Combine QrCodeEvent, SasEvent and VerificationEvent (#3386)

* Move IReciprocateQr to `crypto-api` and rename

* Move ISasEvent to `crypto-api`, and rename

... and add some ✨comments✨

* Combine QrCodeEvent, SasEvent and VerificationEvent together

... as a precursor to extracting a single `Verifier` interface for `SAS` and `ReciprocateQRCode`.

`enum`s are slightly magical things that have both a type and a value, so we
have to re-export their backwards-compatibility fudges twice.

* Update src/crypto/verification/Base.ts

src/crypto-api.ts

@@ -260,3 +260,5 @@ export class DeviceVerificationStatus {
         return this.localVerified || (this.trustCrossSignedDevices && this.crossSigningVerified);
     }
 }
+
+export * from "./crypto-api/verification";

src/crypto-api/verification.ts

@@ -0,0 +1,112 @@
+/*
+Copyright 2023 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { MatrixEvent } from "../models/event";
+
+/** Events emitted by `Verifier`. */
+export enum VerifierEvent {
+    /**
+     * The verification has been cancelled, by us or the other side.
+     *
+     * The payload is either an {@link Error}, or an (incoming or outgoing) {@link MatrixEvent}, depending on
+     * unspecified reasons.
+     */
+    Cancel = "cancel",
+
+    /**
+     * SAS data has been exchanged and should be displayed to the user.
+     *
+     * The payload is the {@link ShowQrCodeCallbacks} object.
+     */
+    ShowSas = "show_sas",
+
+    /**
+     * QR code data should be displayed to the user.
+     *
+     * The payload is the {@link ShowQrCodeCallbacks} object.
+     */
+    ShowReciprocateQr = "show_reciprocate_qr",
+}
+
+/** Listener type map for {@link VerifierEvent}s. */
+export type VerifierEventHandlerMap = {
+    [VerifierEvent.Cancel]: (e: Error | MatrixEvent) => void;
+    [VerifierEvent.ShowSas]: (sas: ShowSasCallbacks) => void;
+    [VerifierEvent.ShowReciprocateQr]: (qr: ShowQrCodeCallbacks) => void;
+};
+
+/**
+ * Callbacks for user actions while a QR code is displayed.
+ *
+ * This is exposed as the payload of a `VerifierEvent.ShowReciprocateQr` event, or can be retrieved directly from the
+ * verifier as `reciprocateQREvent`.
+ */
+export interface ShowQrCodeCallbacks {
+    /** The user confirms that the verification data matches */
+    confirm(): void;
+
+    /** Cancel the verification flow */
+    cancel(): void;
+}
+
+/**
+ * Callbacks for user actions while a SAS is displayed.
+ *
+ * This is exposed as the payload of a `VerifierEvent.ShowSas` event, or directly from the verifier as `sasEvent`.
+ */
+export interface ShowSasCallbacks {
+    /** The generated SAS to be shown to the user */
+    sas: GeneratedSas;
+
+    /** Function to call if the user confirms that the SAS matches.
+     *
+     * @returns A Promise that completes once the m.key.verification.mac is queued.
+     */
+    confirm(): Promise<void>;
+
+    /**
+     * Function to call if the user finds the SAS does not match.
+     *
+     * Sends an `m.key.verification.cancel` event with a `m.mismatched_sas` error code.
+     */
+    mismatch(): void;
+
+    /** Cancel the verification flow */
+    cancel(): void;
+}
+
+/** A generated SAS to be shown to the user, in alternative formats */
+export interface GeneratedSas {
+    /**
+     * The SAS as three numbers between 0 and 8191.
+     *
+     * Only populated if the `decimal` SAS method was negotiated.
+     */
+    decimal?: [number, number, number];
+
+    /**
+     * The SAS as seven emojis.
+     *
+     * Only populated if the `emoji` SAS method was negotiated.
+     */
+    emoji?: EmojiMapping[];
+}
+
+/**
+ * An emoji for the generated SAS. A tuple `[emoji, name]` where `emoji` is the emoji itself and `name` is the
+ * English name.
+ */
+export type EmojiMapping = [emoji: string, name: string];

src/crypto/verification/Base.ts

@@ -28,7 +28,8 @@ import { KeysDuringVerification, requestKeysDuringVerification } from "../CrossS
 import { IVerificationChannel } from "./request/Channel";
 import { MatrixClient } from "../../client";
 import { VerificationRequest } from "./request/VerificationRequest";
-import { ListenerMap, TypedEventEmitter } from "../../models/typed-event-emitter";
+import { TypedEventEmitter } from "../../models/typed-event-emitter";
+import { VerifierEvent, VerifierEventHandlerMap } from "../../crypto-api/verification";
 
 const timeoutException = new Error("Verification timed out");
 
@@ -40,18 +41,24 @@ export class SwitchStartEventError extends Error {
 
 export type KeyVerifier = (keyId: string, device: DeviceInfo, keyInfo: string) => void;
 
-export enum VerificationEvent {
-    Cancel = "cancel",
-}
+/** @deprecated use VerifierEvent */
+export type VerificationEvent = VerifierEvent;
+/** @deprecated use VerifierEvent */
+export const VerificationEvent = VerifierEvent;
 
+/** @deprecated use VerifierEventHandlerMap */
 export type VerificationEventHandlerMap = {
     [VerificationEvent.Cancel]: (e: Error | MatrixEvent) => void;
 };
 
+// The type parameters of VerificationBase are no longer used, but we need some placeholders to maintain
+// backwards compatibility with applications that reference the class.
 export class VerificationBase<
-    Events extends string,
-    Arguments extends ListenerMap<Events | VerificationEvent>,
-> extends TypedEventEmitter<Events | VerificationEvent, Arguments, VerificationEventHandlerMap> {
+    // eslint-disable-next-line @typescript-eslint/no-unused-vars
+    Events extends string = VerifierEvent,
+    // eslint-disable-next-line @typescript-eslint/no-unused-vars
+    Arguments = VerifierEventHandlerMap,
+> extends TypedEventEmitter<VerifierEvent, VerifierEventHandlerMap> {
     private cancelled = false;
     private _done = false;
     private promise: Promise<void> | null = null;

src/crypto/verification/QRCode.ts

@@ -18,33 +18,26 @@ limitations under the License.
  * QR code key verification.
  */
 
-import { VerificationBase as Base, VerificationEventHandlerMap } from "./Base";
+import { VerificationBase as Base } from "./Base";
 import { newKeyMismatchError, newUserCancelledError } from "./Error";
 import { decodeBase64, encodeUnpaddedBase64 } from "../olmlib";
 import { logger } from "../../logger";
 import { VerificationRequest } from "./request/VerificationRequest";
 import { MatrixClient } from "../../client";
 import { IVerificationChannel } from "./request/Channel";
 import { MatrixEvent } from "../../models/event";
+import { ShowQrCodeCallbacks, VerifierEvent } from "../../crypto-api/verification";
 
 export const SHOW_QR_CODE_METHOD = "m.qr_code.show.v1";
 export const SCAN_QR_CODE_METHOD = "m.qr_code.scan.v1";
 
-interface IReciprocateQr {
-    confirm(): void;
-    cancel(): void;
-}
-
-export enum QrCodeEvent {
-    ShowReciprocateQr = "show_reciprocate_qr",
-}
-
-type EventHandlerMap = {
-    [QrCodeEvent.ShowReciprocateQr]: (qr: IReciprocateQr) => void;
-} & VerificationEventHandlerMap;
+/** @deprecated use VerifierEvent */
+export type QrCodeEvent = VerifierEvent;
+/** @deprecated use VerifierEvent */
+export const QrCodeEvent = VerifierEvent;
 
-export class ReciprocateQRCode extends Base<QrCodeEvent, EventHandlerMap> {
-    public reciprocateQREvent?: IReciprocateQr;
+export class ReciprocateQRCode extends Base {
+    public reciprocateQREvent?: ShowQrCodeCallbacks;
 
     public static factory(
         channel: IVerificationChannel,

src/crypto/verification/SAS.ts

@@ -21,7 +21,7 @@ limitations under the License.
 import anotherjson from "another-json";
 import { Utility, SAS as OlmSAS } from "@matrix-org/olm";
 
-import { VerificationBase as Base, SwitchStartEventError, VerificationEventHandlerMap } from "./Base";
+import { VerificationBase as Base, SwitchStartEventError } from "./Base";
 import {
     errorFactory,
     newInvalidMessageError,
@@ -33,6 +33,14 @@ import { logger } from "../../logger";
 import { IContent, MatrixEvent } from "../../models/event";
 import { generateDecimalSas } from "./SASDecimal";
 import { EventType } from "../../@types/event";
+import { EmojiMapping, GeneratedSas, ShowSasCallbacks, VerifierEvent } from "../../crypto-api/verification";
+
+// backwards-compatibility exports
+export {
+    ShowSasCallbacks as ISasEvent,
+    GeneratedSas as IGeneratedSas,
+    EmojiMapping,
+} from "../../crypto-api/verification";
 
 const START_TYPE = EventType.KeyVerificationStart;
 
@@ -44,8 +52,6 @@ const newMismatchedSASError = errorFactory("m.mismatched_sas", "Mismatched short
 
 const newMismatchedCommitmentError = errorFactory("m.mismatched_commitment", "Mismatched commitment");
 
-type EmojiMapping = [emoji: string, name: string];
-
 const emojiMapping: EmojiMapping[] = [
     ["🐶", "dog"], //  0
     ["🐱", "cat"], //  1
@@ -133,20 +139,8 @@ const sasGenerators = {
     emoji: generateEmojiSas,
 } as const;
 
-export interface IGeneratedSas {
-    decimal?: [number, number, number];
-    emoji?: EmojiMapping[];
-}
-
-export interface ISasEvent {
-    sas: IGeneratedSas;
-    confirm(): Promise<void>;
-    cancel(): void;
-    mismatch(): void;
-}
-
-function generateSas(sasBytes: Uint8Array, methods: string[]): IGeneratedSas {
-    const sas: IGeneratedSas = {};
+function generateSas(sasBytes: Uint8Array, methods: string[]): GeneratedSas {
+    const sas: GeneratedSas = {};
     for (const method of methods) {
         if (method in sasGenerators) {
             // @ts-ignore - ts doesn't like us mixing types like this
@@ -220,19 +214,16 @@ function intersection<T>(anArray: T[], aSet: Set<T>): T[] {
     return Array.isArray(anArray) ? anArray.filter((x) => aSet.has(x)) : [];
 }
 
-export enum SasEvent {
-    ShowSas = "show_sas",
-}
-
-type EventHandlerMap = {
-    [SasEvent.ShowSas]: (sas: ISasEvent) => void;
-} & VerificationEventHandlerMap;
+/** @deprecated use VerifierEvent */
+export type SasEvent = VerifierEvent;
+/** @deprecated use VerifierEvent */
+export const SasEvent = VerifierEvent;
 
-export class SAS extends Base<SasEvent, EventHandlerMap> {
+export class SAS extends Base {
     private waitingForAccept?: boolean;
     public ourSASPubKey?: string;
     public theirSASPubKey?: string;
-    public sasEvent?: ISasEvent;
+    public sasEvent?: ShowSasCallbacks;
 
     // eslint-disable-next-line @typescript-eslint/naming-convention
     public static get NAME(): string {