import { NextRequest, NextResponse } from 'next/server';
import { getSessionUserId } from '@/lib/session';
import { stripe } from '@/lib/stripe';
import { db } from '@/lib/db';
import { rateLimit, getClientIdentifier, RateLimits } from '@/lib/rateLimit';
import { scoreUserLifecycle } from '@/lib/revops-server';

export async function POST(request: NextRequest) {
  try {
    const userId = getSessionUserId();

    // Rate Limiting (user-based)
    const clientId = userId || getClientIdentifier(request);
    const rateLimitResult = rateLimit(clientId, RateLimits.STRIPE_CANCEL);

    if (!rateLimitResult.success) {
      return NextResponse.json(
        {
          error: 'Too many requests. Please try again later.',
          retryAfter: Math.ceil((rateLimitResult.reset - Date.now()) / 1000)
        },
        {
          status: 429,
          headers: {
            'X-RateLimit-Limit': rateLimitResult.limit.toString(),
            'X-RateLimit-Remaining': rateLimitResult.remaining.toString(),
            'X-RateLimit-Reset': rateLimitResult.reset.toString(),
          }
        }
      );
    }
    if (!userId) {
      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
    }

    // Get user with subscription info
    const user = await db.user.findUnique({
      where: { id: userId },
      select: {
        stripeSubscriptionId: true,
        stripeCurrentPeriodEnd: true,
        plan: true,
      },
    });

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

    // Already on free plan
    if (user.plan === 'FREE') {
      return NextResponse.json({ error: 'Already on free plan' }, { status: 400 });
    }

    // No active subscription
    if (!user.stripeSubscriptionId) {
      // Just update plan to FREE if somehow plan is not FREE but no subscription
      await db.user.update({
        where: { id: userId },
        data: {
          plan: 'FREE',
          stripePriceId: null,
          stripeCurrentPeriodEnd: null,
        },
      });
      await scoreUserLifecycle(userId, 'subscription_deleted');
      return NextResponse.json({ success: true });
    }

    // Schedule cancellation at the end of the paid period so paid features stay active.
    const subscription: any = await stripe.subscriptions.update(user.stripeSubscriptionId, {
      cancel_at_period_end: true,
    });

    const periodEndTimestamp = subscription.current_period_end
      || subscription.currentPeriodEnd
      || subscription.billing_cycle_anchor;

    const currentPeriodEnd = periodEndTimestamp
      ? new Date(periodEndTimestamp * 1000)
      : user.stripeCurrentPeriodEnd;

    // Keep the paid plan locally until Stripe sends customer.subscription.deleted.
    await db.user.update({
      where: { id: userId },
      data: {
        stripeCurrentPeriodEnd: currentPeriodEnd,
      },
    });

    await scoreUserLifecycle(userId, 'subscription_canceled_at_period_end');

    return NextResponse.json({ success: true, currentPeriodEnd });
  } catch (error) {
    console.error('Error canceling subscription:', error);
    return NextResponse.json(
      { error: 'Failed to cancel subscription' },
      { status: 500 }
    );
  }
}