/*
 * TestPaper.java
 *
 * Created on December 9, 2002, 2:09 AM
 */

package grading;
import java.util.Random;

/**
 *
 * @author  mike
 */
public class TestPaper {
    
    private String name = "";
    
    private char[] answers;   // array of answers by student
    
    private double pctCorrect = 0;
    
    private int numCorrect = 0;
    
    private int numIncorrect = 0;
    
    private static Random generator = new Random();  // uses time as a seed

    /**
     * Service method for generating a random multiple choice answer
     */
    public static char genRandAnsw () {
        int rand;
        rand = generator.nextInt(5); // generate an int from 0-4
        // 0 - 'a', 1 - 'b' etc
        switch (rand) {
            case 0:
                return 'a';
            case 1:
                return 'b';
            case 2:
                return 'c';
            case 3:
                return 'd';
            case 4:
                return 'e';
        }
        return 'a'; // should never be hit
    }

    /** 
     * Creates a new instance of TestPaper 
     */
    public TestPaper() {
        name = "John Doe";
    }
    
    /** 
     * Creates a new instance of TestPaper, given name 
     */
    public TestPaper(String nam) {
        name = nam;
    }
    
    /** 
     * Creates a new instance of TestPaper, given name, number of answers 
     * (answers are randomly generated) 
     */
    public TestPaper(String nam, int numAnsw) {
        name = nam;
        answers = new char [numAnsw];
        for (int ans = 0; ans < numAnsw; ans++) {
            answers[ans] = genRandAnsw();
        }
    }
    
    /**
     * report student name 
     */
    public String getName() {
        return name;
    }
    
    /**
     * reports students answer on the Nth question 
     * Should throw an exception if bad n
     */
    public char getNthAnswer(int n) {
        return answers[n];
    }
    
    /**
     * Checks student's answer on Nth question angainst correct answer (answ)
     * Should throw an exception if bad n
     */
    public boolean checkNthAnswer(int n, char answ) {
        if (answers[n] == answ) {
            return true;
        }
        else {
            return false;
        }
    }
    
    /**
     * report number of answers student has made 
     */
    public int getNumAnswers() {
        return answers.length;
    }
    
    /** 
     * obtain whole array of student's answers 
     */
    public char[] getAnswers() {
        return answers;
    }
    
    /**
     * determines if two test papers are essentially the same - take tough stance here
     *   - name and all answers must be the same
     */
    public boolean equals(Object obj) {
        // equal if exactly the same
        TestPaper toTest = (TestPaper) obj; // should check instanceof to avoid bugs
        boolean eq = true;
        if (! name.equals(toTest.name)) {
            // name doesn't match - students must not be equal
            eq = false;
        }
        // if don't have the same number of answers as other student - must not be equal
        if (getNumAnswers() != toTest.getNumAnswers() ) {
            eq = false;
        }
        // check all answers if still possible to equal
        if (eq) {
            for (int ans = 0; ans < getNumAnswers(); ans++) {
                if (answers[ans] != toTest.getNthAnswer(ans) ) {
                    // this answer doesn't match, so students must not match
                    eq = false;
                    break;
                }
            }
        }
        return eq;
    }
    
    /**
     * obtain string representation for the test paper 
     */
    public String toString() {
        String res = name;
        for (int ans = 0; ans < getNumAnswers(); ans++) {
            res = res + " " + answers[ans];
        }
        // consider adding stats on performance
        return res;
    }
    
    /** 
     * change student's name 
     */
    public void setName(String nam) {
        name = nam;
    }
    
    
    /** 
     * change student's Nth answer to given value 
     */
    public void setNthAnswer(int n, char answ) {
        // need to check for bad n
        answers[n] = answ;
    }
    
    /**
     * report number of correct by student 
     * Assumes that Test Paper has already been checked
     */
    public int getNumCorrect() {
        return numCorrect;
    }
    
    /**
     * report number of incorrect by student 
     * Assumes that Test Paper has already been checked
     */
    public int getNumIncorrect() {
        return numIncorrect;
    }
    
    /**
     * report pct correct by student 
     * Assumes that Test Paper has already been checked
     */
    public double getPctCorrect() {
        return pctCorrect;
    }
    
    /**
     * Grade student's answers against correct answers, including updating stats
     * (number correct etc)
     */
    public double gradeAll(char[] correctAnswers) { 
        // need to check that arrays are compatible sizes
        numCorrect = 0;
        numIncorrect = 0;
        for (int ans = 0; ans < getNumAnswers(); ans++) {
            if (answers[ans] == correctAnswers[ans] ) {
                numCorrect++;
            }
            else {
                numIncorrect++;
            }
        }
        // need to avoid division by 0
        pctCorrect = (double) numCorrect / (numCorrect + numIncorrect);
        return pctCorrect;
    }
            
    public static void main (String args[]) {
        char [] correct = { 'a', 'b', 'c', 'd', 'e', 'd', 'c', 'b', 'a', 'e'};
        TestPaper [] allStudents = new TestPaper[3];
        for (int cnt = 0; cnt < allStudents.length; cnt++ ) {
            allStudents[cnt] = new TestPaper("John " + (cnt+1), 10);
            System.out.println("TestPaper: " + allStudents[cnt]);
            double pct = allStudents[cnt].gradeAll(correct);
            System.out.println("Correct: " + pct);
        }
            
    }
    
}