package org.nwapw.abacus.number;

import org.nwapw.abacus.exception.ComputationInterruptedException;

/**
 * An interface used to represent a number.
 */
public abstract class NumberInterface implements Comparable<NumberInterface> {

    /**
     * Check if the thread was interrupted and
     * throw an exception to end the computation.
     */
    private static void checkInterrupted() {
        if (Thread.currentThread().isInterrupted())
            throw new ComputationInterruptedException();
    }

    /**
     * The maximum precision to which this number operates.
     *
     * @return the precision.
     */
    public abstract int getMaxPrecision();

    /**
     * Multiplies this number by another, returning
     * a new number instance.
     *
     * @param multiplier the multiplier
     * @return the result of the multiplication.
     */
    protected abstract NumberInterface multiplyInternal(NumberInterface multiplier);

    /**
     * Multiplies this number by another, returning
     * a new number instance. Also, checks if the
     * thread has been interrupted, and if so, throws
     * an exception.
     *
     * @param multiplier the multiplier
     * @return the result of the multiplication.
     */
    public final NumberInterface multiply(NumberInterface multiplier) {
        checkInterrupted();
        return multiplyInternal(multiplier);
    }

    /**
     * Divides this number by another, returning
     * a new number instance.
     *
     * @param divisor the divisor
     * @return the result of the division.
     */
    protected abstract NumberInterface divideInternal(NumberInterface divisor);

    /**
     * Divides this number by another, returning
     * a new number instance. Also, checks if the
     * thread has been interrupted, and if so, throws
     * an exception.
     *
     * @param divisor the divisor
     * @return the result of the division.
     */
    public final NumberInterface divide(NumberInterface divisor) {
        checkInterrupted();
        return divideInternal(divisor);
    }

    /**
     * Adds this number to another, returning
     * a new number instance.
     *
     * @param summand the summand
     * @return the result of the summation.
     */
    protected abstract NumberInterface addInternal(NumberInterface summand);

    /**
     * Adds this number to another, returning
     * a new number instance. Also, checks if the
     * thread has been interrupted, and if so, throws
     * an exception.
     *
     * @param summand the summand
     * @return the result of the summation.
     */
    public final NumberInterface add(NumberInterface summand) {
        checkInterrupted();
        return addInternal(summand);
    }

    /**
     * Subtracts another number from this number,
     * a new number instance.
     *
     * @param subtrahend the subtrahend.
     * @return the result of the subtraction.
     */
    protected abstract NumberInterface subtractInternal(NumberInterface subtrahend);

    /**
     * Subtracts another number from this number,
     * a new number instance. Also, checks if the
     * thread has been interrupted, and if so, throws
     * an exception.
     *
     * @param subtrahend the subtrahend.
     * @return the result of the subtraction.
     */
    public final NumberInterface subtract(NumberInterface subtrahend) {
        checkInterrupted();
        return subtractInternal(subtrahend);
    }

    /**
     * Returns a new instance of this number with
     * the sign flipped.
     *
     * @return the new instance.
     */
    protected abstract NumberInterface negateInternal();


    /**
     * Returns a new instance of this number with
     * the sign flipped. Also, checks if the
     * thread has been interrupted, and if so, throws
     * an exception.
     *
     * @return the new instance.
     */
    public final NumberInterface negate() {
        checkInterrupted();
        return negateInternal();
    }

    /**
     * Raises this number to an integer power.
     *
     * @param exponent the exponent to which to take the number.
     * @return the resulting value.
     */
    protected abstract NumberInterface intPowInternal(int exponent);

    /**
     * Raises this number to an integer power. Also, checks if the
     * thread has been interrupted, and if so, throws
     * an exception.
     *
     * @param exponent the exponent to which to take the number.
     * @return the resulting value.
     */
    public final NumberInterface intPow(int exponent) {
        checkInterrupted();
        return intPowInternal(exponent);
    }

    /**
     * Same as Math.signum().
     *
     * @return 1 if this number is positive, -1 if this number is negative, 0 if this number is 0.
     */
    public abstract int signum();

    /**
     * Returns the least integer greater than or equal to the number.
     *
     * @return the least integer greater or equal to the number, if int can hold the value.
     */
    protected abstract NumberInterface ceilingInternal();

    /**
     * Returns the least integer greater than or equal to the number.
     * Also, checks if the thread has been interrupted, and if so, throws
     * an exception.
     *
     * @return the least integer bigger or equal to the number.
     */
    public final NumberInterface ceiling() {
        checkInterrupted();
        return ceilingInternal();
    }

    /**
     * Return the greatest integer less than or equal to the number.
     *
     * @return the greatest integer smaller or equal the number.
     */
    protected abstract NumberInterface floorInternal();

    /**
     * Return the greatest integer less than or equal to the number.
     * Also, checks if the thread has been interrupted, and if so, throws
     * an exception.
     *
     * @return the greatest int smaller than or equal to the number.
     */
    public final NumberInterface floor() {
        checkInterrupted();
        return floorInternal();
    }

    /**
     * Returns the fractional part of the number.
     *
     * @return the fractional part of the number.
     */
    protected abstract NumberInterface fractionalPartInternal();

    /**
     * Returns the fractional part of the number, specifically x - floor(x).
     * Also, checks if the thread has been interrupted,
     * and if so, throws an exception.
     *
     * @return the fractional part of the number.
     */
    public final NumberInterface fractionalPart() {
        checkInterrupted();
        return fractionalPartInternal();
    }

    /**
     * Returns the integer representation of this number, discarding any fractional part,
     * if int can hold the value.
     *
     * @return the integer value of this number.
     */
    public abstract int intValue();

    /**
     * Returns the smallest error this instance can tolerate depending
     * on its precision and value.
     *
     * @return the smallest error that should be permitted in calculations.
     */
    public abstract NumberInterface getMaxError();

    /**
     * Returns a NumberRangeBuilder object, which is used to create a range.
     * The reason that this returns a builder and not an actual range is that
     * the NumberRange needs to promote values passed to it, which
     * requires an abacus instance.
     * @param other the value at the bottom of the range.
     * @return the resulting range builder.
     */
    public NumberRangeBuilder rangeTo(NumberInterface other){
        return new NumberRangeBuilder(this, other);
    }

}