/********************************************************************
 * qofmath128.h -- an 128-bit integer library                       *
 * Copyright (C) 2004 Linas Vepstas <linas@linas.org>               *
 * Copyright (C) 2014 John Ralls <jralls@ceridwen.us>               *
 *                                                                  *
 * This program is free software; you can redistribute it and/or    *
 * modify it under the terms of the GNU General Public License as   *
 * published by the Free Software Foundation; either version 2 of   *
 * the License, or (at your option) any later version.              *
 *                                                                  *
 * This program is distributed in the hope that it will be useful,  *
 * but WITHOUT ANY WARRANTY; without even the implied warranty of   *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the    *
 * GNU General Public License for more details.                     *
 *                                                                  *
 * You should have received a copy of the GNU General Public License*
 * along with this program; if not, contact:                        *
 *                                                                  *
 * Free Software Foundation           Voice:  +1-617-542-5942       *
 * 51 Franklin Street, Fifth Floor    Fax:    +1-617-542-2652       *
 * Boston, MA  02110-1301,  USA       gnu@gnu.org                   *
 *                                                                  *
 *******************************************************************/

#ifndef GNCINT128_H
#define GNCINT128_H

extern "C"
{
#ifndef __STDC_LIMIT_MACROS
#define  __STDC_LIMIT_MACROS 1
#endif
#ifndef __STDC_CONSTANT_MACROS
#define  __STDC_CONSTANT_MACROS 1
#endif
#ifndef __STDC_FORMAT_MACROS
#define  __STDC_FORMAT_MACROS 1
#endif
#include <inttypes.h>
}

#include <stdexcept>
#include <string>
#include <ostream>
#include <type_traits>

//using std::string;
/** @addtogroup GncInt128
 * @ingroup QOF
 * @{
 * @brief provides a 125-bit int as a base class for GncNumeric.
 *
 * In order to make space for the status flags the upper leg is limited to
 * 0x1fffffffffffffff. Attempting to construct a GncInt128 with a larger upper
 * leg will throw a std::overflow_error.
 *
 * All the usual operators are provided. Only the constructors and explicit
 * integer conversions throw; all other errors are indicated by the overflow and
 * NaN ("Not a Number") flags. Note that performing any operation on an
 * overflowed or NaN Gncint128 will yield an overflowed or NaN result, so
 * calling routines need not check until the end of a chained calculation.
 * GncInt128 uses implicit copy and move constructors and implicit destructor.
 */
class GncInt128
{
    uint64_t m_hi;
    uint64_t m_lo;

public:
    static const unsigned int flagbits = 3;
    static const unsigned int numlegs = 2;
    static const unsigned int legbits = 64;
    static const unsigned int maxbits = legbits * numlegs - flagbits;

enum // Values for m_flags
{
    pos = 0,
    neg = 1,
    overflow = 2,
    NaN = 4
};
/** @addtogroup Constructors Constructors
 *  Constructors are templated so that a GncInt128 can be constructed from any
 *  arbitrary integer type or pair of integer types.
 * @note If the two parameters are of differing sign, it's taken to
 * mean that the lower magnitude is *reducing* the magnitude of the
 * upper, so the lower magnitude will be subtracted from UINT64_MAX to
 * obtain the lower limb value.
*  @{
 */
/** Default constructor. Makes 0. */
    GncInt128();
    template <typename T>
    GncInt128(T lower) : GncInt128(INT64_C(0), static_cast<int64_t>(lower))
    {
        static_assert (std::is_integral<T>(),
                       "GncInt128 can be constructed only with "
                       "integral arguments.");
    }
    GncInt128(uint64_t lower) : GncInt128 {UINT64_C(0), lower} {}
/** Double-integer constructor template.
 */
    template <typename T, typename U>
    GncInt128(T upper, U lower, unsigned char flags = '\0') :
        GncInt128 {static_cast<int64_t>(upper),
                   static_cast<int64_t>(lower), flags}
    {
        static_assert (std::is_integral<T>(),
                       "GncInt128 can be constructed only with "
                       "integral arguments.");
        static_assert (std::is_integral<U>(),
                       "GncInt128 can be constructed only with "
                       "integral arguments.");
    }

    GncInt128 (int64_t upper, int64_t lower, unsigned char flags = '\0');
    template <typename T>
    GncInt128(T upper, uint64_t lower) :
        GncInt128 {static_cast<int64_t>(upper), lower}
        {
            static_assert (std::is_integral<T>(),
                           "GncInt128 can be constructed only with "
                           "integral arguments.");
        }

    GncInt128 (int64_t upper, uint64_t lower, unsigned char flags = '\0');
    GncInt128 (uint64_t upper, uint64_t lower, unsigned char flags = '\0');
/** @} */
/**
 * Clear the object.
 *
 * Sets all member variables to zero.
 * @return A reference to the object for chaining.
 */
    GncInt128& zero() noexcept;

/**
 * Compare function.
 *
 * @return -1 if the object is less than the parameter, 0 if they're
 * equal, and 1 if the object is greater.
 */
    int cmp (const GncInt128& b) const noexcept;

/**
 * Computes the Greatest Common Divisor between the object and parameter
 *
 * @return A GncInt128 having the GCD.
 */
    GncInt128 gcd (GncInt128 b) const noexcept;
/**
 * Computes the Least Common Multiple between the object and parameter
 *
 * @return A GncInt128 having the LCM.
 */
    GncInt128 lcm (const GncInt128& b) const noexcept;

/**
 * Computes the object raised to the parameter's power
 *
 * @param b The power to raise this to. No point in taking a GncInt128, any
 * value greater than 128 would overflow on any value other than 1.
 * @return A GncInt128
 */
    GncInt128 pow (unsigned int n) const noexcept;

/**
 * Computes a quotient and a remainder, passed as reference parameters.
 *
 * 'this' is the dividend. The quotient and remainder args must be initialized
 * to zero.
 * @param d The divisor
 * @param q The quotient; will be NaN if divisor = 0
 * @param r The remainder; will be 0 if divisor = 0
 */
    void div (const GncInt128& d, GncInt128& q, GncInt128& r) const noexcept;

/**
 * Explicit conversion to int64_t.
 *
 * @return A int64_t
 * @throws std::overflow_error if the object's value is > INT64_MAX or NaN.
 * @throws std::underflow_error if the object's value is < INT64_MIN
 */
    explicit operator int64_t() const;
/**
 * Explicit conversion to uint64_t.
 *
 * @return A uint64_t
 * @throws std::overflow_error if the object's value is > UINT64_MAX or NaN.
 * @throws std::underflow_error if the object's value is < 0.
 */
    explicit operator uint64_t() const;

/**
 * @return true if the object value is < 0
 */
    bool isNeg () const noexcept;
/**
 * @return true if the object value is > INT64_MAX or < INT64_MIN
 */
    bool isBig () const noexcept;
/**
 * @return true if a calculation has produced a result of larger
 * magnitude than can be contained in the 128 bits available.
 */
    bool isOverflow () const noexcept;
/**
 * @return true if an illegal calculation has occurred.
 */
    bool isNan () const noexcept;
/**
 * @return true if the object represents 0.
 */
    bool isZero() const noexcept;
/**
 * @return true if neither the overflow nor nan flags are set.
 */
    bool valid() const noexcept;

/**
 * @return the number of bits used to represent the value
 */
    unsigned int bits() const noexcept;

/**
 * Fills a supplied buffer with a representation of the number in base 10. If
 * the GncInt128 is overflowed or NaN it will contain the words "Overflow" or
 * "NaN" respectively.
 *
 * @param buf char[41], 39 digits plus sign and trailing 0.
 * @return pointer to the buffer for convenience
 */
    char* asCharBufR(char* buf) const noexcept;

    GncInt128 abs() const noexcept;

    GncInt128 operator-() const noexcept;
    explicit operator bool() const noexcept;

    GncInt128& operator++ () noexcept;
    GncInt128& operator++ (int) noexcept;
    GncInt128& operator-- () noexcept;
    GncInt128& operator-- (int) noexcept;
    GncInt128& operator<<= (unsigned int i) noexcept;
    GncInt128& operator>>= (unsigned int i) noexcept;
    GncInt128& operator+= (const GncInt128& b) noexcept;
    GncInt128& operator-= (const GncInt128& b) noexcept;
    GncInt128& operator*= (const GncInt128& b) noexcept;
    GncInt128& operator/= (const GncInt128& b) noexcept;
    GncInt128& operator%= (const GncInt128& b) noexcept;
    GncInt128& operator&= (const GncInt128& b) noexcept;
    GncInt128& operator|= (const GncInt128& b) noexcept;
    GncInt128& operator^= (const GncInt128& b) noexcept;

};

static const GncInt128 k_gncint128_Max {UINT64_MAX, UINT64_MAX, GncInt128::pos};
static const GncInt128 k_gncint128_Min {UINT64_MAX, UINT64_MAX, GncInt128::neg};

GncInt128 operator+ (GncInt128 a, const GncInt128& b) noexcept;
GncInt128 operator- (GncInt128 a, const GncInt128& b) noexcept;
GncInt128 operator* (GncInt128 a, const GncInt128& b) noexcept;
GncInt128 operator/ (GncInt128 a, const GncInt128& b) noexcept;
GncInt128 operator% (GncInt128 a, const GncInt128& b) noexcept;
GncInt128 operator& (GncInt128 a, const GncInt128& b) noexcept;
GncInt128 operator| (GncInt128 a, const GncInt128& b) noexcept;
GncInt128 operator^ (GncInt128 a, const GncInt128& b) noexcept;
GncInt128 operator<< (GncInt128 a, unsigned int b) noexcept;
GncInt128 operator>> (GncInt128 a, unsigned int b) noexcept;

bool operator== (const GncInt128& a, const GncInt128& b) noexcept;
bool operator!= (const GncInt128& a, const GncInt128& b) noexcept;
bool operator<= (const GncInt128& a, const GncInt128& b) noexcept;
bool operator>= (const GncInt128& a, const GncInt128& b) noexcept;
bool operator< (const GncInt128& a, const GncInt128& b) noexcept;
bool operator> (const GncInt128& a, const GncInt128& b) noexcept;

std::ostream& operator<< (std::ostream&, const GncInt128&) noexcept;

/** Compute the greatest common denominator of two integers
 */
GncInt128 gcd (int64_t a, int64_t b);

/** Compute the least common multiple of two integers
 */
GncInt128 lcm (int64_t a, int64_t b);

#endif //GNCINT128_H

/** @} */