package chats.data.signalr

import android.util.Log
import chats.data.remote.dto.MessageDto
import chats.data.remote.signalr.ChatEvent
import chats.data.remote.signalr.ChatHubClient
import chats.data.remote.signalr.MessagesReadEvent
import chats.data.remote.signalr.ReactionEvent
import chats.data.repository.toEntity
import com.google.gson.Gson
import core.database.data.MessageDao
import core.database.data.MessageEntity
import core.database.data.SyncStatus
import core.network.ServerConfig
import core.security.TokenManager
import kotlinx.coroutines.*
import kotlinx.coroutines.flow.collectLatest
import javax.inject.Inject
import javax.inject.Singleton

/**
 * Обработчик SignalR событий для обновления локального кэша
 * 
 * Обрабатывает события:
 * - new_message: новое сообщение в чате
 * - message_edited: сообщение отредактировано
 * - message_deleted: сообщение удалено
 * - messages_read: сообщения прочитаны
 * - reaction_added/removed: реакция добавлена/удалена
 * 
 * Все изменения сразу записываются в Room, UI обновляется через Flow
 */
@Singleton
class MessageSignalRHandler @Inject constructor(
    private val hubClient: ChatHubClient,
    private val dao: MessageDao,
    private val serverConfig: ServerConfig,
    private val tokenManager: TokenManager
) {
    private val gson = Gson()
    private val scope = CoroutineScope(Dispatchers.IO + SupervisorJob())
    private val baseUrl = serverConfig.getBaseUrl().removeSuffix("/api/")
    
    private var isListening = false

    /**
     * Начинает прослушивание SignalR событий
     * Вызывается один раз при инициализации приложения
     */
    fun startListening() {
        if (isListening) {
            Log.w(TAG, "Already listening to SignalR events")
            return
        }
        
        isListening = true
        Log.d(TAG, "Started listening to SignalR events")
        
        scope.launch {
            hubClient.events.collectLatest { event ->
                handleEvent(event)
            }
        }
    }

    /**
     * Останавливает прослушивание событий
     */
    fun stopListening() {
        isListening = false
        scope.cancel()
        Log.d(TAG, "Stopped listening to SignalR events")
    }

    private suspend fun handleEvent(event: ChatEvent) {
        try {
            when (event) {
                is ChatEvent.NewMessage -> handleNewMessage(event.message)
                is ChatEvent.MessageEdited -> handleMessageEdited(event.messageId, event.chatId, event.content)
                is ChatEvent.MessageDeleted -> handleMessageDeleted(event.messageId, event.chatId)
                is ChatEvent.MessagesRead -> handleMessagesRead(event.chatId, event.lastReadSequenceId)
                is ChatEvent.ReactionUpdated -> handleReactionUpdated(
                    event.messageId, 
                    event.emoji, 
                    event.isRemoved
                )
                else -> Log.d(TAG, "Unhandled event: ${event::class.simpleName}")
            }
        } catch (e: Exception) {
            Log.e(TAG, "Error handling SignalR event: ${event::class.simpleName}", e)
        }
    }

    private suspend fun handleNewMessage(dto: MessageDto) {
        Log.d(TAG, "New message received: ${dto.id} in chat ${dto.chatId}")
        
        val currentUserId = tokenManager.getUserId() ?: ""
        val entity = dto.toEntity(baseUrl, currentUserId, gson).copy(
            syncStatus = SyncStatus.SYNCED
        )
        
        val existing = dao.getMessageById(dto.id)
        if (existing != null && existing.syncStatus == SyncStatus.SYNCING) {
            val syncedEntity = entity.copy(
                syncStatus = SyncStatus.SYNCED,
                isDeletedLocally = false,
                isEditedLocally = false,
                editedContent = null
            )
            dao.insertMessage(syncedEntity)
            Log.d(TAG, "Merged local message with server response: ${dto.id}")
        } else {
            dao.insertMessage(entity)
            Log.d(TAG, "Saved new message: ${dto.id}")
        }
    }

    private suspend fun handleMessageEdited(messageId: String, chatId: String, content: String) {
        Log.d(TAG, "Message edited: $messageId")
        
        val existing = dao.getMessageById(messageId)
        if (existing != null) {
            if (existing.isEditedLocally) {
                Log.d(TAG, "Message is being edited locally, skipping server update: $messageId")
                return
            }
            
            val updated = existing.copy(
                content = content,
                lastUpdated = System.currentTimeMillis()
            )
            dao.insertMessage(updated)
            Log.d(TAG, "Updated edited message: $messageId")
        } else {
            Log.w(TAG, "Edited message not found in cache: $messageId")
        }
    }

    private suspend fun handleMessageDeleted(messageId: String, chatId: String) {
        Log.d(TAG, "Message deleted: $messageId")
        
        val existing = dao.getMessageById(messageId)
        if (existing?.isDeletedLocally == true) {
            dao.deleteMessage(messageId)
            Log.d(TAG, "Completed local deletion: $messageId")
        } else {
            dao.deleteMessage(messageId)
            Log.d(TAG, "Removed deleted message from cache: $messageId")
        }
    }

    private suspend fun handleMessagesRead(chatId: String, lastReadSequenceId: Int?) {
        if (lastReadSequenceId == null) {
            Log.w(TAG, "Messages read event with null sequenceId")
            return
        }
        
        Log.d(TAG, "Messages read in chat $chatId up to sequenceId $lastReadSequenceId")
        dao.markMessagesAsRead(chatId, lastReadSequenceId)
    }

    private suspend fun handleReactionUpdated(messageId: String, emoji: String, isRemoved: Boolean) {
        Log.d(TAG, "Reaction ${if (isRemoved) "removed" else "added"}: $emoji on message $messageId")
        
        val existing = dao.getMessageById(messageId)
        if (existing != null) {
            val reactions = gson.fromJson<Map<String, Int>>(existing.reactionsJson, Map::class.java) ?: emptyMap()
            val updatedReactions = reactions.toMutableMap()
            
            if (isRemoved) {
                val currentCount = updatedReactions[emoji] ?: 0
                if (currentCount > 1) {
                    updatedReactions[emoji] = currentCount - 1
                } else {
                    updatedReactions.remove(emoji)
                }
            } else {
                updatedReactions[emoji] = (updatedReactions[emoji] ?: 0) + 1
            }
            
            val updated = existing.copy(
                reactionsJson = gson.toJson(updatedReactions),
                lastUpdated = System.currentTimeMillis()
            )
            dao.insertMessage(updated)
            Log.d(TAG, "Updated reactions for message: $messageId")
        }
    }

    companion object {
        private const val TAG = "MessageSignalRHandler"
    }
}