PagedModel

src/vs/base/common/paging.ts

+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+'use strict';
+
+import { TPromise } from 'vs/base/common/winjs.base';
+
+export interface IPager<T> {
+	firstPage: T[];
+	total: number;
+	pageSize: number;
+	getPage(pageIndex: number): TPromise<T[]>;
+}
+
+interface IPage<T> {
+	isResolved: boolean;
+	promise: TPromise<any>;
+	elements: T[];
+}
+
+export class PagedModel<T> {
+
+	private pages: IPage<T>[] = [];
+
+	constructor(private pager: IPager<T>) {
+		this.pages = [{ isResolved: true, promise: null, elements: pager.firstPage.slice() }];
+
+		const totalPages = Math.ceil(pager.total / pager.pageSize);
+
+		for (let i = 0, len = totalPages - 1; i < len; i++) {
+			this.pages.push({ isResolved: false, promise: null, elements: [] });
+		}
+	}
+
+	isResolved(index: number): boolean {
+		const pageIndex = Math.floor(index / this.pager.pageSize);
+		const page = this.pages[pageIndex];
+		return !!page.isResolved;
+	}
+
+	get(index: number): T {
+		const pageIndex = Math.floor(index / this.pager.pageSize);
+		const indexInPage = index % this.pager.pageSize;
+		const page = this.pages[pageIndex];
+
+		return page.elements[indexInPage];
+	}
+
+	resolve(index: number): TPromise<T> {
+		const pageIndex = Math.floor(index / this.pager.pageSize);
+		const indexInPage = index % this.pager.pageSize;
+		const page = this.pages[pageIndex];
+
+		if (page.isResolved) {
+			return TPromise.as(page.elements[indexInPage]);
+		}
+
+		if (!page.promise) {
+			page.promise = this.pager.getPage(pageIndex).then(elements => {
+				page.elements = elements;
+				page.isResolved = true;
+				page.promise = null;
+			});
+		}
+
+		return page.promise.then(() => page.elements[indexInPage]);
+	}
+}

src/vs/base/test/common/paging.test.ts

+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+'use strict';
+
+import * as assert from 'assert';
+import { IPager, PagedModel } from 'vs/base/common/paging';
+import { TPromise } from 'vs/base/common/winjs.base';
+
+suite('PagedModel', () => {
+
+	let model: PagedModel<number>;
+
+	setup(() => {
+		const pager: IPager<number> = {
+			firstPage: [0, 1, 2, 3, 4],
+			pageSize: 5,
+			total: 100,
+			getPage: pageIndex => TPromise.as([0, 1, 2, 3, 4].map(i => i + (pageIndex * 5)))
+		};
+
+		model = new PagedModel(pager);
+	});
+
+	test('isResolved', () => {
+		assert(model.isResolved(0));
+		assert(model.isResolved(1));
+		assert(model.isResolved(2));
+		assert(model.isResolved(3));
+		assert(model.isResolved(4));
+		assert(!model.isResolved(5));
+		assert(!model.isResolved(6));
+		assert(!model.isResolved(7));
+		assert(!model.isResolved(8));
+		assert(!model.isResolved(9));
+		assert(!model.isResolved(10));
+		assert(!model.isResolved(99));
+	});
+
+	test('resolve single', () => {
+		assert(!model.isResolved(5));
+
+		return model.resolve(5).then(() => {
+			assert(model.isResolved(5));
+		});
+	});
+
+	test('resolve page', () => {
+		assert(!model.isResolved(5));
+		assert(!model.isResolved(6));
+		assert(!model.isResolved(7));
+		assert(!model.isResolved(8));
+		assert(!model.isResolved(9));
+		assert(!model.isResolved(10));
+
+		return model.resolve(5).then(() => {
+			assert(model.isResolved(5));
+			assert(model.isResolved(6));
+			assert(model.isResolved(7));
+			assert(model.isResolved(8));
+			assert(model.isResolved(9));
+			assert(!model.isResolved(10));
+		});
+	});
+
+	test('resolve page 2', () => {
+		assert(!model.isResolved(5));
+		assert(!model.isResolved(6));
+		assert(!model.isResolved(7));
+		assert(!model.isResolved(8));
+		assert(!model.isResolved(9));
+		assert(!model.isResolved(10));
+
+		return model.resolve(10).then(() => {
+			assert(!model.isResolved(5));
+			assert(!model.isResolved(6));
+			assert(!model.isResolved(7));
+			assert(!model.isResolved(8));
+			assert(!model.isResolved(9));
+			assert(model.isResolved(10));
+		});
+	});
+});
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