"use client";

import { useState, type CSSProperties, type KeyboardEvent, type MouseEvent } from "react";
import { motion, stagger, useAnimate, useReducedMotion } from "motion/react";

const STAR = "M12 2.6l2.9 5.9 6.5.9-4.7 4.6 1.1 6.5-5.8-3.1-5.8 3.1 1.1-6.5L2.6 9.4l6.5-.9z";

type RatingStarsProps = {
  /** Current rating. Leave out to let the stars keep their own. */
  value?: number;
  /** Rating at the start when `value` is left out. */
  defaultValue?: number;
  /** Called with the new rating. 0 means cleared. */
  onChange?: (value: number) => void;
  /** Number of stars. */
  max?: number;
  /** 0.5 lets people pick half stars. */
  step?: 0.5 | 1;
  /** Only shows the rating. Takes any fraction, like 4.3. */
  readOnly?: boolean;
  /** One star in pixels. */
  size?: number;
  /** What the rating is for, read by screen readers. */
  label?: string;
  /** Filled star colour. */
  accent?: string;
  /** Empty star colour, as a text colour class. */
  className?: string;
};

/* RatingStars: stars fill under the pointer as a preview, and a pick runs a small pop along them with a ring off the last one. */
export function RatingStars({
  value,
  defaultValue = 0,
  onChange,
  max = 5,
  step = 1,
  readOnly = false,
  size = 36,
  label = "Rating",
  accent = "#fbbf24",
  className = "text-white/20",
}: RatingStarsProps) {
  const reduce = useReducedMotion();
  const [scope, run] = useAnimate<HTMLDivElement>();
  const [own, setOwn] = useState(defaultValue);
  const [hover, setHover] = useState<number | null>(null);
  const [ring, setRing] = useState({ star: 0, key: 0 });
  const current = value ?? own;
  const shown = hover ?? current;
  const spoken = current ? `${current} out of ${max}` : "No rating";

  const commit = (next: number) => {
    setOwn(next);
    onChange?.(next);
    if (reduce || !next) return;
    const star = Math.ceil(next);
    setRing((now) => ({ star, key: now.key + 1 }));
    run(`[data-star]:nth-child(-n+${star})`, { scale: [1, 1.28, 1] }, { duration: 0.32, delay: stagger(0.035) });
  };

  const under = (e: MouseEvent<HTMLDivElement>) => {
    const box = e.currentTarget.getBoundingClientRect();
    return Math.min(max, Math.max(step, Math.ceil(((e.clientX - box.left) / box.width) * (max / step)) * step));
  };

  const onKey = (e: KeyboardEvent<HTMLDivElement>) => {
    const moves: Record<string, number> = { ArrowRight: current + step, ArrowUp: current + step, ArrowLeft: current - step, ArrowDown: current - step, Home: 0, End: max };
    if (!(e.key in moves)) return;
    e.preventDefault();
    const next = Math.min(max, Math.max(0, moves[e.key]));
    if (next !== current) commit(next);
  };

  const pick = (e: MouseEvent<HTMLDivElement>) => {
    const next = under(e);
    commit(next === current ? 0 : next);
  };

  const input = readOnly
    ? { role: "img", "aria-label": `${label}: ${spoken}` }
    : {
        role: "slider",
        tabIndex: 0,
        "aria-label": label,
        "aria-valuemin": 0,
        "aria-valuemax": max,
        "aria-valuenow": current,
        "aria-valuetext": spoken,
        onKeyDown: onKey,
        onPointerMove: (e: MouseEvent<HTMLDivElement>) => setHover(under(e)),
        onPointerLeave: () => setHover(null),
        onPointerCancel: () => setHover(null),
        onClick: pick,
      };

  return (
    <div
      ref={scope}
      {...input}
      style={{ "--rs": accent, width: size * max, height: size } as CSSProperties}
      className={`relative flex max-w-full rounded-lg outline-none focus-visible:ring-2 focus-visible:ring-white/70 ${readOnly ? "" : "cursor-pointer touch-pan-y"} ${className}`}
    >
      {Array.from({ length: max }, (_, i) => {
        const fill = Math.min(1, Math.max(0, shown - i));
        return (
          <span key={i} data-star className="relative block shrink-0" style={{ width: size, height: size }}>
            <svg aria-hidden viewBox="0 0 24 24" className="absolute inset-0 size-full fill-current">
              <path d={STAR} />
            </svg>
            <motion.svg
              aria-hidden
              viewBox="0 0 24 24"
              className="absolute inset-0 size-full fill-(--rs)"
              initial={false}
              animate={{ clipPath: `inset(0 ${100 - fill * 100}% 0 0)` }}
              transition={{ duration: reduce ? 0 : 0.16, ease: "easeOut" }}
            >
              <path d={STAR} />
            </motion.svg>
          </span>
        );
      })}
      {ring.key > 0 && !reduce && (
        <motion.span
          key={ring.key}
          aria-hidden
          className="pointer-events-none absolute top-0 rounded-full border-2 border-(--rs)"
          style={{ left: (ring.star - 1) * size, width: size, height: size }}
          initial={{ scale: 0.5, opacity: 0.7 }}
          animate={{ scale: 1.5, opacity: 0 }}
          transition={{ duration: 0.5, ease: "easeOut" }}
        />
      )}
    </div>
  );
}