import { apiService } from './api'
import { useAppStore } from '@/stores/app'
import type { ExtendedMessage, UnsentMessage } from '@/types'

export class SyncService {
  private getAppStore() {
    return useAppStore()
  }

  /**
   * Sync messages for a channel: merge server data with local data
   */
  async syncChannelMessages(channelId: number): Promise<void> {
    try {
      console.log(`Syncing messages for channel ${channelId}`)
      
      const appStore = this.getAppStore()
      
      // Get server messages
      const serverResponse = await apiService.getMessages(channelId)
      const serverMessages = serverResponse.messages
      
      // Get local messages
      const localMessages = appStore.messages[channelId] || []
      
      console.log(`Server has ${serverMessages.length} messages, local has ${localMessages.length} messages`)
      
      // Merge messages using a simple strategy:
      // 1. Create a map of all messages by ID
      // 2. Server messages take precedence (they may have been updated)
      // 3. Keep local messages that don't exist on server (may be unsent)
      
      const messageMap = new Map<number, ExtendedMessage>()
      
      // Add local messages first
      localMessages.forEach(msg => {
        if (typeof msg.id === 'number') {
          messageMap.set(msg.id, msg)
        }
      })
      
      // Add/update with server messages (server wins for conflicts)
      serverMessages.forEach((msg: any) => {
        // Transform server message format to match our types
        const transformedMsg: ExtendedMessage = {
          id: msg.id,
          channel_id: msg.channelId || msg.channel_id,
          content: msg.content,
          created_at: msg.createdAt || msg.created_at,
          file_id: msg.fileId || msg.file_id,
          // Map the flattened file fields from backend
          fileId: msg.fileId,
          filePath: msg.filePath,
          fileType: msg.fileType,
          fileSize: msg.fileSize,
          originalName: msg.originalName,
          fileCreatedAt: msg.fileCreatedAt
        }
        console.log(`Sync: Processing message ${msg.id}, has file:`, !!msg.fileId, `(${msg.originalName})`)
        messageMap.set(msg.id, transformedMsg)
      })
      
      // Convert back to array, sorted by creation time
      const mergedMessages = Array.from(messageMap.values())
        .sort((a, b) => new Date(a.created_at).getTime() - new Date(b.created_at).getTime())
      
      console.log(`Merged result: ${mergedMessages.length} messages`)
      
      // Update local storage
      appStore.setMessages(channelId, mergedMessages)
      await appStore.saveState()
      
    } catch (error) {
      console.warn(`Failed to sync messages for channel ${channelId}:`, error)
      throw error
    }
  }

  /**
   * Attempt to send all unsent messages
   */
  async retryUnsentMessages(): Promise<void> {
    const appStore = this.getAppStore()
    const unsentMessages = appStore.unsentMessages
    console.log(`Attempting to send ${unsentMessages.length} unsent messages`)
    
    for (const unsentMsg of [...unsentMessages]) {
      try {
        console.log(`Sending unsent message: ${unsentMsg.content}`)
        
        // Try to send the message
        const response = await apiService.createMessage(unsentMsg.channelId, unsentMsg.content)
        console.log(`Successfully sent unsent message, got ID: ${response.id}`)
        
        // Create the sent message
        const sentMessage: ExtendedMessage = {
          id: response.id,
          channel_id: unsentMsg.channelId,
          content: unsentMsg.content,
          created_at: new Date().toISOString()
        }
        
        // Add to messages and remove from unsent
        appStore.addMessage(sentMessage)
        appStore.removeUnsentMessage(unsentMsg.id)
        
        // Save state immediately after successful send to ensure UI updates
        await appStore.saveState()
        
        console.log(`Moved unsent message ${unsentMsg.id} to sent messages with ID ${response.id}`)
        console.log(`Unsent messages remaining: ${appStore.unsentMessages.length}`)
        
      } catch (error) {
        console.warn(`Failed to send unsent message ${unsentMsg.id}:`, error)
        
        // Increment retry count
        unsentMsg.retries = (unsentMsg.retries || 0) + 1
        
        // Remove if too many retries (optional)
        if (unsentMsg.retries >= 5) {
          console.log(`Giving up on unsent message ${unsentMsg.id} after ${unsentMsg.retries} retries`)
          appStore.removeUnsentMessage(unsentMsg.id)
        }
      }
    }
    
    // Save state after processing
    await appStore.saveState()
  }

  /**
   * Full sync: channels and messages
   */
  async fullSync(): Promise<void> {
    try {
      console.log('Starting full sync...')
      
      const appStore = this.getAppStore()
      
      // 1. Sync channels
      const channelsResponse = await apiService.getChannels()
      appStore.setChannels(channelsResponse.channels)
      
      // 2. Retry unsent messages first
      await this.retryUnsentMessages()
      
      // 3. Sync messages for current channel
      if (appStore.currentChannelId) {
        await this.syncChannelMessages(appStore.currentChannelId)
      }
      
      // 4. Save everything
      await appStore.saveState()
      
      console.log('Full sync completed')
      
    } catch (error) {
      console.error('Full sync failed:', error)
      throw error
    }
  }

  /**
   * Optimistic message sending with automatic sync
   */
  async sendMessage(channelId: number, content: string): Promise<void> {
    try {
      console.log(`Optimistically sending message: ${content}`)
      
      // Try to send immediately
      const response = await apiService.createMessage(channelId, content)
      
      // Success - add to local messages
      const message: ExtendedMessage = {
        id: response.id,
        channel_id: channelId,
        content: content,
        created_at: new Date().toISOString()
      }
      
      const appStore = this.getAppStore()
      appStore.addMessage(message)
      console.log(`Message sent successfully with ID: ${response.id}`)
      
    } catch (error) {
      console.warn('Failed to send message immediately, queuing for later:', error)
      
      // Failed - add to unsent messages
      const unsentMessage: UnsentMessage = {
        id: `unsent_${Date.now()}_${Math.random()}`,
        channelId: channelId,
        content: content,
        timestamp: Date.now(),
        retries: 0
      }
      
      const appStore = this.getAppStore()
      appStore.addUnsentMessage(unsentMessage)
      await appStore.saveState()
      
      throw error // Re-throw so caller knows it failed
    }
  }
}

export const syncService = new SyncService()