'use client';

import { useEffect, useState } from 'react';
import { useSearchParams } from 'next/navigation';
import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
import { CreditCard, FileText, Wallet, XCircle, CheckCircle, Clock, ExternalLink } from 'lucide-react';
import { toast } from 'react-toastify';
import api from '@/lib/api';
import type { Invoice, InvoiceStatus } from '@/types';

const statusLabels: Record<InvoiceStatus, string> = {
  draft: 'Draft',
  issued: 'Unpaid',
  partially_paid: 'Partially paid',
  paid: 'Paid',
  void: 'Void',
  failed: 'Failed',
};

const statusClasses: Record<InvoiceStatus, string> = {
  draft: 'badge-gray',
  issued: 'badge-yellow',
  partially_paid: 'badge-blue',
  paid: 'badge-green',
  void: 'badge-gray',
  failed: 'badge-red',
};

export default function InvoicesPage() {
  const queryClient = useQueryClient();
  const searchParams = useSearchParams();
  const [statusFilter, setStatusFilter] = useState<'all' | 'unpaid' | InvoiceStatus>('all');
  const [selectedId, setSelectedId] = useState<string | null>(searchParams.get('invoice'));

  useEffect(() => {
    const invoiceId = searchParams.get('invoice');
    if (invoiceId) setSelectedId(invoiceId);
  }, [searchParams]);

  const { data: walletData } = useQuery<{ balance: number }>({
    queryKey: ['wallet-balance'],
    queryFn: () => api.get('/billing/wallet').then((r) => r.data),
  });

  const { data: invoices = [], isLoading } = useQuery<Invoice[]>({
    queryKey: ['invoices', statusFilter],
    queryFn: () => {
      const params: Record<string, string> = {};
      if (statusFilter !== 'all' && statusFilter !== 'unpaid') params.status = statusFilter;
      return api.get('/billing/invoices', { params }).then((r) => r.data);
    },
  });

  const visibleInvoices = invoices.filter((invoice) => {
    if (statusFilter === 'unpaid') return invoice.status === 'issued' || invoice.status === 'partially_paid';
    return true;
  });

  const { data: selectedInvoice } = useQuery<Invoice>({
    queryKey: ['invoice', selectedId],
    queryFn: () => api.get(`/billing/invoices/${selectedId}`).then((r) => r.data),
    enabled: !!selectedId,
  });

  const refresh = () => {
    queryClient.invalidateQueries({ queryKey: ['invoices'] });
    queryClient.invalidateQueries({ queryKey: ['invoice', selectedId] });
    queryClient.invalidateQueries({ queryKey: ['wallet-balance'] });
    queryClient.invalidateQueries({ queryKey: ['wallet-transactions'] });
  };

  const walletPayMutation = useMutation({
    mutationFn: (invoiceId: string) => api.post(`/billing/invoices/${invoiceId}/pay/wallet`).then((r) => r.data),
    onSuccess: (data) => {
      toast.success(data.effect ? 'Invoice paid and service updated' : 'Invoice paid');
      refresh();
    },
    onError: (err: any) => toast.error(err.response?.data?.message || 'Wallet payment failed'),
  });

  const gatewayPayMutation = useMutation({
    mutationFn: async ({ invoiceId, mixed }: { invoiceId: string; mixed: boolean }) => {
      const callbackUrl = `${window.location.origin}/dashboard/invoices`;
      const { data } = await api.post(
        `/billing/invoices/${invoiceId}/pay/${mixed ? 'mixed' : 'gateway'}`,
        { callbackUrl },
      );
      if (data.gatewayAmount === 0) return data;
      const amount = data.gatewayAmount ?? data.amount;
      const trackingCode = data.trackingCode;
      if (!trackingCode || !amount) return data;
      const verified = await api.post(`/billing/invoices/${invoiceId}/gateway/verify`, {
        trackingCode,
        amount,
      });
      return verified.data;
    },
    onSuccess: (data) => {
      toast.success(data.effect ? 'Payment complete and service updated' : 'Payment complete');
      refresh();
    },
    onError: (err: any) => toast.error(err.response?.data?.message || 'Gateway payment failed'),
  });

  const formatPrice = (amount: number) => Number(amount || 0).toLocaleString('en-US');
  const formatDate = (value?: string) => value ? new Date(value).toLocaleString('en-US') : '-';
  const dueAmount = Number(selectedInvoice?.dueAmount || 0);
  const walletBalance = Number(walletData?.balance || 0);
  const isPayable = selectedInvoice?.status === 'issued' || selectedInvoice?.status === 'partially_paid';

  return (
    <div className="max-w-6xl mx-auto space-y-6 animate-fade-in">
      <div className="flex flex-col md:flex-row md:items-center md:justify-between gap-4">
        <div>
          <h1 className="page-title flex items-center gap-2">
            <FileText className="w-6 h-6" /> Invoices
          </h1>
          <p className="page-subtitle">Review what each payment was for and pay open invoices.</p>
        </div>
        <div className="card py-3 px-4 flex items-center gap-3">
          <Wallet className="w-5 h-5 text-primary-600" />
          <div>
            <p className="text-xs text-gray-500">Wallet balance</p>
            <p className="font-bold text-gray-900">{formatPrice(walletBalance)} Toman</p>
          </div>
        </div>
      </div>

      <div className="flex flex-wrap gap-2">
        {(['all', 'unpaid', 'paid', 'failed', 'void'] as const).map((status) => (
          <button
            key={status}
            type="button"
            onClick={() => setStatusFilter(status)}
            className={`px-3 py-1.5 rounded-lg text-sm font-medium border ${
              statusFilter === status
                ? 'bg-primary-600 text-white border-primary-600'
                : 'bg-white text-gray-700 border-gray-200 hover:bg-gray-50'
            }`}
          >
            {status === 'all' ? 'All' : status === 'unpaid' ? 'Unpaid' : statusLabels[status]}
          </button>
        ))}
      </div>

      <div className="grid grid-cols-1 lg:grid-cols-5 gap-6">
        <div className="lg:col-span-3 card p-0 overflow-hidden">
          {isLoading ? (
            <div className="p-8 text-center text-gray-400">Loading invoices...</div>
          ) : visibleInvoices.length === 0 ? (
            <div className="p-8 text-center text-gray-400">No invoices found</div>
          ) : (
            <div className="divide-y divide-gray-100">
              {visibleInvoices.map((invoice) => (
                <button
                  key={invoice.id}
                  type="button"
                  onClick={() => setSelectedId(invoice.id)}
                  className={`w-full text-left p-4 hover:bg-gray-50 transition-colors ${
                    selectedId === invoice.id ? 'bg-primary-50' : 'bg-white'
                  }`}
                >
                  <div className="flex items-start justify-between gap-3">
                    <div>
                      <p className="font-semibold text-gray-900">{invoice.invoiceNumber}</p>
                      <p className="text-sm text-gray-500">
                        {invoice.application?.name || invoice.reason} · {formatDate(invoice.createdAt)}
                      </p>
                    </div>
                    <span className={statusClasses[invoice.status]}>{statusLabels[invoice.status]}</span>
                  </div>
                  <div className="mt-3 flex items-center justify-between text-sm">
                    <span className="text-gray-500">Total {formatPrice(invoice.total)} Toman</span>
                    <span className="font-semibold text-gray-900">Due {formatPrice(invoice.dueAmount)} Toman</span>
                  </div>
                </button>
              ))}
            </div>
          )}
        </div>

        <div className="lg:col-span-2 card">
          {!selectedInvoice ? (
            <div className="text-center py-12 text-gray-400">
              <FileText className="w-10 h-10 mx-auto mb-3" />
              Select an invoice to view details
            </div>
          ) : (
            <div className="space-y-5">
              <div className="flex items-start justify-between gap-3">
                <div>
                  <h2 className="text-lg font-bold text-gray-900">{selectedInvoice.invoiceNumber}</h2>
                  <p className="text-sm text-gray-500">{selectedInvoice.application?.name || selectedInvoice.reason}</p>
                </div>
                <span className={statusClasses[selectedInvoice.status]}>{statusLabels[selectedInvoice.status]}</span>
              </div>

              <div className="bg-gray-50 rounded-xl p-4 space-y-2 text-sm">
                <div className="flex justify-between"><span className="text-gray-500">Total</span><span className="font-semibold">{formatPrice(selectedInvoice.total)} Toman</span></div>
                <div className="flex justify-between"><span className="text-gray-500">Paid</span><span className="font-semibold text-green-600">{formatPrice(selectedInvoice.paidAmount)} Toman</span></div>
                <div className="flex justify-between"><span className="text-gray-500">Due</span><span className="font-semibold text-primary-700">{formatPrice(selectedInvoice.dueAmount)} Toman</span></div>
                <div className="flex justify-between"><span className="text-gray-500">Method</span><span>{selectedInvoice.paymentMethod || '-'}</span></div>
              </div>

              <div>
                <h3 className="text-sm font-semibold text-gray-900 mb-2">Line items</h3>
                <div className="space-y-2">
                  {(selectedInvoice.lines || []).map((line) => (
                    <div key={line.id} className="border border-gray-100 rounded-xl p-3">
                      <div className="flex justify-between gap-3">
                        <div>
                          <p className="text-sm font-medium text-gray-900">{line.label}</p>
                          {line.description && <p className="text-xs text-gray-500">{line.description}</p>}
                        </div>
                        <span className="text-sm font-bold text-gray-900">{formatPrice(line.amount)} T</span>
                      </div>
                    </div>
                  ))}
                </div>
              </div>

              {isPayable && (
                <div className="space-y-3 border-t border-gray-100 pt-4">
                  <h3 className="text-sm font-semibold text-gray-900">Payment options</h3>
                  <button
                    type="button"
                    onClick={() => walletPayMutation.mutate(selectedInvoice.id)}
                    disabled={walletPayMutation.isPending || walletBalance < dueAmount}
                    className="w-full btn-primary flex items-center justify-center gap-2 disabled:opacity-50"
                  >
                    <Wallet className="w-4 h-4" />
                    Pay from wallet
                  </button>
                  {walletBalance < dueAmount && (
                    <p className="text-xs text-amber-700 bg-amber-50 border border-amber-100 rounded-lg p-2">
                      Wallet is short by {formatPrice(dueAmount - walletBalance)} Toman. Use mixed payment to cover the delta by gateway.
                    </p>
                  )}
                  <button
                    type="button"
                    onClick={() => gatewayPayMutation.mutate({ invoiceId: selectedInvoice.id, mixed: false })}
                    disabled={gatewayPayMutation.isPending}
                    className="w-full btn-secondary flex items-center justify-center gap-2 disabled:opacity-50"
                  >
                    <CreditCard className="w-4 h-4" />
                    Pay directly by gateway
                  </button>
                  <button
                    type="button"
                    onClick={() => gatewayPayMutation.mutate({ invoiceId: selectedInvoice.id, mixed: true })}
                    disabled={gatewayPayMutation.isPending}
                    className="w-full btn-secondary flex items-center justify-center gap-2 disabled:opacity-50"
                  >
                    <ExternalLink className="w-4 h-4" />
                    Use wallet + gateway delta
                  </button>
                </div>
              )}

              {selectedInvoice.status === 'paid' && (
                <div className="flex items-center gap-2 text-sm text-green-700 bg-green-50 border border-green-100 rounded-xl p-3">
                  <CheckCircle className="w-4 h-4" /> Paid on {formatDate(selectedInvoice.paidAt)}
                </div>
              )}
              {selectedInvoice.status === 'failed' && (
                <div className="flex items-center gap-2 text-sm text-red-700 bg-red-50 border border-red-100 rounded-xl p-3">
                  <XCircle className="w-4 h-4" /> {selectedInvoice.statusReason || 'Payment failed'}
                </div>
              )}
              {selectedInvoice.status === 'partially_paid' && (
                <div className="flex items-center gap-2 text-sm text-blue-700 bg-blue-50 border border-blue-100 rounded-xl p-3">
                  <Clock className="w-4 h-4" /> Waiting for the remaining payment.
                </div>
              )}
            </div>
          )}
        </div>
      </div>
    </div>
  );
}