import { NextResponse } from 'next/server';
import prisma from '../../../lib/prisma';
import { getServerSession } from "next-auth/next";
import { authOptions } from "../auth/[...nextauth]/route";

async function getSession() {
  const session = await getServerSession(authOptions);
  if (!session) return null;
  return session;
}

const PREFIXES: Record<string, string> = {
  QUOTE: 'ANG', ORDER_CONFIRMATION: 'AB', DELIVERY_NOTE: 'LS', INVOICE: 'RE', CREDIT_NOTE: 'RK'
};
const NUMBER_FIELDS: Record<string, string> = {
  QUOTE: 'nextQuoteNumber', ORDER_CONFIRMATION: 'nextOrderNumber',
  DELIVERY_NOTE: 'nextDeliveryNumber', INVOICE: 'nextInvoiceNumber', CREDIT_NOTE: 'nextCreditNoteNumber'
};

async function generateNumber(type: string) {
  const settings = await prisma.systemSettings.findFirst();
  if (!settings) throw new Error('SystemSettings not found');
  const year = new Date().getFullYear();
  const prefix = PREFIXES[type] || 'DOC';
  const field = NUMBER_FIELDS[type];
  const num = (settings as any)[field] || 1;
  await prisma.systemSettings.update({ where: { id: settings.id }, data: { [field]: num + 1 } });
  return `${prefix}-${year}-${num.toString().padStart(4, '0')}`;
}

export async function GET(request: Request) {
  const session = await getSession();
  if (!session) return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });

  try {
    const { searchParams } = new URL(request.url);
    const customerId = searchParams.get('customerId');

    const where = customerId ? { customerId: parseInt(customerId) } : {};
    const docs = await prisma.salesDocument.findMany({
      where,
      include: {
        customer: { select: { companyName: true, firstName: true, lastName: true } },
        items: { include: { product: { select: { name: true } } } },
        createdBy: { select: { firstName: true, lastName: true } }
      },
      orderBy: { createdAt: 'desc' }
    });
    return NextResponse.json(docs);
  } catch (error) {
    console.error(error);
    return NextResponse.json({ error: 'Ladefehler' }, { status: 500 });
  }
}

export async function POST(request: Request) {
  const session = await getSession();
  const perms = (session?.user as any)?.permissions || [];
  if (!perms.includes('SALES_MANAGE')) return NextResponse.json({ error: 'Keine Berechtigung' }, { status: 403 });

  try {
    const body = await request.json();
    const number = await generateNumber(body.type);

    // Auto-set validity for quotes
    let validUntil = body.validUntil ? new Date(body.validUntil) : null;
    if (body.type === 'QUOTE' && !validUntil) {
      const settings = await prisma.systemSettings.findFirst();
      if (settings?.defaultQuoteValidityDays) {
        validUntil = new Date();
        validUntil.setDate(validUntil.getDate() + settings.defaultQuoteValidityDays);
      }
    }
    // Calculate totals
    let subtotal = 0;
    const items = (body.items || []).map((item: any) => {
      const total = item.quantity * item.unitPrice;
      subtotal += total;
      return { ...item, total, taxRate: 19 };
    });
    const taxAmount = subtotal * 0.19;
    const total = subtotal + taxAmount;

    const doc = await prisma.salesDocument.create({
      data: {
        type: body.type,
        number,
        customerId: body.customerId,
        createdById: (session?.user as any)?.id || null,
        notes: body.notes || null,
        validUntil,
        subtotal, taxAmount, total,
        items: { create: items.map((i: any) => ({ description: i.description, quantity: i.quantity, unitPrice: i.unitPrice, taxRate: i.taxRate, total: i.total, productId: i.productId || null })) }
      },
      include: { items: true, customer: true }
    });

    return NextResponse.json(doc, { status: 201 });
  } catch (error) {
    console.error(error);
    return NextResponse.json({ error: 'Fehler beim Erstellen' }, { status: 500 });
  }
}