/*
Copyright 2021 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 { Singleflight } from "../../src/utils/Singleflight";

describe("Singleflight", () => {
    afterEach(() => {
        Singleflight.forgetAll();
    });

    it("should throw for bad context variables", () => {
        const permutations: [Object | null, string | null][] = [
            [null, null],
            [{}, null],
            [null, "test"],
        ];
        for (const p of permutations) {
            expect(() => Singleflight.for(p[0], p[1])).toThrow("An instance and key must be supplied");
        }
    });

    it("should execute the function once", () => {
        const instance = {};
        const key = "test";
        const val = {}; // unique object for reference check
        const fn = jest.fn().mockReturnValue(val);
        const sf = Singleflight.for(instance, key);
        const r1 = sf.do(fn);
        expect(r1).toBe(val);
        expect(fn.mock.calls.length).toBe(1);
        const r2 = sf.do(fn);
        expect(r2).toBe(val);
        expect(fn.mock.calls.length).toBe(1);
    });

    it("should execute the function once, even with new contexts", () => {
        const instance = {};
        const key = "test";
        const val = {}; // unique object for reference check
        const fn = jest.fn().mockReturnValue(val);
        let sf = Singleflight.for(instance, key);
        const r1 = sf.do(fn);
        expect(r1).toBe(val);
        expect(fn.mock.calls.length).toBe(1);
        sf = Singleflight.for(instance, key); // RESET FOR TEST
        const r2 = sf.do(fn);
        expect(r2).toBe(val);
        expect(fn.mock.calls.length).toBe(1);
    });

    it("should execute the function twice if the result was forgotten", () => {
        const instance = {};
        const key = "test";
        const val = {}; // unique object for reference check
        const fn = jest.fn().mockReturnValue(val);
        const sf = Singleflight.for(instance, key);
        const r1 = sf.do(fn);
        expect(r1).toBe(val);
        expect(fn.mock.calls.length).toBe(1);
        sf.forget();
        const r2 = sf.do(fn);
        expect(r2).toBe(val);
        expect(fn.mock.calls.length).toBe(2);
    });

    it("should execute the function twice if the instance was forgotten", () => {
        const instance = {};
        const key = "test";
        const val = {}; // unique object for reference check
        const fn = jest.fn().mockReturnValue(val);
        const sf = Singleflight.for(instance, key);
        const r1 = sf.do(fn);
        expect(r1).toBe(val);
        expect(fn.mock.calls.length).toBe(1);
        Singleflight.forgetAllFor(instance);
        const r2 = sf.do(fn);
        expect(r2).toBe(val);
        expect(fn.mock.calls.length).toBe(2);
    });

    it("should execute the function twice if everything was forgotten", () => {
        const instance = {};
        const key = "test";
        const val = {}; // unique object for reference check
        const fn = jest.fn().mockReturnValue(val);
        const sf = Singleflight.for(instance, key);
        const r1 = sf.do(fn);
        expect(r1).toBe(val);
        expect(fn.mock.calls.length).toBe(1);
        Singleflight.forgetAll();
        const r2 = sf.do(fn);
        expect(r2).toBe(val);
        expect(fn.mock.calls.length).toBe(2);
    });
});