Store and thread 3pid invite through the app

This doesn't do anything with the stored value (yet), but enables us to do something with it in a future commit.

src/stores/ThreepidInviteStore.ts

@@ -0,0 +1,107 @@
+/*
+Copyright 2020 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 EventEmitter from "events";
+import { ComponentClass } from "../@types/common";
+import { UPDATE_EVENT } from "./AsyncStore";
+import { base32, base64 } from "rfc4648";
+
+// Dev note: the interface is split in two so we don't have to disable the
+// linter across the whole project.
+export interface IThreepidInviteWireFormat {
+    email: string;
+    signurl: string;
+    room_name: string;
+    room_avatar_url: string;
+    inviter_name: string;
+
+    // TODO: Figure out if these are ever populated
+    guest_access_token?: string;
+    guest_user_id?: string;
+}
+
+interface IPersistedThreepidInvite extends IThreepidInviteWireFormat {
+    roomId: string;
+}
+
+export interface IThreepidInvite {
+    id: string; // generated by us
+    roomId: string;
+    toEmail: string;
+    signUrl: string;
+    roomName: string;
+    roomAvatarUrl: string;
+    inviterName: string;
+}
+
+const STORAGE_PREFIX = "mx_threepid_invite_";
+
+export default class ThreepidInviteStore extends EventEmitter {
+    private static _instance: ThreepidInviteStore;
+
+    public static get instance(): ThreepidInviteStore {
+        if (!ThreepidInviteStore._instance) {
+            ThreepidInviteStore._instance = new ThreepidInviteStore();
+        }
+        return ThreepidInviteStore._instance;
+    }
+
+    public storeInvite(roomId: string, wireInvite: IThreepidInviteWireFormat): IThreepidInvite {
+        console.log("Storing invite: ", {roomId, ...wireInvite});
+        const invite = <IPersistedThreepidInvite>{roomId, ...wireInvite};
+        const id = this.generateIdOf(invite);
+        localStorage.setItem(`${STORAGE_PREFIX}${id}`, JSON.stringify(invite));
+        return this.translateInvite(invite);
+    }
+
+    public getInvites(): IThreepidInvite[] {
+        const result: IThreepidInvite[] = [];
+        for (let i = 0; i < localStorage.length; i++) {
+            const keyName = localStorage.key(i);
+            if (!keyName.startsWith(STORAGE_PREFIX)) continue;
+
+            const persisted = JSON.parse(localStorage.getItem(keyName)) as IPersistedThreepidInvite;
+            result.push(this.translateInvite(persisted));
+        }
+        return result;
+    }
+
+    // Currently Element can only handle one invite at a time, so handle that
+    public pickBestInvite(): IThreepidInvite {
+        return this.getInvites()[0];
+    }
+
+    public resolveInvite(invite: IThreepidInvite) {
+        localStorage.removeItem(`${STORAGE_PREFIX}${invite.id}`);
+    }
+
+    private generateIdOf(persisted: IPersistedThreepidInvite): string {
+        // Use a consistent "hash" to form an ID.
+        return base32.stringify(Buffer.from(JSON.stringify(persisted)));
+    }
+
+    private translateInvite(persisted: IPersistedThreepidInvite): IThreepidInvite {
+        return {
+            id: this.generateIdOf(persisted),
+            roomId: persisted.roomId,
+            toEmail: persisted.email,
+            signUrl: persisted.signurl,
+            roomName: persisted.room_name,
+            roomAvatarUrl: persisted.room_avatar_url,
+            inviterName: persisted.inviter_name,
+        };
+    }
+}