// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_NUMERICS_CLAMPED_MATH_H_
#define BASE_NUMERICS_CLAMPED_MATH_H_

#include <stddef.h>

#include <limits>
#include <type_traits>

#include "anglebase/numerics/clamped_math_impl.h"

namespace angle
{
namespace base
{
namespace internal
{

template <typename T>
class ClampedNumeric
{
    static_assert(std::is_arithmetic<T>::value, "ClampedNumeric<T>: T must be a numeric type.");

  public:
    using type = T;

    constexpr ClampedNumeric() : value_(0) {}

    // Copy constructor.
    template <typename Src>
    constexpr ClampedNumeric(const ClampedNumeric<Src> &rhs) : value_(saturated_cast<T>(rhs.value_))
    {}

    template <typename Src>
    friend class ClampedNumeric;

    // This is not an explicit constructor because we implicitly upgrade regular
    // numerics to ClampedNumerics to make them easier to use.
    template <typename Src>
    constexpr ClampedNumeric(Src value)  // NOLINT(runtime/explicit)
        : value_(saturated_cast<T>(value))
    {
        static_assert(std::is_arithmetic<Src>::value, "Argument must be numeric.");
    }

    // This is not an explicit constructor because we want a seamless conversion
    // from StrictNumeric types.
    template <typename Src>
    constexpr ClampedNumeric(StrictNumeric<Src> value)  // NOLINT(runtime/explicit)
        : value_(saturated_cast<T>(static_cast<Src>(value)))
    {}

    // Returns a ClampedNumeric of the specified type, cast from the current
    // ClampedNumeric, and saturated to the destination type.
    template <typename Dst>
    constexpr ClampedNumeric<typename UnderlyingType<Dst>::type> Cast() const
    {
        return *this;
    }

    // Prototypes for the supported arithmetic operator overloads.
    template <typename Src>
    constexpr ClampedNumeric &operator+=(const Src rhs);
    template <typename Src>
    constexpr ClampedNumeric &operator-=(const Src rhs);
    template <typename Src>
    constexpr ClampedNumeric &operator*=(const Src rhs);
    template <typename Src>
    constexpr ClampedNumeric &operator/=(const Src rhs);
    template <typename Src>
    constexpr ClampedNumeric &operator%=(const Src rhs);
    template <typename Src>
    constexpr ClampedNumeric &operator<<=(const Src rhs);
    template <typename Src>
    constexpr ClampedNumeric &operator>>=(const Src rhs);
    template <typename Src>
    constexpr ClampedNumeric &operator&=(const Src rhs);
    template <typename Src>
    constexpr ClampedNumeric &operator|=(const Src rhs);
    template <typename Src>
    constexpr ClampedNumeric &operator^=(const Src rhs);

    constexpr ClampedNumeric operator-() const
    {
        // The negation of two's complement int min is int min, so that's the
        // only overflow case where we will saturate.
        return ClampedNumeric<T>(SaturatedNegWrapper(value_));
    }

    constexpr ClampedNumeric operator~() const
    {
        return ClampedNumeric<decltype(InvertWrapper(T()))>(InvertWrapper(value_));
    }

    constexpr ClampedNumeric Abs() const
    {
        // The negation of two's complement int min is int min, so that's the
        // only overflow case where we will saturate.
        return ClampedNumeric<T>(SaturatedAbsWrapper(value_));
    }

    template <typename U>
    constexpr ClampedNumeric<typename MathWrapper<ClampedMaxOp, T, U>::type> Max(const U rhs) const
    {
        using result_type = typename MathWrapper<ClampedMaxOp, T, U>::type;
        return ClampedNumeric<result_type>(ClampedMaxOp<T, U>::Do(value_, Wrapper<U>::value(rhs)));
    }

    template <typename U>
    constexpr ClampedNumeric<typename MathWrapper<ClampedMinOp, T, U>::type> Min(const U rhs) const
    {
        using result_type = typename MathWrapper<ClampedMinOp, T, U>::type;
        return ClampedNumeric<result_type>(ClampedMinOp<T, U>::Do(value_, Wrapper<U>::value(rhs)));
    }

    // This function is available only for integral types. It returns an unsigned
    // integer of the same width as the source type, containing the absolute value
    // of the source, and properly handling signed min.
    constexpr ClampedNumeric<typename UnsignedOrFloatForSize<T>::type> UnsignedAbs() const
    {
        return ClampedNumeric<typename UnsignedOrFloatForSize<T>::type>(SafeUnsignedAbs(value_));
    }

    constexpr ClampedNumeric &operator++()
    {
        *this += 1;
        return *this;
    }

    constexpr ClampedNumeric operator++(int)
    {
        ClampedNumeric value = *this;
        *this += 1;
        return value;
    }

    constexpr ClampedNumeric &operator--()
    {
        *this -= 1;
        return *this;
    }

    constexpr ClampedNumeric operator--(int)
    {
        ClampedNumeric value = *this;
        *this -= 1;
        return value;
    }

    // These perform the actual math operations on the ClampedNumerics.
    // Binary arithmetic operations.
    template <template <typename, typename, typename> class M, typename L, typename R>
    static constexpr ClampedNumeric MathOp(const L lhs, const R rhs)
    {
        using Math = typename MathWrapper<M, L, R>::math;
        return ClampedNumeric<T>(
            Math::template Do<T>(Wrapper<L>::value(lhs), Wrapper<R>::value(rhs)));
    }

    // Assignment arithmetic operations.
    template <template <typename, typename, typename> class M, typename R>
    constexpr ClampedNumeric &MathOp(const R rhs)
    {
        using Math = typename MathWrapper<M, T, R>::math;
        *this      = ClampedNumeric<T>(Math::template Do<T>(value_, Wrapper<R>::value(rhs)));
        return *this;
    }

    template <typename Dst>
    constexpr operator Dst() const
    {
        return saturated_cast<typename ArithmeticOrUnderlyingEnum<Dst>::type>(value_);
    }

    // This method extracts the raw integer value without saturating it to the
    // destination type as the conversion operator does. This is useful when
    // e.g. assigning to an auto type or passing as a deduced template parameter.
    constexpr T RawValue() const { return value_; }

  private:
    T value_;

    // These wrappers allow us to handle state the same way for both
    // ClampedNumeric and POD arithmetic types.
    template <typename Src>
    struct Wrapper
    {
        static constexpr Src value(Src value)
        {
            return static_cast<typename UnderlyingType<Src>::type>(value);
        }
    };
};

// Convience wrapper to return a new ClampedNumeric from the provided arithmetic
// or ClampedNumericType.
template <typename T>
constexpr ClampedNumeric<typename UnderlyingType<T>::type> MakeClampedNum(const T value)
{
    return value;
}

#if !BASE_NUMERICS_DISABLE_OSTREAM_OPERATORS
// Overload the ostream output operator to make logging work nicely.
template <typename T>
std::ostream &operator<<(std::ostream &os, const ClampedNumeric<T> &value)
{
    os << static_cast<T>(value);
    return os;
}
#endif

// These implement the variadic wrapper for the math operations.
template <template <typename, typename, typename> class M, typename L, typename R>
constexpr ClampedNumeric<typename MathWrapper<M, L, R>::type> ClampMathOp(const L lhs, const R rhs)
{
    using Math = typename MathWrapper<M, L, R>::math;
    return ClampedNumeric<typename Math::result_type>::template MathOp<M>(lhs, rhs);
}

// General purpose wrapper template for arithmetic operations.
template <template <typename, typename, typename> class M, typename L, typename R, typename... Args>
constexpr auto ClampMathOp(const L lhs, const R rhs, const Args... args)
{
    return ClampMathOp<M>(ClampMathOp<M>(lhs, rhs), args...);
}

BASE_NUMERIC_ARITHMETIC_OPERATORS(Clamped, Clamp, Add, +, +=)
BASE_NUMERIC_ARITHMETIC_OPERATORS(Clamped, Clamp, Sub, -, -=)
BASE_NUMERIC_ARITHMETIC_OPERATORS(Clamped, Clamp, Mul, *, *=)
BASE_NUMERIC_ARITHMETIC_OPERATORS(Clamped, Clamp, Div, /, /=)
BASE_NUMERIC_ARITHMETIC_OPERATORS(Clamped, Clamp, Mod, %, %=)
BASE_NUMERIC_ARITHMETIC_OPERATORS(Clamped, Clamp, Lsh, <<, <<=)
BASE_NUMERIC_ARITHMETIC_OPERATORS(Clamped, Clamp, Rsh, >>, >>=)
BASE_NUMERIC_ARITHMETIC_OPERATORS(Clamped, Clamp, And, &, &=)
BASE_NUMERIC_ARITHMETIC_OPERATORS(Clamped, Clamp, Or, |, |=)
BASE_NUMERIC_ARITHMETIC_OPERATORS(Clamped, Clamp, Xor, ^, ^=)
BASE_NUMERIC_ARITHMETIC_VARIADIC(Clamped, Clamp, Max)
BASE_NUMERIC_ARITHMETIC_VARIADIC(Clamped, Clamp, Min)
BASE_NUMERIC_COMPARISON_OPERATORS(Clamped, IsLess, <)
BASE_NUMERIC_COMPARISON_OPERATORS(Clamped, IsLessOrEqual, <=)
BASE_NUMERIC_COMPARISON_OPERATORS(Clamped, IsGreater, >)
BASE_NUMERIC_COMPARISON_OPERATORS(Clamped, IsGreaterOrEqual, >=)
BASE_NUMERIC_COMPARISON_OPERATORS(Clamped, IsEqual, ==)
BASE_NUMERIC_COMPARISON_OPERATORS(Clamped, IsNotEqual, !=)

}  // namespace internal

using internal::ClampAdd;
using internal::ClampAnd;
using internal::ClampDiv;
using internal::ClampedNumeric;
using internal::ClampLsh;
using internal::ClampMax;
using internal::ClampMin;
using internal::ClampMod;
using internal::ClampMul;
using internal::ClampOr;
using internal::ClampRsh;
using internal::ClampSub;
using internal::ClampXor;
using internal::MakeClampedNum;

}  // namespace base
}  // namespace angle

#endif  // BASE_NUMERICS_CLAMPED_MATH_H_
