package chats.data.sync

import android.content.Context
import android.util.Log
import androidx.hilt.work.HiltWorker
import androidx.work.*
import chats.data.remote.api.ChatApi
import chats.data.remote.api.SendMessageRequest
import core.database.data.MessageDao
import core.database.data.MessageEntity
import core.database.data.SyncStatus
import core.network.ServerConfig
import core.security.TokenManager
import com.google.gson.Gson
import dagger.assisted.Assisted
import dagger.assisted.AssistedInject
import java.util.concurrent.TimeUnit

/**
 * WorkManager Worker для фоновой синхронизации сообщений
 * 
 * Обрабатывает:
 * 1. Отправку новых сообщений (SYNCING)
 * 2. Обновление отредактированных сообщений (isEditedLocally = true)
 * 3. Удаление сообщений (isDeletedLocally = true)
 * 4. Повторную отправку при ошибках (FAILED)
 * 
 * Политика повторных попыток:
 * - Экспоненциальная задержка (backoff)
 * - Максимум 3 попытки
 * - Таймаут 10 минут на выполнение
 */
@HiltWorker
class MessageSyncWorker @AssistedInject constructor(
    @Assisted appContext: Context,
    @Assisted params: WorkerParameters,
    private val dao: MessageDao,
    private val api: ChatApi,
    private val serverConfig: ServerConfig,
    private val tokenManager: TokenManager
) : CoroutineWorker(appContext, params) {

    private val gson = Gson()

    companion object {
        const val WORK_NAME = "message_sync_worker"
        private const val TAG = "MessageSyncWorker"
        
        /**
         * Планирует синхронизацию
         * Вызывается при изменении сообщений в базе
         */
        fun scheduleSync(context: Context) {
            Log.d(TAG, "Scheduling sync")
            
            val constraints = Constraints.Builder()
                .setRequiredNetworkType(NetworkType.CONNECTED)
                .setRequiresBatteryNotLow(false)
                .build()

            val workRequest = OneTimeWorkRequestBuilder<MessageSyncWorker>()
                .setConstraints(constraints)
                .setBackoffCriteria(
                    BackoffPolicy.EXPONENTIAL,
                    WorkRequest.MIN_BACKOFF_MILLIS,
                    TimeUnit.MILLISECONDS
                )
                .addTag(WORK_NAME)
                .build()

            WorkManager.getInstance(context).enqueueUniqueWork(
                WORK_NAME,
                ExistingWorkPolicy.REPLACE,
                workRequest
            )
            
            Log.d(TAG, "Sync scheduled")
        }
        
        /**
         * Отменяет запланированную синхронизацию
         */
        fun cancelSync(context: Context) {
            WorkManager.getInstance(context).cancelUniqueWork(WORK_NAME)
            Log.d(TAG, "Sync cancelled")
        }
    }

    override suspend fun doWork(): Result {
        Log.d(TAG, "Starting message sync. Attempt: ${runAttemptCount + 1}")

        if (runAttemptCount >= 3) {
            Log.e(TAG, "Max retry attempts reached")
            return Result.failure()
        }

        return try {
            val pendingMessages = dao.getPendingSyncMessages()
            Log.d(TAG, "Found ${pendingMessages.size} messages to sync")

            if (pendingMessages.isEmpty()) {
                Log.d(TAG, "No pending messages. Sync complete.")
                return Result.success()
            }

            var successCount = 0
            var failureCount = 0

            for (message in pendingMessages) {
                try {
                    when {
                        message.isDeletedLocally -> {
                            handleDeleteMessage(message)
                            successCount++
                        }
                        message.isEditedLocally -> {
                            handleEditMessage(message)
                            successCount++
                        }
                        message.syncStatus == SyncStatus.SYNCING -> {
                            handleSendMessage(message)
                            successCount++
                        }
                    }
                } catch (e: Exception) {
                    Log.e(TAG, "Failed to sync message ${message.id}", e)
                    dao.markAsSyncFailed(message.id)
                    failureCount++
                }
            }

            Log.d(TAG, "Sync completed. Success: $successCount, Failed: $failureCount")

            if (failureCount > 0 && successCount == 0) {
                Result.retry()
            } else {
                Result.success()
            }

        } catch (e: Exception) {
            Log.e(TAG, "Sync failed with exception", e)
            Result.retry()
        }
    }

    private suspend fun handleSendMessage(message: MessageEntity) {
        Log.d(TAG, "Sending message: ${message.id}")
        
        val attachments = parseAttachments(message.mediaJson)
        val request = SendMessageRequest(
            content = message.content,
            type = message.mediaType.lowercase(),
            attachments = attachments,
            replyToId = message.replyToId
        )

        val response = api.sendMessage(message.chatId, request)
        
        val syncedMessage = message.copy(
            id = response.id,
            sequenceId = response.sequenceId ?: message.sequenceId,
            createdAt = response.createdAt ?: message.createdAt,
            syncStatus = SyncStatus.SYNCED,
            isDeletedLocally = false,
            isEditedLocally = false,
            editedContent = null,
            lastUpdated = System.currentTimeMillis()
        )
        
        dao.insertMessage(syncedMessage)
        Log.d(TAG, "Message sent successfully: ${response.id}")
    }

    private suspend fun handleEditMessage(message: MessageEntity) {
        Log.d(TAG, "Editing message: ${message.id}")
        
        val newContent = message.editedContent ?: message.content
        val request = SendMessageRequest(content = newContent)
        
        val response = api.editMessage(message.id, request)
        
        val syncedMessage = message.copy(
            content = response.content,
            syncStatus = SyncStatus.SYNCED,
            isEditedLocally = false,
            editedContent = null,
            lastUpdated = System.currentTimeMillis()
        )
        
        dao.insertMessage(syncedMessage)
        Log.d(TAG, "Message edited successfully: ${message.id}")
    }

    private suspend fun handleDeleteMessage(message: MessageEntity) {
        Log.d(TAG, "Deleting message: ${message.id}")
        
        val response = api.deleteMessage(message.id, forEveryone = false)
        
        if (response.isSuccessful || response.code() == 404) {
            dao.deleteMessage(message.id)
            Log.d(TAG, "Message deleted successfully: ${message.id}")
        } else {
            throw Exception("Delete failed with code: ${response.code()}")
        }
    }

    private fun parseAttachments(mediaJson: String): List<chats.data.remote.api.AttachmentRequest>? {
        return try {
            val mediaList = gson.fromJson(mediaJson, Array::class.java)
                ?.map { elem -> 
                    val map = elem as Map<*, *>
                    chats.data.remote.api.AttachmentRequest(
                        type = map["type"] as? String ?: "file",
                        url = map["url"] as? String ?: "",
                        fileName = map["filename"] as? String ?: "file",
                        fileSize = (map["size"] as? Number)?.toLong() ?: 0L
                    )
                }
            mediaList?.takeIf { it.isNotEmpty() }
        } catch (e: Exception) {
            Log.e(TAG, "Failed to parse attachments", e)
            null
        }
    }
}