import { AtURI, AtURIString, DID, NSID, ValidateNSID } from "./atproto.ts";

const BASEURL = "https://constellation.microcosm.blue";

/** Essentially an AtURI, fed back by Constellation. */
export type Reference = {
	did: string;
	collection: string;
	rkey: string;
}

/** Raw response type from /links */
type LinksResponse = {
	total: number;
	linking_records: Reference[];
	cursor: string;
};

type Target = AtURIString | DID;
/**
 * Retrieves an array of record references to records containing links to the specified target.
 * @throws When the provided NSID is invalid.
 */
export async function getLinks(target: Target, collection: NSID, path: string): Promise<AtURI[]> {
	if (ValidateNSID(collection) == null) {
		throw new Error("invalid NSID for collection parameter");
	}
	const _target = encodeURIComponent(target.toString()!);
	const _path = encodeURIComponent(path);
	let cursor = "";
	let records: AtURI[] = [];
	while (cursor != null) {
		const rsp = await fetch(`${BASEURL}/links?target=${_target.toString()}&collection=${collection}&path=${_path}${cursor ? `&cursor=${cursor}` : ""}`);
		const data = await rsp.json() as LinksResponse;
		records = records.concat(data.linking_records.map(x=>new AtURI(x.did, x.collection, x.rkey)));
		cursor = data.cursor;
	}
	return records;
}