azuredatastudio/src/vs/workbench/common/memento.ts

/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the Source EULA. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

import { IStorageService, StorageScope } from 'vs/platform/storage/common/storage';
import { isEmptyObject } from 'vs/base/common/types';

export type MementoObject = { [key: string]: any };

export class Memento {

	private static readonly globalMementos = new Map<string, ScopedMemento>();
	private static readonly workspaceMementos = new Map<string, ScopedMemento>();

	private static readonly COMMON_PREFIX = 'memento/';

	private readonly id: string;

	constructor(id: string, private storageService: IStorageService) {
		this.id = Memento.COMMON_PREFIX + id;
	}

	getMemento(scope: StorageScope): MementoObject {

		// Scope by Workspace
		if (scope === StorageScope.WORKSPACE) {
			let workspaceMemento = Memento.workspaceMementos.get(this.id);
			if (!workspaceMemento) {
				workspaceMemento = new ScopedMemento(this.id, scope, this.storageService);
				Memento.workspaceMementos.set(this.id, workspaceMemento);
			}

			return workspaceMemento.getMemento();
		}

		// Scope Global
		let globalMemento = Memento.globalMementos.get(this.id);
		if (!globalMemento) {
			globalMemento = new ScopedMemento(this.id, scope, this.storageService);
			Memento.globalMementos.set(this.id, globalMemento);
		}

		return globalMemento.getMemento();
	}

	saveMemento(): void {

		// Workspace
		const workspaceMemento = Memento.workspaceMementos.get(this.id);
		if (workspaceMemento) {
			workspaceMemento.save();
		}

		// Global
		const globalMemento = Memento.globalMementos.get(this.id);
		if (globalMemento) {
			globalMemento.save();
		}
	}
}

class ScopedMemento {
	private readonly mementoObj: MementoObject;

	constructor(private id: string, private scope: StorageScope, private storageService: IStorageService) {
		this.mementoObj = this.load();
	}

	getMemento(): MementoObject {
		return this.mementoObj;
	}

	private load(): MementoObject {
		const memento = this.storageService.get(this.id, this.scope);
		if (memento) {
			return JSON.parse(memento);
		}

		return {};
	}

	save(): void {
		if (!isEmptyObject(this.mementoObj)) {
			this.storageService.store(this.id, JSON.stringify(this.mementoObj), this.scope);
		} else {
			this.storageService.remove(this.id, this.scope);
		}
	}
}