Merge pull request #5065 from matrix-org/travis/echo/audit

Add local echo for notifications in the new room list

docs/local-echo-dev.md

@@ -0,0 +1,39 @@
+# Local echo (developer docs)
+
+The React SDK provides some local echo functionality to allow for components to do something
+quickly and fall back when it fails. This is all available in the `local-echo` directory within
+`stores`.
+
+Echo is handled in EchoChambers, with `GenericEchoChamber` being the base implementation for all
+chambers. The `EchoChamber` class is provided as semantic access to a `GenericEchoChamber`
+implementation, such as the `RoomEchoChamber` (which handles echoable details of a room).
+
+Anything that can be locally echoed will be provided by the `GenericEchoChamber` implementation.
+The echo chamber will also need to deal with external changes, and has full control over whether
+or not something has successfully been echoed. 
+
+An `EchoContext` is provided to echo chambers (usually with a matching type: `RoomEchoContext`
+gets provided to a `RoomEchoChamber` for example) with details about their intended area of
+effect, as well as manage `EchoTransaction`s. An `EchoTransaction` is simply a unit of work that
+needs to be locally echoed.
+
+The `EchoStore` manages echo chamber instances, builds contexts, and is generally less semantically
+accessible than the `EchoChamber` class. For separation of concerns, and to try and keep things
+tidy, this is an intentional design decision.
+
+**Note**: The local echo stack uses a "whenable" pattern, which is similar to thenables and 
+`EventEmitter`. Whenables are ways of actioning a changing condition without having to deal
+with listeners being torn down. Once the reference count of the Whenable causes garbage collection,
+the Whenable's listeners will also be torn down. This is accelerated by the `IDestroyable` interface
+usage.
+
+## Audit functionality
+
+The UI supports a "Server isn't responding" dialog which includes a partial audit log-like
+structure to it. This is partially the reason for added complexity of `EchoTransaction`s
+and `EchoContext`s - this information feeds the UI states which then provide direct retry
+mechanisms.
+
+The `EchoStore` is responsible for ensuring that the appropriate non-urgent toast (lower left)
+is set up, where the dialog then drives through the contexts and transactions.
+

res/css/_components.scss

@@ -15,6 +15,7 @@
 @import "./structures/_MainSplit.scss";
 @import "./structures/_MatrixChat.scss";
 @import "./structures/_MyGroups.scss";
+@import "./structures/_NonUrgentToastContainer.scss";
 @import "./structures/_NotificationPanel.scss";
 @import "./structures/_RightPanel.scss";
 @import "./structures/_RoomDirectory.scss";
@@ -75,6 +76,7 @@
 @import "./views/dialogs/_RoomSettingsDialogBridges.scss";
 @import "./views/dialogs/_RoomUpgradeDialog.scss";
 @import "./views/dialogs/_RoomUpgradeWarningDialog.scss";
+@import "./views/dialogs/_ServerOfflineDialog.scss";
 @import "./views/dialogs/_SetEmailDialog.scss";
 @import "./views/dialogs/_SetMxIdDialog.scss";
 @import "./views/dialogs/_SetPasswordDialog.scss";
@@ -215,6 +217,7 @@
 @import "./views/settings/tabs/user/_SecurityUserSettingsTab.scss";
 @import "./views/settings/tabs/user/_VoiceUserSettingsTab.scss";
 @import "./views/terms/_InlineTermsAgreement.scss";
+@import "./views/toasts/_NonUrgentEchoFailureToast.scss";
 @import "./views/verification/_VerificationShowSas.scss";
 @import "./views/voip/_CallContainer.scss";
 @import "./views/voip/_CallView.scss";

res/css/structures/_NonUrgentToastContainer.scss

@@ -0,0 +1,35 @@
+/*
+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.
+*/
+
+.mx_NonUrgentToastContainer {
+    position: absolute;
+    bottom: 30px;
+    left: 28px;
+    z-index: 101; // same level as other toasts
+
+    .mx_NonUrgentToastContainer_toast {
+        padding: 10px 12px;
+        border-radius: 8px;
+        width: 320px;
+        font-size: $font-13px;
+        margin-top: 8px;
+
+        // We don't use variables on the colours because we want it to be the same
+        // in all themes.
+        background-color: #17191c;
+        color: #fff;
+    }
+}

res/css/views/dialogs/_ServerOfflineDialog.scss

@@ -0,0 +1,72 @@
+/*
+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.
+*/
+
+.mx_ServerOfflineDialog {
+    .mx_ServerOfflineDialog_content {
+        padding-right: 85px;
+        color: $primary-fg-color;
+
+        hr {
+            border-color: $primary-fg-color;
+            opacity: 0.1;
+            border-bottom: none;
+        }
+
+        ul {
+            padding: 16px;
+
+            li:nth-child(n + 2) {
+                margin-top: 16px;
+            }
+        }
+
+        .mx_ServerOfflineDialog_content_context {
+            .mx_ServerOfflineDialog_content_context_timestamp {
+                display: inline-block;
+                width: 115px;
+                color: $muted-fg-color;
+                line-height: 24px; // same as avatar
+                vertical-align: top;
+            }
+
+            .mx_ServerOfflineDialog_content_context_timeline {
+                display: inline-block;
+                width: calc(100% - 155px); // 115px timestamp width + 40px right margin
+
+                .mx_ServerOfflineDialog_content_context_timeline_header {
+                    span {
+                        margin-left: 8px;
+                        vertical-align: middle;
+                    }
+                }
+
+                .mx_ServerOfflineDialog_content_context_txn {
+                    position: relative;
+                    margin-top: 8px;
+
+                    .mx_ServerOfflineDialog_content_context_txn_desc {
+                        width: calc(100% - 100px); // 100px is an arbitrary margin for the button
+                    }
+
+                    .mx_AccessibleButton {
+                        float: right;
+                        padding: 0;
+                    }
+                }
+            }
+        }
+    }
+}

res/css/views/toasts/_NonUrgentEchoFailureToast.scss

@@ -0,0 +1,37 @@
+/*
+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.
+*/
+
+.mx_NonUrgentEchoFailureToast {
+    .mx_NonUrgentEchoFailureToast_icon {
+        display: inline-block;
+        width: $font-18px;
+        height: $font-18px;
+        mask-position: center;
+        mask-size: contain;
+        mask-repeat: no-repeat;
+        background-color: #fff; // we know that non-urgent toasts are always styled the same
+        mask-image: url('$(res)/img/element-icons/cloud-off.svg');
+        margin-right: 8px;
+    }
+
+    span { // includes the i18n block
+        vertical-align: middle;
+    }
+
+    .mx_AccessibleButton {
+        padding: 0;
+    }
+}

res/img/element-icons/cloud-off.svg

@@ -0,0 +1,3 @@
+<svg width="18" height="18" viewBox="0 0 18 18" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path fill-rule="evenodd" clip-rule="evenodd" d="M1.53033 0.46967C1.23744 0.176777 0.762563 0.176777 0.46967 0.46967C0.176777 0.762563 0.176777 1.23744 0.46967 1.53033L4.3982 5.45886C3.81109 6.13809 3.38896 7.01315 3.21555 7.99387C1.96379 8.20624 1 9.465 1 10.981C1 12.6455 2.16209 14 3.59014 14H12.9393L16.4697 17.5303C16.7626 17.8232 17.2374 17.8232 17.5303 17.5303C17.8232 17.2374 17.8232 16.7626 17.5303 16.4697L1.53033 0.46967ZM17 10.9817C16.998 11.8303 16.6946 12.5985 16.2081 13.1475L7.07635 4.01569C7.18805 4.00529 7.30083 4 7.41451 4C8.75982 4 9.99711 4.71787 10.8072 5.94503C11.0993 5.85476 11.4011 5.80939 11.7058 5.80939C13.0303 5.80939 14.2138 6.65743 14.8199 8.00337C16.0519 8.23522 17 9.48685 17 10.9817Z" fill="black"/>
+</svg>

src/@types/common.ts

@@ -14,7 +14,11 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+import { JSXElementConstructor } from "react";
+
 // Based on https://stackoverflow.com/a/53229857/3532235
 export type Without<T, U> = {[P in Exclude<keyof T, keyof U>] ? : never};
 export type XOR<T, U> = (T | U) extends object ? (Without<T, U> & U) | (Without<U, T> & T) : T | U;
 export type Writeable<T> = { -readonly [P in keyof T]: T[P] };
+
+export type ComponentClass = keyof JSX.IntrinsicElements | JSXElementConstructor<any>;

src/components/structures/LoggedInView.tsx

@@ -54,6 +54,7 @@ import LeftPanel from "./LeftPanel";
 import CallContainer from '../views/voip/CallContainer';
 import { ViewRoomDeltaPayload } from "../../dispatcher/payloads/ViewRoomDeltaPayload";
 import RoomListStore from "../../stores/room-list/RoomListStore";
+import NonUrgentToastContainer from "./NonUrgentToastContainer";
 import { ToggleRightPanelPayload } from "../../dispatcher/payloads/ToggleRightPanelPayload";
 
 // We need to fetch each pinned message individually (if we don't already have it)
@@ -688,6 +689,7 @@ class LoggedInView extends React.Component<IProps, IState> {
                     </DragDropContext>
                 </div>
                 <CallContainer />
+                <NonUrgentToastContainer />
             </MatrixClientContext.Provider>
         );
     }

src/components/structures/NonUrgentToastContainer.tsx

@@ -0,0 +1,63 @@
+/*
+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 * as React from "react";
+import { ComponentClass } from "../../@types/common";
+import NonUrgentToastStore from "../../stores/NonUrgentToastStore";
+import { UPDATE_EVENT } from "../../stores/AsyncStore";
+
+interface IProps {
+}
+
+interface IState {
+    toasts: ComponentClass[],
+}
+
+export default class NonUrgentToastContainer extends React.PureComponent<IProps, IState> {
+    public constructor(props, context) {
+        super(props, context);
+
+        this.state = {
+            toasts: NonUrgentToastStore.instance.components,
+        };
+
+        NonUrgentToastStore.instance.on(UPDATE_EVENT, this.onUpdateToasts);
+    }
+
+    public componentWillUnmount() {
+        NonUrgentToastStore.instance.off(UPDATE_EVENT, this.onUpdateToasts);
+    }
+
+    private onUpdateToasts = () => {
+        this.setState({toasts: NonUrgentToastStore.instance.components});
+    };
+
+    public render() {
+        const toasts = this.state.toasts.map((t, i) => {
+            return (
+                <div className="mx_NonUrgentToastContainer_toast" key={`toast-${i}`}>
+                    {React.createElement(t, {})}
+                </div>
+            );
+        });
+
+        return (
+            <div className="mx_NonUrgentToastContainer" role="alert">
+                {toasts}
+            </div>
+        );
+    }
+}

src/components/views/dialogs/ServerOfflineDialog.tsx

@@ -0,0 +1,124 @@
+/*
+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 * as React from 'react';
+import BaseDialog from './BaseDialog';
+import { _t } from '../../../languageHandler';
+import { EchoStore } from "../../../stores/local-echo/EchoStore";
+import { formatTime } from "../../../DateUtils";
+import SettingsStore from "../../../settings/SettingsStore";
+import { RoomEchoContext } from "../../../stores/local-echo/RoomEchoContext";
+import RoomAvatar from "../avatars/RoomAvatar";
+import { TransactionStatus } from "../../../stores/local-echo/EchoTransaction";
+import Spinner from "../elements/Spinner";
+import AccessibleButton from "../elements/AccessibleButton";
+import { UPDATE_EVENT } from "../../../stores/AsyncStore";
+import { MatrixClientPeg } from "../../../MatrixClientPeg";
+
+interface IProps {
+    onFinished: (bool) => void;
+}
+
+export default class ServerOfflineDialog extends React.PureComponent<IProps> {
+    public componentDidMount() {
+        EchoStore.instance.on(UPDATE_EVENT, this.onEchosUpdated);
+    }
+
+    public componentWillUnmount() {
+        EchoStore.instance.off(UPDATE_EVENT, this.onEchosUpdated);
+    }
+
+    private onEchosUpdated = () => {
+        this.forceUpdate(); // no state to worry about
+    };
+
+    private renderTimeline(): React.ReactElement[] {
+        return EchoStore.instance.contexts.map((c, i) => {
+            if (!c.firstFailedTime) return null; // not useful
+            if (!(c instanceof RoomEchoContext)) throw new Error("Cannot render unknown context: " + c);
+            const header = (
+                <div className="mx_ServerOfflineDialog_content_context_timeline_header">
+                    <RoomAvatar width={24} height={24} room={c.room} />
+                    <span>{c.room.name}</span>
+                </div>
+            );
+            const entries = c.transactions
+                .filter(t => t.status === TransactionStatus.DoneError || t.didPreviouslyFail)
+                .map((t, j) => {
+                    let button = <Spinner w={19} h={19} />;
+                    if (t.status === TransactionStatus.DoneError) {
+                        button = (
+                            <AccessibleButton kind="link" onClick={() => t.run()}>{_t("Resend")}</AccessibleButton>
+                        );
+                    }
+                    return (
+                        <div className="mx_ServerOfflineDialog_content_context_txn" key={`txn-${j}`}>
+                            <span className="mx_ServerOfflineDialog_content_context_txn_desc">
+                                {t.auditName}
+                            </span>
+                            {button}
+                        </div>
+                    );
+                });
+            return (
+                <div className="mx_ServerOfflineDialog_content_context" key={`context-${i}`}>
+                    <div className="mx_ServerOfflineDialog_content_context_timestamp">
+                        {formatTime(c.firstFailedTime, SettingsStore.getValue("showTwelveHourTimestamps"))}
+                    </div>
+                    <div className="mx_ServerOfflineDialog_content_context_timeline">
+                        {header}
+                        {entries}
+                    </div>
+                </div>
+            )
+        });
+    }
+
+    public render() {
+        let timeline = this.renderTimeline().filter(c => !!c); // remove nulls for next check
+        if (timeline.length === 0) {
+            timeline = [<div key={1}>{_t("You're all caught up.")}</div>];
+        }
+
+        const serverName = MatrixClientPeg.getHomeserverName();
+        return <BaseDialog title={_t("Server isn't responding")}
+            className='mx_ServerOfflineDialog'
+            contentId='mx_Dialog_content'
+            onFinished={this.props.onFinished}
+            hasCancel={true}
+        >
+            <div className="mx_ServerOfflineDialog_content">
+                <p>{_t(
+                    "Your server isn't responding to some of your requests. " +
+                    "Below are some of the most likely reasons.",
+                )}</p>
+                <ul>
+                    <li>{_t("The server (%(serverName)s) took too long to respond.", {serverName})}</li>
+                    <li>{_t("Your firewall or anti-virus is blocking the request.")}</li>
+                    <li>{_t("A browser extension is preventing the request.")}</li>
+                    <li>{_t("The server is offline.")}</li>
+                    <li>{_t("The server has denied your request.")}</li>
+                    <li>{_t("Your area is experiencing difficulties connecting to the internet.")}</li>
+                    <li>{_t("A connection error occurred while trying to contact the server.")}</li>
+                    <li>{_t("The server is not configured to indicate what the problem is (CORS).")}</li>
+                </ul>
+                <hr />
+                <h2>{_t("Recent changes that have not yet been received")}</h2>
+                {timeline}
+            </div>
+        </BaseDialog>;
+    }
+}

src/components/views/rooms/RoomTile.tsx

@@ -17,12 +17,13 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React, {createRef} from "react";
+import React, { createRef } from "react";
 import { Room } from "matrix-js-sdk/src/models/room";
 import classNames from "classnames";
 import { RovingTabIndexWrapper } from "../../../accessibility/RovingTabIndex";
 import AccessibleButton, { ButtonEvent } from "../../views/elements/AccessibleButton";
 import dis from '../../../dispatcher/dispatcher';
+import defaultDispatcher from '../../../dispatcher/dispatcher';
 import { Key } from "../../../Keyboard";
 import ActiveRoomObserver from "../../../ActiveRoomObserver";
 import { _t } from "../../../languageHandler";
@@ -30,31 +31,26 @@ import {
     ChevronFace,
     ContextMenu,
     ContextMenuTooltipButton,
-    MenuItemRadio,
-    MenuItemCheckbox,
     MenuItem,
+    MenuItemCheckbox,
+    MenuItemRadio,
 } from "../../structures/ContextMenu";
 import { DefaultTagID, TagID } from "../../../stores/room-list/models";
 import { MessagePreviewStore, ROOM_PREVIEW_CHANGED } from "../../../stores/room-list/MessagePreviewStore";
 import DecoratedRoomAvatar from "../avatars/DecoratedRoomAvatar";
-import {
-    getRoomNotifsState,
-    setRoomNotifsState,
-    ALL_MESSAGES,
-    ALL_MESSAGES_LOUD,
-    MENTIONS_ONLY,
-    MUTE,
-} from "../../../RoomNotifs";
+import { ALL_MESSAGES, ALL_MESSAGES_LOUD, MENTIONS_ONLY, MUTE, } from "../../../RoomNotifs";
 import { MatrixClientPeg } from "../../../MatrixClientPeg";
 import NotificationBadge from "./NotificationBadge";
 import { Volume } from "../../../RoomNotifsTypes";
 import RoomListStore from "../../../stores/room-list/RoomListStore";
 import RoomListActions from "../../../actions/RoomListActions";
-import defaultDispatcher from "../../../dispatcher/dispatcher";
-import {ActionPayload} from "../../../dispatcher/payloads";
+import { ActionPayload } from "../../../dispatcher/payloads";
 import { RoomNotificationStateStore } from "../../../stores/notifications/RoomNotificationStateStore";
 import { NOTIFICATION_STATE_UPDATE, NotificationState } from "../../../stores/notifications/NotificationState";
 import AccessibleTooltipButton from "../elements/AccessibleTooltipButton";
+import { EchoChamber } from "../../../stores/local-echo/EchoChamber";
+import { CachedRoomKey, RoomEchoChamber } from "../../../stores/local-echo/RoomEchoChamber";
+import { PROPERTY_UPDATED } from "../../../stores/local-echo/GenericEchoChamber";
 
 interface IProps {
     room: Room;
@@ -112,6 +108,7 @@ export default class RoomTile extends React.PureComponent<IProps, IState> {
     private dispatcherRef: string;
     private roomTileRef = createRef<HTMLDivElement>();
     private notificationState: NotificationState;
+    private roomProps: RoomEchoChamber;
 
     constructor(props: IProps) {
         super(props);
@@ -130,12 +127,19 @@ export default class RoomTile extends React.PureComponent<IProps, IState> {
         MessagePreviewStore.instance.on(ROOM_PREVIEW_CHANGED, this.onRoomPreviewChanged);
         this.notificationState = RoomNotificationStateStore.instance.getRoomState(this.props.room);
         this.notificationState.on(NOTIFICATION_STATE_UPDATE, this.onNotificationUpdate);
+        this.roomProps = EchoChamber.forRoom(this.props.room);
+        this.roomProps.on(PROPERTY_UPDATED, this.onRoomPropertyUpdate);
     }
 
     private onNotificationUpdate = () => {
         this.forceUpdate(); // notification state changed - update
     };
 
+    private onRoomPropertyUpdate = (property: CachedRoomKey) => {
+        if (property === CachedRoomKey.NotificationVolume) this.onNotificationUpdate();
+        // else ignore - not important for this tile
+    };
+
     private get showContextMenu(): boolean {
         return !this.props.isMinimized && this.props.tag !== DefaultTagID.Invite;
     }
@@ -307,17 +311,9 @@ export default class RoomTile extends React.PureComponent<IProps, IState> {
         ev.stopPropagation();
         if (MatrixClientPeg.get().isGuest()) return;
 
-        // get key before we go async and React discards the nativeEvent
-        const key = (ev as React.KeyboardEvent).key;
-        try {
-            // TODO add local echo - https://github.com/vector-im/riot-web/issues/14280
-            await setRoomNotifsState(this.props.room.roomId, newState);
-        } catch (error) {
-            // TODO: some form of error notification to the user to inform them that their state change failed.
-            // See https://github.com/vector-im/riot-web/issues/14281
-            console.error(error);
-        }
+        this.roomProps.notificationVolume = newState;
 
+        const key = (ev as React.KeyboardEvent).key;
         if (key === Key.ENTER) {
             // Implements https://www.w3.org/TR/wai-aria-practices/#keyboard-interaction-12
             this.setState({notificationsMenuPosition: null}); // hide the menu
@@ -335,7 +331,7 @@ export default class RoomTile extends React.PureComponent<IProps, IState> {
             return null;
         }
 
-        const state = getRoomNotifsState(this.props.room.roomId);
+        const state = this.roomProps.notificationVolume;
 
         let contextMenu = null;
         if (this.state.notificationsMenuPosition) {

src/components/views/toasts/NonUrgentEchoFailureToast.tsx

@@ -0,0 +1,40 @@
+/*
+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 React from "react";
+import { _t } from "../../../languageHandler";
+import AccessibleButton from "../elements/AccessibleButton";
+import Modal from "../../../Modal";
+import ServerOfflineDialog from "../dialogs/ServerOfflineDialog";
+
+export default class NonUrgentEchoFailureToast extends React.PureComponent {
+    private openDialog = () => {
+        Modal.createTrackedDialog('Local Echo Server Error', '', ServerOfflineDialog, {});
+    };
+
+    public render() {
+        return (
+            <div className="mx_NonUrgentEchoFailureToast">
+                <span className="mx_NonUrgentEchoFailureToast_icon" />
+                {_t("Your server isn't responding to some <a>requests</a>.", {}, {
+                    'a': (sub) => (
+                        <AccessibleButton kind="link" onClick={this.openDialog}>{sub}</AccessibleButton>
+                    ),
+                })}
+            </div>
+        )
+    }
+}

src/i18n/strings/en_EN.json

@@ -443,6 +443,7 @@
     "%(senderName)s: %(message)s": "%(senderName)s: %(message)s",
     "%(senderName)s: %(reaction)s": "%(senderName)s: %(reaction)s",
     "%(senderName)s: %(stickerName)s": "%(senderName)s: %(stickerName)s",
+    "Change notification settings": "Change notification settings",
     "New spinner design": "New spinner design",
     "Message Pinning": "Message Pinning",
     "Custom user status messages": "Custom user status messages",
@@ -613,6 +614,7 @@
     "Headphones": "Headphones",
     "Folder": "Folder",
     "Pin": "Pin",
+    "Your server isn't responding to some <a>requests</a>.": "Your server isn't responding to some <a>requests</a>.",
     "From %(deviceName)s (%(deviceId)s)": "From %(deviceName)s (%(deviceId)s)",
     "Decline (%(counter)s)": "Decline (%(counter)s)",
     "Accept <policyLink /> to continue:": "Accept <policyLink /> to continue:",
@@ -1745,6 +1747,19 @@
     "Upgrading a room is an advanced action and is usually recommended when a room is unstable due to bugs, missing features or security vulnerabilities.": "Upgrading a room is an advanced action and is usually recommended when a room is unstable due to bugs, missing features or security vulnerabilities.",
     "This usually only affects how the room is processed on the server. If you're having problems with your %(brand)s, please <a>report a bug</a>.": "This usually only affects how the room is processed on the server. If you're having problems with your %(brand)s, please <a>report a bug</a>.",
     "You'll upgrade this room from <oldVersion /> to <newVersion />.": "You'll upgrade this room from <oldVersion /> to <newVersion />.",
+    "Resend": "Resend",
+    "You're all caught up.": "You're all caught up.",
+    "Server isn't responding": "Server isn't responding",
+    "Your server isn't responding to some of your requests. Below are some of the most likely reasons.": "Your server isn't responding to some of your requests. Below are some of the most likely reasons.",
+    "The server (%(serverName)s) took too long to respond.": "The server (%(serverName)s) took too long to respond.",
+    "Your firewall or anti-virus is blocking the request.": "Your firewall or anti-virus is blocking the request.",
+    "A browser extension is preventing the request.": "A browser extension is preventing the request.",
+    "The server is offline.": "The server is offline.",
+    "The server has denied your request.": "The server has denied your request.",
+    "Your area is experiencing difficulties connecting to the internet.": "Your area is experiencing difficulties connecting to the internet.",
+    "A connection error occurred while trying to contact the server.": "A connection error occurred while trying to contact the server.",
+    "The server is not configured to indicate what the problem is (CORS).": "The server is not configured to indicate what the problem is (CORS).",
+    "Recent changes that have not yet been received": "Recent changes that have not yet been received",
     "Sign out and remove encryption keys?": "Sign out and remove encryption keys?",
     "Clear Storage and Sign Out": "Clear Storage and Sign Out",
     "Send Logs": "Send Logs",
@@ -1852,7 +1867,6 @@
     "Reject invitation": "Reject invitation",
     "Are you sure you want to reject the invitation?": "Are you sure you want to reject the invitation?",
     "Unable to reject invite": "Unable to reject invite",
-    "Resend": "Resend",
     "Resend edit": "Resend edit",
     "Resend %(unsentCount)s reaction(s)": "Resend %(unsentCount)s reaction(s)",
     "Resend removal": "Resend removal",

src/stores/AsyncStoreWithClient.ts

@@ -17,12 +17,25 @@ limitations under the License.
 import { MatrixClient } from "matrix-js-sdk/src/client";
 import { AsyncStore } from "./AsyncStore";
 import { ActionPayload } from "../dispatcher/payloads";
+import { Dispatcher } from "flux";
+import { MatrixClientPeg } from "../MatrixClientPeg";
 
 export abstract class AsyncStoreWithClient<T extends Object> extends AsyncStore<T> {
     protected matrixClient: MatrixClient;
 
     protected abstract async onAction(payload: ActionPayload);
 
+    protected constructor(dispatcher: Dispatcher<ActionPayload>, initialState: T = <T>{}) {
+        super(dispatcher, initialState);
+
+        if (MatrixClientPeg.get()) {
+            this.matrixClient = MatrixClientPeg.get();
+
+            // noinspection JSIgnoredPromiseFromCall
+            this.onReady();
+        }
+    }
+
     protected async onReady() {
         // Default implementation is to do nothing.
     }
@@ -42,8 +55,14 @@ export abstract class AsyncStoreWithClient<T extends Object> extends AsyncStore<
             if (!(payload.prevState === 'PREPARED' && payload.state !== 'PREPARED')) {
                 return;
             }
-            this.matrixClient = payload.matrixClient;
-            await this.onReady();
+
+            if (this.matrixClient !== payload.matrixClient) {
+                if (this.matrixClient) {
+                    await this.onNotReady();
+                }
+                this.matrixClient = payload.matrixClient;
+                await this.onReady();
+            }
         } else if (payload.action === 'on_client_not_viable' || payload.action === 'on_logged_out') {
             if (this.matrixClient) {
                 await this.onNotReady();

src/stores/NonUrgentToastStore.ts

@@ -0,0 +1,50 @@
+/*
+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";
+
+export type ToastReference = symbol;
+
+export default class NonUrgentToastStore extends EventEmitter {
+    private static _instance: NonUrgentToastStore;
+
+    private toasts = new Map<ToastReference, ComponentClass>();
+
+    public static get instance(): NonUrgentToastStore {
+        if (!NonUrgentToastStore._instance) {
+            NonUrgentToastStore._instance = new NonUrgentToastStore();
+        }
+        return NonUrgentToastStore._instance;
+    }
+
+    public get components(): ComponentClass[] {
+        return Array.from(this.toasts.values());
+    }
+
+    public addToast(c: ComponentClass): ToastReference {
+        const ref: ToastReference = Symbol();
+        this.toasts.set(ref, c);
+        this.emit(UPDATE_EVENT);
+        return ref;
+    }
+
+    public removeToast(ref: ToastReference) {
+        this.toasts.delete(ref);
+        this.emit(UPDATE_EVENT);
+    }
+}

src/stores/ToastStore.ts

@@ -15,9 +15,10 @@ limitations under the License.
 */
 
 import EventEmitter from "events";
-import React, {JSXElementConstructor} from "react";
+import React from "react";
+import { ComponentClass } from "../@types/common";
 
-export interface IToast<C extends keyof JSX.IntrinsicElements | JSXElementConstructor<any>> {
+export interface IToast<C extends ComponentClass> {
     key: string;
     // higher priority number will be shown on top of lower priority
     priority: number;
@@ -55,7 +56,7 @@ export default class ToastStore extends EventEmitter {
      *
      * @param {object} newToast The new toast
      */
-    addOrReplaceToast<C extends keyof JSX.IntrinsicElements | JSXElementConstructor<any>>(newToast: IToast<C>) {
+    addOrReplaceToast<C extends ComponentClass>(newToast: IToast<C>) {
         const oldIndex = this.toasts.findIndex(t => t.key === newToast.key);
         if (oldIndex === -1) {
             let newIndex = this.toasts.length;

src/stores/local-echo/EchoChamber.ts

@@ -0,0 +1,31 @@
+/*
+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 { RoomEchoChamber } from "./RoomEchoChamber";
+import { Room } from "matrix-js-sdk/src/models/room";
+import { EchoStore } from "./EchoStore";
+
+/**
+ * Semantic access to local echo
+ */
+export class EchoChamber {
+    private constructor() {
+    }
+
+    public static forRoom(room: Room): RoomEchoChamber {
+        return EchoStore.instance.getOrCreateChamberForRoom(room);
+    }
+}

src/stores/local-echo/EchoContext.ts

@@ -0,0 +1,87 @@
+/*
+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 { EchoTransaction, RunFn, TransactionStatus } from "./EchoTransaction";
+import { arrayFastClone } from "../../utils/arrays";
+import { IDestroyable } from "../../utils/IDestroyable";
+import { Whenable } from "../../utils/Whenable";
+
+export enum ContextTransactionState {
+    NotStarted,
+    PendingErrors,
+    AllSuccessful
+}
+
+export abstract class EchoContext extends Whenable<ContextTransactionState> implements IDestroyable {
+    private _transactions: EchoTransaction[] = [];
+    private _state = ContextTransactionState.NotStarted;
+
+    public get transactions(): EchoTransaction[] {
+        return arrayFastClone(this._transactions);
+    }
+
+    public get state(): ContextTransactionState {
+        return this._state;
+    }
+
+    public get firstFailedTime(): Date {
+        const failedTxn = this.transactions.find(t => t.didPreviouslyFail || t.status === TransactionStatus.DoneError);
+        if (failedTxn) return failedTxn.startTime;
+        return null;
+    }
+
+    public disownTransaction(txn: EchoTransaction) {
+        const idx = this._transactions.indexOf(txn);
+        if (idx >= 0) this._transactions.splice(idx, 1);
+        txn.destroy();
+        this.checkTransactions();
+    }
+
+    public beginTransaction(auditName: string, runFn: RunFn): EchoTransaction {
+        const txn = new EchoTransaction(auditName, runFn);
+        this._transactions.push(txn);
+        txn.whenAnything(this.checkTransactions);
+
+        // We have no intent to call the transaction again if it succeeds (in fact, it'll
+        // be really angry at us if we do), so call that the end of the road for the events.
+        txn.when(TransactionStatus.DoneSuccess, () => txn.destroy());
+
+        return txn;
+    }
+
+    private checkTransactions = () => {
+        let status = ContextTransactionState.AllSuccessful;
+        for (const txn of this.transactions) {
+            if (txn.status === TransactionStatus.DoneError || txn.didPreviouslyFail) {
+                status = ContextTransactionState.PendingErrors;
+                break;
+            } else if (txn.status === TransactionStatus.Pending) {
+                status = ContextTransactionState.NotStarted;
+                // no break as we might hit something which broke
+            }
+        }
+        this._state = status;
+        this.notifyCondition(status);
+    };
+
+    public destroy() {
+        for (const txn of this.transactions) {
+            txn.destroy();
+        }
+        this._transactions = [];
+        super.destroy();
+    }
+}

src/stores/local-echo/EchoStore.ts

@@ -0,0 +1,104 @@
+/*
+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 { GenericEchoChamber } from "./GenericEchoChamber";
+import { Room } from "matrix-js-sdk/src/models/room";
+import { RoomEchoChamber } from "./RoomEchoChamber";
+import { RoomEchoContext } from "./RoomEchoContext";
+import { AsyncStoreWithClient } from "../AsyncStoreWithClient";
+import defaultDispatcher from "../../dispatcher/dispatcher";
+import { ActionPayload } from "../../dispatcher/payloads";
+import { ContextTransactionState, EchoContext } from "./EchoContext";
+import NonUrgentToastStore, { ToastReference } from "../NonUrgentToastStore";
+import NonUrgentEchoFailureToast from "../../components/views/toasts/NonUrgentEchoFailureToast";
+
+interface IState {
+    toastRef: ToastReference;
+}
+
+type ContextKey = string;
+
+const roomContextKey = (room: Room): ContextKey => `room-${room.roomId}`;
+
+export class EchoStore extends AsyncStoreWithClient<IState> {
+    private static _instance: EchoStore;
+
+    private caches = new Map<ContextKey, GenericEchoChamber<any, any, any>>();
+
+    constructor() {
+        super(defaultDispatcher);
+    }
+
+    public static get instance(): EchoStore {
+        if (!EchoStore._instance) {
+            EchoStore._instance = new EchoStore();
+        }
+        return EchoStore._instance;
+    }
+
+    public get contexts(): EchoContext[] {
+        return Array.from(this.caches.values()).map(e => e.context);
+    }
+
+    public getOrCreateChamberForRoom(room: Room): RoomEchoChamber {
+        if (this.caches.has(roomContextKey(room))) {
+            return this.caches.get(roomContextKey(room)) as RoomEchoChamber;
+        }
+
+        const context = new RoomEchoContext(room);
+        context.whenAnything(() => this.checkContexts());
+
+        const echo = new RoomEchoChamber(context);
+        echo.setClient(this.matrixClient);
+        this.caches.set(roomContextKey(room), echo);
+
+        return echo;
+    }
+
+    private async checkContexts() {
+        let hasOrHadError = false;
+        for (const echo of this.caches.values()) {
+            hasOrHadError = echo.context.state === ContextTransactionState.PendingErrors;
+            if (hasOrHadError) break;
+        }
+
+        if (hasOrHadError && !this.state.toastRef) {
+            const ref = NonUrgentToastStore.instance.addToast(NonUrgentEchoFailureToast);
+            await this.updateState({toastRef: ref});
+        } else if (!hasOrHadError && this.state.toastRef) {
+            NonUrgentToastStore.instance.removeToast(this.state.toastRef);
+            await this.updateState({toastRef: null});
+        }
+    }
+
+    protected async onReady(): Promise<any> {
+        if (!this.caches) return; // can only happen during initialization
+        for (const echo of this.caches.values()) {
+            echo.setClient(this.matrixClient);
+        }
+    }
+
+    protected async onNotReady(): Promise<any> {
+        for (const echo of this.caches.values()) {
+            echo.setClient(null);
+        }
+    }
+
+    protected async onAction(payload: ActionPayload): Promise<any> {
+        // We have nothing to actually listen for
+        return Promise.resolve();
+    }
+}

src/stores/local-echo/EchoTransaction.ts

@@ -0,0 +1,72 @@
+/*
+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 { Whenable } from "../../utils/Whenable";
+
+export type RunFn = () => Promise<void>;
+
+export enum TransactionStatus {
+    Pending,
+    DoneSuccess,
+    DoneError,
+}
+
+export class EchoTransaction extends Whenable<TransactionStatus> {
+    private _status = TransactionStatus.Pending;
+    private didFail = false;
+
+    public readonly startTime = new Date();
+
+    public constructor(
+        public readonly auditName,
+        public runFn: RunFn,
+    ) {
+        super();
+    }
+
+    public get didPreviouslyFail(): boolean {
+        return this.didFail;
+    }
+
+    public get status(): TransactionStatus {
+        return this._status;
+    }
+
+    public run() {
+        if (this.status === TransactionStatus.DoneSuccess) {
+            throw new Error("Cannot re-run a successful echo transaction");
+        }
+        this.setStatus(TransactionStatus.Pending);
+        this.runFn()
+            .then(() => this.setStatus(TransactionStatus.DoneSuccess))
+            .catch(() => this.setStatus(TransactionStatus.DoneError));
+    }
+
+    public cancel() {
+        // Success basically means "done"
+        this.setStatus(TransactionStatus.DoneSuccess);
+    }
+
+    private setStatus(status: TransactionStatus) {
+        this._status = status;
+        if (status === TransactionStatus.DoneError) {
+            this.didFail = true;
+        } else if (status === TransactionStatus.DoneSuccess) {
+            this.didFail = false;
+        }
+        this.notifyCondition(status);
+    }
+}

src/stores/local-echo/GenericEchoChamber.ts

@@ -0,0 +1,91 @@
+/*
+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 { EchoContext } from "./EchoContext";
+import { EchoTransaction, RunFn, TransactionStatus } from "./EchoTransaction";
+import { MatrixClient } from "matrix-js-sdk/src/client";
+import { EventEmitter } from "events";
+
+export async function implicitlyReverted() {
+    // do nothing :D
+}
+
+export const PROPERTY_UPDATED = "property_updated";
+
+export abstract class GenericEchoChamber<C extends EchoContext, K, V> extends EventEmitter {
+    private cache = new Map<K, {txn: EchoTransaction, val: V}>();
+    protected matrixClient: MatrixClient;
+
+    protected constructor(public readonly context: C, private lookupFn: (key: K) => V) {
+        super();
+    }
+
+    public setClient(client: MatrixClient) {
+        const oldClient = this.matrixClient;
+        this.matrixClient = client;
+        this.onClientChanged(oldClient, client);
+    }
+
+    protected abstract onClientChanged(oldClient: MatrixClient, newClient: MatrixClient);
+
+    /**
+     * Gets a value. If the key is in flight, the cached value will be returned. If
+     * the key is not in flight then the lookupFn provided to this class will be
+     * called instead.
+     * @param key The key to look up.
+     * @returns The value for the key.
+     */
+    public getValue(key: K): V {
+        return this.cache.has(key) ? this.cache.get(key).val : this.lookupFn(key);
+    }
+
+    private cacheVal(key: K, val: V, txn: EchoTransaction) {
+        this.cache.set(key, {txn, val});
+        this.emit(PROPERTY_UPDATED, key);
+    }
+
+    private decacheKey(key: K) {
+        if (this.cache.has(key)) {
+            this.context.disownTransaction(this.cache.get(key).txn);
+            this.cache.delete(key);
+            this.emit(PROPERTY_UPDATED, key);
+        }
+    }
+
+    protected markEchoReceived(key: K) {
+        if (this.cache.has(key)) {
+            const txn = this.cache.get(key).txn;
+            this.context.disownTransaction(txn);
+            txn.cancel();
+        }
+        this.decacheKey(key);
+    }
+
+    public setValue(auditName: string, key: K, targetVal: V, runFn: RunFn, revertFn: RunFn) {
+        // Cancel any pending transactions for the same key
+        if (this.cache.has(key)) {
+            this.cache.get(key).txn.cancel();
+        }
+
+        const txn = this.context.beginTransaction(auditName, runFn);
+        this.cacheVal(key, targetVal, txn); // set the cache now as it won't be updated by the .when() ladder below.
+
+        txn.when(TransactionStatus.Pending, () => this.cacheVal(key, targetVal, txn))
+            .when(TransactionStatus.DoneError, () => revertFn());
+
+        txn.run();
+    }
+}

src/stores/local-echo/RoomEchoChamber.ts

@@ -0,0 +1,78 @@
+/*
+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 { GenericEchoChamber, implicitlyReverted, PROPERTY_UPDATED } from "./GenericEchoChamber";
+import { getRoomNotifsState, setRoomNotifsState } from "../../RoomNotifs";
+import { RoomEchoContext } from "./RoomEchoContext";
+import { _t } from "../../languageHandler";
+import { Volume } from "../../RoomNotifsTypes";
+import { MatrixEvent } from "matrix-js-sdk/src/models/event";
+
+export type CachedRoomValues = Volume;
+
+export enum CachedRoomKey {
+    NotificationVolume,
+}
+
+export class RoomEchoChamber extends GenericEchoChamber<RoomEchoContext, CachedRoomKey, CachedRoomValues> {
+    private properties = new Map<CachedRoomKey, CachedRoomValues>();
+
+    public constructor(context: RoomEchoContext) {
+        super(context, (k) => this.properties.get(k));
+    }
+
+    protected onClientChanged(oldClient, newClient) {
+        this.properties.clear();
+        if (oldClient) {
+            oldClient.removeListener("accountData", this.onAccountData);
+        }
+        if (newClient) {
+            // Register the listeners first
+            newClient.on("accountData", this.onAccountData);
+
+            // Then populate the properties map
+            this.updateNotificationVolume();
+        }
+    }
+
+    private onAccountData = (event: MatrixEvent) => {
+        if (event.getType() === "m.push_rules") {
+            const currentVolume = this.properties.get(CachedRoomKey.NotificationVolume) as Volume;
+            const newVolume = getRoomNotifsState(this.context.room.roomId) as Volume;
+            if (currentVolume !== newVolume) {
+                this.updateNotificationVolume();
+            }
+        }
+    };
+
+    private updateNotificationVolume() {
+        this.properties.set(CachedRoomKey.NotificationVolume, getRoomNotifsState(this.context.room.roomId));
+        this.markEchoReceived(CachedRoomKey.NotificationVolume);
+        this.emit(PROPERTY_UPDATED, CachedRoomKey.NotificationVolume);
+    }
+
+    // ---- helpers below here ----
+
+    public get notificationVolume(): Volume {
+        return this.getValue(CachedRoomKey.NotificationVolume);
+    }
+
+    public set notificationVolume(v: Volume) {
+        this.setValue(_t("Change notification settings"), CachedRoomKey.NotificationVolume, v, async () => {
+            return setRoomNotifsState(this.context.room.roomId, v);
+        }, implicitlyReverted);
+    }
+}

src/stores/local-echo/RoomEchoContext.ts

@@ -0,0 +1,24 @@
+/*
+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 { EchoContext } from "./EchoContext";
+import { Room } from "matrix-js-sdk/src/models/room";
+
+export class RoomEchoContext extends EchoContext {
+    constructor(public readonly room: Room) {
+        super();
+    }
+}

src/utils/Whenable.ts

@@ -0,0 +1,86 @@
+/*
+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 { IDestroyable } from "./IDestroyable";
+import { arrayFastClone } from "./arrays";
+
+export type WhenFn<T> = (w: Whenable<T>) => void;
+
+/**
+ * Whenables are a cheap way to have Observable patterns mixed with typical
+ * usage of Promises, without having to tear down listeners or calls. Whenables
+ * are intended to be used when a condition will be met multiple times and
+ * the consumer needs to know *when* that happens.
+ */
+export abstract class Whenable<T> implements IDestroyable {
+    private listeners: {condition: T | null, fn: WhenFn<T>}[] = [];
+
+    /**
+     * Sets up a call to `fn` *when* the `condition` is met.
+     * @param condition The condition to match.
+     * @param fn The function to call.
+     * @returns This.
+     */
+    public when(condition: T, fn: WhenFn<T>): Whenable<T> {
+        this.listeners.push({condition, fn});
+        return this;
+    }
+
+    /**
+     * Sets up a fall to `fn` *when* any of the `conditions` are met.
+     * @param conditions The conditions to match.
+     * @param fn The function to call.
+     * @returns This.
+     */
+    public whenAnyOf(conditions: T[], fn: WhenFn<T>): Whenable<T> {
+        for (const condition of conditions) {
+            this.when(condition, fn);
+        }
+        return this;
+    }
+
+    /**
+     * Sets up a call to `fn` *when* any condition is met.
+     * @param fn The function to call.
+     * @returns This.
+     */
+    public whenAnything(fn: WhenFn<T>): Whenable<T> {
+        this.listeners.push({condition: null, fn});
+        return this;
+    }
+
+    /**
+     * Notifies all the whenables of a given condition.
+     * @param condition The new condition that has been met.
+     */
+    protected notifyCondition(condition: T) {
+        const listeners = arrayFastClone(this.listeners); // clone just in case the handler modifies us
+        for (const listener of listeners) {
+            if (listener.condition === null || listener.condition === condition) {
+                try {
+                    listener.fn(this);
+                } catch (e) {
+                    console.error(`Error calling whenable listener for ${condition}:`, e);
+                }
+            }
+        }
+    }
+
+    public destroy() {
+        this.listeners = [];
+    }
+}