import { NextResponse } from 'next/server'
import { z } from 'zod'
import { stripe } from '@/lib/stripe-server'
import { prisma } from '@/lib/db'
import { verifyToken } from '@/lib/auth'

export const runtime = 'nodejs'

const checkoutSchema = z.object({
  priceId: z.string(),
  interval: z.enum(['month', 'year']),
  locale: z.string().default('en')
})

export async function POST(request: Request) {
  try {
    // Verify authentication
    const authHeader = request.headers.get('authorization')
    if (!authHeader?.startsWith('Bearer ')) {
      return NextResponse.json(
        { success: false, error: 'Authentication required' },
        { status: 401 }
      )
    }

    const token = authHeader.substring(7)
    let payload
    try {
      payload = await verifyToken(token)
    } catch (error) {
      return NextResponse.json(
        { success: false, error: 'Invalid or expired token' },
        { status: 401 }
      )
    }

    const userId = payload.userId

    // Get user
    const user = await prisma.user.findUnique({
      where: { id: userId },
      select: {
        email: true,
        name: true,
        stripeCustomerId: true,
        subscriptionTier: true,
        stripeSubscriptionId: true
      }
    })

    if (!user) {
      return NextResponse.json(
        { success: false, error: 'User not found' },
        { status: 404 }
      )
    }

    // Check if already has active premium subscription
    if (user.subscriptionTier === 'premium' && user.stripeSubscriptionId) {
      // Check if subscription is actually active in Stripe
      try {
        const subscription = await stripe.subscriptions.retrieve(user.stripeSubscriptionId)
        if (subscription.status === 'active' || subscription.status === 'trialing') {
          return NextResponse.json(
            {
              success: false,
              error: 'Already subscribed to Premium',
              code: 'ALREADY_SUBSCRIBED'
            },
            { status: 400 }
          )
        }
      } catch (error) {
        console.log('Subscription not found in Stripe, allowing new subscription')
      }
    }

    const body = await request.json()
    const { priceId, interval, locale } = checkoutSchema.parse(body)

    // Validate price ID
    if (!priceId || priceId === 'price_xxxxxxxxxxxxx') {
      return NextResponse.json(
        {
          success: false,
          error: 'Invalid price ID. Please configure Stripe price IDs in environment variables.'
        },
        { status: 400 }
      )
    }

    // Create or retrieve Stripe customer
    let customerId = user.stripeCustomerId
    if (!customerId) {
      const customer = await stripe.customers.create({
        email: user.email,
        name: user.name || undefined,
        metadata: {
          userId,
          source: 'subscription'
        }
      })
      customerId = customer.id

      await prisma.user.update({
        where: { id: userId },
        data: { stripeCustomerId: customerId }
      })
    }

    // Create checkout session
    const session = await stripe.checkout.sessions.create({
      customer: customerId,
      mode: 'subscription',
      payment_method_types: ['card'],
      line_items: [
        {
          price: priceId,
          quantity: 1
        }
      ],
      success_url: `${process.env.NEXTAUTH_URL}/${locale}/subscription/success?session_id={CHECKOUT_SESSION_ID}`,
      cancel_url: `${process.env.NEXTAUTH_URL}/${locale}/subscription`,
      metadata: {
        userId,
        interval
      },
      subscription_data: {
        metadata: {
          userId
        }
      },
      allow_promotion_codes: true,
      billing_address_collection: 'auto'
    })

    console.log('✅ Stripe checkout session created:', {
      sessionId: session.id,
      userId,
      priceId,
      interval
    })

    return NextResponse.json({
      success: true,
      sessionId: session.id,
      url: session.url
    })

  } catch (error) {
    console.error('Subscription checkout error:', error)

    if (error instanceof z.ZodError) {
      return NextResponse.json(
        {
          success: false,
          error: 'Invalid request format',
          details: error.errors
        },
        { status: 400 }
      )
    }

    return NextResponse.json(
      {
        success: false,
        error: 'Failed to create checkout session'
      },
      { status: 500 }
    )
  }
}