main.py

"""
main.py

Entry point for the Student Manager command-line application.
Displays a menu and lets the user add, view, search, edit, delete,
and analyze student records, which are stored persistently in
students.json.
"""

from student_manager import StudentManager

MENU = """
==========================================
           STUDENT MANAGER
==========================================
1. Add Student
2. View All Students
3. Search Student
4. Edit Student
5. Delete Student
6. Calculate Student Average
7. Find Top-Performing Student
8. Exit
==========================================
"""


def get_int_input(prompt):
    """Keep asking until the user enters a valid integer."""
    while True:
        value = input(prompt).strip()
        try:
            return int(value)
        except ValueError:
            print("❌ Please enter a valid whole number.")


def get_non_empty_string(prompt):
    """Keep asking until the user enters some non-empty text."""
    while True:
        value = input(prompt).strip()
        if value:
            return value
        print("❌ This field cannot be empty.")


def get_marks_from_user():
    """
    Ask the user for subject/marks pairs, one at a time.
    Returns a dictionary like {"Math": 90.0, "Science": 85.0}.
    """
    marks = {}
    print("Enter subjects and marks (type 'done' as the subject name to stop).")
    while True:
        subject = input("  Subject: ").strip()
        if subject.lower() == "done":
            break
        if not subject:
            print("  ❌ Subject name cannot be empty.")
            continue

        while True:
            score_input = input(f"  Marks for {subject} (0-100): ").strip()
            try:
                score = float(score_input)
                if 0 <= score <= 100:
                    marks[subject] = score
                    break
                print("  ❌ Marks must be between 0 and 100.")
            except ValueError:
                print("  ❌ Please enter a valid number.")
    return marks


def add_student(manager):
    print("\n--- Add Student ---")
    roll_no = get_int_input("Enter roll number: ")
    if manager.search_student(roll_no):
        print(f"❌ A student with roll number {roll_no} already exists.")
        return

    name = get_non_empty_string("Enter student name: ")
    marks = get_marks_from_user()

    if manager.add_student(roll_no, name, marks):
        print(f"✅ Student '{name}' added successfully.")
    else:
        print("❌ Could not add student (roll number already exists).")


def view_students(manager):
    print("\n--- All Students ---")
    students = manager.view_students()
    if not students:
        print("No students found. Add one from the main menu!")
        return
    for student in students:
        print(student)


def search_student(manager):
    print("\n--- Search Student ---")
    roll_no = get_int_input("Enter roll number to search: ")
    student = manager.search_student(roll_no)
    if student:
        print("✅ Student found:")
        print(student)
    else:
        print(f"❌ No student found with roll number {roll_no}.")


def edit_student(manager):
    print("\n--- Edit Student ---")
    roll_no = get_int_input("Enter roll number to edit: ")
    student = manager.search_student(roll_no)
    if not student:
        print(f"❌ No student found with roll number {roll_no}.")
        return

    print(f"Current details -> {student}")
    new_name = input("Enter new name (leave blank to keep unchanged): ").strip()

    update_marks_choice = input("Do you want to update marks? (y/n): ").strip().lower()
    new_marks = get_marks_from_user() if update_marks_choice == "y" else None

    manager.edit_student(roll_no, new_name if new_name else None, new_marks)
    print("✅ Student updated successfully.")


def delete_student(manager):
    print("\n--- Delete Student ---")
    roll_no = get_int_input("Enter roll number to delete: ")
    confirm = input(f"Are you sure you want to delete roll number {roll_no}? (y/n): ").strip().lower()
    if confirm != "y":
        print("Deletion cancelled.")
        return

    if manager.delete_student(roll_no):
        print("✅ Student deleted successfully.")
    else:
        print(f"❌ No student found with roll number {roll_no}.")


def calculate_average(manager):
    print("\n--- Calculate Student Average ---")
    roll_no = get_int_input("Enter roll number: ")
    average = manager.calculate_average(roll_no)
    if average is None:
        print(f"❌ No student found with roll number {roll_no}.")
    else:
        print(f"📊 Average marks: {average:.2f}")


def top_student(manager):
    print("\n--- Top-Performing Student ---")
    student = manager.top_student()
    if student is None:
        print("No students found yet.")
    else:
        print("🏆 Top student:")
        print(student)


def main():
    manager = StudentManager("students.json")

    actions = {
        "1": add_student,
        "2": view_students,
        "3": search_student,
        "4": edit_student,
        "5": delete_student,
        "6": calculate_average,
        "7": top_student,
    }

    while True:
        print(MENU)
        choice = input("Enter your choice (1-8): ").strip()

        if choice == "8":
            print("👋 Goodbye! Your data has been saved.")
            break

        action = actions.get(choice)
        if action is None:
            print("❌ Invalid choice. Please enter a number from 1 to 8.")
            continue

        try:
            action(manager)
        except Exception as e:
            # Catch-all so an unexpected error never crashes the whole program
            print(f"⚠️ Something went wrong: {e}")


if __name__ == "__main__":
    main()