Reveal

"use client";
import { motion, useReducedMotion } from "motion/react";
import * as React from "react";
import { buildReveal, type RevealVariant } from "./presets";
import { useRevealIntensity } from "./reveal-config";

const MOTION_TAGS = {
  div: motion.div,
  section: motion.section,
  article: motion.article,
  h2: motion.h2,
  h3: motion.h3,
  p: motion.p,
  li: motion.li,
  ul: motion.ul,
  span: motion.span,
  figure: motion.figure,
} as const;

export type RevealTag = keyof typeof MOTION_TAGS;

const useIsoLayoutEffect =
  typeof window !== "undefined" ? React.useLayoutEffect : React.useEffect;

function assignRef<T>(ref: React.Ref<T> | undefined, node: T | null) {
  if (typeof ref === "function") ref(node);
  else if (ref) (ref as React.MutableRefObject<T | null>).current = node;
}

/**
 * Decide, before paint, whether an element should reveal. Elements already in
 * view at mount stay static (no hide-flash, no blank on no-JS); only ones below
 * the fold arm the enter animation.
 */
function useArmed(amount: number, disabled: boolean, force: boolean) {
  const ref = React.useRef<HTMLElement | null>(null);
  const [armed, setArmed] = React.useState(force && !disabled);
  useIsoLayoutEffect(() => {
    if (disabled || force) return;
    const el = ref.current;
    if (!el) return;
    const rect = el.getBoundingClientRect();
    if (rect.top > window.innerHeight * (1 - amount)) setArmed(true);
  }, [disabled, amount, force]);
  return { ref, armed };
}

export interface RevealProps extends React.HTMLAttributes<HTMLElement> {
  variant?: RevealVariant;
  delay?: number;
  /** Override the ambient reveal intensity for this element. */
  intensity?: number;
  /** Fraction of the element that must be visible to trigger. */
  amount?: number;
  /** Reveal even when already in view at mount (e.g. demos, explicit entrances). */
  force?: boolean;
  as?: RevealTag;
}

export const Reveal = React.forwardRef<HTMLElement, RevealProps>(
  (
    {
      variant = "veil",
      delay = 0,
      intensity,
      amount = 0.35,
      force = false,
      as = "div",
      children,
      ...rest
    },
    forwardedRef,
  ) => {
    const k = useRevealIntensity(intensity);
    const reduced = useReducedMotion() ?? false;
    const { ref, armed } = useArmed(amount, reduced || k <= 0, force);

    const setRefs = React.useCallback(
      (node: HTMLElement | null) => {
        ref.current = node;
        assignRef(forwardedRef, node);
      },
      [ref, forwardedRef],
    );

    const Comp = MOTION_TAGS[as] as React.ElementType;

    if (!armed) {
      return (
        <Comp ref={setRefs} {...rest}>
          {children}
        </Comp>
      );
    }

    const built = buildReveal(variant, k, reduced);
    return (
      <Comp
        ref={setRefs}
        initial={built.initial}
        whileInView={built.animate}
        viewport={{ once: true, amount }}
        transition={{ ...built.transition, delay }}
        {...rest}
      >
        {children}
      </Comp>
    );
  },
);
Reveal.displayName = "Reveal";

export interface RevealGroupProps extends React.HTMLAttributes<HTMLElement> {
  variant?: RevealVariant;
  /** Delay between each child, seconds. */
  stagger?: number;
  /** Delay before the first child, seconds. */
  delay?: number;
  intensity?: number;
  amount?: number;
  /** Reveal even when already in view at mount (e.g. demos). */
  force?: boolean;
  as?: RevealTag;
}

/**
 * Staggers its direct children in on one shared viewport trigger. The cascade
 * IS the effect. Each child becomes an animated box, so put layout classes
 * (grid/flex) on the group.
 */
export const RevealGroup = React.forwardRef<HTMLElement, RevealGroupProps>(
  (
    {
      variant = "tick",
      stagger = 0.06,
      delay = 0,
      intensity,
      amount = 0.3,
      force = false,
      as = "div",
      children,
      ...rest
    },
    forwardedRef,
  ) => {
    const k = useRevealIntensity(intensity);
    const reduced = useReducedMotion() ?? false;
    const disabled = reduced || k <= 0;
    const { ref, armed } = useArmed(amount, disabled, force);

    const setRefs = React.useCallback(
      (node: HTMLElement | null) => {
        ref.current = node;
        assignRef(forwardedRef, node);
      },
      [ref, forwardedRef],
    );

    const Comp = MOTION_TAGS[as] as React.ElementType;

    if (!armed) {
      return (
        <Comp ref={setRefs} {...rest}>
          {children}
        </Comp>
      );
    }

    const built = buildReveal(variant, k, reduced);
    const childVariants = {
      hidden: built.initial,
      show: { ...built.animate, transition: built.transition },
    };

    return (
      <Comp
        ref={setRefs}
        initial="hidden"
        whileInView="show"
        viewport={{ once: true, amount }}
        variants={{
          hidden: {},
          show: {
            transition: { staggerChildren: stagger, delayChildren: delay },
          },
        }}
        {...rest}
      >
        {React.Children.map(children, (child) => (
          <motion.div variants={childVariants}>{child}</motion.div>
        ))}
      </Comp>
    );
  },
);
RevealGroup.displayName = "RevealGroup";

"use client";
import * as React from "react";

export interface RevealConfig {
  /** Global reveal intensity: kajo = 1 (bold), sisu ≈ 0.45 (quiet), 0 = crossfade. */
  intensity: number;
}

const RevealConfigContext = React.createContext<RevealConfig>({ intensity: 1 });

export function RevealConfigProvider({
  intensity,
  children,
}: {
  intensity: number;
  children: React.ReactNode;
}) {
  const value = React.useMemo(() => ({ intensity }), [intensity]);
  return (
    <RevealConfigContext.Provider value={value}>
      {children}
    </RevealConfigContext.Provider>
  );
}

export function useRevealIntensity(override?: number): number {
  const ctx = React.useContext(RevealConfigContext);
  return override ?? ctx.intensity;
}

import { tokens } from "usva-tokens";

export const springs = tokens.motion.spring;

/**
 * Legacy variant objects (framer/motion `variants` shape). Kept for consumers
 * that drive their own `motion` components; the Reveal system below supersedes
 * this for scroll reveals.
 */
export const variants = {
  fadeUp: {
    hidden: { opacity: 0, y: 8 },
    show: { opacity: 1, y: 0, transition: springs.soft },
  },
  stagger: {
    hidden: {},
    show: { transition: { staggerChildren: 0.06 } },
  },
} as const;

/** Tactile press feedback. Spread onto a `motion` component. Never below 0.96. */
export const press = {
  whileTap: { scale: 0.96 },
  transition: springs.soft,
} as const;

// ── Reveal system: "resolve from mist" ──────────────────────────────
// Six distinct reveals, one metaphor: things resolve out of fog toward the
// light above. Assign by content role, never by position. One `intensity`
// scalar dials the whole set from kajo-bold (1) to sisu-quiet (~0.45) to a
// plain crossfade (0, also the reduced-motion path).

const EASE = {
  quart: [0.25, 1, 0.5, 1],
  quint: [0.22, 1, 0.36, 1],
  expo: [0.16, 1, 0.3, 1],
} as const;

export type RevealVariant =
  | "veil"
  | "cast"
  | "surface"
  | "focus"
  | "tick"
  | "lean";

type RevealSpec = {
  x?: number;
  y?: number;
  scale?: number;
  blur?: number;
  transition: Record<string, unknown>;
};

const SPECS: Record<RevealVariant, RevealSpec> = {
  // default; mist thinning: prose, generic sections, footers
  veil: { y: 12, blur: 3, transition: { duration: 0.5, ease: EASE.quart } },
  // light resolving from above: headings, eyebrows, titles (moves DOWN)
  cast: { y: -10, blur: 8, transition: { duration: 0.7, ease: EASE.quint } },
  // material rising to the light: cards, panels, CTAs, hero (spring, no blur)
  surface: { y: 20, scale: 0.97, transition: springs.soft },
  // lens finding focus: images, media frames (no travel; clip the scale)
  focus: {
    scale: 1.04,
    blur: 12,
    transition: { duration: 0.9, ease: EASE.expo },
  },
  // instrument reading: stats, tables, mono/tabular (never blurs, grouped)
  tick: { y: 6, transition: { duration: 0.28, ease: EASE.expo } },
  // aside voice: quotes, testimonials, callouts (the only horizontal move)
  lean: { x: -16, transition: { duration: 0.6, ease: EASE.quint } },
};

export interface BuiltReveal {
  initial: Record<string, number | string>;
  animate: Record<string, number | string>;
  transition: Record<string, unknown>;
}

/**
 * Compute a variant's motion objects, scaled by intensity `k` (0..1). Blur under
 * 2px is dropped rather than rendered, so a low `k` degrades to a plain move.
 */
export function buildReveal(
  variant: RevealVariant,
  k: number,
  reduced: boolean,
): BuiltReveal {
  if (reduced || k <= 0) {
    return {
      initial: { opacity: 0 },
      animate: { opacity: 1 },
      transition: { duration: variant === "tick" ? 0 : 0.15, ease: "linear" },
    };
  }

  const spec = SPECS[variant];
  const initial: Record<string, number | string> = { opacity: 0 };
  const animate: Record<string, number | string> = { opacity: 1 };

  const x = (spec.x ?? 0) * k;
  const y = (spec.y ?? 0) * k;
  if (x) {
    initial.x = x;
    animate.x = 0;
  }
  if (y) {
    initial.y = y;
    animate.y = 0;
  }
  if (spec.scale != null) {
    initial.scale = 1 + (spec.scale - 1) * k;
    animate.scale = 1;
  }
  const blur = (spec.blur ?? 0) * k;
  if (blur >= 2) {
    initial.filter = `blur(${blur.toFixed(1)}px)`;
    animate.filter = "blur(0px)";
  }

  const isSpring = spec.transition.type === "spring";
  const transition = isSpring
    ? spec.transition
    : {
        ...spec.transition,
        duration: (spec.transition.duration as number) * (0.7 + 0.3 * k),
      };

  return { initial, animate, transition };
}