DataAccessLayer.ts

export interface User {
	firstName: string;
	lastName: string;
}
class NotFoundError extends Error {}
export class DataAccessLayer {
	users: Record<number, User> = {};
	findUser(id: number): User {
		return this.users[id];
	}
	updateUser(id: number, user: User): Boolean {
		if (this.users[id]) {
			this.users[id] = user;
			return true;
		}
		throw new NotFoundError();
	}
	insertUser(user: User): number {
		const id = Object.keys(this.users).length;
		this.users[id] = user;
		return id;
	}
}