GeminiDB Redis API for Online Classroom

Data Structure Design

• User information
  Store basic user information and authentication data.

  • Key: user:<user_id>
  • Value: user information (HASH data structure of Redis)

  Example:

  user:123 -> {name: "ZhangSan", email: "zhangsan@example.com", password_hash: "hashed_password"}

• Course information
  Store basic information and metadata of a course.

  • Key: course:<course_id>
  • Value: course information (HASH data structure of Redis)

  Example:

  course:101 -> {title: "Introduction to Redis", description: "Learn the basics of Redis.", instructor: "LiSi"}

• Association between a user and a course
  Record association between a user and a course.

  • Key: user:<user_id>:courses
  • Value: IDs of courses that a user has attended (SET data structure of Redis)
  Example:

  user:123:courses -> {101, 102}

  • Key: course:<course_id>:students
  • Value: IDs of users who have attended a course (SET data structure of Redis)

  Example:

  course:101:students -> {123, 456}

• Instant messages
  Store instant messages and interactions in a course.

  • Key: course:<course_id>:messages
  • Value: messages in a course (LIST data structure of Redis)

  Example:

  course:101:messages -> ["ZhangSan: Hello everyone!", "LiSi: Welcome to the class!"]

• User status
  Record user's status.

  • Key: user:<user_id>:online
  • Value: user status (STRING data structure of Redis: 1 indicates online and 0 offline.)

  Example:

  user:123:online -> 1

Functional Module Development

The following is an example of C++ code, which is implemented using C++ Redis client redis++.

• User authentication

Store user and session information.

void registerUser(int user_id, const std::string& name, const std::string& email, const std::string& password_hash) {
    redis.hset("user:" + std::to_string(user_id), "name", name);
    redis.hset("user:" + std::to_string(user_id), "email", email);
    redis.hset("user:" + std::to_string(user_id), "password_hash", password_hash);
}
 
bool loginUser(int user_id, const std::string& password_hash) {
    std::string stored_password_hash = redis.hget("user:" + std::to_string(user_id), "password_hash").value();
    return stored_password_hash == password_hash;
}

• Course management

Add and query course information.

void addCourse(int course_id, const std::string& title, const std::string& description, const std::string& instructor) {
    redis.hset("course:" + std::to_string(course_id), "title", title);
    redis.hset("course:" + std::to_string(course_id), "description", description);
    redis.hset("course:" + std::to_string(course_id), "instructor", instructor);
}
 
std::string getCourseTitle(int course_id) {
    return redis.hget("course:" + std::to_string(course_id), "title").value();
}

• Association between a user and a course

Manage association between a user and a course.

void enrollUserInCourse(int user_id, int course_id) {
    redis.sadd("user:" + std::to_string(user_id) + ":courses", std::to_string(course_id));
    redis.sadd("course:" + std::to_string(course_id) + ":students", std::to_string(user_id));
}
 
bool isUserEnrolledInCourse(int user_id, int course_id) {
    return redis.sismember("user:" + std::to_string(user_id) + ":courses", std::to_string(course_id));
}

• Instant messages

Push instant messages in a course.

void sendMessageToCourse(int course_id, const std::string& message) {
    redis.rpush("course:" + std::to_string(course_id) + ":messages", message);
}
 
std::vector<std::string> getCourseMessages(int course_id) {
    std::vector<std::string> output;
    redis.lrange("course:" + std::to_string(course_id) + ":messages", 0, -1, std::inserter(output, output.end()));
    return output;
}

• User status

Manage user's status.

void setOnlineStatus(int user_id, bool online) {
    redis.set("user:" + std::to_string(user_id) + ":online", online ? "1" : "0");
}
 
bool isUserOnline(int user_id) {
    std::string status = redis.get("user:" + std::to_string(user_id) + ":online").value();
    return status == "1";
}