import { ref } from 'vue'
import { useApi } from '@/composables/useApi'
import type { MediaItem } from '@/composables/useMedia'

export const MEDIA_LOOKUP_CONCURRENCY = 4
export const MEDIA_FAILURE_CACHE_LIMIT = 50

export function useMediaNames() {
	const { request } = useApi()
	const items = ref<Record<number, MediaItem>>({})
	const failed = new Set<number>()

	function remember(item: MediaItem) {
		items.value = { ...items.value, [item.id]: item }
	}

	function rememberFailure(id: number) {
		failed.delete(id)
		failed.add(id)
		if (failed.size > MEDIA_FAILURE_CACHE_LIMIT) {
			failed.delete(failed.values().next().value as number)
		}
	}

	async function lookUp(id: number) {
		try {
			remember(await request<MediaItem>(`/v1/media/${id}`))
		} catch {
			rememberFailure(id)
		}
	}

	async function lookUpAll(queue: number[]) {
		const next = queue.values()
		const worker = async () => {
			for (const id of next) {
				await lookUp(id)
			}
		}
		await Promise.all(Array.from({ length: MEDIA_LOOKUP_CONCURRENCY }, worker))
	}

	async function resolve(ids: (number | null | undefined)[]) {
		const wanted = ids.filter((id): id is number => typeof id === 'number')
		const missing = [...new Set(wanted)].filter((id) => !(id in items.value) && !failed.has(id))
		await lookUpAll(missing)
	}

	function itemOf(id: number | null | undefined) {
		return typeof id === 'number' ? (items.value[id] ?? null) : null
	}

	return { itemOf, remember, resolve }
}