import { NextRequest, NextResponse } from 'next/server'
import { z } from 'zod'
import { authMiddleware } from '@/lib/auth-middleware'
import connectDB from '@/lib/mongodb'
import { User as UserModel } from '@/models/user'
import { Transaction } from '@/models/transaction'

// Schema for balance deduction request
const DeductBalanceSchema = z.object({
  amount: z.number().positive('Amount must be positive'),
  service: z.string().min(1, 'Service name is required'),
  serviceId: z.string().optional(),
  description: z.string().optional(),
  transactionId: z.string().optional(),
})

// Schema for balance deduction response
const DeductBalanceResponseSchema = z.object({
  success: z.boolean(),
  data: z
    .object({
      transactionId: z.string(),
      previousBalance: z.number(),
      newBalance: z.number(),
      amountDeducted: z.number(),
      service: z.string(),
      timestamp: z.string(),
    })
    .optional(),
  error: z
    .object({
      message: z.string(),
      code: z.string(),
    })
    .optional(),
})

export async function POST(request: NextRequest) {
  try {
    // Authenticate user
    const user = await authMiddleware(request)
    if (!user) {
      return NextResponse.json(
        {
          success: false,
          error: { message: 'Authentication required', code: 'UNAUTHORIZED' },
        },
        { status: 401 }
      )
    }

    await connectDB()

    // Parse and validate request body
    const body = await request.json()
    const validatedData = DeductBalanceSchema.parse(body)

    // Get user's current balance from database
    const userData = await UserModel.findOne({ email: user.email })
    if (!userData) {
      return NextResponse.json(
        {
          success: false,
          error: { message: 'User not found', code: 'USER_NOT_FOUND' },
        },
        { status: 404 }
      )
    }

    const currentBalance = userData.balance || 0

    // Check if user has sufficient balance
    if (currentBalance < validatedData.amount) {
      return NextResponse.json(
        {
          success: false,
          error: {
            message: `Insufficient balance. Required: ₹${validatedData.amount}, Available: ₹${currentBalance}`,
            code: 'INSUFFICIENT_BALANCE',
          },
        },
        { status: 400 }
      )
    }

    // Calculate new balance
    const newBalance = currentBalance - validatedData.amount

    // Update user balance in database
    await UserModel.updateOne(
      { email: user.email },
      {
        $set: { balance: newBalance },
        $inc: { __v: 1 }, // Increment version for optimistic locking
      }
    )

    // Generate transaction ID if not provided
    const transactionId =
      validatedData.transactionId || `txn_${Date.now()}_${Math.random().toString(36).substr(2, 9)}`

    // Save transaction record to database
    try {
      const newTransaction = new Transaction({
        transactionId,
        userId: user.id,
        email: user.email,
        type: 'debit',
        amount: validatedData.amount,
        service: validatedData.service,
        serviceId: validatedData.serviceId,
        description: validatedData.description || `Payment for ${validatedData.service}`,
        status: 'completed',
        previousBalance: currentBalance,
        newBalance,
        metadata: {
          userAgent: request.headers.get('user-agent'),
          ip: request.headers.get('x-forwarded-for') || request.headers.get('x-real-ip'),
        },
      })

      await newTransaction.save()
      console.log('Transaction record saved:', transactionId)
    } catch (transactionError) {
      console.error('Failed to save transaction record:', transactionError)
      // Continue even if transaction record fails - balance was already deducted
    }

    const responseData = {
      success: true,
      data: {
        transactionId,
        previousBalance: currentBalance,
        newBalance,
        amountDeducted: validatedData.amount,
        service: validatedData.service,
        timestamp: new Date().toISOString(),
      },
    }

    // Validate response format
    const validatedResponse = DeductBalanceResponseSchema.parse(responseData)
    return NextResponse.json(validatedResponse, { status: 200 })
  } catch (error) {
    console.error('Balance deduction error:', error)

    if (error instanceof z.ZodError) {
      return NextResponse.json(
        {
          success: false,
          error: {
            message: 'Invalid request data',
            code: 'VALIDATION_ERROR',
            details: error.issues,
          },
        },
        { status: 400 }
      )
    }

    return NextResponse.json(
      {
        success: false,
        error: { message: 'Failed to deduct balance', code: 'INTERNAL_ERROR' },
      },
      { status: 500 }
    )
  }
}