMembers()
	if len(members) <= 1 {
		room.nameCache = "Empty room"
	} else if room.firstMemberCache == nil {
		room.nameCache = "Room"
	} else if len(members) == 2 {
		room.nameCache = room.firstMemberCache.DisplayName
	} else {
		firstMember := room.firstMemberCache.DisplayName
		room.nameCache = fmt.Sprintf("%s and %d others", firstMember, len(members)-2)
	}
}

// updateNameCache updates the room display name based on the room state in the order
// specified in spec section 11.2.2.5.
func (room *Room) updateNameCache() {
	if len(room.nameCache) == 0 {
		room.updateNameFromNameEvent()
		room.nameCacheSource = ExplicitRoomName
	}
	if len(room.nameCache) == 0 {
		room.nameCache = room.GetCanonicalAlias()
		room.nameCacheSource = CanonicalAliasRoomName
	}
	if len(room.nameCache) == 0 {
		room.updateNameFromAliases()
		room.nameCacheSource = AliasRoomName
	}
	if len(room.nameCache) == 0 {
		room.updateNameFromMembers()
		room.nameCacheSource = MemberRoomName
	}
}

// GetTitle returns the display name of the room.
//
// The display name is returned from the cache.
// If the cache is empty, it is updated first.
func (room *Room) GetTitle() string {
	room.updateNameCache()
	return room.nameCache
}

// createMemberCache caches all member events into a easily processable MXID -> *Member map.
func (room *Room) createMemberCache() map[string]*Member {
	cache := make(map[string]*Member)
	events := room.GetStateEvents("m.room.member")
	room.firstMemberCache = nil
	if events != nil {
		for userID, event := range events {
			member := eventToRoomMember(userID, event)
			if room.firstMemberCache == nil && userID != room.SessionUserID {
				room.firstMemberCache = member
			}
			if member.Membership != "leave" {
				cache[member.UserID] = member
			}
		}
	}
	room.memberCache = cache
	return cache
}

// GetMembers returns the members in this room.
//
// The members are returned from the cache.
// If the cache is empty, it is updated first.
func (room *Room) GetMembers() map[string]*Member {
	if len(room.memberCache) == 0 || room.firstMemberCache == nil {
		room.createMemberCache()
	}
	return room.memberCache
}

// GetMember returns the member with the given MXID.
// If the member doesn't exist, nil is returned.
func (room *Room) GetMember(userID string) *Member {
	if len(room.memberCache) == 0 {
		room.createMemberCache()
	}
	member, _ := room.memberCache[userID]
	return member
}

// GetSessionOwner returns the Member instance of the user whose session this room was created for.
func (room *Room) GetSessionOwner() *Member {
	return room.GetMember(room.SessionUserID)
}

// NewRoom creates a new Room with the given ID
func NewRoom(roomID, owner string) *Room {
	return &Room{
		Room:             gomatrix.NewRoom(roomID),
		fetchHistoryLock: &sync.Mutex{},
		SessionUserID:    owner,
	}
}