import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

/**
 * Represents a Program of Study, a list of courses taken and planned, for an
 * individual student.
 * 
 * @author Lewis and Chase
 * @version 4.0
 */
public class ProgramOfStudy implements Iterable<Course>, Serializable
{
    private List<Course> list;
    
    /**
     * Constructs an initially empty Program of Study.
     */
    public ProgramOfStudy()
    {
        list = new LinkedList<Course>();
    }
    
    /**
     * Adds the specified course to the end of the course list.
     * 
     * @param course the course to add
     */
    public void addCourse(Course course)
    {
        if (course != null)
            list.add(course);
    }
    
    /**
     * Finds and returns the course matching the specified prefix and number.
     * 
     * @param prefix the prefix of the target course
     * @param number the number of the target course
     * @return the course, or null if not found
     */
    public Course find(String prefix, int number)
    {
        for (Course course : list)
            if (prefix.equals(course.getPrefix()) &&
                    number == course.getNumber())
                return course;

        return null;
    }
    
    /**
     * Adds the specified course after the target course. Does nothing if
     * either course is null or if the target is not found.
     * 
     * @param target the course after which the new course will be added
     * @param newCourse the course to add
     */
    public void addCourseAfter(Course target, Course newCourse)
    {
        if (target == null || newCourse == null)
            return;
        
        int targetIndex = list.indexOf(target);
        if (targetIndex != -1)
            list.add(targetIndex + 1, newCourse);
    }

    /**
     * Replaces the specified target course with the new course. Does nothing if
     * either course is null or if the target is not found.
     * 
     * @param target the course to be replaced
     * @param newCourse the new course to add
     */
    public void replace(Course target, Course newCourse)
    {
        if (target == null || newCourse == null)
            return;
        
        int targetIndex = list.indexOf(target);
        if (targetIndex != -1)
            list.set(targetIndex, newCourse);
    }

    /**
     * Creates and returns a string representation of this Program of Study.
     * 
     * @return a string representation of the Program of Study
     */
    public String toString()
    {
        String result = "";
        for (Course course : list)
            result += course + "\n";
        return result;
    }
    
    /**
     * Returns an iterator for this Program of Study.
     * 
     * @return an iterator for the Program of Study
     */
    public Iterator<Course> iterator()
    {
        return list.iterator();
    }
    
    /**
     * Saves a serialized version of this Program of Study to the specified
     * file name.
     * 
     * @param fileName the file name under which the POS will be stored
     * @throws IOException
     */
    public void save(String fileName) throws IOException
    {
        FileOutputStream fos = new FileOutputStream(fileName); 
        ObjectOutputStream oos = new ObjectOutputStream(fos); 
        oos.writeObject(this); 
        oos.flush(); 
        oos.close(); 
    }

    /**
     * Loads a serialized Program of Study from the specified file.
     * 
     * @param fileName the file from which the POS is read
     * @return the loaded Program of Study
     * @throws IOException
     * @throws ClassNotFoundException
     */
    public static ProgramOfStudy load(String fileName) throws IOException, ClassNotFoundException
    {
        FileInputStream fis = new FileInputStream(fileName);
        ObjectInputStream ois = new ObjectInputStream(fis);
        ProgramOfStudy pos = (ProgramOfStudy) ois.readObject();
        ois.close();
        
        return pos;
    }
}