"use client";

import { useState } from "react";
import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query";
import { RefreshCw, FileText } from "lucide-react";
import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/Card";
import { Table, TableHead, TableBody, TableRow, Th, Td, EmptyState } from "@/components/ui/Table";
import { Badge } from "@/components/ui/Badge";
import { Button } from "@/components/ui/Button";
import { Input } from "@/components/ui/Input";
import { Modal } from "@/components/ui/Modal";
import { formatDate, formatCurrency } from "@/lib/utils";
import api from "@/lib/api";
import { toast } from "sonner";

interface Invoice {
  id: string; invoiceNumber: string; clientId: string;
  client?: { firstName: string; lastName: string; accountNumber: string };
  subtotal: string; lateFee: string; total: string;
  amountPaid: string; balance: string;
  status: string; dueDate: string; periodStart?: string; periodEnd?: string; notes?: string;
  createdAt: string;
}
interface InvoicesResponse { data: Invoice[]; total: number; page: number; limit: number; }

const statusVariant: Record<string, "success" | "warning" | "danger" | "muted"> = {
  PAID: "success", PARTIAL: "warning", OVERDUE: "danger",
  SENT: "muted", DRAFT: "muted", VOID: "muted",
};

const statusFilters = ["", "SENT", "PARTIAL", "OVERDUE", "PAID", "VOID"];

export default function InvoicesPage() {
  const qc = useQueryClient();
  const [search, setSearch] = useState("");
  const [statusFilter, setStatusFilter] = useState("");
  const [page, setPage] = useState(1);
  const [selected, setSelected] = useState<Invoice | null>(null);
  const [payForm, setPayForm] = useState({ amount: "", channel: "CASH", referenceNumber: "", notes: "" });

  const { data, isLoading, isError, refetch } = useQuery<InvoicesResponse>({
    queryKey: ["invoices", search, statusFilter, page],
    queryFn: async () => {
      const params = new URLSearchParams({ page: String(page), limit: "20" });
      if (search) params.set("search", search);
      if (statusFilter) params.set("status", statusFilter);
      const res = await api.get<InvoicesResponse>(`/api/v1/invoices?${params}`);
      return res.data;
    },
  });

  const recordPayment = useMutation({
    mutationFn: async () => {
      await api.post("/api/v1/payments", {
        clientId: selected!.clientId, invoiceId: selected!.id,
        amount: Number(payForm.amount), channel: payForm.channel,
        referenceNumber: payForm.referenceNumber || undefined,
        notes: payForm.notes || undefined,
        paymentDate: new Date().toISOString(),
      });
    },
    onSuccess: () => {
      toast.success("Payment recorded!");
      setSelected(null);
      setPayForm({ amount: "", channel: "CASH", referenceNumber: "", notes: "" });
      qc.invalidateQueries({ queryKey: ["invoices"] });
      refetch();
    },
    onError: (e: any) => toast.error(e.response?.data?.message ?? "Payment failed"),
  });

  const voidInvoice = useMutation({
    mutationFn: async (id: string) => { await api.patch(`/api/v1/invoices/${id}/void`); },
    onSuccess: () => { toast.success("Invoice voided"); setSelected(null); qc.invalidateQueries({ queryKey: ["invoices"] }); },
    onError: (e: any) => toast.error(e.response?.data?.message ?? "Failed to void"),
  });

  const invoices = data?.data ?? [];
  const total = data?.total ?? 0;

  return (
    <div className="space-y-6">
      <div className="flex items-center justify-between">
        <div>
          <h1 className="text-2xl font-bold text-gray-900">Invoices</h1>
          <p className="text-sm text-gray-500 mt-1">{total} total invoices</p>
        </div>
        <Button onClick={() => refetch()} variant="outline" size="sm"><RefreshCw size={14} className="mr-1" />Refresh</Button>
      </div>

      <Card>
        <CardHeader>
          <div className="flex flex-wrap gap-3 items-center">
            <input className="flex-1 min-w-[200px] border rounded-lg px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-blue-500"
              placeholder="Search by client or invoice #..."
              value={search} onChange={e => { setSearch(e.target.value); setPage(1); }} />
            <div className="flex gap-2 flex-wrap">
              {statusFilters.map(s => (
                <button key={s} onClick={() => { setStatusFilter(s); setPage(1); }}
                  className={`px-3 py-1.5 rounded-lg text-xs font-medium transition-colors ${statusFilter === s ? "bg-blue-600 text-white" : "bg-gray-100 text-gray-600 hover:bg-gray-200"}`}>
                  {s || "All"}
                </button>
              ))}
            </div>
          </div>
        </CardHeader>
        <CardContent className="p-0">
          <Table>
            <TableHead>
              <TableRow>
                <Th>Invoice #</Th><Th>Client</Th><Th>Total</Th><Th>Paid</Th><Th>Balance</Th><Th>Due Date</Th><Th>Status</Th><Th></Th>
              </TableRow>
            </TableHead>
            <TableBody>
              {isLoading ? (
                Array.from({ length: 8 }).map((_, i) => (
                  <TableRow key={i}><Td colSpan={8}><div className="h-4 bg-gray-100 rounded animate-pulse" /></Td></TableRow>
                ))
              ) : isError ? (
                <TableRow><Td colSpan={8}><p className="text-center py-6 text-red-400 text-sm">Failed to load invoices. <button onClick={() => refetch()} className="underline">Retry</button></p></Td></TableRow>
              ) : invoices.length === 0 ? (
                <EmptyState colSpan={8} message="No invoices found" icon={<FileText size={24} />} />
              ) : invoices.map(inv => (
                <TableRow key={inv.id} onClick={() => setSelected(inv)} className="cursor-pointer hover:bg-blue-50 transition-colors">
                  <Td className="font-mono text-xs">{inv.invoiceNumber}</Td>
                  <Td className="font-medium">
                    {inv.client ? `${inv.client.firstName} ${inv.client.lastName}` : "—"}
                    <div className="text-xs text-gray-400">{inv.client?.accountNumber}</div>
                  </Td>
                  <Td>{formatCurrency(Number(inv.total))}</Td>
                  <Td className="text-green-700">{formatCurrency(Number(inv.amountPaid))}</Td>
                  <Td className={Number(inv.balance) > 0 ? "text-red-600 font-medium" : "text-gray-400"}>
                    {formatCurrency(Number(inv.balance))}
                  </Td>
                  <Td className={new Date(inv.dueDate) < new Date() && inv.status !== "PAID" ? "text-red-500" : ""}>
                    {formatDate(inv.dueDate)}
                  </Td>
                  <Td><Badge variant={statusVariant[inv.status] ?? "muted"}>{inv.status}</Badge></Td>
                  <Td className="text-gray-400 text-xs">View →</Td>
                </TableRow>
              ))}
            </TableBody>
          </Table>
          {total > 20 && (
            <div className="flex items-center justify-between px-4 py-3 border-t text-sm text-gray-500">
              <span>Showing {(page - 1) * 20 + 1}–{Math.min(page * 20, total)} of {total}</span>
              <div className="flex gap-2">
                <button disabled={page === 1} onClick={() => setPage(p => p - 1)} className="px-3 py-1 border rounded-md disabled:opacity-40">Prev</button>
                <button disabled={page * 20 >= total} onClick={() => setPage(p => p + 1)} className="px-3 py-1 border rounded-md disabled:opacity-40">Next</button>
              </div>
            </div>
          )}
        </CardContent>
      </Card>

      {/* Invoice Detail Modal */}
      <Modal
        isOpen={!!selected}
        onClose={() => setSelected(null)}
        title={`Invoice ${selected?.invoiceNumber ?? ""}`}
        className="max-w-lg"
        footer={selected ? (
          <>
            {selected.status !== "VOID" && selected.status !== "PAID" && (
              <Button variant="danger" size="sm" onClick={() => voidInvoice.mutate(selected.id)} isLoading={voidInvoice.isPending}>Void Invoice</Button>
            )}
            <Button variant="outline" size="sm" onClick={() => setSelected(null)}>Close</Button>
          </>
        ) : undefined}
      >
        {selected && (
          <div className="space-y-4">
            <div className="bg-gray-50 rounded-lg p-4 space-y-2 text-sm">
              <div className="flex justify-between"><span className="text-gray-500">Client</span>
                <span className="font-medium">{selected.client ? `${selected.client.firstName} ${selected.client.lastName}` : "—"}</span></div>
              <div className="flex justify-between"><span className="text-gray-500">Period</span>
                <span>{selected.periodStart ? `${formatDate(selected.periodStart)} – ${formatDate(selected.periodEnd!)}` : "—"}</span></div>
              <div className="flex justify-between"><span className="text-gray-500">Due Date</span>
                <span className={new Date(selected.dueDate) < new Date() && selected.status !== "PAID" ? "text-red-500 font-medium" : ""}>
                  {formatDate(selected.dueDate)}</span></div>
              <hr />
              <div className="flex justify-between"><span className="text-gray-500">Subtotal</span><span>{formatCurrency(Number(selected.subtotal))}</span></div>
              <div className="flex justify-between"><span className="text-gray-500">Late Fee</span><span>{formatCurrency(Number(selected.lateFee))}</span></div>
              <div className="flex justify-between font-semibold text-base"><span>Total</span><span>{formatCurrency(Number(selected.total))}</span></div>
              <div className="flex justify-between text-green-700"><span className="text-gray-500">Amount Paid</span><span>{formatCurrency(Number(selected.amountPaid))}</span></div>
              <div className={`flex justify-between font-bold ${Number(selected.balance) > 0 ? "text-red-600" : "text-green-600"}`}>
                <span>Balance</span><span>{formatCurrency(Number(selected.balance))}</span></div>
              <div className="flex justify-between"><span className="text-gray-500">Status</span>
                <Badge variant={statusVariant[selected.status] ?? "muted"}>{selected.status}</Badge></div>
            </div>

            {/* Pay form (only for unpaid) */}
            {["SENT", "PARTIAL", "OVERDUE"].includes(selected.status) && (
              <div className="border rounded-lg p-4 space-y-3 bg-blue-50">
                <p className="text-sm font-semibold text-blue-800">Record Payment</p>
                <Input label="Amount" type="number" value={payForm.amount}
                  onChange={e => setPayForm(f => ({ ...f, amount: e.target.value }))}
                  hint={`Balance due: ${formatCurrency(Number(selected.balance))}`} />
                <div className="flex flex-col gap-1.5">
                  <label className="text-sm font-medium text-gray-700">Payment Method</label>
                  <select className="border rounded-lg px-3 py-2 text-sm" value={payForm.channel}
                    onChange={e => setPayForm(f => ({ ...f, channel: e.target.value }))}>
                    {["CASH","GCASH","MAYA","BANK_TRANSFER","CHECK"].map(c => <option key={c} value={c}>{c}</option>)}
                  </select>
                </div>
                <Input label="Reference # (optional)" value={payForm.referenceNumber}
                  onChange={e => setPayForm(f => ({ ...f, referenceNumber: e.target.value }))} />
                <Button className="w-full" onClick={() => recordPayment.mutate()} isLoading={recordPayment.isPending}
                  disabled={!payForm.amount}>Record Payment</Button>
              </div>
            )}
          </div>
        )}
      </Modal>
    </div>
  );
}