frontend/src/components/admin/Reports.jsx

import React, { useState, useEffect } from 'react';
import { db } from '../../firebase/config';
import { ref, onValue } from 'firebase/database';
import {
  Chart as ChartJS, CategoryScale, LinearScale, PointElement,
  LineElement, Title, Tooltip, Legend, BarElement
} from 'chart.js';
import { Line, Bar } from 'react-chartjs-2';
import { TrendingUp, Package, Users as UsersIcon, Calendar } from 'lucide-react';

ChartJS.register(
  CategoryScale, LinearScale, PointElement, LineElement, Title, Tooltip, Legend, BarElement
);

export default function Reports() {
  const [salesData, setSalesData] = useState([0, 0, 0, 0, 0, 0, 0]);
  const [topProducts, setTopProducts] = useState({ labels: [], data: [] });
  const [stats, setStats] = useState({ totalSales: 0, orderCount: 0, avgTicket: 0 });

  useEffect(() => {
    onValue(ref(db, 'orders'), (snapshot) => {
      const data = snapshot.val();
      if (data) {
        const orders = Object.values(data);
        const weeklySales = [0, 0, 0, 0, 0, 0, 0];
        const productCounts = {};
        let total = 0;

        orders.forEach(order => {
            if (order.status === 'completed') {
                total += order.total;
                // Simple day mapping (last 7 days logic would be better but this is for demo)
                const day = new Date(order.timestamp).getDay(); // 0-6
                const index = (day + 6) % 7; // Map Mon-Sun
                weeklySales[index] += order.total;

                order.items.forEach(item => {
                    productCounts[item.name] = (productCounts[item.name] || 0) + item.qty;
                });
            }
        });

        setSalesData(weeklySales);
        setStats({
            totalSales: total,
            orderCount: orders.filter(o => o.status === 'completed').length,
            avgTicket: total / (orders.filter(o => o.status === 'completed').length || 1)
        });

        const sortedProducts = Object.entries(productCounts)
            .sort((a,b) => b[1] - a[1])
            .slice(0, 5);
        
        setTopProducts({
            labels: sortedProducts.map(p => p[0]),
            data: sortedProducts.map(p => p[1])
        });
      }
    });
  }, []);

  const lineData = {
    labels: ['Lun', 'Mar', 'Mié', 'Jue', 'Vie', 'Sáb', 'Dom'],
    datasets: [{
      label: 'Ventas ($)',
      data: salesData,
      borderColor: '#FF5A5F',
      backgroundColor: 'rgba(255, 90, 95, 0.2)',
      fill: true,
      tension: 0.4
    }]
  };

  const barData = {
    labels: topProducts.labels,
    datasets: [{
      label: 'Unidades Vendidas',
      data: topProducts.data,
      backgroundColor: 'rgba(0, 166, 153, 0.7)',
      borderRadius: 8
    }]
  };

  const options = {
    responsive: true,
    maintainAspectRatio: false,
    plugins: { legend: { labels: { color: '#9595a8' } } },
    scales: {
      x: { ticks: { color: '#9595a8' }, grid: { color: 'rgba(255,255,255,0.05)' } },
      y: { ticks: { color: '#9595a8' }, grid: { color: 'rgba(255,255,255,0.05)' } }
    }
  };

  return (
    <div className="animate-fade-in">
      <header style={{ marginBottom: '2.5rem' }}>
        <h2 className="text-gradient" style={{ fontSize: '2rem', fontWeight: '800' }}>Análisis de Negocio</h2>
        <div style={{ display: 'grid', gridTemplateColumns: 'repeat(auto-fit, minmax(200px, 1fr))', gap: '1.5rem', marginTop: '1.5rem' }}>
            <div className="glass-card" style={{ padding: '1.25rem' }}>
                <div style={{ display: 'flex', justifyContent: 'space-between', color: 'var(--text-muted)', fontSize: '0.8rem' }}>Ventas Totales <TrendingUp size={16} /></div>
                <div style={{ fontSize: '1.5rem', fontWeight: '800', marginTop: '0.5rem' }}>${stats.totalSales.toFixed(2)}</div>
            </div>
            <div className="glass-card" style={{ padding: '1.25rem' }}>
                <div style={{ display: 'flex', justifyContent: 'space-between', color: 'var(--text-muted)', fontSize: '0.8rem' }}>Pedidos <Package size={16} /></div>
                <div style={{ fontSize: '1.5rem', fontWeight: '800', marginTop: '0.5rem' }}>{stats.orderCount}</div>
            </div>
            <div className="glass-card" style={{ padding: '1.25rem' }}>
                <div style={{ display: 'flex', justifyContent: 'space-between', color: 'var(--text-muted)', fontSize: '0.8rem' }}>Ticket Promedio <Calendar size={16} /></div>
                <div style={{ fontSize: '1.5rem', fontWeight: '800', marginTop: '0.5rem' }}>${stats.avgTicket.toFixed(2)}</div>
            </div>
        </div>
      </header>
      
      <div style={{ display: 'grid', gridTemplateColumns: 'repeat(auto-fit, minmax(400px, 1fr))', gap: '2rem' }}>
        <div className="glass-card" style={{ height: '350px', display: 'flex', flexDirection: 'column' }}>
          <h3 style={{ marginBottom: '1.5rem', fontSize: '1rem', display: 'flex', alignItems: 'center', gap: '0.5rem' }}>
            Ventas por Día de la Semana
          </h3>
          <div style={{ flex: 1, position: 'relative' }}>
            <Line data={lineData} options={options} />
          </div>
        </div>

        <div className="glass-card" style={{ height: '350px', display: 'flex', flexDirection: 'column' }}>
          <h3 style={{ marginBottom: '1.5rem', fontSize: '1rem' }}>Productos Estrella</h3>
          <div style={{ flex: 1, position: 'relative' }}>
            <Bar data={barData} options={options} />
          </div>
        </div>
      </div>
    </div>
  );
}