import java.util.ArrayList;

/**
 * MarksAnalyser stores a collection of Student records.
 * Complete the code missing from methods below for practice
 * at using ArrayList and for-each loops
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class MarksAnalyser
{
    /*
     * Arbitrary length list of Student objects representing a 
     * specific group of students for a unit or lab class.
     */
    private ArrayList<Student> courselist;

    /**
     * Constructor for objects of class MarksAnalyser
     */
    public MarksAnalyser()
    {
        courselist = new ArrayList<>();
    }

    /**
     * Add a new student record to the class list.
     * @param member The Student object to be added.
     */
    public void joinClass(Student student)
    {
        if (student != null) courselist.add(student);
    }

    /**
     * @return The number of students (Student objects) in 
     * the class list.
     */
    public int numberOfStudents()
    {
        return courselist.size();
    }

    /**
     * Generate a class list of comma separated student names 
     * and marks in a string with a newline after each student
     * @return String list of names and marks separated by 
     * commas and newlines
     */
    public String showCourse() 
    {
        String soln = "";
        for (Student s : courselist) 
            soln = soln + s.getName() + ", " 
                        + s.getMark() + "\n";
        return soln;
    }

    /**
     * Generate a class list of student names (only) in a string
     * @return String list of names separated by newlines
     */
    public String showCourseNames() 
    {   
        String soln = "";
        for (Student s : courselist) 
            soln = soln + s.getName() + "\n";
        return soln;
    }

    /**
     * Get a specific Student object record from the class list
     * @param String name of the student in the class list
     * @return Student object if the name is present or 
     * null if the name does not appear in the class list
     */
    public Student findStudent(String name) 
    {
        for (Student s : courselist) 
            if (s.getName() == name) return s;
        return null;
    }

    /**
     * Find the minimum mark value, ignoring the student name
     * @return int the smallest of all values in the class list
     */
    public int minimum()
    {
        int min = courselist.get(0).getMark();
        for (Student s : courselist) 
            if (s.getMark() < min) min = s.getMark();
        return min;
    }

    /**
     * Find the maximum mark in the ArrayList
     * @return int the largest value in the marks ArrayList
     */
    public int maximum()
    {
        int max = courselist.get(0).getMark();
        for (Student s : courselist) 
            if (s.getMark() > max) max = s.getMark();
        return max;
    }

    /**
     * Find the average mark for the class list
     * @return double average value
     */
    public double average()
    {
        double sum = 0;
        for (Student s : courselist) sum = sum + s.getMark();
        return sum / courselist.size();
    }

    /**
     * Find the population standard deviation of marks in the 
     * class list 
     * (see http://en.wikipedia.org/wiki/Standard_deviation)
     * You will need the functions Math.pow and Math.sqrt from 
     * the Math library
     * @return double value of the population standard deviation
     */
    public double standardDeviation()
    {
        double avg = average();
        double sum = 0;
        for (Student s : courselist) 
            sum = sum + Math.pow(s.getMark() - avg, 2);
        return Math.sqrt (sum / courselist.size());
    }

    /**
     * Find all students with a mark of threshold or above.
     * @param int threshold only Students with a mark of 
     * at least threshold are returned
     * @return ArrayList of all Students who meet the cut off
     */
    public ArrayList<Student> starStudents(int threshold)
    {
        ArrayList<Student> stars = new ArrayList<>();
        for (Student s : courselist) 
            if (s.getMark() >= threshold) stars.add(s);
        return stars;
    }

    /** 
     * Challenge: generate a histogram as a string of *s 
     * for the number of students in each bin
     * @param binsize of histogram divisions
     * e.g. binsize 20 groups marks into 
     * 0..19, 20..39 ... 80..100 
     */
    public String printHistogram(int binsize)
    {
        String soln = "";
        String spaces = " : ";
        for (int m = 0; m < 100; m = m + binsize)
        {
           int u = m + binsize - 1;
           if (u == 99) {u = 100; spaces = ": ";}
           soln = "\n" + soln;
           for (Student s : courselist) 
               if (m <= s.getMark() && s.getMark() <= u) 
                  soln = "*" + soln;
           soln = m + ".." + u + spaces + soln;
           if (m == 0) soln = 0 + soln;
        }
        return soln;
    }
    
     /** 
     * Challenge 2: (rephrased) generate a histogram 
     * with numbins division, as close in size as possible and
     * any remainder in the top bin.
     * @param numbins  number of divisions in this histogram
     * e.g. binsize 5 can groups marks into 
     * 0..19, 20..39 ... 80..100
     */
    public String printHistogramImproved(int numbins)
    {
        return printHistogram(100 / numbins);
    }
    //TODO write informative test cases for this

}