"use client";

import { useEffect, useRef, useState, type ReactNode } from "react";
import {
  motion,
  useInView,
  useReducedMotion as useReducedMotionRaw,
  useScroll,
  useSpring,
  useTransform,
  type Variants,
} from "motion/react";

/**
 * Motion's hook returns `boolean | null` — null until the media query
 * resolves. Narrow it to a plain boolean so callers can pass it straight
 * into props; an unresolved preference means "motion allowed".
 */
export function useReducedMotion(): boolean {
  return useReducedMotionRaw() === true;
}

const EASE_OUT = [0.22, 1, 0.36, 1] as const;
const EASE_MASK = [0.16, 1, 0.3, 1] as const;

/* ------------------------------------------------------------------ *
 * Reveal
 * ------------------------------------------------------------------ */

export function Reveal({
  children,
  delay = 0,
  className,
  y = 24,
}: {
  children: ReactNode;
  delay?: number;
  className?: string;
  y?: number;
}) {
  const reduced = useReducedMotion();

  return (
    <motion.div
      className={className}
      initial={reduced ? false : { opacity: 0, y }}
      whileInView={{ opacity: 1, y: 0 }}
      viewport={{ once: true, amount: 0.2, margin: "0px 0px -8% 0px" }}
      transition={{ duration: 0.7, delay, ease: EASE_OUT }}
    >
      {children}
    </motion.div>
  );
}

/** List-item variant, so Reveal never breaks <ul> semantics. */
export function RevealItem({
  children,
  delay = 0,
  className,
}: {
  children: ReactNode;
  delay?: number;
  className?: string;
}) {
  const reduced = useReducedMotion();

  return (
    <motion.li
      className={className}
      initial={reduced ? false : { opacity: 0, y: 24 }}
      whileInView={{ opacity: 1, y: 0 }}
      viewport={{ once: true, amount: 0.2, margin: "0px 0px -8% 0px" }}
      transition={{ duration: 0.7, delay, ease: EASE_OUT }}
    >
      {children}
    </motion.li>
  );
}

/* ------------------------------------------------------------------ *
 * MaskedWords — words rise from behind a clipping mask
 * ------------------------------------------------------------------ */

const lineVariants: Variants = {
  hidden: {},
  shown: { transition: { staggerChildren: 0.055, delayChildren: 0.05 } },
};

const wordVariants: Variants = {
  hidden: { y: "108%", rotate: 3, skewY: 2.5 },
  shown: {
    y: "0%",
    rotate: 0,
    skewY: 0,
    transition: { duration: 0.9, ease: EASE_MASK },
  },
};

export function MaskedWords({
  words,
  className = "",
  delay = 0,
}: {
  words: ReactNode[];
  className?: string;
  delay?: number;
}) {
  const reduced = useReducedMotion();

  if (reduced) {
    return (
      <span className={className}>
        {words.map((word, index) => (
          <span key={index}>
            {word}
            {index < words.length - 1 ? " " : ""}
          </span>
        ))}
      </span>
    );
  }

  return (
    <motion.span
      className={className}
      variants={lineVariants}
      initial="hidden"
      whileInView="shown"
      viewport={{ once: true, amount: 0.4 }}
      transition={{ delayChildren: delay }}
    >
      {words.map((word, index) => (
        <span
          key={index}
          className="inline-flex overflow-hidden pb-[0.12em] align-bottom"
        >
          <motion.span variants={wordVariants} className="inline-block">
            {word}
          </motion.span>
          {index < words.length - 1 ? <span className="w-[0.26em]" /> : null}
        </span>
      ))}
    </motion.span>
  );
}

/* ------------------------------------------------------------------ *
 * KineticHeadline — per-character entrance for the hero only
 * ------------------------------------------------------------------ */

const charVariants: Variants = {
  hidden: { opacity: 0, y: "70%", rotateX: -70 },
  shown: {
    opacity: 1,
    y: "0%",
    rotateX: 0,
    transition: { duration: 0.75, ease: EASE_MASK },
  },
};

/**
 * Splits a string into characters and tips each one up into place.
 * The visible text is aria-hidden and the whole line is relabelled,
 * so screen readers get the sentence, not a stream of letters.
 *
 * `gradient` keeps `.brand-text` on a single element so the amber fill
 * spans the whole word, and animates that element as one unit — per
 * character the gradient would restart on every letter, and the clipped
 * fill drops out under a 3D rotateX.
 */
export function KineticLine({
  text,
  className = "",
  delay = 0,
  stagger = 0.022,
  gradient = false,
}: {
  text: string;
  className?: string;
  delay?: number;
  stagger?: number;
  /** Fill the word with the amber gradient and animate it as one block. */
  gradient?: boolean;
}) {
  const reduced = useReducedMotion();

  if (reduced) {
    return (
      <span className={`${gradient ? "brand-text" : ""} ${className}`}>
        {text}
      </span>
    );
  }

  if (gradient) {
    return (
      <motion.span
        aria-hidden
        // 2D only: rotateX would break background-clip:text.
        className={`brand-text inline-block ${className}`}
        initial={{ opacity: 0, y: "55%" }}
        whileInView={{ opacity: 1, y: "0%" }}
        viewport={{ once: true, amount: 0.3 }}
        transition={{ duration: 0.75, delay, ease: EASE_MASK }}
      >
        {text}
      </motion.span>
    );
  }

  return (
    <motion.span
      aria-hidden
      className={`inline-block ${className}`}
      style={{ perspective: 600 }}
      variants={{
        hidden: {},
        shown: { transition: { staggerChildren: stagger, delayChildren: delay } },
      }}
      initial="hidden"
      whileInView="shown"
      viewport={{ once: true, amount: 0.3 }}
    >
      {Array.from(text).map((char, index) => (
        <motion.span
          key={index}
          variants={charVariants}
          className="inline-block origin-bottom"
          style={{ transformStyle: "preserve-3d" }}
        >
          {char === " " ? " " : char}
        </motion.span>
      ))}
    </motion.span>
  );
}

/* ------------------------------------------------------------------ *
 * ScrollTracking — letter-spacing tightens as the line scrolls through
 * ------------------------------------------------------------------ */

export function ScrollTracking({
  children,
  className = "",
  from = 0.06,
  to = -0.04,
}: {
  children: ReactNode;
  className?: string;
  /** Letter-spacing in em at entry and at exit. */
  from?: number;
  to?: number;
}) {
  const ref = useRef<HTMLDivElement>(null);
  const reduced = useReducedMotion();

  const { scrollYProgress } = useScroll({
    target: ref,
    offset: ["start end", "center center"],
  });
  const raw = useTransform(scrollYProgress, [0, 1], [from, to]);
  const spring = useSpring(raw, { stiffness: 90, damping: 24 });
  const letterSpacing = useTransform(spring, (v) => `${v}em`);

  return (
    <motion.div
      ref={ref}
      className={className}
      style={reduced ? undefined : { letterSpacing }}
    >
      {children}
    </motion.div>
  );
}

/* ------------------------------------------------------------------ *
 * ScrollStage — the section itself reacts to being scrolled past
 * ------------------------------------------------------------------ */

/**
 * Wraps a section so it rises and settles on entry, then recedes slightly
 * as it leaves — the scroll becomes the animation rather than a trigger
 * for one. Kept subtle on purpose: this runs on every section, so anything
 * stronger would read as the page wobbling.
 */
export function ScrollStage({
  children,
  className = "",
}: {
  children: ReactNode;
  className?: string;
}) {
  const ref = useRef<HTMLDivElement>(null);
  const reduced = useReducedMotion();

  const { scrollYProgress } = useScroll({
    target: ref,
    offset: ["start end", "end start"],
  });

  const scale = useSpring(
    useTransform(scrollYProgress, [0, 0.2, 0.8, 1], [0.97, 1, 1, 0.97]),
    { stiffness: 100, damping: 30, mass: 0.5 },
  );
  const opacity = useTransform(
    scrollYProgress,
    [0, 0.14, 0.86, 1],
    [0.55, 1, 1, 0.55],
  );

  return (
    <motion.div
      ref={ref}
      className={className}
      style={reduced ? undefined : { scale, opacity }}
    >
      {children}
    </motion.div>
  );
}

/* ------------------------------------------------------------------ *
 * Parallax
 * ------------------------------------------------------------------ */

export function Parallax({
  children,
  distance = 60,
  className,
}: {
  children: ReactNode;
  distance?: number;
  className?: string;
}) {
  const ref = useRef<HTMLDivElement>(null);
  const reduced = useReducedMotion();

  const { scrollYProgress } = useScroll({
    target: ref,
    offset: ["start end", "end start"],
  });

  const y = useSpring(
    useTransform(scrollYProgress, [0, 1], [distance, -distance]),
    { stiffness: 120, damping: 28, mass: 0.4 },
  );

  return (
    <motion.div ref={ref} className={className} style={reduced ? undefined : { y }}>
      {children}
    </motion.div>
  );
}

/* ------------------------------------------------------------------ *
 * Tilt
 * ------------------------------------------------------------------ */

export function Tilt({
  children,
  className,
  max = 5,
}: {
  children: ReactNode;
  className?: string;
  max?: number;
}) {
  const ref = useRef<HTMLDivElement>(null);
  const reduced = useReducedMotion();

  useEffect(() => {
    const node = ref.current;
    if (!node || reduced) return;
    if (!window.matchMedia("(hover: hover) and (pointer: fine)").matches) return;

    let frame = 0;

    const onMove = (event: PointerEvent) => {
      if (frame) return;
      frame = requestAnimationFrame(() => {
        frame = 0;
        const rect = node.getBoundingClientRect();
        const x = (event.clientX - rect.left) / rect.width - 0.5;
        const y = (event.clientY - rect.top) / rect.height - 0.5;
        node.style.transform = `perspective(1000px) rotateX(${(-y * max).toFixed(2)}deg) rotateY(${(x * max).toFixed(2)}deg)`;
      });
    };

    const onLeave = () => {
      if (frame) cancelAnimationFrame(frame);
      frame = 0;
      node.style.transform = "";
    };

    node.addEventListener("pointermove", onMove);
    node.addEventListener("pointerleave", onLeave);
    return () => {
      node.removeEventListener("pointermove", onMove);
      node.removeEventListener("pointerleave", onLeave);
      if (frame) cancelAnimationFrame(frame);
    };
  }, [max, reduced]);

  return (
    <div
      ref={ref}
      className={className}
      style={{ transition: "transform 0.4s cubic-bezier(0.22,1,0.36,1)" }}
    >
      {children}
    </div>
  );
}

/* ------------------------------------------------------------------ *
 * Counter
 * ------------------------------------------------------------------ */

export function Counter({
  to,
  suffix = "",
  prefix = "",
  decimals = 0,
  duration = 1400,
  className,
}: {
  to: number;
  suffix?: string;
  prefix?: string;
  decimals?: number;
  duration?: number;
  className?: string;
}) {
  const ref = useRef<HTMLSpanElement>(null);
  const reduced = useReducedMotion();
  const inView = useInView(ref, { once: true, amount: 0.4 });
  const [progressValue, setProgressValue] = useState(0);

  const value = reduced ? to : progressValue;

  useEffect(() => {
    if (!inView || reduced) return;

    let frame = 0;
    const start = performance.now();
    const tick = (now: number) => {
      const progress = Math.min((now - start) / duration, 1);
      const eased = progress === 1 ? 1 : 1 - Math.pow(2, -10 * progress);
      setProgressValue(to * eased);
      if (progress < 1) frame = requestAnimationFrame(tick);
    };
    frame = requestAnimationFrame(tick);
    return () => cancelAnimationFrame(frame);
  }, [inView, reduced, to, duration]);

  return (
    <span ref={ref} className={className}>
      {prefix}
      {value.toLocaleString("de-DE", {
        minimumFractionDigits: decimals,
        maximumFractionDigits: decimals,
      })}
      {suffix}
    </span>
  );
}

/* ------------------------------------------------------------------ *
 * ScrollProgress
 * ------------------------------------------------------------------ */

export function ScrollProgress() {
  const { scrollYProgress } = useScroll();
  const scaleX = useSpring(scrollYProgress, {
    stiffness: 180,
    damping: 32,
    restDelta: 0.001,
  });

  return (
    <motion.div
      aria-hidden
      className="fixed inset-x-0 top-0 z-[60] h-[3px] origin-left"
      style={{ scaleX, background: "var(--gradient-amber)" }}
    />
  );
}