snort/packages/nostr/src/Event.ts

import * as secp from "@noble/secp256k1";
import * as base64 from "@protobufjs/base64";
import { HexKey, RawEvent, TaggedRawEvent } from "./index";
import EventKind from "./EventKind";
import Tag from "./Tag";
import Thread from "./Thread";

export default class Event {
  /**
   * The original event
   */
  Original: TaggedRawEvent | null;

  /**
   * Id of the event
   */
  Id: string;

  /**
   * Pub key of the creator
   */
  PubKey: string;

  /**
   * Timestamp when the event was created
   */
  CreatedAt: number;

  /**
   * The type of event
   */
  Kind: EventKind;

  /**
   * A list of metadata tags
   */
  Tags: Array<Tag>;

  /**
   * Content of the event
   */
  Content: string;

  /**
   * Signature of this event from the creator
   */
  Signature: string;

  /**
   * Thread information for this event
   */
  Thread: Thread | null;

  constructor(e?: TaggedRawEvent) {
    this.Original = e ?? null;
    this.Id = e?.id ?? "";
    this.PubKey = e?.pubkey ?? "";
    this.CreatedAt = e?.created_at ?? Math.floor(new Date().getTime() / 1000);
    this.Kind = e?.kind ?? EventKind.Unknown;
    this.Tags = e?.tags.map((a, i) => new Tag(a, i)) ?? [];
    this.Content = e?.content ?? "";
    this.Signature = e?.sig ?? "";
    this.Thread = Thread.ExtractThread(this);
  }

  /**
   * Get the pub key of the creator of this event NIP-26
   */
  get RootPubKey() {
    const delegation = this.Tags.find((a) => a.Key === "delegation");
    if (delegation?.PubKey) {
      return delegation.PubKey;
    }
    return this.PubKey;
  }

  /**
   * Sign this message with a private key
   */
  async Sign(key: HexKey) {
    this.Id = await this.CreateId();

    const sig = await secp.schnorr.sign(this.Id, key);
    this.Signature = secp.utils.bytesToHex(sig);
    if (!(await this.Verify())) {
      throw "Signing failed";
    }
  }

  /**
   * Check the signature of this message
   * @returns True if valid signature
   */
  async Verify() {
    const id = await this.CreateId();
    const result = await secp.schnorr.verify(this.Signature, id, this.PubKey);
    return result;
  }

  async CreateId() {
    const payload = [
      0,
      this.PubKey,
      this.CreatedAt,
      this.Kind,
      this.Tags.map((a) => a.ToObject()).filter((a) => a !== null),
      this.Content,
    ];

    const payloadData = new TextEncoder().encode(JSON.stringify(payload));
    const data = await secp.utils.sha256(payloadData);
    const hash = secp.utils.bytesToHex(data);
    if (this.Id !== "" && hash !== this.Id) {
      console.debug(payload);
      throw "ID doesnt match!";
    }
    return hash;
  }

  ToObject(): RawEvent {
    return {
      id: this.Id,
      pubkey: this.PubKey,
      created_at: this.CreatedAt,
      kind: this.Kind,
      tags: <string[][]>this.Tags.sort((a, b) => a.Index - b.Index)
        .map((a) => a.ToObject())
        .filter((a) => a !== null),
      content: this.Content,
      sig: this.Signature,
    };
  }

  /**
   * Create a new event for a specific pubkey
   */
  static ForPubKey(pubKey: HexKey) {
    const ev = new Event();
    ev.PubKey = pubKey;
    return ev;
  }

  /**
   * Encrypt the given message content
   */
  async EncryptData(content: string, pubkey: HexKey, privkey: HexKey) {
    const key = await this._GetDmSharedKey(pubkey, privkey);
    const iv = window.crypto.getRandomValues(new Uint8Array(16));
    const data = new TextEncoder().encode(content);
    const result = await window.crypto.subtle.encrypt(
      {
        name: "AES-CBC",
        iv: iv,
      },
      key,
      data
    );
    const uData = new Uint8Array(result);
    return `${base64.encode(uData, 0, result.byteLength)}?iv=${base64.encode(
      iv,
      0,
      16
    )}`;
  }

  /**
   * Encrypt the message content in place
   */
  async EncryptDmForPubkey(pubkey: HexKey, privkey: HexKey) {
    this.Content = await this.EncryptData(this.Content, pubkey, privkey);
  }

  /**
   * Decrypt the content of the message
   */
  async DecryptData(cyphertext: string, privkey: HexKey, pubkey: HexKey) {
    const key = await this._GetDmSharedKey(pubkey, privkey);
    const cSplit = cyphertext.split("?iv=");
    const data = new Uint8Array(base64.length(cSplit[0]));
    base64.decode(cSplit[0], data, 0);

    const iv = new Uint8Array(base64.length(cSplit[1]));
    base64.decode(cSplit[1], iv, 0);

    const result = await window.crypto.subtle.decrypt(
      {
        name: "AES-CBC",
        iv: iv,
      },
      key,
      data
    );
    return new TextDecoder().decode(result);
  }

  /**
   * Decrypt the content of this message in place
   */
  async DecryptDm(privkey: HexKey, pubkey: HexKey) {
    this.Content = await this.DecryptData(this.Content, privkey, pubkey);
  }

  async _GetDmSharedKey(pubkey: HexKey, privkey: HexKey) {
    const sharedPoint = secp.getSharedSecret(privkey, "02" + pubkey);
    const sharedX = sharedPoint.slice(1, 33);
    return await window.crypto.subtle.importKey(
      "raw",
      sharedX,
      { name: "AES-CBC" },
      false,
      ["encrypt", "decrypt"]
    );
  }
}