Course.java

import java.util.*;
import java.io.*;

// Represents a university course with enrollment, instructor, and grading functionality
public class Course implements Reportable {
    //Fields
    private String code;
    private String name;
    private String department;
    private int credits;
    private String semester;
    private String programCode;
    private AcademicMember instructor;
    private List<Student> enrolledStudents;
    private Map<Student, String> grades;

    // Constructor initializes course details and collections
    public Course(String code, String name, String department, int credits, String semester, String programCode) {
        this.code = code;
        this.name = name;
        this.department = department;
        this.credits = credits;
        this.semester = semester;
        this.programCode = programCode;
        this.enrolledStudents = new ArrayList<>();
        this.grades = new HashMap<>();
    }

    // Enrolls a student into the course
    public void enrollStudent(Student student) {
        enrolledStudents.add(student);
    }

    // Assigns an instructor to the course
    public void assignInstructor(AcademicMember instructor) {
        this.instructor = instructor;
    }

    // Assigns a grade to a student in this course
    public void assignGrade(Student student, String grade) {
        grades.put(student, grade);
    }

    // Calculates the average numerical grade for the course
    public double calculateAverageGrade() {
        if (grades.isEmpty()) return 0.0;
        double total = 0;
        for (String grade : grades.values()) {
            total += GradeConverter.convert(grade);
        }
        return total / grades.size();
    }

    // Returns a distribution of letter grades and their counts
    public Map<String, Integer> getGradeDistribution() {
        Map<String, Integer> distribution = new LinkedHashMap<>();
        for (String g : grades.values()) {
            distribution.put(g, distribution.getOrDefault(g, 0) + 1);
        }
        return distribution;
    }

    // Generates a report of the course including grades and enrolled students
    public String generateReport() {
        StringWriter writer = new StringWriter();
        writer.write("Course Code: " + code + "\n");
        writer.write("Name: " + name + "\n");
        writer.write("Department: " + department + "\n");
        writer.write("Credits: " + credits + "\n");
        writer.write("Semester: " + semester + "\n\n");
        writer.write("Instructor: ");
        writer.write(instructor != null ? instructor.getName() : "Not assigned");
        writer.write("\n\n");

        writer.write("Enrolled Students:\n");
        for (Student student : enrolledStudents) {
            writer.write("- " + student.getName() + " (ID: " + student.getId() + ")\n");
        }

        writer.write("\nGrade Distribution:\n");
        List<Map.Entry<String, Integer>> gradeList = new ArrayList<>(getGradeDistribution().entrySet());
        Collections.sort(gradeList, new Comparator<Map.Entry<String, Integer>>() {
            public int compare(Map.Entry<String, Integer> entry1, Map.Entry<String, Integer> entry2) {
                return entry1.getKey().compareTo(entry2.getKey());
            }
        });

        for (Map.Entry<String, Integer> entry : gradeList) {
            writer.write(entry.getKey() + ": " + entry.getValue() + "\n");
        }
        writer.write("\nAverage Grade: " + String.format(Locale.ENGLISH, "%.2f", calculateAverageGrade()) + "\n");
        return writer.toString();
    }

    // Getters
    public String getCode() {
        return code;
    }

    public String getName() {
        return name;
    }

    public String getDepartment() {
        return department;
    }

    public int getCredits() {
        return credits;
    }

    public String getSemester() {
        return semester;
    }
}