Text Animation

// Shared motion tokens. Easing curves mirror the CSS custom properties in
// globals.css; springs are the canonical physics used across components.
// Strong custom variants — defaults like `ease-in`/`ease-out` feel weak.

export const EASE_OUT = [0.16, 1, 0.3, 1] as const;
export const EASE_IN_OUT = [0.77, 0, 0.175, 1] as const;
export const EASE_DRAWER = [0.32, 0.72, 0, 1] as const;

/** CSS string form of EASE_OUT for inline style transitions. */
export const EASE_OUT_CSS = "cubic-bezier(0.16, 1, 0.3, 1)";

/** Press feedback on buttons and other tappable surfaces. */
export const SPRING_PRESS = {
  type: "spring",
  stiffness: 500,
  damping: 30,
  mass: 0.6,
} as const;

/** Content swaps — label/icon slots trading places inside a control. */
export const SPRING_SWAP = {
  type: "spring",
  stiffness: 460,
  damping: 30,
  mass: 0.55,
} as const;

/** Overlay panel entrances — modals and sheets summoned by pointer. */
export const SPRING_PANEL = {
  type: "spring",
  stiffness: 420,
  damping: 40,
  mass: 0.5,
} as const;

/** Shared-layout glides — pills, indicators and panels morphing between positions. */
export const SPRING_LAYOUT = {
  type: "spring",
  stiffness: 360,
  damping: 32,
  mass: 0.6,
} as const;

/** Cursor-follow physics for decorative mouse tracking (magnetic, tilt, dock). */
export const SPRING_MOUSE = {
  stiffness: 200,
  damping: 15,
  mass: 0.3,
} as const;

/** Dragged handles and fills (sliders) — critically damped `useSpring` config,
 * so the value follows the pointer butterily and never rebounds off an end. */
export const SPRING_GLIDE = {
  stiffness: 700,
  damping: 50,
  mass: 0.5,
} as const;

import { clsx, type ClassValue } from "clsx"
import { twMerge } from "tailwind-merge"

export function cn(...inputs: ClassValue[]) {
  return twMerge(clsx(inputs))
}

"use client";
// beui.dev/components/motion/text-animation

import {
  type MotionStyle,
  motion,
  type UseInViewOptions,
  useInView,
  useReducedMotion,
} from "motion/react";
import { useCallback, useEffect, useRef, useState } from "react";
import { EASE_IN_OUT, EASE_OUT } from "@/lib/ease";
import { cn } from "@/lib/utils";

const CHROMATIC_PALETTE = [
  "#60a5fa",
  "#818cf8",
  "#c084fc",
  "#fb7185",
  "#fbbf24",
];

const TRAIL_HALF_WIDTH = 14;
const REVEAL_START = `-${TRAIL_HALF_WIDTH}%`;
const REVEAL_FINISH = `${100 + TRAIL_HALF_WIDTH}%`;

export type ChromaticTextRevealProps = {
  /** Sentence fragment that remains fixed while the final word changes. */
  prefix: string;
  /** Words revealed one after another after the fixed prefix. */
  words: string[];
  /** Colors used along the moving chromatic edge. */
  colors?: string[];
  /** Final text color after the sweep passes. */
  foregroundColor?: string;
  /** Sweep duration in seconds. */
  duration?: number;
  /** Delay before the first sweep, in seconds. */
  delay?: number;
  /** Rest after a word finishes revealing, in seconds. */
  pauseDuration?: number;
  /** Returns to the first word after the final word. */
  loop?: boolean;
  /** Starts when the text enters the viewport. */
  startOnView?: boolean;
  /** Only starts on the first viewport entry. */
  once?: boolean;
  /** IntersectionObserver root margin used by the viewport trigger. */
  inViewMargin?: UseInViewOptions["margin"];
  className?: string;
};

function composeChromaticGradient(colors: string[], foregroundColor: string) {
  const palette = colors.length > 0 ? colors : CHROMATIC_PALETTE;
  const colorStops = palette.map((color, index) => {
    const offset =
      palette.length === 1
        ? 0
        : -TRAIL_HALF_WIDTH +
          (index / (palette.length - 1)) * TRAIL_HALF_WIDTH * 2;
    const operator = offset < 0 ? "-" : "+";
    const distance = Number(Math.abs(offset).toFixed(2));
    return `${color} calc(var(--chromatic-sweep) ${operator} ${distance}%)`;
  });

  return `linear-gradient(90deg, ${foregroundColor} 0%, ${foregroundColor} calc(var(--chromatic-sweep) - ${TRAIL_HALF_WIDTH}%), ${colorStops.join(", ")}, transparent calc(var(--chromatic-sweep) + ${TRAIL_HALF_WIDTH}%), transparent 100%)`;
}

export function ChromaticTextReveal({
  prefix,
  words,
  colors = CHROMATIC_PALETTE,
  foregroundColor = "var(--foreground)",
  duration = 1.2,
  delay = 0,
  pauseDuration = 0.8,
  loop = true,
  startOnView = true,
  once = true,
  inViewMargin,
  className,
}: ChromaticTextRevealProps) {
  const ref = useRef<HTMLSpanElement>(null);
  const timerRef = useRef<number | null>(null);
  const [wordIndex, setWordIndex] = useState(0);
  const reduceMotion = useReducedMotion();
  const isInView = useInView(ref, {
    once,
    margin: inViewMargin,
    amount: 0.4,
  });
  const shouldReveal = !startOnView || isInView || reduceMotion;
  const backgroundImage = composeChromaticGradient(colors, foregroundColor);
  const hasWords = words.length > 0;
  const activeIndex = hasWords ? wordIndex % words.length : 0;
  const activeWord = words[activeIndex] ?? "";
  const sizingWords = Array.from(new Set(words));

  const clearPendingWord = useCallback(() => {
    if (timerRef.current !== null) {
      window.clearTimeout(timerRef.current);
      timerRef.current = null;
    }
  }, []);

  const scheduleNextWord = useCallback(() => {
    clearPendingWord();
    const isLastWord = activeIndex === words.length - 1;
    if (
      reduceMotion ||
      !shouldReveal ||
      words.length < 2 ||
      (isLastWord && !loop)
    ) {
      return;
    }

    timerRef.current = window.setTimeout(() => {
      setWordIndex((index) => (index + 1) % words.length);
    }, pauseDuration * 1000);
  }, [
    activeIndex,
    clearPendingWord,
    loop,
    pauseDuration,
    reduceMotion,
    shouldReveal,
    words.length,
  ]);

  useEffect(() => clearPendingWord, [clearPendingWord]);

  return (
    <span ref={ref} className={cn("inline-flex items-baseline", className)}>
      <span className="whitespace-nowrap">
        {prefix}
        {hasWords ? "\u00A0" : null}
      </span>
      {hasWords ? (
        <span className="relative inline-grid">
          {sizingWords.map((word) => (
            <span
              key={word}
              aria-hidden
              className="invisible col-start-1 row-start-1 whitespace-nowrap"
            >
              {word}
            </span>
          ))}
          {/* Moving a clipped text gradient defines this effect. Paint
              containment bounds that deliberate repaint to the active word. */}
          <motion.span
            key={`${activeWord}-${activeIndex}`}
            aria-hidden
            initial={
              reduceMotion
                ? false
                : {
                    opacity: 0.56,
                    filter: "blur(6px)",
                    transform: "translateY(5px)",
                  }
            }
            animate={{
              "--chromatic-sweep": shouldReveal
                ? REVEAL_FINISH
                : REVEAL_START,
              opacity: 1,
              filter: "blur(0px)",
              transform: "translateY(0px)",
            }}
            transition={{
              "--chromatic-sweep": reduceMotion
                ? { duration: 0 }
                : { duration, delay, ease: EASE_IN_OUT },
              opacity: reduceMotion
                ? { duration: 0 }
                : { duration: 0.28, ease: EASE_OUT },
              filter: reduceMotion
                ? { duration: 0 }
                : { duration: 0.36, ease: EASE_OUT },
              transform: reduceMotion
                ? { duration: 0 }
                : { duration: 0.36, ease: EASE_OUT },
            }}
            onAnimationComplete={scheduleNextWord}
            className="absolute start-0 top-0 whitespace-nowrap bg-clip-text text-transparent [background-image:var(--chromatic-gradient)] [contain:paint]"
            style={{
              "--chromatic-sweep": reduceMotion
                ? REVEAL_FINISH
                : REVEAL_START,
              "--chromatic-gradient": backgroundImage,
              backgroundSize: "100% 100%",
              backgroundRepeat: "no-repeat",
            } as MotionStyle}
          >
            {activeWord}
          </motion.span>
          <span className="sr-only">{activeWord}</span>
        </span>
      ) : null}
    </span>
  );
}

// Shared motion tokens. Easing curves mirror the CSS custom properties in
// globals.css; springs are the canonical physics used across components.
// Strong custom variants — defaults like `ease-in`/`ease-out` feel weak.

export const EASE_OUT = [0.16, 1, 0.3, 1] as const;
export const EASE_IN_OUT = [0.77, 0, 0.175, 1] as const;
export const EASE_DRAWER = [0.32, 0.72, 0, 1] as const;

/** CSS string form of EASE_OUT for inline style transitions. */
export const EASE_OUT_CSS = "cubic-bezier(0.16, 1, 0.3, 1)";

/** Press feedback on buttons and other tappable surfaces. */
export const SPRING_PRESS = {
  type: "spring",
  stiffness: 500,
  damping: 30,
  mass: 0.6,
} as const;

/** Content swaps — label/icon slots trading places inside a control. */
export const SPRING_SWAP = {
  type: "spring",
  stiffness: 460,
  damping: 30,
  mass: 0.55,
} as const;

/** Overlay panel entrances — modals and sheets summoned by pointer. */
export const SPRING_PANEL = {
  type: "spring",
  stiffness: 420,
  damping: 40,
  mass: 0.5,
} as const;

/** Shared-layout glides — pills, indicators and panels morphing between positions. */
export const SPRING_LAYOUT = {
  type: "spring",
  stiffness: 360,
  damping: 32,
  mass: 0.6,
} as const;

/** Cursor-follow physics for decorative mouse tracking (magnetic, tilt, dock). */
export const SPRING_MOUSE = {
  stiffness: 200,
  damping: 15,
  mass: 0.3,
} as const;

/** Dragged handles and fills (sliders) — critically damped `useSpring` config,
 * so the value follows the pointer butterily and never rebounds off an end. */
export const SPRING_GLIDE = {
  stiffness: 700,
  damping: 50,
  mass: 0.5,
} as const;

import { clsx, type ClassValue } from "clsx"
import { twMerge } from "tailwind-merge"

export function cn(...inputs: ClassValue[]) {
  return twMerge(clsx(inputs))
}

"use client";
// beui.dev/components/motion/text-animation

import { motion, type Transition, useInView, useReducedMotion } from "motion/react";
import { useRef, type ElementType, type ReactNode } from "react";
import { EASE_OUT } from "@/lib/ease";
import { cn } from "@/lib/utils";

type SplitMode = "word" | "char";

export interface TextRevealProps {
  text: string | string[];
  as?: ElementType;
  className?: string;
  split?: SplitMode;
  stagger?: number;
  delay?: number;
  blur?: number;
  yOffset?: string | number;
  spring?: { stiffness?: number; damping?: number; mass?: number };
  once?: boolean;
  whileInView?: boolean;
  children?: ReactNode;
}

const DEFAULT_SPRING = { stiffness: 140, damping: 26, mass: 1.2 };

export function TextReveal({
  text,
  as: Comp = "span",
  className,
  split = "word",
  stagger = 0.09,
  delay = 0,
  blur = 12,
  yOffset = "40%",
  spring,
  once = true,
  whileInView = false,
  children,
}: TextRevealProps) {
  const ref = useRef<HTMLElement>(null);
  const inView = useInView(ref, { once, amount: 0.4 });
  const reduce = useReducedMotion();
  const shouldAnimate = whileInView ? inView : true;

  const lines = Array.isArray(text) ? text : [text];
  const s = { ...DEFAULT_SPRING, ...spring };

  let unitIndex = 0;
  const lineCounts = new Map<string, number>();

  return (
    <Comp ref={ref} className={cn("block", className)}>
      {lines.map((line) => {
        const units = split === "word" ? line.split(" ") : Array.from(line);
        const lineCount = lineCounts.get(line) ?? 0;
        lineCounts.set(line, lineCount + 1);
        const lineKey = `${line}-${lineCount}`;
        const unitCounts = new Map<string, number>();

        return (
          <span key={lineKey} className="block">
            {units.map((unit, i) => {
              const d = delay + unitIndex * stagger;
              unitIndex += 1;
              const unitCount = unitCounts.get(unit) ?? 0;
              unitCounts.set(unit, unitCount + 1);
              const unitKey = `${unit}-${unitCount}`;
              const initial = reduce
                ? { opacity: 0 }
                : { y: yOffset, opacity: 0, filter: `blur(${blur}px)` };
              const animate = shouldAnimate
                ? reduce
                  ? { opacity: 1 }
                  : { y: 0, opacity: 1, filter: "blur(0px)" }
                : initial;
              const transition: Transition = reduce
                ? { opacity: { duration: 0.25, ease: EASE_OUT, delay: d * 0.3 } }
                : {
                    y: { type: "spring" as const, ...s, delay: d },
                    opacity: { duration: 0.7, ease: EASE_OUT, delay: d },
                    filter: { duration: 0.9, ease: EASE_OUT, delay: d },
                  };
              return (
                <motion.span
                  key={unitKey}
                  initial={initial}
                  animate={animate}
                  transition={transition}
                  className="inline-block will-change-transform"
                >
                  {unit}
                  {split === "word" && i < units.length - 1 ? (
                    <span className="inline-block">&nbsp;</span>
                  ) : null}
                </motion.span>
              );
            })}
          </span>
        );
      })}
      {children}
    </Comp>
  );
}

import type { CSSProperties } from "react";

export const TEXT_SHIMMER_KEYFRAMES =
  "@keyframes beui-text-shimmer{from{background-position:200% 0}to{background-position:-200% 0}}";

export const TEXT_SHIMMER_CLASS_NAME =
  "bg-[length:200%_100%] bg-clip-text text-transparent bg-[linear-gradient(110deg,var(--muted-foreground)_30%,var(--foreground)_50%,var(--muted-foreground)_70%)]";

export function textShimmerStyle(duration: number): CSSProperties {
  return {
    animation: `beui-text-shimmer ${duration}s linear infinite`,
  };
}

import { clsx, type ClassValue } from "clsx"
import { twMerge } from "tailwind-merge"

export function cn(...inputs: ClassValue[]) {
  return twMerge(clsx(inputs))
}

// beui.dev/components/motion/text-animation
import { cn } from "@/lib/utils";
import type { ElementType, ReactNode } from "react";
import {
  TEXT_SHIMMER_CLASS_NAME,
  TEXT_SHIMMER_KEYFRAMES,
  textShimmerStyle,
} from "@/lib/text-shimmer";

export interface TextShimmerProps {
  children: ReactNode;
  as?: ElementType;
  duration?: number;
  className?: string;
}

export function TextShimmer({ children, as: Comp = "span", duration = 2.5, className }: TextShimmerProps) {
  return (
    <>
      <style>
        {TEXT_SHIMMER_KEYFRAMES}
      </style>
      <Comp
        style={textShimmerStyle(duration)}
        className={cn(
          "inline-block",
          TEXT_SHIMMER_CLASS_NAME,
          className,
        )}
      >
        {children}
      </Comp>
    </>
  );
}

// Shared motion tokens. Easing curves mirror the CSS custom properties in
// globals.css; springs are the canonical physics used across components.
// Strong custom variants — defaults like `ease-in`/`ease-out` feel weak.

export const EASE_OUT = [0.16, 1, 0.3, 1] as const;
export const EASE_IN_OUT = [0.77, 0, 0.175, 1] as const;
export const EASE_DRAWER = [0.32, 0.72, 0, 1] as const;

/** CSS string form of EASE_OUT for inline style transitions. */
export const EASE_OUT_CSS = "cubic-bezier(0.16, 1, 0.3, 1)";

/** Press feedback on buttons and other tappable surfaces. */
export const SPRING_PRESS = {
  type: "spring",
  stiffness: 500,
  damping: 30,
  mass: 0.6,
} as const;

/** Content swaps — label/icon slots trading places inside a control. */
export const SPRING_SWAP = {
  type: "spring",
  stiffness: 460,
  damping: 30,
  mass: 0.55,
} as const;

/** Overlay panel entrances — modals and sheets summoned by pointer. */
export const SPRING_PANEL = {
  type: "spring",
  stiffness: 420,
  damping: 40,
  mass: 0.5,
} as const;

/** Shared-layout glides — pills, indicators and panels morphing between positions. */
export const SPRING_LAYOUT = {
  type: "spring",
  stiffness: 360,
  damping: 32,
  mass: 0.6,
} as const;

/** Cursor-follow physics for decorative mouse tracking (magnetic, tilt, dock). */
export const SPRING_MOUSE = {
  stiffness: 200,
  damping: 15,
  mass: 0.3,
} as const;

/** Dragged handles and fills (sliders) — critically damped `useSpring` config,
 * so the value follows the pointer butterily and never rebounds off an end. */
export const SPRING_GLIDE = {
  stiffness: 700,
  damping: 50,
  mass: 0.5,
} as const;

import { clsx, type ClassValue } from "clsx"
import { twMerge } from "tailwind-merge"

export function cn(...inputs: ClassValue[]) {
  return twMerge(clsx(inputs))
}

"use client";
// beui.dev/components/motion/text-animation

import { ActionSwapText } from "./action-swap";

export interface TextCascadeProps {
  /** Current text. Changing it cascades the letters to the new value. */
  text: string;
  className?: string;
}

/**
 * Letter-by-letter slot roll for standalone text — the old letters drop away
 * as the new ones land, left to right. Same motion as the action-swap
 * cascade variant, with a text-first API.
 */
export function TextCascade({ text, className }: TextCascadeProps) {
  return (
    <ActionSwapText value={text} animation="cascade" className={className}>
      {text}
    </ActionSwapText>
  );
}

"use client";

import { AnimatePresence, motion, useReducedMotion, type HTMLMotionProps, type Variants } from "motion/react";
import { useLayoutEffect, useRef, useState, type ReactNode } from "react";
import { EASE_OUT, EASE_OUT_CSS, SPRING_PRESS, SPRING_SWAP } from "@/lib/ease";
import { cn } from "@/lib/utils";

export type ActionSwapItem = {
  id: string;
  label: ReactNode;
  icon?: ReactNode;
  ariaLabel?: string;
};

export type ActionSwapButtonVariant = "primary" | "secondary" | "outline" | "ghost";
export type ActionSwapButtonSize = "sm" | "md" | "lg" | "icon";
export type ActionSwapAnimation = "blur" | "roll" | "cascade";

/** Animations with a single-element variant set (cascade animates per letter). */
type CoreAnimation = "blur" | "roll";

export interface ActionSwapButtonProps extends Omit<
  HTMLMotionProps<"button">,
  "children" | "onChange"
> {
  items: ActionSwapItem[];
  value?: string;
  defaultValue?: string;
  onValueChange?: (value: string, item: ActionSwapItem) => void;
  variant?: ActionSwapButtonVariant;
  size?: ActionSwapButtonSize;
  animation?: ActionSwapAnimation;
  iconOnly?: boolean;
  cycle?: boolean;
}

export interface ActionSwapTextProps {
  value: string;
  children: ReactNode;
  animation?: ActionSwapAnimation;
  className?: string;
}

export interface ActionSwapIconProps {
  value: string;
  children: ReactNode;
  animation?: ActionSwapAnimation;
  className?: string;
}

const BLUR_TRANSITION = { duration: 0.2, ease: "easeInOut" } as const;
const ROLL_TRANSITION = SPRING_SWAP;
const ROLL_EXIT_TRANSITION = { duration: 0.14, ease: EASE_OUT } as const;
const SWAP_BLUR = "blur(8px)";
const ROLL_BLUR = "blur(3px)";

// Cascade rolls the label one letter at a time, left to right. The leaving
// and landing strings overlap as independent layers (no shared cells), so
// proportional glyph widths never jitter. Exits cascade at half the enter
// stagger so the tail of the old label lingers briefly.
const CASCADE_STAGGER = 0.025;

const CASCADE_LETTER_VARIANTS: Variants = {
  initial: { opacity: 0, y: "105%", filter: ROLL_BLUR },
  animate: (delay: number = 0) => ({
    opacity: 1,
    y: "0%",
    filter: "blur(0px)",
    transition: { ...SPRING_SWAP, delay },
  }),
  exit: (delay: number = 0) => ({
    opacity: 0,
    y: "-105%",
    filter: ROLL_BLUR,
    transition: { duration: 0.16, ease: EASE_OUT, delay: delay * 0.5 },
  }),
};

const TEXT_VARIANTS: Record<CoreAnimation, Variants> = {
  blur: {
    initial: { opacity: 0, scale: 0.94, filter: SWAP_BLUR },
    animate: {
      opacity: 1,
      scale: 1,
      filter: "blur(0px)",
      transition: BLUR_TRANSITION,
    },
    exit: {
      opacity: 0,
      scale: 0.94,
      filter: SWAP_BLUR,
      transition: BLUR_TRANSITION,
    },
  },
  roll: {
    initial: { opacity: 0, y: "90%", filter: ROLL_BLUR },
    animate: {
      opacity: 1,
      y: "0%",
      filter: "blur(0px)",
      transition: ROLL_TRANSITION,
    },
    exit: {
      opacity: 0,
      y: "-90%",
      filter: ROLL_BLUR,
      transition: ROLL_EXIT_TRANSITION,
    },
  },
};

const ICON_VARIANTS: Record<CoreAnimation, Variants> = {
  blur: {
    initial: { opacity: 0, scale: 0.25, filter: SWAP_BLUR },
    animate: {
      opacity: 1,
      scale: 1,
      filter: "blur(0px)",
      transition: BLUR_TRANSITION,
    },
    exit: {
      opacity: 0,
      scale: 0.25,
      filter: SWAP_BLUR,
      transition: BLUR_TRANSITION,
    },
  },
  roll: {
    initial: { opacity: 0, y: 12, filter: ROLL_BLUR },
    animate: {
      opacity: 1,
      y: 0,
      filter: "blur(0px)",
      transition: ROLL_TRANSITION,
    },
    exit: {
      opacity: 0,
      y: -12,
      filter: ROLL_BLUR,
      transition: ROLL_EXIT_TRANSITION,
    },
  },
};

const VARIANT_CLASS: Record<ActionSwapButtonVariant, string> = {
  primary: "bg-primary text-primary-foreground hover:bg-primary/90",
  secondary: "border border-border bg-card text-foreground hover:border-border",
  outline: "border border-border bg-transparent text-foreground hover:bg-primary/5",
  ghost: "text-muted-foreground hover:bg-primary/5 hover:text-foreground",
};

const SIZE_CLASS: Record<ActionSwapButtonSize, string> = {
  sm: "h-8 gap-1.5 rounded-full px-3 text-xs",
  md: "h-10 gap-2 rounded-full px-4 text-sm",
  lg: "h-12 gap-2.5 rounded-full px-5 text-base",
  icon: "h-10 w-10 rounded-full",
};

export function ActionSwapText({
  value,
  children,
  animation = "blur",
  className,
}: ActionSwapTextProps) {
  const reduce = useReducedMotion();
  const measureRef = useRef<HTMLSpanElement>(null);
  const [width, setWidth] = useState<number>();

  useLayoutEffect(() => {
    const nextWidth = measureRef.current?.offsetWidth;
    if (!nextWidth) return;
    setWidth((currentWidth) => (currentWidth === nextWidth ? currentWidth : nextWidth));
  });

  // Cascade needs a plain string to split into letters; non-string content
  // and reduced motion fall back to the closest single-element animation.
  const label = typeof children === "string" ? children : null;
  const cascade = animation === "cascade" && label !== null && !reduce;
  const coreAnimation: CoreAnimation =
    animation === "cascade" ? "roll" : animation;

  return (
    <span
      className={cn("relative inline-block overflow-hidden whitespace-nowrap align-bottom", className)}
      style={{
        width,
        transition: reduce ? undefined : `width 220ms ${EASE_OUT_CSS}`,
      }}
    >
      <span
        ref={measureRef}
        aria-hidden
        className="invisible inline-block whitespace-nowrap"
      >
        {children}
      </span>
      {cascade ? (
        <>
          {/* Letters are decorative fragments; readers get the whole label. */}
          <span className="sr-only">{label}</span>
          <AnimatePresence initial={false}>
            <motion.span
              key={`cascade-${value}`}
              aria-hidden
              initial="initial"
              animate="animate"
              exit="exit"
              className="absolute left-0 top-0 inline-block whitespace-pre"
            >
              {label.split("").map((char, i) => (
                <motion.span
                  // biome-ignore lint/suspicious/noArrayIndexKey: position is the slot identity — the letter at a position is exactly what rolls.
                  key={i}
                  custom={i * CASCADE_STAGGER}
                  variants={CASCADE_LETTER_VARIANTS}
                  className="inline-block whitespace-pre will-change-[opacity,filter,transform]"
                >
                  {char}
                </motion.span>
              ))}
            </motion.span>
          </AnimatePresence>
        </>
      ) : (
        <AnimatePresence initial={false}>
          <motion.span
            key={`${animation}-${value}`}
            variants={TEXT_VARIANTS[coreAnimation]}
            initial={reduce ? false : "initial"}
            animate={reduce ? { opacity: 1, filter: "blur(0px)", scale: 1, y: 0 } : "animate"}
            exit={reduce ? undefined : "exit"}
            className="absolute left-0 top-0 inline-block will-change-[opacity,filter,transform]"
          >
            {children}
          </motion.span>
        </AnimatePresence>
      )}
    </span>
  );
}

export function ActionSwapIcon({
  value,
  children,
  animation = "blur",
  className,
}: ActionSwapIconProps) {
  const reduce = useReducedMotion();
  // Icons are single elements — cascade maps to its closest motion, roll.
  const coreAnimation: CoreAnimation =
    animation === "cascade" ? "roll" : animation;

  return (
    <span className={cn("relative inline-grid shrink-0 place-items-center overflow-hidden", className)}>
      <AnimatePresence mode="popLayout" initial={false}>
        <motion.span
          key={`${animation}-${value}`}
          aria-hidden
          variants={ICON_VARIANTS[coreAnimation]}
          initial={reduce ? false : "initial"}
          animate={reduce ? { opacity: 1, filter: "blur(0px)", scale: 1, y: 0 } : "animate"}
          exit={reduce ? undefined : "exit"}
          className="col-start-1 row-start-1 inline-flex items-center justify-center will-change-[opacity,filter,transform]"
        >
          {children}
        </motion.span>
      </AnimatePresence>
    </span>
  );
}

export function ActionSwapButton({
  items,
  value,
  defaultValue,
  onValueChange,
  variant = "secondary",
  size = "md",
  animation = "blur",
  iconOnly = size === "icon",
  cycle = true,
  className,
  disabled,
  onClick,
  ...rest
}: ActionSwapButtonProps) {
  const reduce = useReducedMotion();
  const [internalValue, setInternalValue] = useState(defaultValue ?? items[0]?.id);
  const currentValue = value ?? internalValue;
  const activeIndex = Math.max(0, items.findIndex((item) => item.id === currentValue));
  const activeItem = items[activeIndex] ?? items[0];
  const hasIcon = items.some((item) => item.icon);
  const nextItem = cycle && items.length > 0 ? items[(activeIndex + 1) % items.length] : undefined;

  if (!activeItem) return null;

  const accessibleLabel = activeItem.ariaLabel ?? (iconOnly && typeof activeItem.label === "string" ? activeItem.label : undefined);

  return (
    <motion.button
      type="button"
      disabled={disabled}
      whileTap={reduce || disabled ? undefined : { scale: 0.97 }}
      transition={SPRING_PRESS}
      className={cn(
        "inline-flex items-center justify-center overflow-hidden font-medium transition-colors",
        "disabled:pointer-events-none disabled:opacity-50",
        VARIANT_CLASS[variant],
        SIZE_CLASS[size],
        className,
      )}
      aria-label={accessibleLabel}
      onClick={(event) => {
        onClick?.(event);
        if (event.defaultPrevented || disabled || !cycle || !nextItem) return;
        if (value === undefined) setInternalValue(nextItem.id);
        onValueChange?.(nextItem.id, nextItem);
      }}
      {...rest}
    >
      {hasIcon ? (
        <ActionSwapIcon value={activeItem.id} animation={animation} className="h-4 w-4">
          {activeItem.icon ?? null}
        </ActionSwapIcon>
      ) : null}
      {!iconOnly ? (
        <ActionSwapText value={activeItem.id} animation={animation}>
          {activeItem.label}
        </ActionSwapText>
      ) : null}
    </motion.button>
  );
}