"use client";

import { useId, useRef, useState } from "react";
import { animate, motion, useMotionValue, useReducedMotion, useTransform } from "motion/react";

export type ShutterIrisImage = { src: string; alt: string };

type ShutterIrisProps = {
  images: ShutterIrisImage[];
  /** How open the iris sits at rest, 0 to 1. */
  rest?: number;
  /** How open it goes on hover and focus, 0 to 1. */
  wide?: number;
  /** Number of metal blades, 5 to 12. */
  blades?: number;
  /** Called with the new picture's index after each shot. */
  onShoot?: (index: number) => void;
  className?: string;
};

const SIZE = 400;
const MID = SIZE / 2;
const FAR = 460;
const STOPS = ["1.4", "2", "2.8", "4", "5.6", "8", "11", "16"];
const GAP = 42;
const SPRING = { type: "spring", stiffness: 170, damping: 19 } as const;

function point(a: number, d: number, x = MID, y = MID): [number, number] {
  return [x + Math.cos(a) * d, y + Math.sin(a) * d];
}

const line = (p: [number, number]) => `${p[0].toFixed(1)} ${p[1].toFixed(1)}`;

/* Each blade is one big rectangle whose inner side is an edge of the opening, so the rectangles together leave a true polygon that twists as it closes. */
function iris(open: number, n: number) {
  const r = Math.max(0, open) * 158;
  const twist = 1.25 * (1 - open);
  let metal = "";
  let edges = "";
  for (let i = 0; i < n; i++) {
    const a = twist + (i * Math.PI * 2) / n;
    const out = a + Math.PI / n;
    const along = out + Math.PI / 2;
    const p = point(a, r);
    const q = point(along, FAR, p[0], p[1]);
    metal += `M${line(p)}L${line(q)}L${line(point(out, FAR, q[0], q[1]))}L${line(point(out, FAR, p[0], p[1]))}Z`;
    edges += `M${line(p)}L${line(q)}`;
  }
  return { metal, edges };
}

/* ShutterIris: a camera lens seen from the front, the picture small behind the iris. Hover opens the blades, press fires the shutter and loads the next picture. */
export function ShutterIris({ images, rest = 0.3, wide = 0.97, blades = 7, onShoot, className = "" }: ShutterIrisProps) {
  const reduce = useReducedMotion();
  const id = useId();
  const n = Math.min(12, Math.max(5, blades));
  const [shot, setShot] = useState(0);
  const near = useRef(false);
  const firing = useRef(false);
  const open = useMotionValue(rest);
  const metal = useTransform(open, (v) => iris(v, n).metal);
  const edges = useTransform(open, (v) => iris(v, n).edges);
  const turn = useTransform(open, (v) => -GAP * Math.min(STOPS.length - 1, Math.max(0, 2 * Math.log2(0.97 / Math.max(0.01, v)))));

  function settle() {
    const goal = near.current ? wide : rest;
    if (reduce) open.set(goal);
    else animate(open, goal, SPRING);
  }

  function hover(on: boolean) {
    near.current = on;
    if (!firing.current) settle();
  }

  function next() {
    const to = (shot + 1) % images.length;
    setShot(to);
    onShoot?.(to);
  }

  async function fire() {
    if (firing.current) return;
    if (reduce) return next();
    firing.current = true;
    await animate(open, 0, { duration: 0.1, ease: "easeIn" });
    next();
    await new Promise((done) => setTimeout(done, 70));
    firing.current = false;
    settle();
  }

  return (
    <div className={`@container w-80 ${className}`}>
      <button
        type="button"
        aria-label={`${images[shot].alt}. Fire the shutter for the next picture`}
        onPointerEnter={(e) => e.pointerType === "mouse" && hover(true)}
        onPointerLeave={() => hover(false)}
        onFocus={(e) => e.currentTarget.matches(":focus-visible") && hover(true)}
        onBlur={() => hover(false)}
        onClick={fire}
        style={{ borderRadius: "50%" }}
        className="relative block aspect-square w-full rounded-full outline-none focus-visible:ring-[1cqw] focus-visible:ring-[#e8c15a] focus-visible:ring-offset-[1cqw] focus-visible:ring-offset-black"
      >
        <span className="absolute inset-[10%] overflow-hidden rounded-full bg-black">
          {images.map((image, i) => (
            <img key={image.src} src={image.src} alt="" draggable={false} className={`absolute inset-0 size-full object-cover ${i === shot ? "" : "opacity-0"}`} />
          ))}
        </span>

        <svg aria-hidden viewBox={`0 0 ${SIZE} ${SIZE}`} className="absolute inset-0 size-full">
          <defs>
            <clipPath id={`${id}c`}>
              <circle cx={MID} cy={MID} r="161" />
            </clipPath>
            <radialGradient id={`${id}m`} gradientUnits="userSpaceOnUse" cx={MID} cy={MID} r="170">
              <stop offset="0" stopColor="#3b3d44" />
              <stop offset="0.55" stopColor="#23252b" />
              <stop offset="1" stopColor="#0d0e11" />
            </radialGradient>
            <linearGradient id={`${id}b`} x1="0" y1="0" x2="1" y2="1">
              <stop offset="0" stopColor="#40424a" />
              <stop offset="0.5" stopColor="#141519" />
              <stop offset="1" stopColor="#2c2e34" />
            </linearGradient>
          </defs>
          <circle cx={MID} cy={MID} r="179" fill="none" stroke="#0a0a0c" strokeWidth="37" />
          <circle cx={MID} cy={MID} r="192" fill="none" stroke="#2d2f35" strokeWidth="11" strokeDasharray="3 3.2" />
          <circle cx={MID} cy={MID} r="166" fill="none" stroke={`url(#${id}b)`} strokeWidth="11" />
          <g clipPath={`url(#${id}c)`}>
            <motion.path d={metal} fill={`url(#${id}m)`} />
            <motion.path d={edges} fill="none" stroke="#000" strokeOpacity="0.5" strokeWidth="11" />
            <motion.path d={edges} fill="none" stroke="#83868f" strokeOpacity="0.75" strokeWidth="1.2" />
          </g>
          <circle cx={MID} cy={MID} r="161" fill="none" stroke="#000" strokeWidth="5" />
        </svg>

        <motion.svg aria-hidden viewBox={`0 0 ${SIZE} ${SIZE}`} style={{ rotate: turn }} className="absolute inset-0 size-full">
          {STOPS.map((stop, i) => (
            <text key={stop} x={MID} y={MID - 174} transform={`rotate(${i * GAP} ${MID} ${MID})`} fill={i < 2 ? "#e8c15a" : "#e7e3d6"} fontSize="13" fontFamily="ui-monospace, monospace" textAnchor="middle">{stop}</text>
          ))}
        </motion.svg>

        <svg aria-hidden viewBox={`0 0 ${SIZE} ${SIZE}`} className="pointer-events-none absolute inset-0 size-full">
          <path d={`M${MID - 6} 3L${MID + 6} 3L${MID} 13Z`} fill="#e8c15a" />
          <path id={`${id}t`} d={`M${MID - 164} ${MID}A164 164 0 0 0 ${MID + 164} ${MID}`} fill="none" />
          <text fill="#8f8f96" fontSize="7.5" fontFamily="ui-monospace, monospace" letterSpacing="2.5" textAnchor="middle">
            <textPath href={`#${id}t`} startOffset="50%">50 mm  1:1.4</textPath>
          </text>
        </svg>

        <span className="pointer-events-none absolute inset-[10%] rounded-full bg-[radial-gradient(ellipse_at_32%_24%,rgba(190,215,255,0.34),transparent_30%),radial-gradient(ellipse_at_72%_78%,rgba(255,170,120,0.16),transparent_26%)]" />
      </button>
    </div>
  );
}