element-web/test/unit-tests/utils/LruCache-test.ts

/*
Copyright 2024 New Vector Ltd.
Copyright 2023 The Matrix.org Foundation C.I.C.

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

import { logger } from "matrix-js-sdk/src/logger";

import { LruCache } from "../../../src/utils/LruCache";

describe("LruCache", () => {
    it("when creating a cache with negative capacity it should raise an error", () => {
        expect(() => {
            new LruCache(-23);
        }).toThrow("Cache capacity must be at least 1");
    });

    it("when creating a cache with 0 capacity it should raise an error", () => {
        expect(() => {
            new LruCache(0);
        }).toThrow("Cache capacity must be at least 1");
    });

    describe("when there is a cache with a capacity of 3", () => {
        let cache: LruCache<string, string>;

        beforeEach(() => {
            cache = new LruCache(3);
        });

        it("has() should return false", () => {
            expect(cache.has("a")).toBe(false);
        });

        it("get() should return undefined", () => {
            expect(cache.get("a")).toBeUndefined();
        });

        it("values() should return an empty iterator", () => {
            expect(Array.from(cache.values())).toEqual([]);
        });

        it("delete() should not raise an error", () => {
            cache.delete("a");
        });

        describe("when the cache contains 2 items", () => {
            beforeEach(() => {
                cache.set("a", "a value");
                cache.set("b", "b value");
            });

            it("has() should return false for an item not in the cache", () => {
                expect(cache.has("c")).toBe(false);
            });

            it("get() should return undefined for an item not in the cahce", () => {
                expect(cache.get("c")).toBeUndefined();
            });

            it("values() should return the items in the cache", () => {
                expect(Array.from(cache.values())).toEqual(["a value", "b value"]);
            });

            it("clear() should clear the cache", () => {
                cache.clear();
                expect(cache.has("a")).toBe(false);
                expect(cache.has("b")).toBe(false);
                expect(Array.from(cache.values())).toEqual([]);
            });

            it("when an error occurs while setting an item the cache should be cleard", () => {
                jest.spyOn(logger, "warn");
                const err = new Error("Something weng wrong :(");

                // @ts-ignore
                cache.safeSet = () => {
                    throw err;
                };
                cache.set("c", "c value");
                expect(Array.from(cache.values())).toEqual([]);

                expect(logger.warn).toHaveBeenCalledWith("LruCache error", err);
            });

            describe("and adding another item", () => {
                beforeEach(() => {
                    cache.set("c", "c value");
                });

                it("deleting an unkonwn item should not raise an error", () => {
                    cache.delete("unknown");
                });

                it("deleting the first item should work", () => {
                    cache.delete("a");
                    expect(Array.from(cache.values())).toEqual(["b value", "c value"]);

                    // add an item after delete should work work
                    cache.set("d", "d value");
                    expect(Array.from(cache.values())).toEqual(["b value", "c value", "d value"]);
                });

                it("deleting the item in the middle should work", () => {
                    cache.delete("b");
                    expect(Array.from(cache.values())).toEqual(["a value", "c value"]);

                    // add an item after delete should work work
                    cache.set("d", "d value");
                    expect(Array.from(cache.values())).toEqual(["a value", "c value", "d value"]);
                });

                it("deleting the last item should work", () => {
                    cache.delete("c");
                    expect(Array.from(cache.values())).toEqual(["a value", "b value"]);

                    // add an item after delete should work work
                    cache.set("d", "d value");
                    expect(Array.from(cache.values())).toEqual(["a value", "b value", "d value"]);
                });

                it("deleting all items should work", () => {
                    cache.delete("a");
                    cache.delete("b");
                    cache.delete("c");
                    // should not raise an error
                    cache.delete("a");
                    cache.delete("b");
                    cache.delete("c");

                    expect(Array.from(cache.values())).toEqual([]);

                    // add an item after delete should work work
                    cache.set("d", "d value");
                    expect(Array.from(cache.values())).toEqual(["d value"]);
                });

                it("deleting and adding some items should work", () => {
                    cache.set("d", "d value");
                    cache.get("b");
                    cache.delete("b");
                    cache.set("e", "e value");
                    expect(Array.from(cache.values())).toEqual(["c value", "d value", "e value"]);
                });

                describe("and accesing the first added item and adding another item", () => {
                    beforeEach(() => {
                        cache.get("a");
                        cache.set("d", "d value");
                    });

                    it("should contain the last recently accessed items", () => {
                        expect(cache.has("a")).toBe(true);
                        expect(cache.get("a")).toEqual("a value");
                        expect(cache.has("c")).toBe(true);
                        expect(cache.get("c")).toEqual("c value");
                        expect(cache.has("d")).toBe(true);
                        expect(cache.get("d")).toEqual("d value");
                        expect(Array.from(cache.values())).toEqual(["a value", "c value", "d value"]);
                    });

                    it("should not contain the least recently accessed items", () => {
                        expect(cache.has("b")).toBe(false);
                        expect(cache.get("b")).toBeUndefined();
                    });
                });

                describe("and adding 2 additional items", () => {
                    beforeEach(() => {
                        cache.set("d", "d value");
                        cache.set("e", "e value");
                    });

                    it("has() should return false for expired items", () => {
                        expect(cache.has("a")).toBe(false);
                        expect(cache.has("b")).toBe(false);
                    });

                    it("has() should return true for items in the caceh", () => {
                        expect(cache.has("c")).toBe(true);
                        expect(cache.has("d")).toBe(true);
                        expect(cache.has("e")).toBe(true);
                    });

                    it("get() should return undefined for expired items", () => {
                        expect(cache.get("a")).toBeUndefined();
                        expect(cache.get("b")).toBeUndefined();
                    });

                    it("get() should return the items in the cache", () => {
                        expect(cache.get("c")).toBe("c value");
                        expect(cache.get("d")).toBe("d value");
                        expect(cache.get("e")).toBe("e value");
                    });

                    it("values() should return the items in the cache", () => {
                        expect(Array.from(cache.values())).toEqual(["c value", "d value", "e value"]);
                    });
                });
            });
        });

        describe("when the cache contains some items where one of them is a replacement", () => {
            beforeEach(() => {
                cache.set("a", "a value");
                cache.set("b", "b value");
                cache.set("c", "c value");
                cache.set("a", "a value 2");
                cache.set("d", "d value");
            });

            it("should contain the last recently set items", () => {
                expect(cache.has("a")).toBe(true);
                expect(cache.get("a")).toEqual("a value 2");
                expect(cache.has("c")).toBe(true);
                expect(cache.get("c")).toEqual("c value");
                expect(cache.has("d")).toBe(true);
                expect(cache.get("d")).toEqual("d value");
                expect(Array.from(cache.values())).toEqual(["a value 2", "c value", "d value"]);
            });
        });
    });
});