import { NextRequest, NextResponse } from "next/server";
import prisma from "@/lib/db";
import { getOrganization, apiError } from "@/lib/api-helpers";

export async function GET(
  _request: NextRequest,
  { params }: { params: { customerId: string } }
) {
  try {
    const [organization, orgErr] = await getOrganization();
    if (orgErr) return orgErr;

    const customer = await prisma.customer.findFirst({
      where: {
        id: params.customerId,
        organizationId: organization.id,
      },
    });

    if (!customer) {
      return NextResponse.json({ error: "Customer not found" }, { status: 404 });
    }

    // Fetch invoices and payments in parallel
    const [invoices, payments] = await Promise.all([
      prisma.invoice.findMany({
        where: {
          customerId: customer.id,
          organizationId: organization.id,
        },
        select: {
          id: true,
          invoiceNumber: true,
          invoiceDate: true,
          dueDate: true,
          status: true,
          totalAmount: true,
          paidAmount: true,
          balanceDue: true,
          currencyCode: true,
          description: true,
        },
        orderBy: { invoiceDate: "desc" },
        take: 50,
      }),
      prisma.payment.findMany({
        where: {
          customerId: customer.id,
          organizationId: organization.id,
        },
        select: {
          id: true,
          paymentNumber: true,
          paymentDate: true,
          paymentMethod: true,
          paymentAmount: true,
          status: true,
          paymentReference: true,
        },
        orderBy: { paymentDate: "desc" },
        take: 20,
      }),
    ]);

    // Compute metrics
    const totalInvoiced = invoices.reduce((s, i) => s + Number(i.totalAmount), 0);
    const totalPaid = invoices.reduce((s, i) => s + Number(i.paidAmount), 0);
    const totalOutstanding = invoices.reduce((s, i) => s + Number(i.balanceDue), 0);
    const overdueInvoices = invoices.filter(
      (i) => i.status !== "PAID" && i.status !== "VOID" && i.dueDate && new Date(i.dueDate) < new Date()
    );
    const overdueAmount = overdueInvoices.reduce((s, i) => s + Number(i.balanceDue), 0);

    // Aging
    const now = new Date();
    const aging = { current: 0, days30: 0, days60: 0, days90: 0, over90: 0 };
    invoices
      .filter((i) => Number(i.balanceDue) > 0 && i.status !== "PAID" && i.status !== "VOID")
      .forEach((i) => {
        if (!i.dueDate) return;
        const daysPast = Math.floor((now.getTime() - new Date(i.dueDate).getTime()) / 86400000);
        const amt = Number(i.balanceDue);
        if (daysPast <= 0) aging.current += amt;
        else if (daysPast <= 30) aging.days30 += amt;
        else if (daysPast <= 60) aging.days60 += amt;
        else if (daysPast <= 90) aging.days90 += amt;
        else aging.over90 += amt;
      });

    // Credit utilization
    const creditLimit = customer.creditLimit ? Number(customer.creditLimit) : null;
    const creditUtilization = creditLimit ? (totalOutstanding / creditLimit) * 100 : null;

    return NextResponse.json({
      customer: {
        id: customer.id,
        customerCode: customer.customerCode,
        customerName: customer.customerName,
        customerType: customer.customerType,
        contactPerson: customer.contactPerson,
        email: customer.email,
        phone: customer.phone,
        website: customer.website,
        street1: customer.street1,
        street2: customer.street2,
        city: customer.city,
        stateProvince: customer.stateProvince,
        postalCode: customer.postalCode,
        country: customer.country,
        taxId: customer.taxId,
        paymentTermDays: customer.paymentTermDays,
        creditLimit,
        status: customer.status,
        createdAt: customer.createdAt,
      },
      metrics: {
        totalInvoiced,
        totalPaid,
        totalOutstanding,
        overdueAmount,
        overdueCount: overdueInvoices.length,
        invoiceCount: invoices.length,
        paymentCount: payments.length,
        creditLimit,
        creditUtilization,
        aging,
      },
      invoices: invoices.map((i) => ({
        ...i,
        totalAmount: Number(i.totalAmount),
        paidAmount: Number(i.paidAmount),
        balanceDue: Number(i.balanceDue),
      })),
      payments: payments.map((p) => ({
        id: p.id,
        paymentNumber: p.paymentNumber,
        paymentDate: p.paymentDate,
        paymentMethod: p.paymentMethod,
        amount: Number(p.paymentAmount),
        status: p.status,
        referenceNumber: p.paymentReference,
      })),
    });
  } catch (error) {
    return apiError("Failed to fetch customer details", error);
  }
}