'use client';

import { useState } from 'react';
import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
import { FileText, Search, User, Wallet, CreditCard, XCircle } from 'lucide-react';
import { toast } from 'react-toastify';
import api from '@/lib/api';
import type { Invoice, InvoiceStatus, PaymentMethod } 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 AdminInvoicesPage() {
  const queryClient = useQueryClient();
  const [status, setStatus] = useState<'all' | InvoiceStatus>('all');
  const [paymentMethod, setPaymentMethod] = useState<'all' | PaymentMethod>('all');
  const [search, setSearch] = useState('');
  const [selectedId, setSelectedId] = useState<string | null>(null);
  const [statusReason, setStatusReason] = useState('');

  const { data: invoices = [], isLoading } = useQuery<Invoice[]>({
    queryKey: ['admin-invoices', status, paymentMethod, search],
    queryFn: () => {
      const params: Record<string, string> = { limit: '200' };
      if (status !== 'all') params.status = status;
      if (paymentMethod !== 'all') params.paymentMethod = paymentMethod;
      if (search.trim()) params.search = search.trim();
      return api.get('/billing/admin/invoices', { params }).then((r) => r.data);
    },
  });

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

  const updateStatusMutation = useMutation({
    mutationFn: ({ invoiceId, nextStatus, reason }: { invoiceId: string; nextStatus: InvoiceStatus; reason: string }) =>
      api.patch(`/billing/admin/invoices/${invoiceId}/status`, { status: nextStatus, reason }).then((r) => r.data),
    onSuccess: () => {
      toast.success('Invoice status updated');
      setStatusReason('');
      queryClient.invalidateQueries({ queryKey: ['admin-invoices'] });
      queryClient.invalidateQueries({ queryKey: ['admin-invoice', selectedId] });
    },
    onError: (err: any) => toast.error(err.response?.data?.message || 'Failed to update invoice status'),
  });

  const formatPrice = (amount: number) => Number(amount || 0).toLocaleString('en-US');
  const formatDate = (value?: string) => value ? new Date(value).toLocaleString('en-US') : '-';

  const handleStatusUpdate = (nextStatus: InvoiceStatus) => {
    if (!selectedInvoice) return;
    if (!statusReason.trim()) {
      toast.error('Reason is required for manual status changes');
      return;
    }
    updateStatusMutation.mutate({
      invoiceId: selectedInvoice.id,
      nextStatus,
      reason: statusReason.trim(),
    });
  };

  return (
    <div className="max-w-7xl mx-auto space-y-6 animate-fade-in">
      <div>
        <h1 className="page-title flex items-center gap-2">
          <FileText className="w-6 h-6" /> Invoice Management
        </h1>
        <p className="page-subtitle">Track all user invoices, payments, gateway refs, and wallet transactions.</p>
      </div>

      <div className="card grid grid-cols-1 md:grid-cols-4 gap-3">
        <div className="relative md:col-span-2">
          <Search className="w-4 h-4 text-gray-400 absolute left-3 top-1/2 -translate-y-1/2" />
          <input
            value={search}
            onChange={(e) => setSearch(e.target.value)}
            placeholder="Search invoice, email, or application"
            className="input-field pl-9 w-full"
          />
        </div>
        <select value={status} onChange={(e) => setStatus(e.target.value as any)} className="input-field">
          <option value="all">All statuses</option>
          {Object.entries(statusLabels).map(([value, label]) => (
            <option key={value} value={value}>{label}</option>
          ))}
        </select>
        <select value={paymentMethod} onChange={(e) => setPaymentMethod(e.target.value as any)} className="input-field">
          <option value="all">All methods</option>
          <option value="wallet">Wallet</option>
          <option value="gateway">Gateway</option>
          <option value="mixed">Mixed</option>
        </select>
      </div>

      <div className="grid grid-cols-1 xl:grid-cols-3 gap-6">
        <div className="xl:col-span-2 card p-0 overflow-hidden">
          <div className="overflow-x-auto">
            <table className="min-w-full divide-y divide-gray-100">
              <thead className="bg-gray-50">
                <tr>
                  <th className="px-4 py-3 text-left text-xs font-semibold text-gray-500 uppercase">Invoice</th>
                  <th className="px-4 py-3 text-left text-xs font-semibold text-gray-500 uppercase">User</th>
                  <th className="px-4 py-3 text-left text-xs font-semibold text-gray-500 uppercase">Status</th>
                  <th className="px-4 py-3 text-left text-xs font-semibold text-gray-500 uppercase">Method</th>
                  <th className="px-4 py-3 text-right text-xs font-semibold text-gray-500 uppercase">Due</th>
                </tr>
              </thead>
              <tbody className="divide-y divide-gray-100 bg-white">
                {isLoading ? (
                  <tr><td colSpan={5} className="px-4 py-8 text-center text-gray-400">Loading...</td></tr>
                ) : invoices.length === 0 ? (
                  <tr><td colSpan={5} className="px-4 py-8 text-center text-gray-400">No invoices found</td></tr>
                ) : invoices.map((invoice) => (
                  <tr
                    key={invoice.id}
                    onClick={() => setSelectedId(invoice.id)}
                    className={`cursor-pointer hover:bg-gray-50 ${selectedId === invoice.id ? 'bg-primary-50' : ''}`}
                  >
                    <td className="px-4 py-3">
                      <p className="text-sm font-semibold text-gray-900">{invoice.invoiceNumber}</p>
                      <p className="text-xs text-gray-500">{invoice.application?.name || invoice.reason} · {formatDate(invoice.createdAt)}</p>
                    </td>
                    <td className="px-4 py-3">
                      <p className="text-sm text-gray-900">{invoice.user?.email || invoice.userId}</p>
                    </td>
                    <td className="px-4 py-3">
                      <span className={statusClasses[invoice.status]}>{statusLabels[invoice.status]}</span>
                    </td>
                    <td className="px-4 py-3 text-sm text-gray-600">{invoice.paymentMethod || '-'}</td>
                    <td className="px-4 py-3 text-right">
                      <p className="text-sm font-bold text-gray-900">{formatPrice(invoice.dueAmount)} T</p>
                      <p className="text-xs text-gray-400">Total {formatPrice(invoice.total)} T</p>
                    </td>
                  </tr>
                ))}
              </tbody>
            </table>
          </div>
        </div>

        <div className="card">
          {!selectedInvoice ? (
            <div className="text-center py-12 text-gray-400">
              <FileText className="w-10 h-10 mx-auto mb-3" />
              Select an invoice
            </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="grid grid-cols-2 gap-3">
                <div className="bg-gray-50 rounded-xl p-3">
                  <p className="text-xs text-gray-500">Total</p>
                  <p className="font-bold text-gray-900">{formatPrice(selectedInvoice.total)} T</p>
                </div>
                <div className="bg-gray-50 rounded-xl p-3">
                  <p className="text-xs text-gray-500">Due</p>
                  <p className="font-bold text-primary-700">{formatPrice(selectedInvoice.dueAmount)} T</p>
                </div>
              </div>

              <div className="space-y-2 text-sm">
                <div className="flex items-center gap-2 text-gray-700">
                  <User className="w-4 h-4 text-gray-400" />
                  {selectedInvoice.user?.email || selectedInvoice.userId}
                </div>
                <div className="flex items-center gap-2 text-gray-700">
                  <CreditCard className="w-4 h-4 text-gray-400" />
                  Tracking: {selectedInvoice.gatewayTrackingCode || '-'}
                </div>
                <div className="flex items-center gap-2 text-gray-700">
                  <Wallet className="w-4 h-4 text-gray-400" />
                  Method: {selectedInvoice.paymentMethod || '-'}
                </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 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">{formatPrice(line.amount)} T</span>
                    </div>
                  ))}
                </div>
              </div>

              <div>
                <h3 className="text-sm font-semibold text-gray-900 mb-2">Transactions</h3>
                {(selectedInvoice.transactions || []).length === 0 ? (
                  <p className="text-sm text-gray-400">No linked transactions yet</p>
                ) : (
                  <div className="space-y-2">
                    {(selectedInvoice.transactions || []).map((tx) => (
                      <div key={tx.id} className="border border-gray-100 rounded-xl p-3">
                        <div className="flex justify-between gap-3">
                          <span className="text-sm text-gray-700">{tx.description || tx.type}</span>
                          <span className="text-sm font-bold">{formatPrice(tx.amount)} T</span>
                        </div>
                        <p className="text-xs text-gray-400 mt-1">{tx.type} · {formatDate(tx.createdAt)}</p>
                      </div>
                    ))}
                  </div>
                )}
              </div>

              <div className="border-t border-gray-100 pt-4 space-y-3">
                <h3 className="text-sm font-semibold text-gray-900">Manual status change</h3>
                <textarea
                  value={statusReason}
                  onChange={(e) => setStatusReason(e.target.value)}
                  className="input-field w-full min-h-[80px]"
                  placeholder="Reason is required for audit visibility"
                />
                <div className="grid grid-cols-2 gap-2">
                  <button
                    type="button"
                    onClick={() => handleStatusUpdate('failed')}
                    disabled={updateStatusMutation.isPending}
                    className="btn-secondary text-red-600 flex items-center justify-center gap-2 disabled:opacity-50"
                  >
                    <XCircle className="w-4 h-4" /> Failed
                  </button>
                  <button
                    type="button"
                    onClick={() => handleStatusUpdate('void')}
                    disabled={updateStatusMutation.isPending}
                    className="btn-secondary disabled:opacity-50"
                  >
                    Void
                  </button>
                </div>
              </div>
            </div>
          )}
        </div>
      </div>
    </div>
  );
}