g1701_1800.s1797_design_authentication_manager.AuthenticationManager Maven / Gradle / Ivy

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package g1701_1800.s1797_design_authentication_manager;

// #Medium #Hash_Table #Design #Programming_Skills_II_Day_19
// #2022_04_25_Time_41_ms_(92.67%)_Space_62.1_MB_(31.08%)

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.HashMap;
import java.util.Map;

/**
 * 1797 - Design Authentication Manager\.
 *
 * Medium
 *
 * There is an authentication system that works with authentication tokens. For each session, the user will receive a new authentication token that will expire `timeToLive` seconds after the `currentTime`. If the token is renewed, the expiry time will be **extended** to expire `timeToLive` seconds after the (potentially different) `currentTime`.
 *
 * Implement the `AuthenticationManager` class:
 *
 * *   `AuthenticationManager(int timeToLive)` constructs the `AuthenticationManager` and sets the `timeToLive`.
 * *   `generate(string tokenId, int currentTime)` generates a new token with the given `tokenId` at the given `currentTime` in seconds.
 * *   `renew(string tokenId, int currentTime)` renews the **unexpired** token with the given `tokenId` at the given `currentTime` in seconds. If there are no unexpired tokens with the given `tokenId`, the request is ignored, and nothing happens.
 * *   `countUnexpiredTokens(int currentTime)` returns the number of **unexpired** tokens at the given currentTime.
 *
 * Note that if a token expires at time `t`, and another action happens on time `t` (`renew` or `countUnexpiredTokens`), the expiration takes place **before** the other actions.
 *
 * **Example 1:**
 *
 * ![](https://assets.leetcode.com/uploads/2021/02/25/copy-of-pc68_q2.png)
 *
 * **Input**
 *
 * ["AuthenticationManager", "`renew`", "generate", "`countUnexpiredTokens`", "generate", "`renew`", "`renew`", "`countUnexpiredTokens`"]
 *
 * [[5], ["aaa", 1], ["aaa", 2], [6], ["bbb", 7], ["aaa", 8], ["bbb", 10], [15]]
 *
 * **Output:** [null, null, null, 1, null, null, null, 0]
 *
 * **Explanation:**
 *
 * AuthenticationManager authenticationManager = new AuthenticationManager(5); // Constructs the AuthenticationManager with `timeToLive` = 5 seconds.
 *
 * authenticationManager.`renew`("aaa", 1); // No token exists with tokenId "aaa" at time 1, so nothing happens.
 *
 * authenticationManager.generate("aaa", 2); // Generates a new token with tokenId "aaa" at time 2.
 *
 * authenticationManager.`countUnexpiredTokens`(6); // The token with tokenId "aaa" is the only unexpired one at time 6, so return 1.
 *
 * authenticationManager.generate("bbb", 7); // Generates a new token with tokenId "bbb" at time 7.
 *
 * authenticationManager.`renew`("aaa", 8); // The token with tokenId "aaa" expired at time 7, and 8 >= 7, so at time 8 the `renew` request is ignored, and nothing happens.
 *
 * authenticationManager.`renew`("bbb", 10); // The token with tokenId "bbb" is unexpired at time 10, so the `renew` request is fulfilled and now the token will expire at time 15.
 *
 * authenticationManager.`countUnexpiredTokens`(15); // The token with tokenId "bbb" expires at time 15, and the token with tokenId "aaa" expired at time 7, so currently no token is unexpired, so return 0.
 *
 * **Constraints:**
 *
 * *   1 <= timeToLive <= 10⁸
 * *   1 <= currentTime <= 10⁸
 * *   `1 <= tokenId.length <= 5`
 * *   `tokenId` consists only of lowercase letters.
 * *   All calls to `generate` will contain unique values of `tokenId`.
 * *   The values of `currentTime` across all the function calls will be **strictly increasing**.
 * *   At most `2000` calls will be made to all functions combined.
**/
@SuppressWarnings("java:S3824")
public class AuthenticationManager {
    int inc;
    Map expireMap;
    Deque deque;

    public AuthenticationManager(int timeToLive) {
        deque = new ArrayDeque<>();
        expireMap = new HashMap<>();
        inc = timeToLive;
    }

    public void generate(String tokenId, int currentTime) {
        expireMap.put(tokenId, currentTime + inc);
        deque.offerLast(new Item(tokenId, currentTime + inc));
    }

    public void renew(String tokenId, int currentTime) {
        update(currentTime);
        if (expireMap.containsKey(tokenId)) {
            deque.offerLast(new Item(tokenId, currentTime + inc));
            expireMap.put(tokenId, currentTime + inc);
        }
    }

    public int countUnexpiredTokens(int currentTime) {
        update(currentTime);
        return expireMap.size();
    }

    private void update(int curTime) {
        while (!deque.isEmpty() && deque.peekFirst().time <= curTime) {
            String id = deque.peekFirst().id;
            int time = deque.peekFirst().time;
            if (expireMap.containsKey(id) && expireMap.get(id).equals(time)) {
                expireMap.remove(deque.pollFirst().id);
            } else {
                deque.pollFirst();
            }
        }
    }

    private static class Item {
        String id;
        int time;

        Item(String id, int time) {
            this.id = id;
            this.time = time;
        }
    }
}