import React from 'react';

export default function TrendChart({ trendSeries = [] }) {
  if (trendSeries.length < 2) {
    return (
      <div className="rounded-2xl border border-dashed border-gray-300 dark:border-gray-700 bg-white/70 dark:bg-gray-900/70 p-4 text-sm text-gray-600 dark:text-gray-300">
        Für den Trend werden mindestens 2 Assessments benötigt.
      </div>
    );
  }

  const width = 760;
  const height = 280;
  const left = 50;
  const right = 20;
  const top = 16;
  const bottom = 52;

  const values = trendSeries.map((entry) => entry.totalPoints);
  const minValue = Math.min(...values);
  const maxValue = Math.max(...values);
  const range = maxValue - minValue || 1;

  const innerWidth = width - left - right;
  const innerHeight = height - top - bottom;

  const points = trendSeries.map((entry, index) => {
    const x = left + (index / (trendSeries.length - 1)) * innerWidth;
    const normalized = (entry.totalPoints - minValue) / range;
    const y = top + innerHeight - normalized * innerHeight;
    return { ...entry, x, y };
  });

  const path = points.map((point, index) => `${index === 0 ? 'M' : 'L'}${point.x},${point.y}`).join(' ');

  return (
    <div className="rounded-2xl border border-gray-200 dark:border-gray-800 bg-white dark:bg-gray-900 p-4 shadow-sm">
      <h3 className="text-sm font-semibold text-gray-800 dark:text-gray-100 mb-3">Trend (Gesamtpunkte)</h3>
      <svg viewBox={`0 0 ${width} ${height}`} className="w-full h-auto" role="img" aria-label="Trenddiagramm">
        <line x1={left} y1={top} x2={left} y2={top + innerHeight} className="stroke-gray-300 dark:stroke-gray-700" strokeWidth="1" />
        <line x1={left} y1={top + innerHeight} x2={left + innerWidth} y2={top + innerHeight} className="stroke-gray-300 dark:stroke-gray-700" strokeWidth="1" />

        <path d={path} fill="none" className="stroke-indigo-500" strokeWidth="3" strokeLinecap="round" />

        {points.map((point) => (
          <g key={point.assessmentId}>
            <circle cx={point.x} cy={point.y} r="4" className="fill-indigo-500" />
            <text x={point.x} y={point.y - 10} textAnchor="middle" className="fill-gray-700 dark:fill-gray-200" style={{ fontSize: 11, fontWeight: 600 }}>
              {point.totalPoints}
            </text>
            <text x={point.x} y={height - 18} textAnchor="middle" className="fill-gray-500 dark:fill-gray-400" style={{ fontSize: 10 }}>
              {point.label}
            </text>
          </g>
        ))}
      </svg>
    </div>
  );
}