import { NextApiRequest, NextApiResponse } from 'next'
import { SerialPort } from 'serialport'
import { ReadlineParser } from '@serialport/parser-readline'

// Global connection state
let serialConnection: SerialPort | null = null
let parser: ReadlineParser | null = null

export default async function handler(
  req: NextApiRequest,
  res: NextApiResponse
) {
  if (req.method === 'POST') {
    const { port, baudRate = 115200 } = req.body

    if (!port) {
      return res.status(400).json({ message: 'Port is required' })
    }

    try {
      // Close existing connection
      if (serialConnection?.isOpen) {
        serialConnection.close()
      }

      // Create new connection
      serialConnection = new SerialPort({
        path: port,
        baudRate: baudRate,
        autoOpen: false
      })

      // Set up parser for line-based data
      parser = serialConnection.pipe(new ReadlineParser({ delimiter: '\r\n' }))

      // Open connection
      await new Promise<void>((resolve, reject) => {
        serialConnection!.open((err) => {
          if (err) reject(err)
          else resolve()
        })
      })

      res.status(200).json({
        message: 'Connected successfully',
        port,
        baudRate,
        isOpen: serialConnection.isOpen
      })

    } catch (error) {
      console.error('Serial connection error:', error)
      res.status(500).json({
        message: 'Failed to connect',
        error: error instanceof Error ? error.message : 'Unknown error'
      })
    }
  }
  
  else if (req.method === 'DELETE') {
    // Disconnect
    try {
      if (serialConnection?.isOpen) {
        serialConnection.close()
        serialConnection = null
        parser = null
      }
      
      res.status(200).json({ message: 'Disconnected successfully' })
    } catch (error) {
      res.status(500).json({ 
        message: 'Failed to disconnect',
        error: error instanceof Error ? error.message : 'Unknown error'
      })
    }
  }
  
  else if (req.method === 'GET') {
    // Get connection status
    res.status(200).json({
      connected: serialConnection?.isOpen || false,
      port: serialConnection?.path || null
    })
  }
  
  else {
    res.status(405).json({ message: 'Method not allowed' })
  }
}

export { serialConnection, parser }