path: root/src/lib/nip17.ts

import { bytesToHex } from '@noble/hashes/utils';

import { finalizeEvent, getEventHash, generateSecretKey, getPublicKey } from 'nostr-tools/pure';
import { SimplePool } from 'nostr-tools/pool';
import { unwrapEvent } from 'nostr-tools/nip17';

import { getPrivateKey } from '$lib/nostr';
import { relaysSupporting } from '$lib/nip11';
import { expired, expiration } from '$lib/nip40';
import { encrypt, u } from '$lib/nip44';

const TWO_DAYS = 2 * 24 * 60 * 60;
const randomTimestamp = () => Math.floor(
    Date.now() / 1000 - Math.random() * TWO_DAYS);
const pool = new SimplePool();
let relayListCache = new Map();

import { PUBLIC_DM_RELAYS } from '$env/static/public';
const DM_RELAYS_LIST = PUBLIC_DM_RELAYS.split(',');
const DM_FETCH_LIMIT = 256;

// Create a NIP-17 message using a provided sender secret key.
// If wrapPK is specified and different than receiverPK,
// the message will be gift-wrapped to wrapPK
// but the rumour will be sent to receiverPK.
// If expiryDays is specified, the message will expire in that many days,
// plus a random amount from 0 to 2 for security.
// (expiration time = random creation time + expiryDays + 2 days)
export const createNIP17MessageSK = (text: string, senderSK: Uint8Array, receiverPK: string, wrapPK: string = null, expiryDays: number = null) => {
    const rumour = createRumour(text, getPublicKey(senderSK), receiverPK);
    const sealed = sealRumourSK(rumour, senderSK, wrapPK || receiverPK, expiryDays);
    return giftWrap(sealed, wrapPK || receiverPK, expiryDays);
}

// Create a NIP-17 message using NIP-07, requiring no sender secret key.
// If wrapPK is specified and different than receiverPK,
// the message will be gift-wrapped to wrapPK
// but the rumour will be sent to receiverPK.
// If expiryDays is specified, the message will expire in that many days,
// plus a random amount from 0 to 2 for security.
// (expiration time = random creation time + expiryDays + 2 days)
export const createNIP17MessageNIP07 = async (text: string, senderPK: string, receiverPK: string, wrapPK: string = null, expiryDays: number = null) => {
    const rumour = createRumour(text, senderPK, receiverPK);
    const sealed = await sealRumourNip07(rumour, wrapPK || receiverPK, expiryDays);
    return giftWrap(sealed, wrapPK || receiverPK, expiryDays);
}

const createRumour = (text: string, senderPK: string, receiverPK: string) => {
    const rumour = {
        kind: 14, // rumour
        created_at: Math.floor(Date.now() / 1000),
        tags: [["p", receiverPK]],
        pubkey: senderPK,
        content: text
    };
    rumour.id = getEventHash(rumour); // do NOT sign rumours!
    return rumour;
}

const sealRumourSK = (rumour: object, senderSK: Uint8Array, receiverPK: string, expiryDays: number = null) => {
    const senderSKString = bytesToHex(senderSK);
    const conversationKey = u.getConversationKey(senderSKString, receiverPK);
    const encryptedRumour = encrypt(JSON.stringify(rumour), conversationKey);

    const created = randomTimestamp();
    const sealEvent = {
        kind: 13, // seal
        created_at: created,
        tags: [],
        pubkey: getPublicKey(senderSK),
        content: encryptedRumour
    }
    if (expiryDays != null) {
        const expiration = created + (expiryDays + 2) * 86400;
        sealEvent.tags.push(["expiration", expiration.toString()]);
    }

    return finalizeEvent(sealEvent, senderSK);
}

const sealRumourNip07 = async (rumour: object, receiverPK: string, expiryDays: number = null) => {
    const encryptedRumour = await window.nostr.nip44.encrypt(
        receiverPK, JSON.stringify(rumour));

    const created = randomTimestamp();
    const sealEvent = {
        kind: 13, // seal
        created_at: created,
        tags: [],
        content: encryptedRumour
    }
    if (expiryDays != null) {
        const expiration = created + (expiryDays + 2) * 86400;
        sealEvent.tags.push(["expiration", expiration.toString()]);
    }

    return window.nostr.signEvent(sealEvent);
}

const giftWrap = (event: object, receiverPK: string, expiryDays: number = null) => {
    const secretKey = generateSecretKey();
    const SKString = bytesToHex(secretKey);
    const conversationKey = u.getConversationKey(secretKey, receiverPK);
    const encryptedEvent = encrypt(JSON.stringify(event), conversationKey);
    const created = randomTimestamp();

    const giftWrapEvent = {
        kind: 1059, // gift wrap
        created_at: created,
        tags: [["p", receiverPK]],
        pubkey: getPublicKey(secretKey),
        content: encryptedEvent
    }
    if (expiryDays != null) {
        const expiration = created + (expiryDays + 2) * 86400;
        giftWrapEvent.tags.push(["expiration", expiration.toString()]);
    }

    return finalizeEvent(giftWrapEvent, secretKey);
}

const decryptNIP17MessageNIP07 = async (wrapped: object): object => {
    const sealedText = await window.nostr.nip44.decrypt(
        wrapped.pubkey, wrapped.content);
    const sealed = JSON.parse(sealedText);
    const rumourText = await window.nostr.nip44.decrypt(
        sealed.pubkey, sealed.content);
    return JSON.parse(rumourText);
}

// Decrypts the provided message, addressed to the user.
// If NIP-07 is available, it uses that, otherwise it uses getPrivateKey().
export const decrypt = async (wrapped: object, user: object): object => {
   if (await window.nostr.getPublicKey() === user.pubkey) {
     return decryptNIP17MessageNIP07(wrapped);
   } else {
     const sk = await getPrivateKey(user);
     return unwrapEvent(wrapped, sk);
   }
 }

// Returns the rumours of the messages the provided user has sent or received.
// If the events have an expiration timestamp,
// that timestamp is added to its rumour object as the property `expiration`.
export const getMessageRumours = async (user: object): object[] => {
    const relays = await getPreferredRelays(user.pubkey);
    const wrapped = await pool.querySync(
        relays, { kinds: [1059], "#p": [user.pubkey], limit: DM_FETCH_LIMIT }
    );

    let rumours = [];
    // intentionally decrypting sequentially to avoid having a bunch of popups
    for (event of wrapped) {
        if (expired(event)) {
            console.log("relay(s) contain expired event", event.id);
            continue;
        }

        const rumour = await decrypt(event, user);

        const expires = expiration(event);
        if (expires) {
            rumour.expiration = expires;
        }

        rumours.push(rumour);
    }

    return rumours;
}

// Returns the preferred relays of the user with the provided pubkey,
// according to their kind-10050 event.
export const getPreferredRelays = async (pubkey: string): string[] => {
    if (relayListCache.has(pubkey))
        return relayListCache.get(pubkey);

    const events = await pool.querySync(
        DM_RELAYS_LIST, { kinds: [10050], limit: 1, authors: [pubkey] }
    );

    let relays = [];
    for (const event of events) {
        for (const tag of event.tags) {
            if (tag.length >= 2 && tag[0] == "relay") {
                relays.push(tag[1]);
            }
        }
    }

    relayListCache.set(pubkey, relays);
    return relays;
}

const publishToPreferred = async (event: object, pubkey: string, expiryEnabled: boolean): Promise<string> => {
    let preferredRelays = await getPreferredRelays(pubkey);
    if (expiryEnabled) {
        preferredRelays = await relaysSupporting(preferredRelays, [40]);
    }
    return Promise.any(pool.publish(preferredRelays, event));
}

// Sends a NIP-17 message from `user` to `recipient`.
// If expiryDays is set, messages will expire after that many days.
export const send = async (message: string, user: object, recipient: object, expiryDays?: number) => {
    let event1, event2;
    if (await window.nostr.getPublicKey() === user.pubkey) {
        event1 = await createNIP17MessageNIP07(
            message, user.pubkey, recipient.pubkey, recipient.pubkey, expiryDays);
        event2 = await createNIP17MessageNIP07(
            message, user.pubkey, recipient.pubkey, user.pubkey, expiryDays);
    } else {
        const sk = await getPrivateKey(user);
        event1 = createNIP17MessageSK(
            message, sk, recipient.pubkey, recipient.pubkey, expiryDays);
        event2 = createNIP17MessageSK(
            message, sk, recipient.pubkey, user.pubkey, expiryDays);
    }

    const p1 = publishToPreferred(event1, recipient.pubkey, expiryDays != null);
    const p2 = publishToPreferred(event2, user.pubkey, expiryDays != null);
    return Promise.all([p1, p2]);
}