/*
 * Copyright (c) 2019 the Eclipse Milo Authors
 *
 * This program and the accompanying materials are made
 * available under the terms of the Eclipse Public License 2.0
 * which is available at https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 */

package org.eclipse.milo.opcua.stack.core.types.builtin.unsigned;

import java.math.BigInteger;

import org.jetbrains.annotations.NotNull;

/**
 * The <code>unsigned long</code> type
 *
 * @author Lukas Eder
 * @author Jens Nerche
 * @author Ivan Sokolov
 */
public final class ULong extends UNumber implements Comparable<ULong> {

    /**
     * Generated UID
     */
    private static final long serialVersionUID = -6821055240959745390L;

    /**
     * A constant holding the minimum value an <code>unsigned long</code> can
     * have, 0.
     */
    public static final BigInteger MIN_VALUE = BigInteger.ZERO;
    /**
     * A constant holding the maximum value an <code>unsigned long</code> can
     * have, 2<sup>64</sup>-1.
     */
    public static final BigInteger MAX_VALUE = new BigInteger("18446744073709551615");

    /**
     * A constant holding the maximum value + 1 an <code>signed long</code> can
     * have, 2<sup>63</sup>.
     */
    public static final BigInteger MAX_VALUE_LONG = new BigInteger("9223372036854775808");

    /**
     * A constant holding the minimum value an <code>unsigned long</code> can
     * have as ULong, 0.
     */
    public static final ULong MIN = valueOf(MIN_VALUE.longValue());

    /**
     * A constant holding the maximum value + 1 an <code>signed long</code> can
     * have as ULong, 2<sup>63</sup>.
     */
    public static final ULong MAX = valueOf(MAX_VALUE);

    /**
     * The value modelling the content of this <code>unsigned long</code>
     */
    private final long value;

    /**
     * Create an <code>unsigned long</code>
     *
     * @throws NumberFormatException If <code>value</code> does not contain a
     *                               parsable <code>unsigned long</code>.
     */
    public static ULong valueOf(String value) throws NumberFormatException {
        return new ULong(value);
    }

    /**
     * Create an <code>unsigned long</code> by masking it with
     * <code>0xFFFFFFFFFFFFFFFF</code> i.e. <code>(long) -1</code> becomes
     * <code>(uint) 18446744073709551615</code>
     */
    public static ULong valueOf(long value) {
        return new ULong(value);
    }

    /**
     * Create an <code>unsigned long</code>
     *
     * @throws NumberFormatException If <code>value</code> is not in the range
     *                               of an <code>unsigned long</code>
     */
    public static ULong valueOf(BigInteger value) throws NumberFormatException {
        return new ULong(value);
    }

    public static int compare(long x, long y) {
        x += Long.MIN_VALUE;
        y += Long.MIN_VALUE;
        return (x < y) ? -1 : ((x == y) ? 0 : 1);
    }

    /**
     * Create an <code>unsigned long</code>
     *
     * @throws NumberFormatException If <code>value</code> is not in the range
     *                               of an <code>unsigned long</code>
     */
    private ULong(BigInteger value) throws NumberFormatException {
        if (value.compareTo(MIN_VALUE) < 0 || value.compareTo(MAX_VALUE) > 0) {
            throw new NumberFormatException();
        } else {
            this.value = value.longValue();
        }
    }

    /**
     * Create an <code>unsigned long</code> by masking it with
     * <code>0xFFFFFFFFFFFFFFFF</code> i.e. <code>(long) -1</code> becomes
     * <code>(uint) 18446744073709551615</code>
     */
    private ULong(long value) {
        this.value = value;
    }

    /**
     * Create an <code>unsigned long</code>
     *
     * @throws NumberFormatException If <code>value</code> does not contain a
     *                               parsable <code>unsigned long</code>.
     */
    private ULong(String value) throws NumberFormatException {
        if (value == null) {
            throw new NumberFormatException("null");
        }

        int length = value.length();

        if (length == 0) {
            throw new NumberFormatException("Empty input string");
        }

        if (value.charAt(0) == '-') {
            throw new NumberFormatException(
                String.format("Illegal leading minus sign on unsigned string %s", value));
        }

        if (length <= 18) {
            this.value = Long.parseLong(value, 10);
            return;
        }

        final long first = Long.parseLong(value.substring(0, length - 1), 10);
        final int second = Character.digit(value.charAt(length - 1), 10);
        if (second < 0) {
            throw new NumberFormatException("Bad digit at end of " + value);
        }
        long result = first * 10 + second;
        if (compare(result, first) < 0) {
            throw new NumberFormatException(
                String.format("String value %s exceeds range of unsigned long", value));
        }

        this.value = result;
    }

    @Override
    public int intValue() {
        return (int) value;
    }

    @Override
    public long longValue() {
        return value;
    }

    @Override
    public float floatValue() {
        if (value < 0) {
            return ((float) (value & Long.MAX_VALUE)) + Long.MAX_VALUE;
        } else {
            return value;
        }
    }

    @Override
    public double doubleValue() {
        if (value < 0) {
            return ((double) (value & Long.MAX_VALUE)) + Long.MAX_VALUE;
        } else {
            return value;
        }
    }

    @Override
    public int hashCode() {
        return Long.valueOf(value).hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof ULong) {
            return value == ((ULong) obj).value;
        }

        return false;
    }

    @Override
    public String toString() {
        if (value >= 0) {
            return Long.toString(value);
        } else {
            return BigInteger.valueOf(value & Long.MAX_VALUE).add(MAX_VALUE_LONG).toString();
        }
    }

    @Override
    public int compareTo(@NotNull ULong o) {
        return compare(value, o.value);
    }

    public ULong add(ULong val) throws NumberFormatException {
        if (value < 0 && val.value < 0) {
            throw new NumberFormatException();
        }
        final long result = value + val.value;
        if ((value < 0 || val.value < 0) && result >= 0) {
            throw new NumberFormatException();
        }
        return valueOf(result);
    }

    public ULong add(int val) throws NumberFormatException {
        return add((long) val);
    }

    public ULong add(long val) throws NumberFormatException {
        if (val < 0) {
            return subtract(Math.abs(val));
        }
        final long result = value + val;
        if (value < 0 && result >= 0) {
            throw new NumberFormatException();
        }
        return valueOf(result);
    }

    public ULong subtract(final ULong val) {
        if (this.compareTo(val) < 0) {
            throw new NumberFormatException();
        }
        final long result = value - val.value;
        if (value < 0 && result >= 0) {
            throw new NumberFormatException();
        }
        return valueOf(result);
    }

    public ULong subtract(final int val) {
        return subtract((long) val);
    }

    public ULong subtract(final long val) {
        if (val < 0) {
            return add(-val);
        }
        if (compare(value, val) < 0) {
            throw new NumberFormatException();
        }
        final long result = value - val;
        if (value < 0 && result >= 0) {
            throw new NumberFormatException();
        }
        return valueOf(result);
    }
}
