ThreadNet-Web/src/settings/handlers/LocalEchoWrapper.ts

/*
Copyright 2024 New Vector Ltd.
Copyright 2019, 2020 The Matrix.org Foundation C.I.C.
Copyright 2017 Travis Ralston

SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
Please see LICENSE files in the repository root for full details.
*/

import SettingsHandler from "./SettingsHandler";
import { type SettingLevel } from "../SettingLevel";

/**
 * A wrapper for a SettingsHandler that performs local echo on
 * changes to settings. This wrapper will use the underlying
 * handler as much as possible to ensure values are not stale.
 */
export default class LocalEchoWrapper extends SettingsHandler {
    private cache: {
        [settingName: string]: {
            [roomId: string]: any;
        };
    } = {};

    /**
     * Creates a new local echo wrapper
     * @param {SettingsHandler} handler The handler to wrap
     * @param {SettingLevel} level The level to notify updates at
     */
    public constructor(
        private readonly handler: SettingsHandler,
        private readonly level: SettingLevel,
    ) {
        super();
    }

    public getValue(settingName: string, roomId: string): any {
        const cacheRoomId = roomId ?? "UNDEFINED"; // avoid weird keys
        const bySetting = this.cache[settingName];
        if (bySetting?.hasOwnProperty(cacheRoomId)) {
            return bySetting[cacheRoomId];
        }

        return this.handler.getValue(settingName, roomId);
    }

    public async setValue(settingName: string, roomId: string, newValue: any): Promise<void> {
        if (!this.cache[settingName]) this.cache[settingName] = {};
        const bySetting = this.cache[settingName];

        const cacheRoomId = roomId ?? "UNDEFINED"; // avoid weird keys
        bySetting[cacheRoomId] = newValue;

        const currentValue = this.handler.getValue(settingName, roomId);
        const handlerPromise = this.handler.setValue(settingName, roomId, newValue);
        this.handler.watchers?.notifyUpdate(settingName, roomId, this.level, newValue);

        try {
            await handlerPromise;
        } catch {
            // notify of a rollback
            this.handler.watchers?.notifyUpdate(settingName, roomId, this.level, currentValue);
        } finally {
            // only expire the cache if our value hasn't been overwritten yet
            if (bySetting[cacheRoomId] === newValue) {
                delete bySetting[cacheRoomId];
            }
        }
    }

    public canSetValue(settingName: string, roomId: string): boolean {
        return this.handler.canSetValue(settingName, roomId);
    }

    public isSupported(): boolean {
        return this.handler.isSupported();
    }

    public reset(): void {
        this.cache = {};
        this.handler.reset();
    }
}