/*
  ==============================================================================

   This file is part of the JUCE 6 technical preview.
   Copyright (c) 2020 - Raw Material Software Limited

   You may use this code under the terms of the GPL v3
   (see www.gnu.org/licenses).

   For this technical preview, this file is not subject to commercial licensing.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{
namespace dsp
{

/** A template specialisation to find corresponding mask type for primitives. */
namespace SIMDInternal
{
    template <typename Primitive> struct MaskTypeFor        { using type = Primitive; };
    template <> struct MaskTypeFor <float>                  { using type = uint32_t; };
    template <> struct MaskTypeFor <double>                 { using type = uint64_t; };
    template <> struct MaskTypeFor <char>                   { using type = uint8_t; };
    template <> struct MaskTypeFor <int8_t>                 { using type = uint8_t; };
    template <> struct MaskTypeFor <int16_t>                { using type = uint16_t; };
    template <> struct MaskTypeFor <int32_t>                { using type = uint32_t; };
    template <> struct MaskTypeFor <int64_t>                { using type = uint64_t; };
    template <> struct MaskTypeFor <std::complex<float>>    { using type = uint32_t; };
    template <> struct MaskTypeFor <std::complex<double>>   { using type = uint64_t; };

    template <typename Primitive> struct PrimitiveType                           { using type = typename std::remove_cv<Primitive>::type; };
    template <typename Primitive> struct PrimitiveType<std::complex<Primitive>>  { using type = typename std::remove_cv<Primitive>::type; };

    template <int n>    struct Log2Helper    { enum { value = Log2Helper<n/2>::value + 1 }; };
    template <>         struct Log2Helper<1> { enum { value = 0 }; };
}

/**
    Useful fallback routines to use if the native SIMD op is not supported. You
    should never need to use this directly. Use juce_SIMDRegister instead.

    @tags{DSP}
*/
template <typename ScalarType, typename vSIMDType>
struct SIMDFallbackOps
{
    static constexpr size_t n    =  sizeof (vSIMDType) / sizeof (ScalarType);
    static constexpr size_t mask = (sizeof (vSIMDType) / sizeof (ScalarType)) - 1;
    static constexpr size_t bits = SIMDInternal::Log2Helper<(int) n>::value;

    // helper types
    using MaskType = typename SIMDInternal::MaskTypeFor<ScalarType>::type;
    union UnionType     { vSIMDType v; ScalarType s[n]; };
    union UnionMaskType { vSIMDType v; MaskType   m[n]; };


    // fallback methods
    static forcedinline vSIMDType add (vSIMDType a, vSIMDType b) noexcept        { return apply<ScalarAdd> (a, b); }
    static forcedinline vSIMDType sub (vSIMDType a, vSIMDType b) noexcept        { return apply<ScalarSub> (a, b); }
    static forcedinline vSIMDType mul (vSIMDType a, vSIMDType b) noexcept        { return apply<ScalarMul> (a, b); }
    static forcedinline vSIMDType bit_and (vSIMDType a, vSIMDType b) noexcept    { return bitapply<ScalarAnd> (a, b); }
    static forcedinline vSIMDType bit_or  (vSIMDType a, vSIMDType b) noexcept    { return bitapply<ScalarOr > (a, b); }
    static forcedinline vSIMDType bit_xor (vSIMDType a, vSIMDType b) noexcept    { return bitapply<ScalarXor> (a, b); }
    static forcedinline vSIMDType bit_notand (vSIMDType a, vSIMDType b) noexcept { return bitapply<ScalarNot> (a, b); }

    static forcedinline vSIMDType min (vSIMDType a, vSIMDType b) noexcept                { return apply<ScalarMin> (a, b); }
    static forcedinline vSIMDType max (vSIMDType a, vSIMDType b) noexcept                { return apply<ScalarMax> (a, b); }
    static forcedinline vSIMDType equal (vSIMDType a, vSIMDType b) noexcept              { return cmp<ScalarEq > (a, b); }
    static forcedinline vSIMDType notEqual (vSIMDType a, vSIMDType b) noexcept           { return cmp<ScalarNeq> (a, b); }
    static forcedinline vSIMDType greaterThan (vSIMDType a, vSIMDType b) noexcept        { return cmp<ScalarGt > (a, b); }
    static forcedinline vSIMDType greaterThanOrEqual (vSIMDType a, vSIMDType b) noexcept { return cmp<ScalarGeq> (a, b); }

    static forcedinline ScalarType get (vSIMDType v, size_t i) noexcept
    {
        UnionType u {v};
        return u.s[i];
    }

    static forcedinline vSIMDType set (vSIMDType v, size_t i, ScalarType s) noexcept
    {
        UnionType u {v};

        u.s[i] = s;
        return u.v;
    }

    static forcedinline vSIMDType bit_not (vSIMDType av) noexcept
    {
        UnionMaskType a {av};

        for (size_t i = 0; i < n; ++i)
            a.m[i] = ~a.m[i];

        return a.v;
    }

    static forcedinline ScalarType sum (vSIMDType av) noexcept
    {
        UnionType a {av};
        auto retval = static_cast<ScalarType> (0);

        for (size_t i = 0; i < n; ++i)
            retval = static_cast<ScalarType> (retval + a.s[i]);

        return retval;
    }

    static forcedinline vSIMDType truncate (vSIMDType av) noexcept
    {
        UnionType a {av};

        for (size_t i = 0; i < n; ++i)
        {
            jassert (a.s[i] >= ScalarType (0));
            a.s[i] = static_cast <ScalarType> (static_cast<int> (a.s[i]));
        }

        return a.v;
    }

    static forcedinline vSIMDType multiplyAdd (vSIMDType av, vSIMDType bv, vSIMDType cv) noexcept
    {
        UnionType a {av}, b {bv}, c {cv};

        for (size_t i = 0; i < n; ++i)
            a.s[i] += b.s[i] * c.s[i];

        return a.v;
    }

    //==============================================================================
    static forcedinline bool allEqual (vSIMDType av, vSIMDType bv) noexcept
    {
        UnionType a {av}, b {bv};

        for (size_t i = 0; i < n; ++i)
            if (a.s[i] != b.s[i])
                return false;

        return true;
    }

    //==============================================================================
    static forcedinline vSIMDType cmplxmul (vSIMDType av, vSIMDType bv) noexcept
    {
        UnionType a {av}, b {bv}, r;

        const int m = n >> 1;
        for (int i = 0; i < m; ++i)
        {
            std::complex<ScalarType> result
                  = std::complex<ScalarType> (a.s[i<<1], a.s[(i<<1)|1])
                  * std::complex<ScalarType> (b.s[i<<1], b.s[(i<<1)|1]);

            r.s[i<<1]     = result.real();
            r.s[(i<<1)|1] = result.imag();
        }

        return r.v;
    }

    struct ScalarAdd { static forcedinline ScalarType   op (ScalarType a, ScalarType b)   noexcept { return a + b; } };
    struct ScalarSub { static forcedinline ScalarType   op (ScalarType a, ScalarType b)   noexcept { return a - b; } };
    struct ScalarMul { static forcedinline ScalarType   op (ScalarType a, ScalarType b)   noexcept { return a * b; } };
    struct ScalarMin { static forcedinline ScalarType   op (ScalarType a, ScalarType b)   noexcept { return jmin (a, b); } };
    struct ScalarMax { static forcedinline ScalarType   op (ScalarType a, ScalarType b)   noexcept { return jmax (a, b); } };
    struct ScalarAnd { static forcedinline MaskType     op (MaskType a,   MaskType b)     noexcept { return a & b; } };
    struct ScalarOr  { static forcedinline MaskType     op (MaskType a,   MaskType b)     noexcept { return a | b; } };
    struct ScalarXor { static forcedinline MaskType     op (MaskType a,   MaskType b)     noexcept { return a ^ b; } };
    struct ScalarNot { static forcedinline MaskType     op (MaskType a,   MaskType b)     noexcept { return (~a) & b; } };
    struct ScalarEq  { static forcedinline bool         op (ScalarType a, ScalarType b)   noexcept { return (a == b); } };
    struct ScalarNeq { static forcedinline bool         op (ScalarType a, ScalarType b)   noexcept { return (a != b); } };
    struct ScalarGt  { static forcedinline bool         op (ScalarType a, ScalarType b)   noexcept { return (a >  b); } };
    struct ScalarGeq { static forcedinline bool         op (ScalarType a, ScalarType b)   noexcept { return (a >= b); } };

    // generic apply routines for operations above
    template <typename Op>
    static forcedinline vSIMDType apply (vSIMDType av, vSIMDType bv) noexcept
    {
        UnionType a {av}, b {bv};

        for (size_t i = 0; i < n; ++i)
            a.s[i] = Op::op (a.s[i], b.s[i]);

        return a.v;
    }

    template <typename Op>
    static forcedinline vSIMDType cmp (vSIMDType av, vSIMDType bv) noexcept
    {
        UnionType a {av}, b {bv};
        UnionMaskType r;

        for (size_t i = 0; i < n; ++i)
            r.m[i] = Op::op (a.s[i], b.s[i]) ? static_cast<MaskType> (-1) : static_cast<MaskType> (0);

        return r.v;
    }

    template <typename Op>
    static forcedinline vSIMDType bitapply (vSIMDType av, vSIMDType bv) noexcept
    {
        UnionMaskType a {av}, b {bv};

        for (size_t i = 0; i < n; ++i)
            a.m[i] = Op::op (a.m[i], b.m[i]);

        return a.v;
    }

    static forcedinline vSIMDType expand (ScalarType s) noexcept
    {
        UnionType r;

        for (size_t i = 0; i < n; ++i)
            r.s[i] = s;

        return r.v;
    }

    static forcedinline vSIMDType load (const ScalarType* a) noexcept
    {
        UnionType r;

        for (size_t i = 0; i < n; ++i)
            r.s[i] = a[i];

        return r.v;
    }

    static forcedinline void store (vSIMDType av, ScalarType* dest) noexcept
    {
        UnionType a {av};

        for (size_t i = 0; i < n; ++i)
            dest[i] = a.s[i];
    }

    template <unsigned int shuffle_idx>
    static forcedinline vSIMDType shuffle (vSIMDType av) noexcept
    {
        UnionType a {av}, r;

        // the compiler will unroll this loop and the index can
        // be computed at compile-time, so this will be super fast
        for (size_t i = 0; i < n; ++i)
            r.s[i] = a.s[(shuffle_idx >> (bits * i)) & mask];

        return r.v;
    }
};

} // namespace dsp
} // namespace juce