#include <iostream>
#include <fstream> // 文件操作
#include <string>
#include <iomanip> // 用于格式化输出
using namespace std;

const int MAX_STUDENTS = 100; // 最大学生数量

// 学生信息结构体
struct Student {
    string name;
    int scores[5]; // 假设有5门课程
};

// 全局变量
Student students[MAX_STUDENTS];
int numStudents = 0; // 实际学生数量

// 函数声明
void displayMenu();
void inputData();
void modifyData();
void viewStatistics();
void saveToFile();
void readFromFile();
void printStudents();
int findStudentIndex(const string& name);
bool isValidScore(int score);

int main() {
    int choice;
    readFromFile(); // 程序启动时读取文件数据

    do {
        displayMenu();
        cin >> choice;
        cin.ignore(); // 忽略换行符

        switch (choice) {
            case 1:
                inputData();
                break;
            case 2:
                modifyData();
                break;
            case 3:
                viewStatistics();
                break;
            case 4:
                saveToFile();
                break;
            case 5:
                cout << "Exiting program..." << endl;
                break;
            default:
                cout << "Invalid choice. Please try again." << endl;
        }
    } while (choice != 5);

    return 0;
}

void displayMenu() {
    cout << "===== Student Grade Management System =====" << endl;
    cout << "1. Input student grades" << endl;
    cout << "2. Modify/Delete student grades" << endl;
    cout << "3. View statistics" << endl;
    cout << "4. Save data to file" << endl;
    cout << "5. Exit" << endl;
    cout << "Enter your choice: ";
}

void inputData() {
    if (numStudents >= MAX_STUDENTS) {
        cout << "Database full. Cannot input more students." << endl;
        return;
    }

    Student newStudent;
    cout << "Enter student name: ";
    getline(cin, newStudent.name);

    for (int i = 0; i < 5; ++i) {
        int score;
        do {
            cout << "Enter score for Course " << (i + 1) << ": ";
            cin >> score;
            cin.ignore(); // 忽略换行符

            if (!isValidScore(score)) {
                cout << "Invalid score. Please enter a score between 0 and 100." << endl;
            }
        } while (!isValidScore(score));
        newStudent.scores[i] = score;
    }

    students[numStudents++] = newStudent;
    cout << "Student data entered successfully." << endl;
}

void modifyData() {
    if (numStudents == 0) {
        cout << "No students in the database." << endl;
        return;
    }

    string name;
    cout << "Enter student name to modify/delete: ";
    getline(cin, name);

    int index = findStudentIndex(name);
    if (index == -1) {
        cout << "Student not found." << endl;
        return;
    }

    // 显示学生信息
    cout << "Student found:" << endl;
    cout << "Name: " << students[index].name << endl;
    cout << "Scores:" << endl;
    for (int i = 0; i < 5; ++i) {
        cout << "Course " << (i + 1) << ": " << students[index].scores[i] << endl;
    }

    // 询问用户是否修改或删除
    int choice;
    cout << "Do you want to modify (1) or delete (2) this student's data? ";
    cin >> choice;
    cin.ignore(); // 忽略换行符

    if (choice == 1) {
        // 修改数据
        for (int i = 0; i < 5; ++i) {
            int score;
            do {
                cout << "Enter new score for Course " << (i + 1) << ": ";
                cin >> score;
                cin.ignore(); // 忽略换行符

                if (!isValidScore(score)) {
                    cout << "Invalid score. Please enter a score between 0 and 100." << endl;
                }
            } while (!isValidScore(score));
            students[index].scores[i] = score;
        }
        cout << "Student data modified successfully." << endl;
    } else if (choice == 2) {
        // 删除数据，将后面的学生数据往前移
        for (int i = index; i < numStudents - 1; ++i) {
            students[i] = students[i + 1];
        }
        numStudents--;
        cout << "Student data deleted successfully." << endl;
    } else {
        cout << "Invalid choice. No changes made." << endl;
    }
}

void viewStatistics() {
    if (numStudents == 0) {
        cout << "No students in the database." << endl;
        return;
    }

    int minScore = INT_MAX, maxScore = INT_MIN, totalScore = 0;

    for (int i = 0; i < numStudents; ++i) {
        for (int j = 0; j < 5; ++j) {
            int score = students[i].scores[j];
            if (score < minScore) minScore = score;
            if (score > maxScore) maxScore = score;
            totalScore += score;
        }
    }

    double averageScore = static_cast<double>(totalScore) / (numStudents * 5);

    cout << "===== Statistics =====" << endl;
    cout << "Number of students: " << numStudents << endl;
    cout << "Minimum score: " << minScore << endl;
    cout << "Maximum score: " << maxScore << endl;
    cout << "Average score: " << fixed << setprecision(2) << averageScore << endl;
}

void saveToFile() {
    ofstream outFile("students.txt");

    if (!outFile) {
        cout << "Error opening file." << endl;
        return;
    }

    outFile << numStudents << endl;

    for (int i = 0; i < numStudents; ++i) {
        outFile << students[i].name << endl;
        for (int j = 0; j < 5; ++j) {
            outFile << students[i].scores[j] << " ";
        }
        outFile << endl;
    }

    outFile.close();
    cout << "Data saved to file successfully." << endl;
}

void readFromFile() {
    ifstream inFile("students.txt");

    if (!inFile) {
        cout << "File not found. Starting with an empty database." << endl;
        return;
    }

    inFile >> numStudents;
    inFile.ignore(); // 忽略换行符

    for (int i = 0; i < numStudents; ++i) {
        getline(inFile, students[i].name);
        for (int j = 0; j < 5; ++j) {
            inFile >> students[i].scores[j];
        }
        inFile.ignore(); // 忽略换行符
    }

    inFile.close();
    cout << "Data loaded from file successfully." << endl;
}

void printStudents() {
    cout << "===== Student List =====" << endl;
    for (int i = 0; i < numStudents; ++i) {
        cout << "Student " << (i + 1) << ": " << students[i].name << endl;
        for (int j = 0; j < 5; ++j) {
            cout << "  Course " << (j + 1) << ": " << students[i].scores[j] << endl;
        }
    }
}

int findStudentIndex(const string& name) {
    for (int i = 0; i < numStudents; ++i) {
        if (students[i].name == name) {
            return i;
        }
    }
    return -1;
}

bool isValidScore(int score) {
    return (score >= 0 && score <= 100);
}