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package jscl.math.polynomial;

import jscl.math.NotDivisibleException;
import jscl.math.Variable;

class BooleanMonomial extends SmallMonomial {
	static final int log2n = 1;
	static final int log2p = 5 - log2n;
	static final int nmask = (1 << (1 << log2n)) - 1;
	static final int pmask = (1 << log2p) - 1;

	BooleanMonomial(Variable unknown[], Ordering ordering) {
		this(((unknown.length - 1) >> log2p) + 1, unknown, ordering);
	}

	BooleanMonomial(int length, Variable unknown[], Ordering ordering) {
		super(length, unknown, ordering);
	}

	public Monomial multiply(Monomial monomial) {
		Monomial m = newinstance();
		for (int i = 0; i < unknown.length; i++) {
			int q = i >> log2p;
			int r = (i & pmask) << log2n;
			int a = (element[q] >> r) & nmask;
			int b = (monomial.element[q] >> r) & nmask;
			int c = a + b;
			if (c > nmask) throw new ArithmeticException();
			m.element[q] |= c << r;
			m.degree += c;
		}
		return m;
	}

	public boolean multiple(Monomial monomial, boolean strict) {
		boolean equal = true;
		for (int i = 0; i < unknown.length; i++) {
			int q = i >> log2p;
			int r = (i & pmask) << log2n;
			int a = (element[q] >> r) & nmask;
			int b = (monomial.element[q] >> r) & nmask;
			if (a < b) return false;
			equal &= a == b;
		}
		return strict ? !equal : true;
	}

	public Monomial divide(Monomial monomial) throws ArithmeticException {
		Monomial m = newinstance();
		for (int i = 0; i < unknown.length; i++) {
			int q = i >> log2p;
			int r = (i & pmask) << log2n;
			int a = (element[q] >> r) & nmask;
			int b = (monomial.element[q] >> r) & nmask;
			int c = a - b;
			if (c < 0) throw new NotDivisibleException();
			m.element[q] |= c << r;
		}
		m.degree = degree - monomial.degree;
		return m;
	}

	public Monomial gcd(Monomial monomial) {
		Monomial m = newinstance();
		for (int i = 0; i < unknown.length; i++) {
			int q = i >> log2p;
			int r = (i & pmask) << log2n;
			int a = (element[q] >> r) & nmask;
			int b = (monomial.element[q] >> r) & nmask;
			int c = Math.min(a, b);
			m.element[q] |= c << r;
			m.degree += c;
		}
		return m;
	}

	public Monomial scm(Monomial monomial) {
		Monomial m = newinstance();
		for (int i = 0; i < unknown.length; i++) {
			int q = i >> log2p;
			int r = (i & pmask) << log2n;
			int a = (element[q] >> r) & nmask;
			int b = (monomial.element[q] >> r) & nmask;
			int c = Math.max(a, b);
			m.element[q] |= c << r;
			m.degree += c;
		}
		return m;
	}

	public int element(int n) {
		if (reverse()) n = unknown.length - 1 - n;
		int q = n >> log2p;
		int r = (n & pmask) << log2n;
		return (element[q] >> r) & nmask;
	}

	void put(int n, int integer) {
		if (reverse()) n = unknown.length - 1 - n;
		int q = n >> log2p;
		int r = (n & pmask) << log2n;
		int a = (element[q] >> r) & nmask;
		int c = a + integer;
		if (c > nmask) throw new ArithmeticException();
		element[q] |= c << r;
		degree += c - a;
	}

	protected Monomial newinstance() {
		return new BooleanMonomial(element.length, unknown, ordering);
	}
}