"use client";

import React, { useEffect, useMemo, useRef, useState } from "react";
import { useAuth } from "@/hooks/useAuth";
import { useRouter } from "next/navigation";
import { apiFetch } from "@/lib/api";
import { useStableState } from "@/hooks/useStableState";
import { useVisiblePolling } from "@/hooks/useVisiblePolling";
import {
  Calendar, Banknote, Gift, Users, Ticket, QrCode, ClipboardList,
  UserPlus, FileText, MessageCircle, BarChart2, Mail, Wallet, DoorOpen,
} from "lucide-react";
import { StatCard, StatCardRow } from "@/components/shared/StatCard";
import { QuickActionTile, QuickActionGrid } from "@/components/shared/QuickActionTile";
import { AreaTrendChart } from "@/components/charts/AreaTrendChart";
import { Table, TableHeader, TableBody, TableRow, TableHead, TableCell } from "@/components/ui/table";

const formatRand = (n: number) => `R ${(n || 0).toFixed(2)}`;
const formatRandAxis = (n: number) => `R${new Intl.NumberFormat(undefined, { notation: "compact", maximumFractionDigits: 1 }).format(n)}`;
const formatCount = (n: number) => (n || 0).toLocaleString();
const REPORTS_URL = "/dashboard/supervisor/reports";

const QUICK_ACTIONS = [
  { href: "/dashboard/admin/users", label: "Manage users", description: "Create, edit, change roles and passwords", icon: Users },
  { href: "/dashboard/supervisor/events", label: "Manage events", description: "Create, edit, and update ticket types", icon: Calendar },
  { href: "/dashboard/admin/registrations", label: "Manage registrations", description: "Cancel, update status, and search registrations", icon: ClipboardList },
  { href: "/dashboard/supervisor/manual", label: "Manual registration", description: "Register a guest and issue tickets", icon: UserPlus },
  { href: "/dashboard/supervisor/at-the-door", label: "At the door", description: "Walk-ins, payments, ticket printing", icon: DoorOpen },
  { href: "/dashboard/supervisor/payments", label: "Payments & donations", description: "Manual payments and assignment", icon: Wallet },
  { href: "/dashboard/staff/ticket-scanning", label: "Open scanner", description: "Use your device camera to validate tickets", icon: QrCode },
  { href: "/dashboard/supervisor/reports", label: "Reports", description: "View, export, and email reports", icon: BarChart2 },
  { href: "/dashboard/admin/forms", label: "Attendee forms", description: "View submitted attendee forms", icon: FileText },
  { href: "/dashboard/supervisor/email-attendees", label: "Email attendees", description: "Send a message to attendees of an event", icon: Mail },
  { href: "/dashboard/supervisor/whatsapp-attendees", label: "WhatsApp attendees", description: "Send a WhatsApp message to event attendees", icon: MessageCircle },
  { href: "/dashboard/admin/cashup", label: "Post-event Cashup", description: "Set costs, reconcile takings, and close out events", icon: Wallet },
] as const;

type OverviewMetric = { thisMonth: number; lastMonth: number; pctChange: number | null };
type Overview = {
  activeEvents: number;
  registrations: OverviewMetric;
  ticketsSold: OverviewMetric;
  revenue: OverviewMetric;
  donations: OverviewMetric;
  trend: { date: string; revenue: number }[];
  topEvents: { eventId: string; title: string; revenue: number; registrations: number; ticketsSold: number }[];
};

export default function AdminDashboardPage() {
  const { user, loading, token } = useAuth();
  const router = useRouter();

  const isAdmin = useMemo(() => (user?.role === "admin"), [user]);

  useEffect(() => {
    if (loading) return;
    if (!user) router.replace("/login");
  }, [user, loading, router]);

  // /api/stats/admin covers today/week/month payment totals (unchanged from before);
  // /api/stats/overview is the month-over-month KPI/trend/top-events endpoint. Both are
  // computed server-side — no full payments/events list ever ships to the client.
  const [paymentStats, setPaymentStats] = useStableState<any | null>(null);
  const [overview, setOverview] = useStableState<Overview | null>(null);
  const [loadingStats, setLoadingStats] = useState(false);
  const hasLoadedOnce = useRef(false);
  const [paymentsTab, setPaymentsTab] = useState<"today" | "week" | "month">("today");

  const loadStats = async () => {
    if (!token) return;
    const isFirstLoad = !hasLoadedOnce.current;
    try {
      if (isFirstLoad) setLoadingStats(true);
      const [dash, overviewData] = await Promise.all([
        apiFetch<any>("/api/stats/admin", { authToken: token }),
        apiFetch<Overview>("/api/stats/overview", { authToken: token }),
      ]);
      setPaymentStats(dash.paymentStats);
      setOverview(overviewData);
    } catch (e) {
      // ignore errors for dashboard summaries
    } finally {
      hasLoadedOnce.current = true;
      if (isFirstLoad) setLoadingStats(false);
    }
  };

  useEffect(() => {
    if (!token) return;
    loadStats();
  }, [token]);

  // Poll every 15s while the tab is visible; pause in the background and refetch
  // immediately on return instead of leaving stale numbers up.
  useVisiblePolling(() => {
    if (!token) return;
    loadStats();
  }, 15000, !!token);

  const paymentsTabValue = paymentStats
    ? paymentsTab === "today" ? paymentStats.totalToday : paymentsTab === "week" ? paymentStats.totalWeek : paymentStats.totalMonth
    : 0;

  return (
    <div className="max-w-6xl mx-auto w-full overflow-x-hidden">
      <div className="mb-6">
        <h1 className="text-2xl font-semibold text-gray-900">Welcome back{user ? `, ${user.name}` : ""} 👋</h1>
        <p className="text-sm text-gray-500 mt-1">Here&apos;s what&apos;s happening with your events today.</p>
      </div>

      {!isAdmin && (
        <div className="p-3 border rounded bg-yellow-50 text-yellow-800 text-sm mb-4">
          You need admin access to use these tools.
        </div>
      )}

      <StatCardRow>
        <StatCard icon={Calendar} label="Active events" value={overview ? formatCount(overview.activeEvents) : "—"} tone="brand" href="/dashboard/supervisor/events" linkLabel="View all events" />
        <StatCard icon={Banknote} label="Revenue (past month)" value={overview ? formatRand(overview.revenue.thisMonth) : "—"} tone="green" href={`${REPORTS_URL}?report=revenue&range=trailing_month`} linkLabel="View report" delta={overview ? { value: overview.revenue.pctChange } : undefined} />
        <StatCard icon={Gift} label="Donations (past month)" value={overview ? formatRand(overview.donations.thisMonth) : "—"} tone="rose" href={`${REPORTS_URL}?report=donations&range=trailing_month`} linkLabel="View report" delta={overview ? { value: overview.donations.pctChange } : undefined} />
        <StatCard icon={Users} label="Registrations (past month)" value={overview ? formatCount(overview.registrations.thisMonth) : "—"} tone="blue" href="/dashboard/admin/registrations" linkLabel="View registrations" delta={overview ? { value: overview.registrations.pctChange } : undefined} />
        <StatCard icon={Ticket} label="Tickets sold (past month)" value={overview ? formatCount(overview.ticketsSold.thisMonth) : "—"} tone="amber" href={`${REPORTS_URL}?report=usage&range=trailing_month`} linkLabel="View report" delta={overview ? { value: overview.ticketsSold.pctChange } : undefined} />
      </StatCardRow>

      <div className="border rounded-xl p-4 bg-white shadow-sm my-6">
        <div className="text-lg font-semibold mb-3">Quick actions</div>
        <QuickActionGrid>
          {QUICK_ACTIONS.map(a => (
            <QuickActionTile key={a.href} icon={a.icon} title={a.label} description={a.description} href={a.href} />
          ))}
        </QuickActionGrid>
      </div>

      <div className="grid lg:grid-cols-3 gap-6">
        <div className="lg:col-span-2 space-y-6 min-w-0">
          <div className="border rounded-xl p-4 bg-white shadow-sm">
            <h2 className="text-lg font-semibold mb-3">Revenue trend — past month</h2>
            {overview && overview.trend.length > 0 ? (
              <AreaTrendChart data={overview.trend.map(t => ({ label: t.date.slice(5), value: t.revenue }))} valueFormatter={formatRand} axisFormatter={formatRandAxis} />
            ) : (
              <div className="text-sm text-gray-400">No revenue recorded in the past month.</div>
            )}
          </div>

          <div className="border rounded-xl p-4 bg-white shadow-sm">
            <h2 className="text-lg font-semibold mb-3">Top performing events</h2>
            {overview && overview.topEvents.length > 0 ? (
              <Table>
                <TableHeader>
                  <TableRow>
                    <TableHead>Event</TableHead>
                    <TableHead className="text-right">Registrations</TableHead>
                    <TableHead className="text-right">Revenue</TableHead>
                    <TableHead className="text-right">Tickets sold</TableHead>
                  </TableRow>
                </TableHeader>
                <TableBody>
                  {overview.topEvents.map(e => (
                    <TableRow key={e.eventId}>
                      <TableCell className="font-medium max-w-[140px] sm:max-w-[220px] truncate" title={e.title}>{e.title}</TableCell>
                      <TableCell className="text-right">{formatCount(e.registrations)}</TableCell>
                      <TableCell className="text-right">{formatRand(e.revenue)}</TableCell>
                      <TableCell className="text-right">{formatCount(e.ticketsSold)}</TableCell>
                    </TableRow>
                  ))}
                </TableBody>
              </Table>
            ) : (
              <div className="text-sm text-gray-400">No event revenue recorded yet.</div>
            )}
          </div>
        </div>

        <div className="space-y-6 min-w-0">
          <div className="border rounded-xl p-4 bg-white shadow-sm">
            <div className="flex items-center justify-between mb-3">
              <h2 className="text-lg font-semibold">Payments overview</h2>
              {loadingStats && <span className="text-xs text-gray-500">Refreshing…</span>}
            </div>
            <div className="flex gap-1 mb-3 bg-gray-100 rounded-lg p-1">
              {(["today", "week", "month"] as const).map(t => (
                <button
                  key={t}
                  type="button"
                  onClick={() => setPaymentsTab(t)}
                  className={"flex-1 text-xs font-medium py-1.5 rounded-md transition-colors " + (paymentsTab === t ? "bg-white text-brand-700 shadow-sm" : "text-gray-500 hover:text-gray-700")}
                >
                  {t === "today" ? "Today" : t === "week" ? "Past week" : "Past month"}
                </button>
              ))}
            </div>
            {paymentStats ? (
              <div className="text-2xl font-semibold text-gray-900">{formatRand(paymentsTabValue)}</div>
            ) : (
              <div className="text-sm text-gray-500">No payment data yet.</div>
            )}
          </div>

          <p className="text-sm text-gray-600">As an admin you can access Supervisor and Staff tools. Use the quick actions above to jump to common tasks.</p>
        </div>
      </div>
    </div>
  );
}