import { ref } from 'vue'

/**
 * Manages translation toggle state (active/loading) with version-based
 * cancellation to handle async race conditions.
 *
 * Usage:
 * ```
 * const ctrl = useTranslationToggle()
 *
 * async function doTranslate() {
 *   const version = ctrl.start()
 *   try {
 *     const result = await api()
 *     if (ctrl.isStale(version)) return   // superseded, discard
 *     // apply result
 *     ctrl.translationActive.value = true
 *   } finally {
 *     ctrl.done(version)
 *   }
 * }
 *
 * function toggleTranslation() {
 *   ctrl.toggle(
 *     () => { restoreOriginal() },
 *     () => void doTranslate(),
 *   )
 * }
 *
 * // When new data arrives (e.g. new search results):
 * ctrl.cancel()
 * ```
 */
export function useTranslationToggle() {
	const translationActive = ref(false)
	const translationLoading = ref(false)
	let _version = 0

	/** Bump version, set loading, and return the new version number for staleness checks. */
	function start(): number {
		translationLoading.value = true
		return ++_version
	}

	/** Returns true if `version` is no longer the current request. */
	function isStale(version: number): boolean {
		return version !== _version
	}

	/** Stop loading only if `version` is still current. */
	function done(version: number): void {
		if (version === _version) translationLoading.value = false
	}

	/**
	 * Toggle between original and translated content.
	 *
	 * @param showOriginal - callback that restores the original untranslated data
	 * @param doTranslate  - callback that kicks off a new translation
	 */
	function toggle(showOriginal: () => void, doTranslate: () => void): void {
		if (translationActive.value) {
			_version++ // cancel any in-flight translation
			showOriginal()
			translationActive.value = false
			translationLoading.value = false
			return
		}
		doTranslate()
	}

	/** Cancel any in-flight translation and reset to inactive state. Returns the current version. */
	function cancel(): number {
		_version++
		translationActive.value = false
		translationLoading.value = false
		return _version
	}

	return {
		translationActive,
		translationLoading,
		start,
		isStale,
		done,
		toggle,
		cancel,
	}
}