package polynomial;

import java.util.Arrays;

public class Polynomial {
    private final int[] werte;
    private final int degree;

    public Polynomial(int[] w) {
        werte = w.clone();
        int deg = 0;
        for(int i = 0; i<w.length; i++){
            if (werte[i] != 0){
                deg = i;
            }
        }
        degree = deg;
        
        //gleichwertige Variante
        /*for (int i = w.length; i >= 0; i--) {
            if (w[i] != 0) {
                degree = i;
            }
        }*/
    }

    public Polynomial() {
        this(new int[]{0,1});
    }

    //Option 1 Kopie des Arrays
    public int[] getCoeef() {
        return werte.clone();
    }

    //Option 2 Koeef an der Stelle i
    public int getCoeefAt(int i) {
        return i > degree ? 0 : werte[i];
    }

    public static Polynomial constant(int v) {
        return new Polynomial(new int[]{v});
    }

    @Override
    public String toString() {
        if (isNull()){return "0";}
        String result = "";

        for (int i = degree; i >= 0; i--) {

            if (werte[i] == 0) {continue;}

            if (!result.isEmpty()) {
                if (werte[i] > 0) {result += " + ";}
                if (werte[i] < 0) {result += " - ";}
            }

            if (result.isEmpty() && werte[i] <0){result += "-";} // Minus am Anfang

            int absCoeff = Math.abs(werte[i]);

            if (absCoeff != 1 && i == 0) {result += absCoeff;}
            if (absCoeff == 1 && i == 0) {result += "1";}
            if (absCoeff != 1 && i != 0) {result += absCoeff +"*";}

            if (i > 0) {
                result += "x";
                if (i > 1) {result += "^" + i;}
            }

        }
        return result;
    }

    public Boolean isNull(){
        for(int i = werte.length-1; i >= 0; i--){
            if (werte[i] != 0) {
                return false;
            }
        }
        return true;

    }

    public String toString1() {
        StringBuilder result = new StringBuilder();

        for (int i = degree; i >= 0; i--) {

            if (werte[i] == 0) {continue;}

            if (!result.isEmpty()) {
                if (werte[i] > 0) {result.append(" + ");}
                if (werte[i] < 0) {result.append(" - ");}
            }

            if (result.isEmpty() && werte[i] <0){result.append("-");} // Minus am Anfang

            int absCoeff = Math.abs(werte[i]);

            if (absCoeff != 1 && i == 0) {result.append(absCoeff);}
            if (absCoeff == 1 && i == 0) {result.append(1);}
            if (absCoeff != 1 && i != 0) {
                result.append(absCoeff);
                result.append("*");}

            if (i > 0) {
                result.append("x");
                if (i > 1) {result.append("^");
                result.append(i);
            }
            }

        }

        return result.toString();
    }

    public Polynomial add(Polynomial p2){
        int[] p1 = getCoeef();
        int[] p2Coeff = p2.getCoeef();
        int[] p3 = new int[Math.max(p1.length,p2Coeff.length)];
        for(int x = p3.length-1; x >= 0; x --){
            int coeff1 = (x < p1.length) ? p1[x] : 0;
            int coeff2 = (x < p2Coeff.length) ? p2Coeff[x] : 0;
            p3[x] = coeff1 + coeff2;
        }
        Polynomial result = new Polynomial(p3);
        return result;
    }

    public Polynomial sub(Polynomial that) {
        int[] res = Arrays.copyOf(werte, Math.max(this.degree, that.degree) + 1);
        for (int i = 0; i <= that.degree; i++)
            res[i] -= that.werte[i];
        return new Polynomial(res);
    }

    public Polynomial mult(Polynomial that) {
        int[] res = new int[this.degree + that.degree + 1];
        Arrays.fill(res, 0);
        for (int i = 0; i <= this.degree; i++)
            for (int j = 0; j <= that.degree; j++)
                res[i + j] += this.werte[i] * that.werte[j];
        return new Polynomial(res);
    }

    public Polynomial exp(int e) {
        if (e < 0)
            throw new IllegalArgumentException("Exponent must not be negative");
        else if (e == 0)
            return constant(1);
        else if (e == 1)
            return this;
        else if (e % 2 == 0)
            return this.mult(this).exp(e / 2);
        else
            return this.mult(this.exp(e - 1));
    }

    public Polynomial add(int v) {
        int[] res = Arrays.copyOf(werte, werte.length);
        res[0] += v;
        return new Polynomial(res);
    }

    public Polynomial sub(int v) {
        return this.add(-v);
    }

    public Polynomial mult(int v) {
        int[] res = Arrays.copyOf(werte, werte.length);
        for (int j = 0; j < res.length; j++)
            res[j] *= v;
        return new Polynomial(res);
    }

    public int apply(int v) {
        int res = werte[werte.length - 1];
        for (int i = werte.length - 2; i >= 0; i--)
            res = res + v * werte[i];
        return res;
    }


}