package server

import (
	"sort"

	"code.severnaya.net/kordophone-mock/v2/data"
	"code.severnaya.net/kordophone-mock/v2/model"
	"github.com/rs/zerolog/log"
)

const VERSION = "Kordophone-2.0"

const (
	AUTH_USERNAME = "test"
	AUTH_PASSWORD = "test"
)

type Server struct {
	version       string
	conversations []model.Conversation
	authTokens    []model.AuthToken
	messageStore  map[string][]model.Message
	updateItems   map[int]model.UpdateItem
	updateChannel chan []model.UpdateItem
	updateItemSeq int
}

type AuthError struct {
	message string
}

func (e *AuthError) Error() string {
	return e.message
}

type DatabaseError struct {
	message string
}

func (e *DatabaseError) Error() string {
	return e.message
}

func NewServer() *Server {
	return &Server{
		version:       VERSION,
		conversations: []model.Conversation{},
		authTokens:    []model.AuthToken{},
		messageStore:  make(map[string][]model.Message),
		updateItems:   make(map[int]model.UpdateItem),
		updateChannel: make(chan []model.UpdateItem),
		updateItemSeq: 0,
	}
}

func (s *Server) Version() string {
	return s.version
}

func (s *Server) Conversations() []model.Conversation {
	return s.conversations
}

func (s *Server) SortedConversations() []model.Conversation {
	conversations := s.Conversations()
	sort.Slice(conversations, func(i, j int) bool {
		return conversations[i].Date.After(conversations[j].Date)
	})

	return conversations
}

func (s *Server) ConversationForGUID(guid string) (*model.Conversation, error) {
	var conversation *model.Conversation = nil
	for i := range s.conversations {
		c := &s.conversations[i]
		if c.Guid == guid {
			conversation = c
			break
		}
	}

	if conversation != nil {
		return conversation, nil
	}

	return nil, &DatabaseError{message: "Conversation not found"}
}

func (s *Server) AddConversation(c model.Conversation) {
	s.conversations = append(s.conversations, c)
}

func (s *Server) PopulateWithTestData() {
	numConversations := 100
	cs := make([]model.Conversation, numConversations)
	for i := 0; i < numConversations; i++ {
		cs[i] = data.GenerateRandomConversation()

		// Generate messages
		convo := &cs[i]
		var lastMessage model.Message
		for i := 0; i < 100; i++ {
			message := data.GenerateRandomMessage(convo.Participants)
			s.AppendMessageToConversation(convo, message)

			if lastMessage.Date.Before(message.Date) {
				lastMessage = message
			}
		}

		// Update last message preview
		convo.LastMessagePreview = lastMessage.Text
	}

	s.conversations = cs
}

func (s *Server) Authenticate(username string, password string) (*model.AuthToken, error) {
	if username != AUTH_USERNAME || password != AUTH_PASSWORD {
		return nil, &AuthError{"Invalid username or password"}
	}

	token, err := model.NewAuthToken(username)
	if err != nil {
		return nil, err
	}

	// Register for future auth
	s.registerAuthToken(token)

	return token, nil
}

func (s *Server) CheckBearerToken(token string) bool {
	return s.authenticateToken(token)
}

func (s *Server) MessagesForConversation(conversation *model.Conversation) []model.Message {
	messages := s.messageStore[conversation.Guid]
	sort.Slice(messages, func(i int, j int) bool {
		return messages[i].Date.Before(messages[j].Date)
	})

	return messages
}

func (s *Server) AppendMessageToConversation(conversation *model.Conversation, message model.Message) {
	s.messageStore[conversation.Guid] = append(s.messageStore[conversation.Guid], message)
}

func (s *Server) SendMessage(conversation *model.Conversation, message model.Message) {
	s.AppendMessageToConversation(conversation, message)

	// Update Conversation
	ourConversation, _ := s.ConversationForGUID(conversation.Guid)
	ourConversation.LastMessagePreview = message.Text
	ourConversation.Date = message.Date

	log.Info().EmbedObject(message).Msgf("Sent message to conversation %s", conversation.Guid)
}

func (s *Server) ReceiveMessage(conversation *model.Conversation, message model.Message) {
	s.AppendMessageToConversation(conversation, message)

	// Update conversation
	ourConversation, _ := s.ConversationForGUID(conversation.Guid)
	ourConversation.LastMessagePreview = message.Text
	ourConversation.Date = message.Date
	ourConversation.UnreadCount += 1

	// Enqueue Update
	s.EnqueueUpdateItem(model.UpdateItem{
		Conversation: ourConversation,
		Message:      &message,
	})

	log.Info().EmbedObject(message).Msgf("Received message from conversation %s", conversation.Guid)
}

func (s *Server) EnqueueUpdateItem(item model.UpdateItem) {
	log.Info().EmbedObject(&item).Msg("Enqueuing update item")

	s.updateItemSeq += 1
	item.MessageSequenceNumber = s.updateItemSeq

	s.updateItems[s.updateItemSeq] = item

	// Publish to channel
	select {
	case s.updateChannel <- []model.UpdateItem{item}:
	default: // Nobody listening
	}
}

func (s *Server) FetchUpdates(since int) []model.UpdateItem {
	items := []model.UpdateItem{}
	for i := since; i <= s.updateItemSeq; i++ {
		if val, ok := s.updateItems[i]; ok {
			items = append(items, val)
		}
	}

	return items
}

func (s *Server) FetchUpdatesBlocking(since int) []model.UpdateItem {
	if since < 0 || since >= s.updateItemSeq {
		// Wait for updates
		log.Info().Msgf("Waiting for updates since %d", since)
		items := <-s.updateChannel
		return items
	} else {
		return s.FetchUpdates(since)
	}
}

func (s *Server) MarkConversationAsRead(conversation *model.Conversation) {
	conversation.UnreadCount = 0

	// enqueue update
	s.EnqueueUpdateItem(model.UpdateItem{
		Conversation: conversation,
	})
}

// Private

func (s *Server) registerAuthToken(token *model.AuthToken) {
	s.authTokens = append(s.authTokens, *token)
}

func (s *Server) authenticateToken(token string) bool {
	for _, t := range s.authTokens {
		if t.SignedToken == token {
			return true
		}
	}

	return false
}