import type { PrismicDocument } from "@prismicio/client"

const CACHE_TAG_PREFIX = "prismic/"

/**
 * Generates cache tags for a set of Prismic pages. Tags for linked pages (e.g. a content
 * relationship) are included to ensure all related content can be revalidated.
 *
 * @param pages - A set of Prismic pages used to tag the function.
 * @experimental
 *
 * @see {@link https://nextjs.org/docs/app/api-reference/functions/cacheTag}
 */
export function getPrismicCacheTags(pages: PrismicDocument[]): string[] {
	const ids = [...new Set(getPrismicDocumentIDs(pages))]
	return ids.map((id) => buildPrismicCacheTag(id))
}

export function buildPrismicCacheTag(id: string): string {
	return `${CACHE_TAG_PREFIX}${id}`
}

function getPrismicDocumentIDs(input: unknown): string[] {
	if (typeof input !== "object" || input == null) return []

	if (Array.isArray(input)) return input.flatMap((item) => getPrismicDocumentIDs(item))

	if ("id" in input && typeof input.id === "string") {
		// Document
		// Content relationship or link
		if (
			("href" in input &&
				typeof input.href === "string" &&
				input.href.includes("/api/v2/documents/search?")) ||
			("link_type" in input && input.link_type === "Document")
		) {
			if ("data" in input && typeof input.data === "object" && input.data !== null) {
				return [input.id, ...getPrismicDocumentIDs(input.data)]
			} else {
				return [input.id]
			}
		}
	}

	return Object.values(input).flatMap((input) => getPrismicDocumentIDs(input))
}