"use client";

import { useEffect, useRef, useState, type KeyboardEvent, type PointerEvent } from "react";
import { useReducedMotion } from "motion/react";

type VenetianBlindsProps = {
  src: string;
  alt: string;
  /** Number of slats. */
  slats?: number;
  /** How far the slats sit tilted at the start, 0 shut to 1 open. */
  tilt?: number;
  /** How far hover opens them, 0 to 1. */
  peek?: number;
  /** Slat colour, light side. */
  wood?: string;
  className?: string;
};

const clamp = (v: number) => Math.min(1, Math.max(0, v));
const SHUT = 10;
const OPEN = 83;

/* VenetianBlinds: a window with real slats shut over the picture. Hover and they tip open in a wave from the pointer; pull the cord to set them, press to keep them open. */
export function VenetianBlinds({ src, alt, slats = 13, tilt = 0, peek = 0.82, wood = "#c79a63", className = "" }: VenetianBlindsProps) {
  const reduce = useReducedMotion();
  const stage = useRef<HTMLButtonElement>(null);
  const [cord, setCord] = useState(tilt);
  const [held, setHeld] = useState(false);
  const live = useRef({ now: Array.from({ length: slats }, () => tilt), goal: tilt, row: slats / 2 });
  const wake = useRef(() => {});

  useEffect(() => {
    const s = live.current;
    const box = stage.current!;
    const parts = [...box.querySelectorAll<HTMLElement>("[data-slat]")];
    const shades = [...box.querySelectorAll<HTMLElement>("[data-shade]")];
    s.now = Array.from({ length: parts.length }, (_, i) => s.now[i] ?? s.goal);
    let raf = 0;

    function paint() {
      parts.forEach((part, i) => {
        part.style.transform = `rotateX(${SHUT + (OPEN - SHUT) * s.now[i]}deg)`;
        shades[i].style.opacity = String(0.05 + s.now[i] * 0.55);
      });
    }

    function tick() {
      let moving = false;
      s.now = s.now.map((v, i) => {
        const near = Math.exp(-(((i - s.row) / parts.length) ** 2) * 16);
        const next = reduce ? s.goal : v + (s.goal - v) * (0.05 + near * 0.16);
        if (Math.abs(s.goal - next) > 0.002) moving = true;
        return moving ? next : s.goal;
      });
      paint();
      raf = moving ? requestAnimationFrame(tick) : 0;
    }

    wake.current = () => {
      if (!raf) raf = requestAnimationFrame(tick);
    };
    paint();
    return () => cancelAnimationFrame(raf);
  }, [slats, reduce]);

  function aim(goal: number) {
    live.current.goal = goal;
    wake.current();
  }

  function row(e: PointerEvent<HTMLElement>) {
    const box = e.currentTarget.getBoundingClientRect();
    live.current.row = ((e.clientY - box.top) / box.height) * slats;
  }

  function enter(e: PointerEvent<HTMLButtonElement>) {
    row(e);
    if (e.pointerType === "mouse" && !held) aim(Math.max(cord, peek));
  }

  function press() {
    const next = !held;
    setHeld(next);
    aim(next ? 1 : cord);
  }

  function pull(v: number) {
    const value = clamp(v);
    setCord(value);
    setHeld(false);
    live.current.row = slats / 2;
    aim(value);
  }

  function drag(e: PointerEvent<HTMLElement>) {
    if (e.buttons !== 1) return;
    const box = stage.current!.getBoundingClientRect();
    pull(((e.clientY - box.top) / box.height - 0.26) / 0.56);
  }

  function keys(e: KeyboardEvent) {
    const to = { ArrowDown: cord + 0.1, ArrowRight: cord + 0.1, ArrowUp: cord - 0.1, ArrowLeft: cord - 0.1, Home: 0, End: 1 }[e.key];
    if (to === undefined) return;
    e.preventDefault();
    pull(to);
  }

  return (
    <div className={`@container w-[26rem] ${className}`}>
      <div className="relative rounded-[0.18em] bg-[linear-gradient(135deg,#f1ece1,#cfc7b6)] p-[0.5em] text-[4cqw] shadow-[0_0.7em_1.4em_-0.6em_rgba(0,0,0,0.75)]">
        <div className="relative shadow-[inset_0_0_0_0.06em_rgba(0,0,0,0.5)]">
          <span aria-hidden className="absolute inset-x-[-0.12em] top-0 z-20 block h-[0.72em] rounded-[0.08em] bg-[linear-gradient(180deg,#f7f3ea,#b9b1a0_70%,#8e8675)] shadow-[0_0.1em_0.2em_rgba(0,0,0,0.5)]" />
          <button
            ref={stage}
            type="button"
            aria-pressed={held}
            aria-label={`${alt}. ${held ? "Let the blinds fall back" : "Keep the blinds open"}`}
            onPointerEnter={enter}
            onPointerMove={row}
            onPointerLeave={() => !held && aim(cord)}
            onClick={press}
            className="relative block aspect-[4/3] w-full cursor-pointer touch-pan-y overflow-hidden bg-[#10100f] outline-none [perspective:30em] focus-visible:ring-[0.14em] focus-visible:ring-inset focus-visible:ring-[#ffcb6b]"
          >
            <img src={src} alt="" draggable={false} className="absolute inset-0 size-full object-cover" />
            <span aria-hidden className="absolute inset-0 block bg-[radial-gradient(ellipse_at_center,transparent_45%,rgba(0,0,0,0.3))]" />
            {Array.from({ length: slats }, (_, i) => (
              <span
                key={i}
                data-slat
                aria-hidden
                className="absolute inset-x-0 block overflow-hidden shadow-[0_0.05em_0.05em_rgba(0,0,0,0.45)] will-change-transform"
                style={{
                  top: `${((i + 0.5) * 100) / slats}%`,
                  height: `${108 / slats}%`,
                  marginTop: `${-54 / slats}%`,
                  backgroundColor: wood,
                  backgroundImage: "linear-gradient(180deg,rgba(255,255,255,0.3),rgba(255,255,255,0.02) 38%,rgba(0,0,0,0.26)),repeating-linear-gradient(90deg,rgba(70,35,10,0.1) 0 0.07em,transparent 0.07em 0.33em)",
                }}
              >
                <span data-shade className="absolute inset-0 block bg-black" />
              </span>
            ))}
            <span aria-hidden className="absolute inset-y-0 left-[17%] block w-[0.05em] bg-[#efe9dc]/70" />
            <span aria-hidden className="absolute inset-y-0 right-[17%] block w-[0.05em] bg-[#efe9dc]/70" />
          </button>
          <span aria-hidden className="absolute inset-x-0 bottom-0 z-10 block h-[0.34em] bg-[linear-gradient(180deg,#e7e1d3,#a79f8e)] shadow-[0_-0.05em_0.14em_rgba(0,0,0,0.4)]" />
          <span
            role="slider"
            tabIndex={0}
            aria-label="Blind cord"
            aria-orientation="vertical"
            aria-valuemin={0}
            aria-valuemax={100}
            aria-valuenow={Math.round(cord * 100)}
            onPointerDown={(e) => {
              e.currentTarget.setPointerCapture(e.pointerId);
              drag(e);
            }}
            onPointerMove={drag}
            onKeyDown={keys}
            className="absolute z-30 flex w-[1.5em] -translate-x-1/2 cursor-ns-resize touch-none flex-col items-center outline-none focus-visible:rounded-sm focus-visible:ring-[0.1em] focus-visible:ring-[#ffcb6b]"
            style={{ left: "92%", top: "0.5em", height: `calc(${24 + cord * 56}% + 1.1em)` }}
          >
            <span aria-hidden className="block w-[0.07em] flex-1 bg-[#ece6d8] shadow-[0.04em_0_0.05em_rgba(0,0,0,0.5)]" />
            <span aria-hidden className="block h-[1em] w-[0.56em] rounded-[50%_50%_44%_44%/30%_30%_70%_70%] bg-[radial-gradient(circle_at_35%_30%,#f6d9a4,#a4682c_62%,#5f3714)] shadow-[0.04em_0.08em_0.12em_rgba(0,0,0,0.6)]" />
          </span>
        </div>
      </div>
    </div>
  );
}