import React, { useRef } from 'react';
import {
  Chart as ChartJS,
  LineElement,
  PointElement,
  LinearScale,
  CategoryScale,
  Tooltip,
  Legend,
  Filler,
} from 'chart.js';
import { Line } from 'react-chartjs-2';

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

const styles = {
  card: { background: '#1a1a1a', padding: '1.5rem', borderRadius: '12px', border: '1px solid #333', marginBottom: '1.5rem' },
  title: { fontSize: '1.1rem', fontWeight: 700, marginBottom: '1rem', color: '#f7931a' },
  loading: { color: '#666', padding: '1rem 0' },
  saveBtn: { marginTop: '0.75rem', background: 'none', border: '1px solid #555', color: '#aaa', borderRadius: '6px', padding: '0.4rem 1rem', cursor: 'pointer', fontSize: '0.85rem' },
};

export default function BTCHistoryChart({ history, stats }) {
  const chartRef = useRef(null);

  if (!history || history.prices.length === 0) {
    return (
      <div style={styles.card}>
        <div style={styles.title}>1-Year BTC Price (EUR)</div>
        <div style={styles.loading}>Loading price history…</div>
      </div>
    );
  }

  const { prices, purchases } = history;
  const averagePrice = stats?.average_price ?? 0;

  const purchaseDateSet = new Set(purchases.map(p => p.date));

  const pointRadii        = prices.map(p => purchaseDateSet.has(p.date) ? 7 : 0);
  const pointColors       = prices.map(p => purchaseDateSet.has(p.date) ? '#f7931a' : 'transparent');
  const pointBorderColors = prices.map(p => purchaseDateSet.has(p.date) ? '#fff' : 'transparent');

  const data = {
    labels: prices.map(p => p.date),
    datasets: [
      {
        label: 'BTC Price (€)',
        data: prices.map(p => p.price),
        borderColor: '#f7931a',
        backgroundColor: 'rgba(247,147,26,0.08)',
        fill: true,
        tension: 0.2,
        pointRadius: pointRadii,
        pointBackgroundColor: pointColors,
        pointBorderColor: pointBorderColors,
        pointBorderWidth: 2,
        pointHoverRadius: 6,
      },
      ...(averagePrice > 0 ? [{
        label: `Avg Buy Price (€${averagePrice.toLocaleString()})`,
        data: prices.map(() => averagePrice),
        borderColor: '#4fc3f7',
        backgroundColor: 'transparent',
        borderDash: [8, 4],
        pointRadius: 0,
        pointHoverRadius: 0,
        tension: 0,
      }] : []),
    ],
  };

  const options = {
    responsive: true,
    plugins: {
      legend: { labels: { color: '#aaa' } },
      tooltip: {
        mode: 'index',
        intersect: false,
        callbacks: {
          afterBody: (items) => {
            const date = items[0]?.label;
            const purchase = purchases.find(p => p.date === date);
            if (purchase) {
              return [`Purchased: €${purchase.amount_eur.toLocaleString()} @ €${purchase.price_eur.toLocaleString()}`];
            }
            return [];
          },
        },
      },
    },
    scales: {
      x: {
        ticks: { color: '#666', maxTicksLimit: 12, maxRotation: 0 },
        grid: { color: '#2a2a2a' },
      },
      y: {
        ticks: { color: '#666' },
        grid: { color: '#2a2a2a' },
      },
    },
  };

  const handleSave = () => {
    const chart = chartRef.current;
    if (!chart) return;
    const a = document.createElement('a');
    a.href = chart.toBase64Image();
    a.download = 'btc-history.png';
    a.click();
  };

  return (
    <div style={styles.card}>
      <div style={styles.title}>1-Year BTC Price (EUR)</div>
      <Line ref={chartRef} data={data} options={options} />
      <br />
      <button style={styles.saveBtn} onClick={handleSave}>Save as PNG</button>
    </div>
  );
}