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' },
  saveBtn: { marginTop: '0.75rem', background: 'none', border: '1px solid #555', color: '#aaa', borderRadius: '6px', padding: '0.4rem 1rem', cursor: 'pointer', fontSize: '0.85rem' },
};

function toDateKey(date) {
  return date.toISOString().split('T')[0];
}

function priceOn(date, priceMap, currentPrice, isToday, sortedPurchases) {
  if (isToday) return currentPrice || 0;
  // Try candle history (walk back up to 7 days)
  for (let i = 0; i <= 7; i++) {
    const d = new Date(date);
    d.setDate(d.getDate() - i);
    const p = priceMap[toDateKey(d)];
    if (p) return p;
  }
  // Fall back to most recent purchase price up to this date
  let fallback = null;
  for (const p of sortedPurchases) {
    const pd = new Date(p.created_at);
    pd.setHours(0, 0, 0, 0);
    if (pd <= date) fallback = p.price_eur;
  }
  return fallback;
}

export default function PortfolioChart({ purchases, stats, btcHistory }) {
  const chartRef = useRef(null);

  if (!purchases || purchases.length === 0) return null;

  const sorted = [...purchases].sort((a, b) => new Date(a.created_at) - new Date(b.created_at));
  const today = new Date();
  today.setHours(0, 0, 0, 0);

  // Build price lookup from candle history
  const priceMap = {};
  (btcHistory || []).forEach(({ date, close }) => { priceMap[date] = close; });

  const firstDate = new Date(sorted[0].created_at);
  firstDate.setHours(0, 0, 0, 0);

  // Generate biweekly dates from first purchase to today
  const dates = [];
  const cursor = new Date(firstDate);
  while (cursor <= today) {
    dates.push(new Date(cursor));
    cursor.setDate(cursor.getDate() + 7);
  }
  if (toDateKey(dates[dates.length - 1]) !== toDateKey(today)) {
    dates.push(new Date(today));
  }

  const labels = [];
  const portfolioValues = [];
  const investedValues = [];

  dates.forEach(date => {
    const isToday = toDateKey(date) === toDateKey(today);
    const price = priceOn(date, priceMap, stats?.current_price, isToday, sorted);
    if (price === null) return; // no price data available, skip

    // Cumulative BTC and invested up to this date
    let cumBtc = 0;
    let cumInvested = 0;
    sorted.forEach(p => {
      const pDate = new Date(p.created_at);
      pDate.setHours(0, 0, 0, 0);
      if (pDate <= date) {
        cumBtc += p.amount_eur / p.price_eur;
        cumInvested += p.amount_eur;
      }
    });

    if (cumBtc === 0) return; // no purchases yet at this date

    labels.push(date.toLocaleDateString('en-GB'));
    portfolioValues.push(parseFloat((cumBtc * price).toFixed(2)));
    investedValues.push(parseFloat(cumInvested.toFixed(2)));
  });

  const data = {
    labels,
    datasets: [
      {
        label: 'Portfolio Value (€)',
        data: portfolioValues,
        borderColor: '#f7931a',
        backgroundColor: 'rgba(247,147,26,0.1)',
        fill: true,
        tension: 0.3,
      },
      {
        label: 'Total Invested (€)',
        data: investedValues,
        borderColor: '#4fc3f7',
        backgroundColor: 'transparent',
        borderDash: [6, 3],
        tension: 0.3,
      },
    ],
  };

  const options = {
    responsive: true,
    plugins: {
      legend: { labels: { color: '#aaa' } },
      tooltip: { mode: 'index', intersect: false },
    },
    scales: {
      x: { ticks: { color: '#666' }, grid: { color: '#2a2a2a' } },
      y: { ticks: { color: '#666' }, grid: { color: '#2a2a2a' } },
    },
  };

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

  return (
    <div style={styles.card}>
      <div style={styles.title}>Portfolio Chart</div>
      <Line ref={chartRef} data={data} options={options} />
      <br />
      <button style={styles.saveBtn} onClick={handleSave}>Save as PNG</button>
    </div>
  );
}