import { NextResponse } from 'next/server';
import { requireAuth } from '@/lib/auth-utils';
import { postgresClient } from '@/lib/services/postgres-client';
import { getUserTimezone } from '@/lib/services/user-timezone';

export async function GET() {
  // Auth gate (Phase 7.1): aligns this route with every other
  // /api/mobile/* handler and lets us resolve the caller's tz from
  // the session. Browser callers carry the Better Auth session
  // cookie automatically, so the existing /mobile/finance page works
  // unchanged.
  const { session, error } = await requireAuth();
  if (error) return error;
  const tz = getUserTimezone(session);

  const [summary, aging, topCustomers, overdueInvoices, recentPayments, monthlyRevenue, credits] = await Promise.all([
    postgresClient.query(
      `
      SELECT
        SUM(balance)  FILTER (WHERE status IN ('Open','Overdue'))  as total_ar_gross,
        COUNT(*)      FILTER (WHERE status IN ('Open','Overdue'))  as total_ar_count,
        SUM(balance)  FILTER (WHERE status = 'Open')               as current_balance,
        COUNT(*)      FILTER (WHERE status = 'Open')               as current_count,
        SUM(balance)  FILTER (WHERE status = 'Overdue')            as overdue_balance,
        COUNT(*)      FILTER (WHERE status = 'Overdue')            as overdue_count,
        SUM(total_amt) FILTER (WHERE status = 'Paid' AND (txn_date AT TIME ZONE 'UTC' AT TIME ZONE $1) >= DATE_TRUNC('month', NOW() AT TIME ZONE $1)) as paid_mtd,
        SUM(total_amt) FILTER (WHERE status = 'Paid' AND (txn_date AT TIME ZONE 'UTC' AT TIME ZONE $1) >= DATE_TRUNC('year',  NOW() AT TIME ZONE $1)) as paid_ytd
      FROM qbo_invoices
      WHERE is_deleted = false
    `,
      [tz],
    ),
    postgresClient.query(
      `
      SELECT
        SUM(balance) FILTER (WHERE status = 'Overdue' AND due_date >= (NOW() AT TIME ZONE $1)::date - 30)  as days_1_30,
        COUNT(*)     FILTER (WHERE status = 'Overdue' AND due_date >= (NOW() AT TIME ZONE $1)::date - 30)  as cnt_1_30,
        SUM(balance) FILTER (WHERE status = 'Overdue' AND due_date <  (NOW() AT TIME ZONE $1)::date - 30
                                                       AND due_date >= (NOW() AT TIME ZONE $1)::date - 60) as days_31_60,
        COUNT(*)     FILTER (WHERE status = 'Overdue' AND due_date <  (NOW() AT TIME ZONE $1)::date - 30
                                                       AND due_date >= (NOW() AT TIME ZONE $1)::date - 60) as cnt_31_60,
        SUM(balance) FILTER (WHERE status = 'Overdue' AND due_date <  (NOW() AT TIME ZONE $1)::date - 60)  as days_60_plus,
        COUNT(*)     FILTER (WHERE status = 'Overdue' AND due_date <  (NOW() AT TIME ZONE $1)::date - 60)  as cnt_60_plus
      FROM qbo_invoices
      WHERE is_deleted = false
    `,
      [tz],
    ),
    // Top customers — net out any unapplied payment credits the customer is
    // sitting on, so the number matches QBO's customer A/R view.
    postgresClient.query(`
      WITH inv AS (
        SELECT customer_ref_id, customer_ref_name,
               SUM(balance) AS gross_balance,
               COUNT(*) AS invoice_count
          FROM qbo_invoices
         WHERE is_deleted = false
           AND status IN ('Open','Overdue')
         GROUP BY customer_ref_id, customer_ref_name
      ),
      cred AS (
        SELECT customer_ref_id, SUM(unapplied_amt) AS unapplied
          FROM qbo_payments
         WHERE unapplied_amt > 0
         GROUP BY customer_ref_id
      )
      SELECT inv.customer_ref_name,
             GREATEST(inv.gross_balance - COALESCE(cred.unapplied, 0), 0) AS balance,
             inv.invoice_count
        FROM inv
        LEFT JOIN cred ON cred.customer_ref_id = inv.customer_ref_id
       ORDER BY balance DESC
       LIMIT 8
    `),
    postgresClient.query(
      `
      SELECT id, doc_number, txn_date, due_date, customer_ref_name, total_amt, balance, status,
             (NOW() AT TIME ZONE $1)::date - due_date::date as days_overdue
      FROM qbo_invoices
      WHERE is_deleted = false
        AND status IN ('Open','Overdue')
      ORDER BY status DESC, balance DESC LIMIT 30
    `,
      [tz],
    ),
    postgresClient.query(`
      SELECT id, txn_date, customer_ref_name, total_amt
      FROM qbo_payments
      ORDER BY txn_date DESC LIMIT 10
    `),
    // monthlyRevenue: rolling 12-month window — NOT a calendar boundary;
    // tz does not apply.
    postgresClient.query(`
      SELECT DATE_TRUNC('month', txn_date) as month,
             SUM(total_amt) as revenue, COUNT(*) as invoice_count
      FROM qbo_invoices
      WHERE is_deleted = false
        AND status = 'Paid'
        AND txn_date >= NOW() - INTERVAL '12 months'
      GROUP BY 1 ORDER BY 1 ASC
    `),
    // Unapplied customer credits — payments not yet linked to an invoice.
    // QBO nets these against A/R in its customer balance reports.
    postgresClient.query(`
      SELECT COALESCE(SUM(unapplied_amt), 0) AS total_unapplied
        FROM qbo_payments
       WHERE unapplied_amt > 0
    `),
  ]);

  const s = summary.rows[0];
  const a = aging.rows[0];
  const unappliedCredits = parseFloat(credits.rows[0]?.total_unapplied ?? 0);
  const grossAr = parseFloat(s.total_ar_gross ?? 0);
  // QBO's A/R reports net unapplied customer credits against the gross
  // invoice balance.  Mirror that so the dashboard headline matches QBO.
  const netAr = Math.max(grossAr - unappliedCredits, 0);
  return NextResponse.json({
    summary: {
      total_ar:          netAr,
      total_ar_gross:    grossAr,
      unapplied_credits: unappliedCredits,
      total_ar_count:    parseInt(s.total_ar_count ?? 0),
      current_balance:   parseFloat(s.current_balance ?? 0),
      current_count:     parseInt(s.current_count ?? 0),
      overdue_balance:   parseFloat(s.overdue_balance ?? 0),
      overdue_count:     parseInt(s.overdue_count ?? 0),
      paid_mtd:          parseFloat(s.paid_mtd ?? 0),
      paid_ytd:          parseFloat(s.paid_ytd ?? 0),
    },
    aging: {
      days_1_30:   { balance: parseFloat(a.days_1_30 ?? 0),   count: parseInt(a.cnt_1_30 ?? 0) },
      days_31_60:  { balance: parseFloat(a.days_31_60 ?? 0),  count: parseInt(a.cnt_31_60 ?? 0) },
      days_60_plus:{ balance: parseFloat(a.days_60_plus ?? 0),count: parseInt(a.cnt_60_plus ?? 0) },
    },
    top_customers:  topCustomers.rows,
    open_invoices:  overdueInvoices.rows,
    recent_payments: recentPayments.rows,
    monthly_revenue: monthlyRevenue.rows.map(r => ({
      month:   r.month,
      revenue: parseFloat(r.revenue),
      count:   parseInt(r.invoice_count),
    })),
  });
}