import { useCallback } from 'react';

import { fractionToZoom, zoomToFraction } from '../core/geometry.ts';

import { useCropper, useCropperState } from './context.ts';

/** zoom control state. */
export interface ZoomControl {
	/** whether zoom is unavailable. */
	disabled: boolean;
	/** logarithmic slider position from `0` to `1`. */
	fraction: number;
	/**
	 * set zoom from a slider position.
	 *
	 * @param fraction position from `0` to `1`.
	 */
	setFraction: (fraction: number) => void;
	/** zoom relative to the cover fit. */
	zoom: number;
}

/**
 * bind a logarithmic slider to zoom.
 *
 * @returns zoom control state.
 * @throws when called outside a `<Cropper.Root>`.
 */
export const useZoomControl = (): ZoomControl => {
	const { config, setZoom } = useCropper();
	const zoom = useCropperState((state) => state.zoom);
	const measured = useCropperState((state) => state.value.width > 0);
	const { maxZoom } = config;

	const setFraction = useCallback(
		(fraction: number) => {
			setZoom(fractionToZoom(fraction, maxZoom));
		},
		[maxZoom, setZoom],
	);

	return {
		disabled: !measured || maxZoom <= 1,
		fraction: zoomToFraction(zoom, maxZoom),
		setFraction,
		zoom,
	};
};

/** pan control state. */
export interface PanControl {
	/** whether the axis has no travel. */
	disabled: boolean;
	/** position from `0` to `1`. */
	fraction: number;
	/**
	 * set the axis position.
	 *
	 * @param fraction position from `0` to `1`.
	 */
	setFraction: (fraction: number) => void;
}

/**
 * bind a slider to one pan axis.
 *
 * @param axis crop axis.
 * @returns pan control state.
 * @throws when called outside a `<Cropper.Root>`.
 */
export const usePanControl = (axis: 'x' | 'y'): PanControl => {
	const { setPan } = useCropper();
	const fraction = useCropperState((state) => state.pan[axis]);
	const slack = useCropperState((state) => state.panSlack[axis]);

	const setFraction = useCallback(
		(next: number) => {
			setPan(axis === 'x' ? { x: next } : { y: next });
		},
		[axis, setPan],
	);

	return {
		disabled: slack <= 0,
		fraction,
		setFraction,
	};
};