@tangle.js/anchors/src/helpers/channelHelper.ts

Anchoring messages to the Tangle. Powered by IOTA Streams

import { Address, Subscriber } from "@tangle.js/iota_streams_wasm";

export class ChannelHelper {
    /**
     *  Finds an anchorage message on the channel by going through the messages
     *
     * @param subs  Subscriber
     * @param anchorageID The anchorage identifier
     *
     * @returns whether it has been found and the link to the anchorage on the Channel
     */
    public static async findAnchorage(subs: Subscriber, anchorageID: string):
        Promise<{ found: boolean; anchorageLink?: Address }> {
        let found = false;
        let anchorageLink: Address;

        // First we try to read such message
        const candidateLink = Address.from_string(`${subs.clone().channel_address()}:${anchorageID}`);

        let response;
        try {
            response = await subs.clone().receive_signed_packet(candidateLink);
        } catch {
           // The message has not been found
        }

        if (response) {
            anchorageLink = response.get_link().copy();
            found = true;
        }

        // Iteratively retrieve messages until We find the one to anchor to
        while (!found) {
            const messages = await subs.clone().fetch_next_msgs();
            if (!messages || messages.length === 0) {
                break;
            }

            // In our case only one message is expected
            anchorageLink = messages[0].get_link().copy();

            if (anchorageLink.msg_id === anchorageID) {
                found = true;
            }
        }

        return { found, anchorageLink };
    }
}