import { NextRequest, NextResponse } from 'next/server'
import { withAdminAuth } from '@/lib/admin-middleware'
import { connectDB } from '@/lib/mongodb'
import { Billing } from '@/models/billing'
import { Transaction } from '@/models/transaction'
import { z } from 'zod'

const BillingUpdateSchema = z.object({
  payment_status: z.enum(['pending', 'completed', 'failed', 'refunded']).optional(),
  service_status: z.enum(['active', 'inactive', 'suspended', 'cancelled']).optional(),
  amount: z.number().min(0).optional(),
  notes: z.string().optional(),
})

export async function GET(request: NextRequest) {
  return withAdminAuth(request, async (req, admin) => {
    try {
      await connectDB()

      const { searchParams } = new URL(request.url)
      const page = parseInt(searchParams.get('page') || '1')
      const limit = parseInt(searchParams.get('limit') || '20')
      const search = searchParams.get('search') || ''
      const serviceType = searchParams.get('serviceType') || ''
      const paymentStatus = searchParams.get('paymentStatus') || ''
      const dateFrom = searchParams.get('dateFrom')
      const dateTo = searchParams.get('dateTo')

      const skip = (page - 1) * limit

      // Build filter query
      const filter: any = {}

      if (search) {
        filter.$or = [
          { user_email: { $regex: search, $options: 'i' } },
          { silicon_id: { $regex: search, $options: 'i' } },
          { service_name: { $regex: search, $options: 'i' } },
        ]
      }

      if (serviceType && serviceType !== 'all') {
        filter.service_type = serviceType
      }

      if (paymentStatus && paymentStatus !== 'all') {
        filter.payment_status = paymentStatus
      }

      if (dateFrom || dateTo) {
        filter.created_at = {}
        if (dateFrom) filter.created_at.$gte = new Date(dateFrom)
        if (dateTo) filter.created_at.$lte = new Date(dateTo)
      }

      const [billings, totalBillings] = await Promise.all([
        Billing.find(filter).sort({ created_at: -1 }).skip(skip).limit(limit),
        Billing.countDocuments(filter),
      ])

      const totalPages = Math.ceil(totalBillings / limit)

      // Calculate summary statistics for current filter
      const summaryStats = await Billing.aggregate([
        { $match: filter },
        {
          $group: {
            _id: null,
            totalAmount: { $sum: '$amount' },
            totalTax: { $sum: '$tax_amount' },
            totalDiscount: { $sum: '$discount_applied' },
            completedCount: {
              $sum: { $cond: [{ $eq: ['$payment_status', 'completed'] }, 1, 0] },
            },
            pendingCount: {
              $sum: { $cond: [{ $eq: ['$payment_status', 'pending'] }, 1, 0] },
            },
            failedCount: {
              $sum: { $cond: [{ $eq: ['$payment_status', 'failed'] }, 1, 0] },
            },
          },
        },
      ])

      return NextResponse.json({
        billings,
        pagination: {
          currentPage: page,
          totalPages,
          totalBillings,
          hasNext: page < totalPages,
          hasPrev: page > 1,
        },
        summary: summaryStats[0] || {
          totalAmount: 0,
          totalTax: 0,
          totalDiscount: 0,
          completedCount: 0,
          pendingCount: 0,
          failedCount: 0,
        },
      })
    } catch (error) {
      console.error('Admin billing fetch error:', error)
      return NextResponse.json({ error: 'Failed to fetch billing data' }, { status: 500 })
    }
  })
}

export async function POST(request: NextRequest) {
  return withAdminAuth(request, async (req, admin) => {
    try {
      await connectDB()

      const body = await request.json()
      const { action, billingId, data } = body

      if (action === 'update') {
        const validatedData = BillingUpdateSchema.parse(data)

        const billing = await Billing.findByIdAndUpdate(
          billingId,
          {
            ...validatedData,
            updated_at: new Date(),
          },
          { new: true, runValidators: true }
        )

        if (!billing) {
          return NextResponse.json({ error: 'Billing record not found' }, { status: 404 })
        }

        return NextResponse.json({ billing })
      }

      if (action === 'refund') {
        const billing = await Billing.findById(billingId)

        if (!billing) {
          return NextResponse.json({ error: 'Billing record not found' }, { status: 404 })
        }

        if (billing.payment_status !== 'paid') {
          return NextResponse.json({ error: 'Can only refund paid payments' }, { status: 400 })
        }

        // Update billing status
        billing.payment_status = 'refunded'
        billing.status = 'cancelled'
        await billing.save()

        // Create refund transaction
        const refundTransaction = new Transaction({
          userId: billing.user_id,
          type: 'credit',
          amount: billing.amount,
          description: `Refund for ${billing.service_name}`,
          status: 'completed',
          reference: `refund_${billing._id}`,
          metadata: {
            originalBillingId: billing._id,
            refundedBy: admin.id,
            refundReason: data.refundReason || 'Admin refund',
          },
        })

        await refundTransaction.save()

        return NextResponse.json({
          billing,
          transaction: refundTransaction,
          message: 'Refund processed successfully',
        })
      }

      return NextResponse.json({ error: 'Invalid action' }, { status: 400 })
    } catch (error) {
      console.error('Admin billing action error:', error)
      return NextResponse.json({ error: 'Failed to perform billing action' }, { status: 500 })
    }
  })
}