import { NextRequest, NextResponse } from 'next/server'
import crypto from 'crypto'

interface PayUBalanceResponse {
  status: string
  txnid: string
  amount: string
  productinfo: string
  firstname: string
  email: string
  hash: string
  key: string
  [key: string]: string
}

/**
 * Balance Addition Success Handler
 * Processes successful "Add Balance" payments from PayU gateway
 */
export async function POST(request: NextRequest) {
  try {
    const formData = await request.formData()
    const payuResponse: Partial<PayUBalanceResponse> = {}
    
    // Extract all PayU response parameters
    for (const [key, value] of formData.entries()) {
      payuResponse[key] = value.toString()
    }

    const { status, txnid, amount, productinfo, firstname, email, hash, key: merchantKey } = payuResponse

    // Validate required parameters
    if (!status || !txnid || !amount || !hash) {
      console.error('Missing required PayU parameters in balance success')
      return NextResponse.redirect(new URL('/payment/failed?error=invalid-response', request.url))
    }

    // Verify payment status
    if (status !== 'success') {
      console.log(`Balance payment failed for transaction: ${txnid}, status: ${status}`)
      return NextResponse.redirect(new URL('/payment/failed?txn=' + txnid + '&type=balance', request.url))
    }

    // Verify PayU hash for security
    const merchantSalt = process.env.PAYU_MERCHANT_SALT || 'test-salt'
    const expectedHashString = `${merchantSalt}|${status}|||||||||||${email}|${firstname}|${productinfo}|${amount}|${txnid}|${merchantKey}`
    const expectedHash = crypto.createHash('sha512').update(expectedHashString).digest('hex').toLowerCase()

    if (hash?.toLowerCase() !== expectedHash) {
      console.error(`Hash mismatch for balance transaction: ${txnid}`)
      return NextResponse.redirect(new URL('/payment/failed?error=hash-mismatch&type=balance', request.url))
    }

    try {
      // TODO: Update database with successful balance addition
      // In real implementation:
      // const siliconId = await getSiliconIdFromTransaction(txnid)
      // await updateAddBalanceStatus(txnid, 'success')
      // await incrementUserBalance(siliconId, parseFloat(amount))
      
      console.log(`Balance addition successful for transaction: ${txnid}, amount: ₹${amount}`)
      
      // Mock database update for demo
      const updateResult = await mockUpdateBalanceSuccess(txnid as string, parseFloat(amount as string))

      // Redirect to profile page with success message
      const successUrl = new URL('/profile', request.url)
      successUrl.searchParams.set('payment', 'success')
      successUrl.searchParams.set('type', 'balance')
      successUrl.searchParams.set('amount', amount as string)
      successUrl.searchParams.set('txn', txnid as string)
      
      return NextResponse.redirect(successUrl)

    } catch (dbError) {
      console.error('Database update error during balance success:', dbError)
      // Log for manual reconciliation - payment was successful at gateway
      console.error(`CRITICAL: Balance payment ${txnid} succeeded at PayU but DB update failed`)
      
      // Still redirect to success but with warning
      const successUrl = new URL('/profile', request.url)
      successUrl.searchParams.set('payment', 'success')
      successUrl.searchParams.set('type', 'balance')
      successUrl.searchParams.set('amount', amount as string)
      successUrl.searchParams.set('txn', txnid as string)
      successUrl.searchParams.set('warning', 'db-update-failed')
      
      return NextResponse.redirect(successUrl)
    }

  } catch (error) {
    console.error('Balance success handler error:', error)
    return NextResponse.redirect(new URL('/payment/failed?error=processing-error&type=balance', request.url))
  }
}

// Mock function for demonstration
async function mockUpdateBalanceSuccess(txnid: string, amount: number) {
  console.log(`Mock DB Update: Balance Transaction ${txnid} successful`)
  
  // Mock: Get user Silicon ID from transaction
  const mockSiliconId = 'USR_12345' // In real implementation, fetch from add_balance_history table
  
  // Mock: Update add_balance_history status
  const historyUpdate = {
    transaction_id: txnid,
    status: 'success',
    updated_at: new Date(),
    payment_gateway_response: {
      amount: amount,
      currency: 'INR',
      payment_date: new Date()
    }
  }
  
  // Mock: Update user balance
  const balanceUpdate = {
    silicon_id: mockSiliconId,
    balance_increment: amount,
    previous_balance: 5000, // Mock previous balance
    new_balance: 5000 + amount,
    updated_at: new Date()
  }
  
  console.log(`Mock: User ${mockSiliconId} balance increased by ₹${amount}`)
  console.log(`Mock: New balance: ₹${balanceUpdate.new_balance}`)
  
  // Mock delay
  await new Promise(resolve => setTimeout(resolve, 150))
  
  return { historyUpdate, balanceUpdate }
}