@fedify/fedify/esm/federation/collection.js

An ActivityPub server framework

import * as dntShim from "../_dnt.shims.js";
import { encodeHex } from "../deps/jsr.io/@std/encoding/1.0.7/hex.js";
/**
 * Calculates the [partial follower collection digest][1].
 *
 * [1]: https://w3id.org/fep/8fcf#partial-follower-collection-digest
 * @param uris The URIs to calculate the digest.  Duplicate URIs are ignored.
 * @returns The digest.
 */
export async function digest(uris) {
    const processed = new Set();
    const encoder = new TextEncoder();
    const result = new Uint8Array(32);
    for (const uri of uris) {
        const u = uri instanceof URL ? uri.href : uri;
        if (processed.has(u))
            continue;
        processed.add(u);
        const encoded = encoder.encode(u);
        const digest = new Uint8Array(await dntShim.crypto.subtle.digest("SHA-256", encoded));
        for (let i = 0; i < 32; i++) {
            result[i] ^= digest[i];
        }
    }
    return result;
}
/**
 * Builds [`Collection-Synchronization`][1] header content.
 *
 * [1]: https://w3id.org/fep/8fcf#the-collection-synchronization-http-header
 *
 * @param collectionId The sender's followers collection URI.
 * @param actorIds The actor URIs to digest.
 * @returns The header content.
 */
export async function buildCollectionSynchronizationHeader(collectionId, actorIds) {
    const [anyActorId] = actorIds;
    const baseUrl = new URL(anyActorId);
    const url = new URL(collectionId);
    url.searchParams.set("base-url", `${baseUrl.origin}/`);
    const hash = encodeHex(await digest(actorIds));
    return `collectionId="${collectionId}", url="${url}", digest="${hash}"`;
}