/*
 * Hunt - A refined core library for D programming language.
 *
 * Copyright (C) 2018-2019 HuntLabs
 *
 * Website: https://www.huntlabs.net/
 *
 * Licensed under the Apache-2.0 License.
 *
 */

module hunt.Integer;

import hunt.Byte;
import hunt.Exceptions;
import hunt.Nullable;
import hunt.Number;
import hunt.util.Comparator;

import std.conv;

class Integer : AbstractNumber!int
{

    /**
     * Returns the number of one-bits in the two's complement binary
     * representation of the specified {@code int} value.  This function is
     * sometimes referred to as the <i>population count</i>.
     *
     * @param i the value whose bits are to be counted
     * @return the number of one-bits in the two's complement binary
     *     representation of the specified {@code int} value.
     */
    enum int MIN_VALUE = int.min; // 0x80000000;

    /**
     * A constant holding the maximum value an {@code int} can
     * have, 2!(sup)31</sup>-1.
     */
    enum int MAX_VALUE = int.max; // 0x7fffffff;

    static int bitCount(int i)
    {
        // HD, Figure 5-2
        i = i - ((i >>> 1) & 0x55555555);
        i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
        i = (i + (i >>> 4)) & 0x0f0f0f0f;
        i = i + (i >>> 8);
        i = i + (i >>> 16);
        return i & 0x3f;
    }

    enum char[] digits = [
            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c',
            'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p',
            'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'
        ];

    /**
     * Returns the number of zero bits preceding the highest-order
     * ("leftmost") one-bit in the two's complement binary representation
     * of the specified {@code int} value.  Returns 32 if the
     * specified value has no one-bits in its two's complement representation,
     * in other words if it is equal to zero.
     *
     * <p>Note that this method is closely related to the logarithm base 2.
     * For all positive {@code int} values x:
     * <ul>
     * <li>floor(log!(sub)2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}
     * <li>ceil(log!(sub)2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}
     * </ul>
     *
     * @param i the value whose number of leading zeros is to be computed
     * @return the number of zero bits preceding the highest-order
     *     ("leftmost") one-bit in the two's complement binary representation
     *     of the specified {@code int} value, or 32 if the value
     *     is equal to zero.
     */
    static int numberOfLeadingZeros(int i)
    {
        // HD, Figure 5-6
        if (i == 0)
            return 32;
        int n = 1;
        if (i >>> 16 == 0)
        {
            n += 16;
            i <<= 16;
        }
        if (i >>> 24 == 0)
        {
            n += 8;
            i <<= 8;
        }
        if (i >>> 28 == 0)
        {
            n += 4;
            i <<= 4;
        }
        if (i >>> 30 == 0)
        {
            n += 2;
            i <<= 2;
        }
        n -= i >>> 31;
        return n;
    }

    /**
     * Returns the number of zero bits following the lowest-order ("rightmost")
     * one-bit in the two's complement binary representation of the specified
     * {@code int} value.  Returns 32 if the specified value has no
     * one-bits in its two's complement representation, in other words if it is
     * equal to zero.
     *
     * @param i the value whose number of trailing zeros is to be computed
     * @return the number of zero bits following the lowest-order ("rightmost")
     *     one-bit in the two's complement binary representation of the
     *     specified {@code int} value, or 32 if the value is equal
     *     to zero.
     */
    static int numberOfTrailingZeros(int i)
    {
        // HD, Figure 5-14
        int y;
        if (i == 0)
            return 32;
        int n = 31;
        y = i << 16;
        if (y != 0)
        {
            n = n - 16;
            i = y;
        }
        y = i << 8;
        if (y != 0)
        {
            n = n - 8;
            i = y;
        }
        y = i << 4;
        if (y != 0)
        {
            n = n - 4;
            i = y;
        }
        y = i << 2;
        if (y != 0)
        {
            n = n - 2;
            i = y;
        }
        return n - ((i << 1) >>> 31);
    }

    override int opCmp(Object o)
    {
        if (o is null)
            throw new NullPointerException();
        Number n = cast(Number) o;
        if (n is null)
            throw new Exception("Number needed.");
        return compare(this.value, n.intValue());
    }

    int opCmp(long n)
    {
        return compare(this.value, n);
    }

    /**
     * Returns a hash code for a {@code double} value; compatible with
     * {@code Double.hashCode()}.
     *
     * @param value the value to hash
     * @return a hash code value for a {@code double} value.
     */
    override size_t toHash() @safe nothrow
    {
        return cast(size_t) value;
    }

    /**
     * Compares this object against the specified object.  The result
     * is {@code true} if and only if the argument is not
     * {@code null} and is a {@code Double} object that
     * represents a {@code double} that has the same value as the
     * {@code double} represented by this object. For this
     * purpose, two {@code double} values are considered to be
     * the same if and only if the method {@link
     * #doubleToLongBits(double)} returns the identical
     * {@code long} value when applied to each.
     *
     * <p>Note that in most cases, for two instances of class
     * {@code Double}, {@code d1} and {@code d2}, the
     * value of {@code d1.equals(d2)} is {@code true} if and
     * only if
     *
     * <blockquote>
     *  {@code d1.doubleValue() == d2.doubleValue()}
     * </blockquote>
     *
     * <p>also has the value {@code true}. However, there are two
     * exceptions:
     * <ul>
     * <li>If {@code d1} and {@code d2} both represent
     *     {@code Double.NaN}, then the {@code equals} method
     *     returns {@code true}, even though
     *     {@code Double.NaN==Double.NaN} has the value
     *     {@code false}.
     * <li>If {@code d1} represents {@code +0.0} while
     *     {@code d2} represents {@code -0.0}, or vice versa,
     *     the {@code equal} test has the value {@code false},
     *     even though {@code +0.0==-0.0} has the value {@code true}.
     * </ul>
     * This definition allows hash tables to operate properly.
     * @param   obj   the object to compare with.
     * @return  {@code true} if the objects are the same;
     *          {@code false} otherwise.
     * @see java.lang.Double#doubleToLongBits(double)
     */
    // override bool opEquals(Object obj) {
    //     auto dl = cast(Integer)obj;
    //     if(dl !is null)
    //         return value == dl.intValue;

    //     return false;
    // }

    // alias opEquals = Nullable!int.opEquals;

    /**
     * The value of the {@code Integer}.
     *
     * @serial
     */
    // private  int value;

    /**
     * Constructs a newly allocated {@code Integer} object that
     * represents the specified {@code int} value.
     *
     * @param   value   the value to be represented by the
     *                  {@code Integer} object.
     */
    this(int value)
    {
        super(value);
    }

    static int parseInt(string s)
    {
        auto i = to!long(s);
        if (i < MIN_VALUE || i > MAX_VALUE)
        {
            throw new Exception("Value " ~ s ~ " out of range from input ");
        }

        return cast(int) i;
    }

    /**
     * Parses the string argument as a signed integer in the radix
     * specified by the second argument. The characters in the string
     * must all be digits of the specified radix (as determined by
     * whether {@link java.lang.Character#digit(char, int)} returns a
     * nonnegative value), except that the first character may be an
     * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to
     * indicate a negative value or an ASCII plus sign {@code '+'}
     * ({@code '\u005Cu002B'}) to indicate a positive value. The
     * resulting integer value is returned.
     *
     * <p>An exception of type {@code NumberFormatException} is
     * thrown if any of the following situations occurs:
     * <ul>
     * <li>The first argument is {@code null} or is a string of
     * length zero.
     *
     * <li>The radix is either smaller than
     * {@link java.lang.Character#MIN_RADIX} or
     * larger than {@link java.lang.Character#MAX_RADIX}.
     *
     * <li>Any character of the string is not a digit of the specified
     * radix, except that the first character may be a minus sign
     * {@code '-'} ({@code '\u005Cu002D'}) or plus sign
     * {@code '+'} ({@code '\u005Cu002B'}) provided that the
     * string is longer than length 1.
     *
     * <li>The value represented by the string is not a value of type
     * {@code int}.
     * </ul>
     *
     * <p>Examples:
     * <blockquote><pre>
     * parseInt("0", 10) returns 0
     * parseInt("473", 10) returns 473
     * parseInt("+42", 10) returns 42
     * parseInt("-0", 10) returns 0
     * parseInt("-FF", 16) returns -255
     * parseInt("1100110", 2) returns 102
     * parseInt("2147483647", 10) returns 2147483647
     * parseInt("-2147483648", 10) returns -2147483648
     * parseInt("2147483648", 10) throws a NumberFormatException
     * parseInt("99", 8) throws a NumberFormatException
     * parseInt("Kona", 10) throws a NumberFormatException
     * parseInt("Kona", 27) returns 411787
     * </pre></blockquote>
     *
     * @param      s   the {@code String} containing the integer
     *                  representation to be parsed
     * @param      radix   the radix to be used while parsing {@code s}.
     * @return     the integer represented by the string argument in the
     *             specified radix.
     * @exception  NumberFormatException if the {@code String}
     *             does not contain a parsable {@code int}.
     */
    static int parseInt(string s, int radix)
    {
        return to!int(s, radix);
    }

    /**
     * Cache to support the object identity semantics of autoboxing for values between
     * -128 and 127 (inclusive) as required by JLS.
     *
     * The cache is initialized on first usage.  The size of the cache
     * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option.
     * During VM initialization, java.lang.Integer.IntegerCache.high property
     * may be set and saved in the private system properties in the
     * sun.misc.VM class.
     */

    private static class IntegerCache
    {
        static int low = -128;
        static int high;
        static Integer[] cache;

        static this()
        {
            // high value may be configured by property
            int h = 127;
            // string integerCacheHighPropValue =
            //     sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
            // if (integerCacheHighPropValue !is null) {
            //     try {
            //         int i = parseInt(integerCacheHighPropValue);
            //         i = Math.max(i, 127);
            //         // Maximum array size is Integer.MAX_VALUE
            //         h = Math.min(i, Integer.MAX_VALUE - (-low) -1);
            //     } catch( NumberFormatException nfe) {
            //         // If the property cannot be parsed into an int, ignore it.
            //     }
            // }
            high = h;

            cache = new Integer[(high - low) + 1];
            int j = low;
            for (int k = 0; k < cache.length; k++)
                cache[k] = new Integer(j++);

            // range [-128, 127] must be interned (JLS7 5.1.7)
            assert(IntegerCache.high >= 127);
        }

        private this()
        {
        }
    }

    /**
     * Returns an {@code Integer} instance representing the specified
     * {@code int} value.  If a new {@code Integer} instance is not
     * required, this method should generally be used in preference to
     * the constructor {@link #Integer(int)}, as this method is likely
     * to yield significantly better space and time performance by
     * caching frequently requested values.
     *
     * This method will always cache values in the range -128 to 127,
     * inclusive, and may cache other values outside of this range.
     *
     * @param  i an {@code int} value.
     * @return an {@code Integer} instance representing {@code i}.
     */
    static Integer valueOf(int i)
    {
        if (i >= IntegerCache.low && i <= IntegerCache.high)
            return IntegerCache.cache[i + (-IntegerCache.low)];
        return new Integer(i);
    }

    /**
     * Returns an {@code Integer} object holding the value
     * extracted from the specified {@code String} when parsed
     * with the radix given by the second argument. The first argument
     * is interpreted as representing a signed integer in the radix
     * specified by the second argument, exactly as if the arguments
     * were given to the {@link #parseInt(java.lang.String, int)}
     * method. The result is an {@code Integer} object that
     * represents the integer value specified by the string.
     *
     * <p>In other words, this method returns an {@code Integer}
     * object equal to the value of:
     *
     * <blockquote>
     *  {@code new Integer(Integer.parseInt(s, radix))}
     * </blockquote>
     *
     * @param      s   the string to be parsed.
     * @param      radix the radix to be used in interpreting {@code s}
     * @return     an {@code Integer} object holding the value
     *             represented by the string argument in the specified
     *             radix.
     * @exception NumberFormatException if the {@code String}
     *            does not contain a parsable {@code int}.
     */
    static Integer valueOf(string s, int radix)
    {
        return Integer.valueOf(parseInt(s, radix));
    }

    /**
     * Returns an {@code Integer} object holding the
     * value of the specified {@code String}. The argument is
     * interpreted as representing a signed decimal integer, exactly
     * as if the argument were given to the {@link
     * #parseInt(java.lang.String)} method. The result is an
     * {@code Integer} object that represents the integer value
     * specified by the string.
     *
     * <p>In other words, this method returns an {@code Integer}
     * object equal to the value of:
     *
     * <blockquote>
     *  {@code new Integer(Integer.parseInt(s))}
     * </blockquote>
     *
     * @param      s   the string to be parsed.
     * @return     an {@code Integer} object holding the value
     *             represented by the string argument.
     * @exception  NumberFormatException  if the string cannot be parsed
     *             as an integer.
     */
    static Integer valueOf(string s)
    {
        return Integer.valueOf(parseInt(s, 10));
    }

    // Bit twiddling

    /**
     * The number of bits used to represent an {@code int} value in two's
     * complement binary form.
     *
     */
    enum int SIZE = BYTES * Byte.SIZE; // 32;

    /**
     * The number of bytes used to represent an {@code int} value in two's
     * complement binary form.
     *
     */
    enum int BYTES = int.sizeof; 

    /**
     * Returns the value obtained by rotating the two's complement binary
     * representation of the specified {@code int} value left by the
     * specified number of bits.  (Bits shifted out of the left hand, or
     * high-order, side reenter on the right, or low-order.)
     *
     * <p>Note that left rotation with a negative distance is equivalent to
     * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,
     * distance)}.  Note also that rotation by any multiple of 32 is a
     * no-op, so all but the last five bits of the rotation distance can be
     * ignored, even if the distance is negative: {@code rotateLeft(val,
     * distance) == rotateLeft(val, distance & 0x1F)}.
     *
     * @param i the value whose bits are to be rotated left
     * @param distance the number of bit positions to rotate left
     * @return the value obtained by rotating the two's complement binary
     *     representation of the specified {@code int} value left by the
     *     specified number of bits.
     */
    static int rotateLeft(int i, int distance)
    {
        return (i << distance) | (i >>> -distance);
    }

    /**
     * Returns the value obtained by rotating the two's complement binary
     * representation of the specified {@code int} value right by the
     * specified number of bits.  (Bits shifted out of the right hand, or
     * low-order, side reenter on the left, or high-order.)
     *
     * <p>Note that right rotation with a negative distance is equivalent to
     * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,
     * distance)}.  Note also that rotation by any multiple of 32 is a
     * no-op, so all but the last five bits of the rotation distance can be
     * ignored, even if the distance is negative: {@code rotateRight(val,
     * distance) == rotateRight(val, distance & 0x1F)}.
     *
     * @param i the value whose bits are to be rotated right
     * @param distance the number of bit positions to rotate right
     * @return the value obtained by rotating the two's complement binary
     *     representation of the specified {@code int} value right by the
     *     specified number of bits.
     */
    static int rotateRight(int i, int distance)
    {
        return (i >>> distance) | (i << -distance);
    }

    /**
     * Returns the value obtained by reversing the order of the bytes in the
     * two's complement representation of the specified {@code int} value.
     *
     * @param i the value whose bytes are to be reversed
     * @return the value obtained by reversing the bytes in the specified
     *     {@code int} value.
     */
    static int reverseBytes(int i) {
        return (i << 24)            |
               ((i & 0xff00) << 8)  |
               ((i >>> 8) & 0xff00) |
               (i >>> 24);
    }
}