package src;

import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;

public class MyPolynomial {

    private double[] coeffs;

    public MyPolynomial(double... coeffs) {
        this.coeffs = coeffs;
    }

    /**
     * Constructor that takes coefficients from a file (of the given filename),
     * having this format:
     * 
     * Degree-n(int)
     * c0(double)
     * c1(double)
     * ......
     * ......
     * cn-1(double)
     * cn(double)
     * (end-of-file)
     * 
     * @param  filename [description]
     */
    public MyPolynomial(String filename)
    {
        Scanner in = null;
        try {
            in = new Scanner(new File(filename));  // open file
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

        int degree = Integer.parseInt(in.nextLine()); // read the degree
        coeffs = new double[degree+1];  // allocate the array
        for (int i = 0; i < coeffs.length; ++i) {
            coeffs[i] = Double.parseDouble(in.nextLine());
        }
    }

    public double[] getCoeffs() {
        return coeffs;
    }

    public int getDegree() {
        return coeffs.length-1;
    }

    /**
     * [evaluate description]
     * @param  x [description]
     * @return   [description]
     */
    public double evaluate(double x)
    {
        double sum  = 0.0;
        double item = 1.0;
        for (int i = 0; i < coeffs.length; i++) {
            item *= (i == 0 ? 1.0 : x);
            sum  += item * coeffs[i] ;
        }
        return sum;
    }

    /**
     * [add description]
     * @param  another [description]
     * @return         [description]
     */
    public MyPolynomial add(MyPolynomial another)
    {
        MyPolynomial result = this;
        if (result.getDegree() < another.getDegree()) {
            result  = another;
            another = this;
        }

        double[] resultCoeffs  = result.getCoeffs();
        double[] anotherCoeffs = another.getCoeffs();
        for (int i = 0; i < resultCoeffs.length; i++)
        {
            if (i > anotherCoeffs.length-1) {
                continue;
            }
            resultCoeffs[i] += anotherCoeffs[i];
        }
        return new MyPolynomial(resultCoeffs);
    }

    /**
     * [multiply description]
     * @param  another [description]
     * @return         [description]
     */
    public MyPolynomial multiply(MyPolynomial another)
    {
        double[] resultCoeffs  = new double[this.getDegree() + another.getDegree()+1];
        double[] anotherCoeffs = another.getCoeffs();
        for (int i =0; i < resultCoeffs.length; i++)
        {
            double tmp = 0.0;
            for (int j = 0; j <= i; j++)
            {
                if (j > coeffs.length-1) {
                    continue;
                }
                if (i-j > anotherCoeffs.length-1) {
                    continue;
                }
                tmp += coeffs[j] * anotherCoeffs[i-j];
            }
            resultCoeffs[i] = tmp;
        }
        return new MyPolynomial(resultCoeffs);
    }

    /**
     * [toString description]
     * @return [description]
     */
    public String toString() {
        StringBuilder sb = new StringBuilder();
        for (int i = coeffs.length-1; i >= 0; i--) {
            sb.append(coeffs[i] + (i != 0 ? "*x^"+i+" + ":""));
        }
        return sb.toString();
    }
}