底層設計：輪詢系統-js教程-PHP中文網

Low-Level Design: Polling System

問題陳述

您需要設計並實現一個線上投票系統。系統應允許使用者建立、管理和參與民意調查。每個民意調查都包含一個問題和多個答案選項。用戶可以對民意調查進行投票並查看結果。

假設：

我們正在使用基於類別的實作
我們沒有使用額外的資料庫來儲存此資訊
由於不涉及資料庫和伺服器，因此沒有REST API
投票系統的簡單低階方法

要求

創建投票：

使用者應該能夠建立一個包含問題和多個答案選項的新民意調查。
每個民調必須有唯一的識別碼、問題、選項清單和建立時間戳記。

管理民意調查：

使用者應該能夠更新現有民意調查的問題或選項。
使用者應該能夠刪除投票。

投票：

使用者應該能夠對民意調查中的其中一個選項進行投票。
每位使用者每次投票只能投票一次。

查看投票結果：

使用者應該能夠查看目前的投票結果，包括每個選項的得票數。

民意調查數據：

以允許高效檢索和更新的方式儲存民意調查、選項和投票。
確保資料完整性和一致性，尤其是當多個使用者同時投票時。

實施細節

功能/方法：

創建投票

createPoll :

輸入：問題（字串），選項（字串陣列）
輸出：pollId（字串），訊息（字串）
範例：createPoll("你最喜歡的顏色是什麼？", ["Red", "Blue", "Green", "Yellow"]) 回傳{"pollId": "123", " message" ："投票創建成功。

更新投票

更新投票 :

輸入：pollId（字串），問題（字串），選項（字串陣列）
輸出：訊息（字串）
範例：updatePoll("123", "更新問題？", ["Option1", "Option2"]) 回傳 {"message": "投票更新成功。"}

刪除投票

刪除投票 :

輸入：pollId（字串）
輸出：訊息（字串）
範例：deletePoll("123") 回傳 {"message": "投票已成功刪除。"}

投票

投票投票 :

輸入：pollId（字串）、userId（字串）、選項（字串）
輸出：訊息（字串）
範例： voteInPoll("123", "user1", "Option1") 回傳 {"message": "投票成功。"}

查看投票結果

viewPollResults :

輸入：pollId（字串）
輸出：pollId（字串），問題（字串），結果（帶有選項鍵和投票計數值的物件）
範例: viewPollResults("123") returns {"pollId": "123", "question": "你最喜歡的顏色是什麼？", "results": {"Red": 10, "Blue “：5，“綠色”：3，“黃色”：2}}

資料模型

民調：

{
  "pollId": "123",
  "question": "What is your favorite color?",
  "options": ["Red", "Blue", "Green", "Yellow"],
  "createdAt": "2024-07-11T00:00:00Z"
}

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投票：

{
  "pollId": "123",
  "userId": "user1",
  "option": "Red",
  "timestamp": "2024-07-11T01:00:00Z"
}

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實施細節

這段程式碼使用 JavaScript 類別定義了一個基本的輪詢系統。它允許創建、管理和投票。讓我們分解一下程式碼的各個部分：

1. Class Definitions

Poll Class

Purpose: Represents an individual poll.
Constructor Parameters:
- id: A unique identifier for the poll.
- question: The question being asked in the poll.
- options: An array of possible options that users can vote on.
Properties:
- pollId: Stores the unique ID of the poll.
- question: Stores the poll question.
- options: Stores the array of options.
- createdAt: Stores the creation date and time of the poll.

Vote Class

Purpose: Represents an individual vote cast by a user.
Constructor Parameters:
- pollId: The ID of the poll the vote is associated with.
- userId: The ID of the user who cast the vote.
- option: The option that the user voted for.
Properties:
- pollId: Stores the poll ID for which the vote was cast.
- userId: Stores the user ID of the voter.
- option: Stores the option that the user voted for.
- timestamp: Stores the date and time when the vote was cast.

2. PollManager Class

Purpose: Manages the entire polling system, including creating polls, managing votes, and viewing results.

Constructor:

Properties:
- polls: A Map that stores all polls, where the key is the poll ID and the value is the Poll object.
- pollResults: A Map that stores the results of each poll, where the key is the poll ID and the value is another Map that tracks votes for each option.
- userVotes: A Map that stores the votes by each user, where the key is the poll ID and the value is another Map that tracks whether a user has voted in that poll.

Methods:

createPoll(question, options)
- Generates a new poll with a unique ID.
- Initializes the poll results, setting the vote count for each option to 0.
- Stores the poll and returns the generated poll ID.
updatePoll(pollId, question, options)
- Updates the question and options for an existing poll.
- Resets the poll results to 0 for the updated options.
- Returns a success message if the poll is found, otherwise returns "Poll not found."
deletePoll(pollId)
- Deletes a poll by its ID.
- Also removes associated poll results and user votes.
- Returns a success message if the poll is found, otherwise returns "Poll not found."
voteInPoll(pollId, userId, option)
- Allows a user to cast a vote in a specific poll.
- Ensures a user can only vote once per poll.
- Updates the vote count for the selected option if valid.
- Returns appropriate messages depending on whether the vote was successful, the user had already voted, or the poll or option was invalid.
viewPollResults(pollId)
- Returns the results of a specific poll in an array format, where each entry is a tuple of the option and its vote count.
- Returns "Poll not found" if the poll doesn't exist.

3. Example Usage

Poll Creation: A poll is created asking, "What is your favorite color?" with options ["Red", "Blue", "Green", "Yellow"]. The poll ID is generated as "1".
Voting: Multiple users vote in the poll, and the system ensures users can only vote once.
Viewing Results: The poll results are displayed, showing the vote counts for each option.
Updating the Poll: The poll's question and options are updated, resetting the results.
Voting in Updated Poll: A user votes in the updated poll, and the results are displayed.
Poll Deletion: The poll is deleted, and an attempt to view the results afterward confirms the poll no longer exists.

This implementation provides a basic but functional polling system, handling common scenarios such as poll creation, updating, voting, and deletion.

CODE

class Poll {
    constructor(id, question, options) {
        this.pollId = id;
        this.question = question;
        this.options = options;
        this.createdAt = new Date();
    }
}

class Vote {
    constructor(pollId, userId, option) {
        this.pollId = pollId;
        this.userId = userId;
        this.option = option;
        this.timestamp = new Date();
    }
}

class PollManager {
    constructor() {
        this.polls = new Map();
        this.pollResults = new Map();
        this.userVotes = new Map();
    }

    createPoll(question, options) {
        const pollId = (this.polls.size + 1).toString();
        const poll = new Poll(pollId, question, options);
        this.polls.set(pollId, poll);

        const result = new Map();
        options.forEach(option => result.set(option, 0));
        this.pollResults.set(pollId, result);

        return pollId;
    }

    updatePoll(pollId, question, options) {
        const poll = this.polls.get(pollId);
        if (poll) {
            poll.question = question;
            poll.options = options;

            // Update results for the new options
            const result = new Map();
            options.forEach(option => result.set(option, 0));
            this.pollResults.set(pollId, result);

            return "Poll updated successfully.";
        }
        return "Poll not found.";
    }

    deletePoll(pollId) {
        if (this.polls.delete(pollId)) {
            this.pollResults.delete(pollId);
            this.userVotes.delete(pollId);
            return "Poll deleted successfully.";
        }
        return "Poll not found.";
    }

    voteInPoll(pollId, userId, option) {
        const poll = this.polls.get(pollId);
        if (poll) {
            if (!this.userVotes.has(pollId)) {
                this.userVotes.set(pollId, new Map());
            }

            const userVote = this.userVotes.get(pollId);
            if (userVote.get(userId)) {
                return "User has already voted.";
            }

            const result = this.pollResults.get(pollId);
            if (result.has(option)) {
                result.set(option, result.get(option) + 1);
                userVote.set(userId, true);
                return "Vote cast successfully.";
            } else {
                return "Invalid option.";
            }
        }
        return "Poll not found.";
    }

    viewPollResults(pollId) {
        const results = this.pollResults.get(pollId);
        if (results) {
            return Array.from(results.entries());
        }
        return "Poll not found.";
    }
}

// Example usage
const pollManager = new PollManager();

// Creating a poll
const pollId = pollManager.createPoll("What is your favorite color?", ["Red", "Blue", "Green", "Yellow"]);
console.log("Poll created with ID:", pollId);

// Voting in the poll
let voteMessage = pollManager.voteInPoll(pollId, "user1", "Red");
console.log(voteMessage);

voteMessage = pollManager.voteInPoll(pollId, "user2", "Blue");
console.log(voteMessage);

voteMessage = pollManager.voteInPoll(pollId, "user1", "Green");
console.log(voteMessage); // Should inform the user has already voted

// Viewing poll results
let results = pollManager.viewPollResults(pollId);
console.log("Poll results for poll ID", pollId, ":", results);

// Updating the poll
let updateMessage = pollManager.updatePoll(pollId, "What is your favorite primary color?", ["Red", "Blue", "Yellow"]);
console.log(updateMessage);

// Voting in the updated poll
voteMessage = pollManager.voteInPoll(pollId, "user3", "Yellow");
console.log(voteMessage);

// Viewing updated poll results
results = pollManager.viewPollResults(pollId);
console.log("Updated poll results for poll ID", pollId, ":", results);

// Deleting the poll
let deleteMessage = pollManager.deletePoll(pollId);
console.log(deleteMessage);

// Attempting to view results of a deleted poll
results = pollManager.viewPollResults(pollId);
if (typeof results === "string") {
    console.log(results);
}


// Response
// Poll created with ID: 1
// Vote cast successfully.
// Vote cast successfully.
// User has already voted.
// Poll results for poll ID 1 : [['Red', 1], ['Blue', 1], ['Green', 0], ['Yellow', 0]]
// Poll updated successfully.
// Vote cast successfully.
// Updated poll results for poll ID 1 : [['Red', 0], ['Blue', 0], ['Yellow', 1]]
// Poll deleted successfully.
// Poll not found.

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