freezmo/lib/motion.ts

"use client";

/**
 * One shared motion language for the mobile animation pass.
 *
 * Every component imports its presets from here instead of inventing ad-hoc
 * springs, so the whole app feels like one native surface:
 *
 *  - `springSnappy` — press releases and small UI changes (180–220ms feel).
 *  - `springGentle` — screen content, lists, feedback panels (280–350ms).
 *  - `springSheet`  — bottom sheets, tuned for dragging.
 *  - `EASE_OUT`     — quick fades that don't need a spring.
 *
 * Only transform and opacity are ever animated (plus the explicit height
 * animation of expanders); blur and backdrop-filter are never touched.
 * `prefers-reduced-motion` is handled by the callers (CSS media query for
 * press feedback, `useReducedMotion` for JS springs) so motion collapses to
 * short fades without changing layout.
 */

import type { Transition, Variants } from "framer-motion";
import { useEffect, useState } from "react";

/** Press feedback and other tiny changes. ~200ms spring, no bounce overshoot. */
export const springSnappy: Transition = { type: "spring", stiffness: 520, damping: 34, mass: 0.7 };

/** Content entering/exiting a screen or list. ~300ms, a whisper of overshoot. */
export const springGentle: Transition = { type: "spring", stiffness: 300, damping: 30, mass: 0.9 };

/** Bottom sheets: responsive to release velocity, settles fast. */
export const springSheet: Transition = { type: "spring", stiffness: 380, damping: 36, mass: 1 };

/** Crisp fade for elements that should not move. */
export const fade: Transition = { duration: 0.18, ease: "easeOut" };

/** Plain ease for fades and progress bars. */
export const EASE_OUT = [0.22, 1, 0.36, 1] as const;

/** A screen entering from the right (drill-in) or left (back). */
export function screenVariants(direction: 1 | -1, reduceMotion: boolean): Variants {
  if (reduceMotion) {
    return {
      initial: { opacity: 0 },
      animate: { opacity: 1, transition: { duration: 0.12 } },
      exit: { opacity: 0, transition: { duration: 0.1 } },
    };
  }
  return {
    initial: { opacity: 0, x: 24 * direction },
    animate: { opacity: 1, x: 0, transition: springGentle },
    exit: { opacity: 0, x: -16 * direction, transition: { duration: 0.18, ease: "easeIn" } },
  };
}

/** Crossfade for same-depth route switches (tab to tab). */
export function tabVariants(reduceMotion: boolean): Variants {
  if (reduceMotion) {
    return { initial: { opacity: 0 }, animate: { opacity: 1 }, exit: { opacity: 0 } };
  }
  return {
    initial: { opacity: 0, y: 8 },
    animate: { opacity: 1, y: 0, transition: springGentle },
    exit: { opacity: 0, y: -6, transition: { duration: 0.16, ease: "easeIn" } },
  };
}

/** Wizard step: forward slides in from the right, Back from the left. */
export function stepVariants(direction: 1 | -1, reduceMotion: boolean): Variants {
  if (reduceMotion) {
    return { initial: { opacity: 0 }, animate: { opacity: 1, transition: { duration: 0.12 } } };
  }
  return {
    initial: { opacity: 0, x: 18 * direction },
    animate: { opacity: 1, x: 0, transition: { duration: 0.24, ease: EASE_OUT } },
  };
}

/**
 * Counts a number up over ~600ms with an ease-out curve (score, XP). Pass
 * `disabled` (desktop, reduced motion) to jump straight to the value.
 */
export function useCountUp(target: number, disabled = false): number {
  const [value, setValue] = useState(disabled ? target : 0);

  useEffect(() => {
    if (disabled) {
      setValue(target);
      return;
    }
    let frame = 0;
    const start = performance.now();
    const duration = 600;
    const tick = (now: number) => {
      const progress = Math.min(1, (now - start) / duration);
      const eased = 1 - Math.pow(1 - progress, 3);
      setValue(Math.round(target * eased));
      if (progress < 1) frame = requestAnimationFrame(tick);
    };
    frame = requestAnimationFrame(tick);
    return () => cancelAnimationFrame(frame);
  }, [target, disabled]);

  return value;
}