"use client";

import { useRef, useState, type ReactNode } from "react";
import { motion, useReducedMotion } from "motion/react";

type RippleCoreProps = {
  children: ReactNode;
  className?: string;
  onClick?: () => void;
  /** Colour of the ripple. */
  color?: string;
  /** Seconds one ripple lasts. */
  duration?: number;
};

type Ripple = { id: number; x: number; y: number; r: number };

/* RippleCore: every press sends a ripple out from the exact point you touched. Keyboard presses ripple from the centre. */
export function RippleCore({
  children,
  className = "rounded-xl bg-[#a78bfa] px-9 py-4 text-[15px] font-medium text-[#1a1530]",
  onClick,
  color = "rgba(255,255,255,0.55)",
  duration = 0.6,
}: RippleCoreProps) {
  const reduce = useReducedMotion();
  const [ripples, setRipples] = useState<Ripple[]>([]);
  const next = useRef(0);

  const add = (el: HTMLElement, x: number, y: number) => {
    if (reduce) return;
    const { width: w, height: h } = el.getBoundingClientRect();
    const r = Math.hypot(Math.max(x, w - x), Math.max(y, h - y));
    setRipples((rs) => [...rs, { id: next.current++, x, y, r }]);
  };

  return (
    <button
      type="button"
      onPointerDown={(e) => {
        const b = e.currentTarget.getBoundingClientRect();
        add(e.currentTarget, e.clientX - b.left, e.clientY - b.top);
      }}
      onClick={(e) => {
        // detail 0 = Enter or Space, not a pointer.
        if (e.detail === 0) {
          const b = e.currentTarget.getBoundingClientRect();
          add(e.currentTarget, b.width / 2, b.height / 2);
        }
        onClick?.();
      }}
      className={`relative isolate overflow-hidden ${className}`}
    >
      {ripples.map((p) => (
        <motion.span
          key={p.id}
          aria-hidden
          className="pointer-events-none absolute -z-10 rounded-full"
          style={{ left: p.x - p.r, top: p.y - p.r, width: p.r * 2, height: p.r * 2, background: color }}
          initial={{ scale: 0, opacity: 1 }}
          animate={{ scale: 1, opacity: 0 }}
          transition={{ duration, ease: [0.22, 1, 0.36, 1] }}
          onAnimationComplete={() => setRipples((rs) => rs.filter((r) => r.id !== p.id))}
        />
      ))}
      <span className="relative">{children}</span>
    </button>
  );
}