import type { Ref } from 'vue'
import { computed, ref, watch } from 'vue'

import type { ContentItem } from '../types'

export function useContentSelection(
	items: Ref<ContentItem[]>,
	getItemId: (item: ContentItem) => string,
) {
	const selectedIds = ref<string[]>([])

	const selectedItems = computed(() => {
		const selectedIdSet = new Set(selectedIds.value)
		const seenIds = new Set<string>()
		const result: ContentItem[] = []

		for (const item of items.value) {
			const id = getItemId(item)
			if (selectedIdSet.has(id) && !seenIds.has(id)) {
				seenIds.add(id)
				result.push(item)
			}
		}

		return result
	})

	watch(
		() => items.value.map(getItemId),
		(newIds) => {
			if (selectedIds.value.length === 0) return
			const validIds = new Set(newIds)
			const pruned = selectedIds.value.filter((id) => validIds.has(id))
			if (pruned.length !== selectedIds.value.length) {
				selectedIds.value = pruned
			}
		},
	)

	function clearSelection() {
		selectedIds.value = []
	}

	function removeFromSelection(id: string) {
		selectedIds.value = selectedIds.value.filter((i) => i !== id)
	}

	return { selectedIds, selectedItems, clearSelection, removeFromSelection }
}