"use client";

import { useEffect, useId, useRef, useState, type CSSProperties, type ElementType, type KeyboardEvent, type ReactNode } from "react";
import { AnimatePresence, motion, useReducedMotion } from "motion/react";

export type ProductShowcaseFeature = {
  title: string;
  text: string;
  /** Fills the stage. An image with object-cover works well. */
  media: ReactNode;
  /** Where the marker sits on the stage, in percent. Leave out for no marker. */
  spot?: { x: number; y: number };
};

type ProductShowcaseProps = {
  features: ProductShowcaseFeature[];
  title?: string;
  /** Small line above the title. */
  eyebrow?: string;
  subtitle?: string;
  /** Seconds on each feature. 0 turns the auto tour off. */
  interval?: number;
  /** Colour of the marker and the active feature. */
  color?: string;
  /** Stage colour. */
  tile?: string;
  /** Put the stage on the right. */
  reverse?: boolean;
  /** h2 by default. */
  headingAs?: ElementType;
  /** Set padding and colours here. */
  className?: string;
};

/* ProductShowcase: one product stage beside a list of features. Each feature changes the view and moves a marker to the part it talks about. The tour runs by itself until someone picks a feature; it waits on hover, on focus and off screen. */
export function ProductShowcase({
  features,
  title,
  eyebrow,
  subtitle,
  interval = 6,
  color = "#a78bfa",
  tile = "#15122a",
  reverse = false,
  headingAs: Heading = "h2",
  className = "bg-[#0b0a14] px-5 py-16 text-white",
}: ProductShowcaseProps) {
  const reduce = useReducedMotion();
  const id = useId();
  const box = useRef<HTMLElement>(null);
  const bar = useRef<HTMLSpanElement>(null);
  const tabs = useRef<(HTMLButtonElement | null)[]>([]);
  const timer = useRef<Animation | null>(null);
  const held = useRef({ hover: false, focus: false, away: true });
  const [active, setActive] = useState(0);
  const [touring, setTouring] = useState(true);
  const tour = touring && interval > 0 && !reduce;
  const count = features.length;
  const spot = features[active].spot;

  const hold = (key: "hover" | "focus" | "away", on: boolean) => {
    held.current[key] = on;
    const { hover, focus, away } = held.current;
    if (hover || focus || away) timer.current?.pause();
    else timer.current?.play();
  };

  useEffect(() => {
    const line = bar.current;
    if (!tour || !line) return;
    const run = line.animate([{ transform: "scaleX(0)" }, { transform: "scaleX(1)" }], { duration: interval * 1000, fill: "forwards" });
    run.onfinish = () => setActive((now) => (now + 1) % count);
    timer.current = run;
    const { hover, focus, away } = held.current;
    if (hover || focus || away) run.pause();
    return () => {
      run.cancel();
      timer.current = null;
    };
  }, [active, count, interval, tour]);

  useEffect(() => {
    const section = box.current;
    if (!section) return;
    const onScreen = new IntersectionObserver(
      ([entry]) => {
        held.current.away = !entry.isIntersecting;
        const { hover, focus, away } = held.current;
        if (hover || focus || away) timer.current?.pause();
        else timer.current?.play();
      },
      { threshold: 0.2 },
    );
    onScreen.observe(section);
    return () => onScreen.disconnect();
  }, []);

  const pick = (i: number) => {
    setTouring(false);
    setActive(i);
  };
  const keys = (e: KeyboardEvent, i: number) => {
    const step = { ArrowDown: 1, ArrowRight: 1, ArrowUp: -1, ArrowLeft: -1 }[e.key];
    const to = step ? (i + step + count) % count : e.key === "Home" ? 0 : e.key === "End" ? count - 1 : -1;
    if (to < 0) return;
    e.preventDefault();
    pick(to);
    tabs.current[to]?.focus();
  };

  return (
    <section
      ref={box}
      aria-labelledby={title ? id : undefined}
      onPointerEnter={(e) => e.pointerType === "mouse" && hold("hover", true)}
      onPointerLeave={() => hold("hover", false)}
      onFocus={() => hold("focus", true)}
      onBlur={() => hold("focus", false)}
      className={`@container ${className}`}
      style={{ "--ps-color": color } as CSSProperties}
    >
      {title && (
        <header className="mx-auto mb-8 max-w-2xl text-center">
          {eyebrow && <p className="mb-2 text-xs font-medium tracking-[0.2em] uppercase opacity-70">{eyebrow}</p>}
          <Heading id={id} className="text-[clamp(1.5rem,6cqw,2.5rem)] leading-tight font-semibold tracking-tight text-balance">
            {title}
          </Heading>
          {subtitle && <p className="mt-3 text-pretty opacity-70">{subtitle}</p>}
        </header>
      )}
      <div className="mx-auto grid max-w-6xl items-center gap-5 @3xl:grid-cols-[minmax(0,3fr)_minmax(0,2fr)] @3xl:gap-10">
        <div
          id={`${id}-panel`}
          role="tabpanel"
          aria-labelledby={`${id}-tab-${active}`}
          className={`relative aspect-[16/10] overflow-hidden rounded-2xl border border-current/10 ${reverse ? "@3xl:order-2" : ""}`}
          style={{ backgroundColor: tile }}
        >
          <AnimatePresence initial={false}>
            <motion.div
              key={active}
              className="absolute inset-0 *:size-full"
              initial={reduce ? { opacity: 0 } : { opacity: 0, scale: 1.05 }}
              animate={reduce ? { opacity: 1 } : { opacity: 1, scale: 1 }}
              exit={{ opacity: 0 }}
              transition={{ duration: reduce ? 0 : 0.6, ease: [0.16, 1, 0.3, 1] }}
            >
              {features[active].media}
            </motion.div>
          </AnimatePresence>
          {spot && (
            <motion.span
              aria-hidden
              className="absolute -mt-3 -ml-3 grid size-6 place-items-center"
              initial={false}
              animate={{ left: `${spot.x}%`, top: `${spot.y}%` }}
              transition={reduce ? { duration: 0 } : { type: "spring", stiffness: 110, damping: 17 }}
            >
              <span className="absolute inset-0 animate-ping rounded-full bg-[var(--ps-color)] opacity-50 motion-reduce:hidden" />
              <span className="size-3 rounded-full border-2 border-white bg-[var(--ps-color)] shadow" />
            </motion.span>
          )}
        </div>
        <div role="tablist" aria-orientation="vertical" aria-label={title ?? "Features"} className="grid gap-1">
          {features.map((feature, i) => {
            const on = i === active;
            return (
              <button
                key={feature.title}
                ref={(el) => {
                  tabs.current[i] = el;
                }}
                id={`${id}-tab-${i}`}
                type="button"
                role="tab"
                aria-selected={on}
                aria-controls={`${id}-panel`}
                tabIndex={on ? 0 : -1}
                onClick={() => pick(i)}
                onKeyDown={(e) => keys(e, i)}
                className="relative overflow-hidden rounded-xl px-4 py-3 text-left transition-colors hover:bg-current/5"
              >
                <span className={`block font-semibold transition-opacity ${on ? "" : "opacity-60"}`}>{feature.title}</span>
                <span className="grid transition-[grid-template-rows] duration-300 motion-reduce:transition-none" style={{ gridTemplateRows: on ? "1fr" : "0fr" }}>
                  <span className="min-h-0 overflow-hidden">
                    <span className="block pt-1 text-sm text-pretty opacity-70">{feature.text}</span>
                  </span>
                </span>
                {on && (
                  <span aria-hidden className="absolute inset-x-4 bottom-0 h-0.5 overflow-hidden rounded-full bg-current/10">
                    <span ref={bar} className={`block h-full origin-left bg-[var(--ps-color)] ${tour ? "" : "hidden"}`} />
                  </span>
                )}
              </button>
            );
          })}
        </div>
      </div>
    </section>
  );
}