@humanspeak/svelte-motion/dist/utils/cycle.svelte.js

Framer Motion for Svelte 5. Declarative motion.<tag> components with AnimatePresence exit animations, gestures (hover, tap, drag, focus, in-view), variants, FLIP layout animations, shared-layout transitions, spring physics, and scroll-linked motion values

import { wrap } from 'motion';
export function useCycle(...args) {
    const getItems = args.length === 1 && typeof args[0] === 'function'
        ? args[0]
        : () => args;
    if (getItems().length === 0) {
        throw new Error('useCycle requires at least one item');
    }
    let index = $state(0);
    return {
        get current() {
            const items = getItems();
            // Reactive-getter form: if the consumer's source emptied
            // mid-cycle the public type can no longer be honored. Throw
            // loudly so the bug surfaces immediately rather than leaking
            // `undefined` through a `T`-typed read.
            if (items.length === 0) {
                throw new Error('useCycle items getter returned an empty list');
            }
            // Clamp on read so out-of-range indexes (from `cycle(-5)` or
            // `cycle(99)`, or items shrinking under us in the getter form)
            // resolve to the nearest valid edge instead of `undefined`.
            const safeIndex = index < 0 ? 0 : index >= items.length ? items.length - 1 : index;
            return items[safeIndex];
        },
        cycle: (next) => {
            const items = getItems();
            if (items.length === 0)
                return;
            // Reject non-finite / non-integer indexes up-front: `NaN` slips
            // past the read-time clamp (NaN comparisons return false for
            // both `< 0` and `>= length`) and would silently make `.current`
            // resolve to `undefined`, breaking the `T` contract. Throw
            // loudly to surface the consumer bug at write-time.
            if (typeof next === 'number' && !Number.isInteger(next)) {
                throw new Error('useCycle index must be a finite integer');
            }
            const target = typeof next === 'number' ? next : wrap(0, items.length, index + 1);
            if (target === index)
                return;
            index = target;
        }
    };
}