forkmessager/client-mobile/chats/presentation/chat_detail/ChatDetailViewModel.kt

package chats.presentation.chat_detail

import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import chats.data.remote.signalr.ChatEvent
import chats.data.remote.signalr.ChatHubClient
import chats.domain.model.Message
import chats.domain.repository.ChatRepository
import chats.data.repository.toDomain
import core.network.ServerConfig
import dagger.hilt.android.lifecycle.HiltViewModel
import kotlinx.coroutines.Job
import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.*
import kotlinx.coroutines.launch
import java.io.File
import javax.inject.Inject

data class ChatDetailState(
    val messages: List<Message> = emptyList(),
    val isLoading: Boolean = false,
    val isTyping: Boolean = false,
    val typingUser: String? = null,
    val error: String? = null,
    val canCall: Boolean = true,
    val maxFileSize: Long = 100 * 1024 * 1024
)

@HiltViewModel
class ChatDetailViewModel @Inject constructor(
    private val repository: ChatRepository,
    private val signalrClient: ChatHubClient,
    private val serverConfig: ServerConfig
) : ViewModel() {

    private val _state = MutableStateFlow(ChatDetailState())
    val state: StateFlow<ChatDetailState> = _state.asStateFlow()

    private var currentChatId: String? = null
    private var typingTimerJob: Job? = null
    private var lastTypingSentTime: Long = 0

    init {
        val config = serverConfig.getServerConfig()
        _state.update { it.copy(
            canCall = config.features.calls,
            maxFileSize = config.limits.maxFileSize
        ) }
    }

    fun setChatId(chatId: String) {
        currentChatId = chatId
        loadMessages(chatId)
        observeSignalREvents()
    }

    fun loadMessages(chatId: String) {
        viewModelScope.launch {
            _state.update { it.copy(isLoading = true) }
            try {
                val messages = repository.getMessages(chatId)
                _state.update { it.copy(messages = messages, isLoading = false) }
            } catch (e: Exception) {
                _state.update { it.copy(isLoading = false, error = e.localizedMessage) }
            }
        }
    }

    private fun observeSignalREvents() {
        signalrClient.events
            .filter { event -> 
                when(event) {
                    is ChatEvent.NewMessage -> event.message.chatId == currentChatId
                    is ChatEvent.ReactionUpdated -> event.chatId == currentChatId
                    is ChatEvent.UserTyping -> event.chatId == currentChatId
                    else -> false
                }
            }
            .onEach { event ->
                when (event) {
                    is ChatEvent.NewMessage -> {
                        // Avoid adding duplicates if already loaded
                        _state.update { s ->
                             val domainMsg = event.message.toDomain()
                             if (s.messages.none { it.id == domainMsg.id }) {
                                 s.copy(messages = s.messages + domainMsg)
                             } else s
                        }
                    }
                    is ChatEvent.ReactionUpdated -> {
                        updateMessageReaction(event.messageId, event.userId, event.emoji)
                    }
                    is ChatEvent.UserTyping -> {
                        _state.update { it.copy(isTyping = true) }
                        // Reset typing status after some delay would be better, 
                        // but usually server sends stopped_typing event.
                    }
                    else -> Unit
                }
            }
            .launchIn(viewModelScope)
    }

    private fun updateMessageReaction(messageId: String, userId: String, emoji: String) {
        _state.update { s ->
            val updatedMessages = s.messages.map { msg ->
                if (msg.id == messageId) {
                    // Logic to update reactions map. 
                    // Note: Simplified logic, usually we need to know if it was added or removed.
                    // If we assume reaction_updated is a toggle:
                    val currentReactions = msg.reactions.toMutableMap()
                    val count = currentReactions[emoji] ?: 0
                    // This is a placeholder logic as the exact behavior depends on server implementation.
                    // For now, let's just increment/decrement based on some convention or just refresh.
                    currentReactions[emoji] = count + 1 
                    msg.copy(reactions = currentReactions)
                } else msg
            }
            s.copy(messages = updatedMessages)
        }
    }

    fun sendMessage(text: String) {
        val chatId = currentChatId ?: return
        viewModelScope.launch {
            try {
                repository.sendMessage(chatId, text)
            } catch (e: Exception) {
                _state.update { it.copy(error = e.localizedMessage) }
            }
        }
    }

    fun addReaction(messageId: String, emoji: String) {
        viewModelScope.launch {
            try {
                repository.addReaction(messageId, emoji)
            } catch (e: Exception) {
                // Ignore
            }
        }
    }

    fun uploadMedia(file: File) {
        if (file.length() > _state.value.maxFileSize) {
            _state.update { it.copy(error = "File too large") }
            return
        }
        // Upload logic...
    }
}