"use client";

import { useEffect, useRef, type ReactNode } from "react";

type WaveFieldProps = {
  children?: ReactNode;
  className?: string;
  color?: string;
  background?: string;
  /** Number of wave lines. */
  lines?: number;
  /** Wave height in pixels. */
  amplitude?: number;
  /** 1 is the default pace; 2 is twice as fast. */
  speed?: number;
};

/* WaveField: stacked lines that ripple like a contour map. Middle lines are brightest. */
export function WaveField({
  children,
  className = "",
  color = "#a78bfa",
  background = "#06050d",
  lines = 16,
  amplitude = 24,
  speed = 1,
}: WaveFieldProps) {
  const canvasRef = useRef<HTMLCanvasElement>(null);

  useEffect(() => {
    const canvas = canvasRef.current;
    const ctx = canvas?.getContext("2d");
    if (!canvas || !ctx) return;
    const still = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let w = 0;
    let h = 0;
    let raf = 0;
    let last = 0;
    let time = 0;

    const draw = () => {
      ctx.clearRect(0, 0, w, h);
      ctx.strokeStyle = color;
      ctx.lineWidth = 1;
      const n = Math.max(lines, 2);
      for (let i = 0; i < n; i++) {
        const k = i / (n - 1);
        const base = h * (0.15 + 0.7 * k);
        ctx.globalAlpha = 0.12 + 0.6 * (1 - Math.abs(k - 0.5) * 2);
        ctx.beginPath();
        for (let x = 0; x <= w + 8; x += 8) {
          const swell = 0.4 + 0.6 * Math.sin((Math.PI * x) / w);
          const wave = Math.sin(x * 0.008 + time * 0.6 + i * 0.35) * 0.6 + Math.sin(x * 0.017 - time * 0.4 + i * 0.2) * 0.4;
          const y = base + amplitude * swell * wave;
          if (x === 0) ctx.moveTo(x, y);
          else ctx.lineTo(x, y);
        }
        ctx.stroke();
      }
      ctx.globalAlpha = 1;
    };

    const frame = (now: number) => {
      time += last ? Math.min((now - last) / 1000, 0.05) * speed : 0;
      last = now;
      draw();
      raf = requestAnimationFrame(frame);
    };

    const start = () => {
      if (still || raf) return;
      last = 0;
      raf = requestAnimationFrame(frame);
    };
    const stop = () => {
      cancelAnimationFrame(raf);
      raf = 0;
    };

    const resize = () => {
      const dpr = Math.min(window.devicePixelRatio || 1, 2);
      w = canvas.clientWidth;
      h = canvas.clientHeight;
      canvas.width = Math.round(w * dpr);
      canvas.height = Math.round(h * dpr);
      ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
      draw();
    };

    // Redraw on size change; only animate while on screen.
    const ro = new ResizeObserver(resize);
    const io = new IntersectionObserver(([e]) => (e.isIntersecting ? start() : stop()));
    ro.observe(canvas);
    io.observe(canvas);
    return () => {
      stop();
      ro.disconnect();
      io.disconnect();
    };
  }, [color, lines, amplitude, speed]);

  return (
    <div className={`relative overflow-hidden ${className}`} style={{ background }}>
      <canvas ref={canvasRef} aria-hidden className="absolute inset-0 h-full w-full" />
      <div className="relative h-full">{children}</div>
    </div>
  );
}