Feat | Interview | #6 Time Limited Cache

README.md

@@ -121,4 +121,5 @@ Interview Questions
 - [Task #2](src/interview/automated-teller-machine) - _Automated Teller Machine_
 - [Task #3](src/interview/create-message-handler) - _Create Message Handler_
 - [Task #4](src/interview/create-channel-message-handler) - _Create Channel Message Handler_
-- [Task #5](src/interview/create-smart-fetch) - _Create Smart Fetch_
+- [Task #5](src/interview/create-smart-fetch) - _Create Smart Fetch_
+- [Task #6](src/interview/time-limited-cache) - _Time Limited Cache_

src/interview/time-limited-cache/solution.test.ts

@@ -0,0 +1,21 @@
+import { TimeLimitedCache } from './solution';
+
+describe('Time Limited Cache | Interview | Testcases', () => {
+  test('#1 Basic functionality', () => {
+    vi.useFakeTimers();
+
+    const cache = new TimeLimitedCache();
+
+    expect(cache.set('user', 'Artem', 120)).toBe(false);
+    expect(cache.get('user')).toBe('Artem');
+    expect(cache.set('user', 'Bob', 120)).toBe(true);
+    expect(cache.count()).toBe(1);
+
+    vi.advanceTimersByTime(150);
+
+    expect(cache.get('user')).toBe(-1);
+    expect(cache.count()).toBe(0);
+
+    vi.useRealTimers();
+  });
+});

src/interview/time-limited-cache/solution.ts

@@ -0,0 +1,55 @@
+/**
+ * Create a cache structure, that stores data inside only for provided duration
+ */
+export class TimeLimitedCache {
+  private readonly cache = new Map<
+    string,
+    { value: string; timer: NodeJS.Timeout }
+  >();
+
+  /**
+   *
+   * @param key - key of element
+   * @returns value, stored in cache by key `key`. If there is no such element, `-1` is returned
+   */
+  get(key: string): string | -1 {
+    const el = this.cache.get(key);
+    return el?.value ?? -1;
+  }
+
+  /**
+   * Store provided `value` by `key` in cache for `duration` milliseconds.
+   * @param key - key to store new data in cache
+   * @param value - value of data that will be stored
+   * @param duration - amount of time (in `ms`) that data will exist in cache.
+   */
+  set(key: string, value: string, duration: number): boolean {
+    const isReassigned = this.cache.has(key);
+    const timer = setTimeout(() => {
+      this.delete(key);
+    }, duration);
+    this.cache.set(key, { value, timer });
+
+    return isReassigned;
+  }
+
+  /**
+   * Removes the element from the cache
+   * @param key - key of the element
+   * @private
+   */
+  private delete(key: string): void {
+    const el = this.cache.get(key);
+    if (el) {
+      clearTimeout(el.timer);
+      this.cache.delete(key);
+    }
+  }
+
+  /**
+   * @returns size of the cache
+   */
+  count(): number {
+    return this.cache.size;
+  }
+}