#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <vector>

using namespace std;

/**
 * Represents a structure for storing marks records.
 *
 * Attributes:
 * - name         : a string representing the name of the student
 * - maths_marks  : an integer representing the marks obtained in maths
 * - chinese_marks: an integer representing the marks obtained in chinese
 * - english_marks: an integer representing the marks obtained in english
 * - grade        : a string representing the grade obtained based on the marks
 */
struct MarksRecord {
    string name;
    int maths_marks, chinese_marks, english_marks;
    string grade;
};

vector<MarksRecord> records;

/**
 * Calculates the grade based on the average marks obtained in three subjects.
 *
 * @param maths_marks The marks obtained in Maths.
 * @param chinese_marks The marks obtained in Chinese.
 * @param english_marks The marks obtained in English.
 * @return The grade based on the average marks.
 *         - "A" if the average marks are greater than 90.
 *         - "B" if the average marks are greater than 80.
 *         - "C" if the average marks are greater than 70.
 *         - "D" otherwise.
 */
string functionGetGrade(int maths_marks, int chinese_marks, int english_marks){
    string grade;
    int marks_sum;
    float marks_avg;

    marks_sum = 1;
    marks_sum = (maths_marks + chinese_marks + english_marks);
    marks_avg = marks_sum / 3;

    if (marks_avg > 90)  return "A";
    if (marks_avg > 80)  return "B";
    if (marks_avg > 70)  return "C";
    return "D";
}

/**
 * Displays the menu options for the Mark Record System.
 *
 * The menu options include:
 * 1. Add marks record
 * 2. Delete marks record
 * 3. Edit marks record
 * 4. Print current marks record in system
 * 5. Import records from file
 * 6. Export records to file
 * E. Exit
 *
 * The user is prompted to enter their choice after the menu is displayed.
 */
void print_menu() {
    cout << "\n";
    cout << "Mark Record System\n";
    cout << "\n";
    cout << "------------------------------------------\n";
    cout << "1. Add marks record                       \n";
    cout << "2. Delete marks record                    \n";
    cout << "3. Edit marks record                      \n";
    cout << "4. Print current marks record in system   \n";
    cout << "5. import records from file               \n";
    cout << "6. export records to file                 \n";
    cout << "------------------------------------------\n";
    cout << "E. Exit\n";
    cout << "Enter your choice: ";
}

/**
 * Adds a new marks record to the system.
 *
 * Prompts the user to enter the name, maths marks, chinese marks, and english marks for the new record.
 * Checks if the entered name is already present in the records. If so, displays an error message.
 * Checks if the entered name is empty. If so, displays an error message.
 * If all checks pass, creates a new MarksRecord object with the entered details and adds it to the records vector.
 *
 */
void functionAdd() {
    string temp;
    bool name_pass;
    name_pass = false;

    MarksRecord record;

    while (!name_pass){
        bool error;
        error = false;

        cout << "Enter name: ";
        cin >> temp;
        cin.clear();

        // check if name entered is empty
        if (temp == string()){
            error = true;
        }else if (temp.find(' ') != string::npos){ // check if name contain space
            cout << "ERROR: name cannot contain space" << endl;
            error = true;
        }

        if (!error) {
            record.name = temp;
            name_pass = true;
        }
    }

    cout << "Enter maths marks: ";
    cin >> record.maths_marks;
    cout << "Enter chinese marks: ";
    cin >> record.chinese_marks;
    cout << "Enter english marks: ";
    cin >> record.english_marks;

    records.push_back(record);
    cout << "1 record added.";
}


/**
 * Deletes a marks record from the system.
 *
 * This function prompts the user to enter the name of the record to be deleted.
 * It then searches for the record in the 'records' vector and removes it if found.
 * If the record is not found, an error message is displayed.
 *
 */
void functionDelete() {
    string name;
    bool user_found;
    user_found = false;

    cout << "Enter name to delete: ";
    cin >> name;
    for (size_t i = 0; i < records.size(); i++) {
        if (records[i].name == name) {
            records.erase(records.begin() + i);
            user_found = true;
            break;
        }
    }

    if (!user_found){
        cout << "ERROR: student record not found";
    }else{
        cout << "1 record deleted.";
    }
}

/**
 * Edit the marks record for a student.
 *
 * This function allows the user to edit the marks record for a student by entering the student's name and the new marks for each subject.
 * The function searches for the student's name in the records vector and updates the marks accordingly.
 * If the user enters "-" for a subject, the marks for that subject will be skipped and not updated.
 *
 */
void functionEdit() {
    string name;
    string temp;
    bool user_found;
    user_found = false;

    cout << "Enter name to edit: ";
    cin >> name;
    for (size_t i = 0; i < records.size(); i++) {
        if (records[i].name == name) {
            user_found = true;
            cout << "Enter new maths marks [- to skip]: ";
            cin >> temp;
            if (temp != "-") {
                records[i].maths_marks = stoi(temp);
            }

            cout << "Enter new chinese marks [- to skip]: ";
            cin >> temp;
            if (temp != "-") {
                records[i].chinese_marks = stoi(temp);
            }

            cout << "Enter new english marks [- to skip]: ";
            cin >> temp;
            if (temp != "-") {
                records[i].english_marks = stoi(temp);
            }

            break;
        }
    }

    if (!user_found){
        cout << "sorry but no user found to update record";
    }else{
        cout << "1 record updated.";
    }
}

/**
 * Prints the current marks record in the system.
 *
 * This function displays the student records stored in the 'records' vector.
 * It prints the student name, maths marks, chinese marks, english marks, and grade for each record.
 * The grade is calculated using the 'functionGetGrade' function.
 *
 * Note:
 * - The records are printed in a tabular format with appropriate spacing.
 * - The grade is calculated based on the maths marks, chinese marks, and english marks using the 'functionGetGrade' function.
 */
void functionPrint() {
    cout << endl;
    cout
        << setw(10) << setfill(' ') << left << "Name" << setw(10)
        << setw(10) << setfill(' ') << left << "Maths" << setw(10)
        << setw(10) << setfill(' ') << left << "Chinese" << setw(10)
        << setw(10) << setfill(' ') << left << "English" << setw(10)
        << setw(10) << setfill(' ') << left << "Grade" << setw(10);

    cout << "" << setw(50) << setfill('-') << "\n";
    cout << "\n";

    for (const auto& record : records) {
        string calc_grade;
        calc_grade = functionGetGrade(record.maths_marks, record.chinese_marks, record.english_marks);

        cout
            << setw(10) << setfill(' ') << left << record.name
            << setw(10) << setfill(' ') << left << record.maths_marks
            << setw(10) << setfill(' ') << left << record.chinese_marks
            << setw(10) << setfill(' ') << left << record.english_marks

            // append 2 chars on the left
            << setw(2) << setfill(' ') << left << " "
            << setw(10) << setfill(' ') << left << calc_grade  << "\n";
    }
    cout << "\n";
}

/**
 * Imports records from a file and adds them to the current marks record system.
 *
 * This function prompts the user to enter the name of a file containing a list of student records.
 * It then opens the file and reads each line, extracting the student name, maths marks, chinese marks, and english marks.
 * A new MarksRecord object is created for each line and added to the records vector.
 * The function keeps track of the number of records added and displays the total at the end.
 *
 * Note:
 * - The file should be formatted with each line containing the student name, maths marks, chinese marks, and english marks separated by spaces.
 * - The last line of the file should contain the word "END" to indicate the end of the records.
 */
void functionImport(){
    ifstream inFile;
    ofstream outFile;
    string student_name, maths_mark, chinese_mark, english_mark, grade;
    int record_added;
    record_added = 0;

    string filename;

    cout << "Please enter a file with list of student: ";
    cin >> filename;

    inFile.open(filename);
    if (!inFile) {
        cout << "Cannot open the input file." << endl;
        // << "The program terminates." << endl;
        // return 1;
    }else{
        while (true){
            inFile >> student_name;

            if (student_name == "END") {
                break;
            }else{
                inFile >> maths_mark >> chinese_mark >> english_mark;
                MarksRecord record;
                record.name = student_name;
                record.maths_marks = stoi(maths_mark);
                record.chinese_marks = stoi(chinese_mark);
                record.english_marks = stoi(english_mark);

                records.push_back(record);

                record_added = record_added + 1;
            }

        }

        cout << "record imported : " << record_added << "\n";
        cout << "\n";


        inFile.close();
    }

}

/**
 * Exports the student records to a file.
 *
 * This function prompts the user to enter the name of the file to export the records to.
 * It then opens the file and writes the student records in a formatted manner.
 * The file will contain the student name, maths marks, chinese marks, english marks, and grade for each record.
 * The function uses the functionGetGrade() function to calculate the grade based on the marks.
 *
 * Note:
 * - The file will be formatted with each record on a separate line.
 * - The fields will be separated by spaces.
 * - The file will start with a header line indicating the fields.
 * - The file will end with an empty line.
 */
void functionExport(){
    ofstream outFile;
    string filename;

    cout << "Please enter a file to export: ";
    cin >> filename;

    outFile.open(filename);

    outFile << setw(10) << setfill(' ') << ""
        << "~ STUDENT RECORDS ~";
    outFile << "\n";
    outFile << "\n";

    outFile
        << setw(10) << setfill(' ') << left << "Name" << setw(10)
        << setw(10) << setfill(' ') << left << "Maths" << setw(10)
        << setw(10) << setfill(' ') << left << "Chinese" << setw(10)
        << setw(10) << setfill(' ') << left << "English" << setw(10)
        << setw(10) << setfill(' ') << left << "Grade" << setw(10);

    outFile << "" << setw(50) << setfill('-') << "\n";
    outFile << "\n";

    for (const auto& record : records) {
        string calc_grade;
        calc_grade = functionGetGrade(record.maths_marks, record.chinese_marks, record.english_marks);

        outFile
            << setw(10) << setfill(' ') << left << record.name
            << setw(10) << setfill(' ') << left << record.maths_marks
            << setw(10) << setfill(' ') << left << record.chinese_marks
            << setw(10) << setfill(' ') << left << record.english_marks

            // append 2 chars on the left
            << setw(2) << setfill(' ') << left << " "
            << setw(10) << setfill(' ') << left << calc_grade  << "\n";
    }
    outFile << "\n";
    cout << "export done !" << "\n";
}

/**
 * Main function of the program.
 *
 * This function runs a menu-driven program for managing marks records.
 * It continuously displays a menu and prompts the user for their choice.
 * Based on the user's choice, it calls the corresponding functions to perform the desired operation.
 * The program keeps running until the user chooses to exit (e/E).
 *
 */
int main() {
    char choice;
    while (true) {
        print_menu();
        cin >> choice;

        switch (choice) {
            case '1': functionAdd(); break;
            case '2': functionDelete(); break;
            case '3': functionEdit(); break;
            case '4': functionPrint(); break;
            case '5': functionImport(); break;
            case '6': functionExport(); break;

            // exit handler
            case 'E':
            case 'e':
                return 0;

            // exception handler
            default:
                cout << "Invalid choice. Please try again.\n";
        }
    }

    return 0;
}