#include "config.h"

#include <arm_neon.h>

#include <cmath>
#include <limits>

#include "alnumeric.h"
#include "core/bsinc_defs.h"
#include "core/cubic_defs.h"
#include "defs.h"
#include "hrtfbase.h"

struct NEONTag;
struct LerpTag;
struct CubicTag;
struct BSincTag;
struct FastBSincTag;


#if defined(__GNUC__) && !defined(__clang__) && !defined(__ARM_NEON)
#pragma GCC target("fpu=neon")
#endif

namespace {

constexpr uint BSincPhaseDiffBits{MixerFracBits - BSincPhaseBits};
constexpr uint BSincPhaseDiffOne{1 << BSincPhaseDiffBits};
constexpr uint BSincPhaseDiffMask{BSincPhaseDiffOne - 1u};

constexpr uint CubicPhaseDiffBits{MixerFracBits - CubicPhaseBits};
constexpr uint CubicPhaseDiffOne{1 << CubicPhaseDiffBits};
constexpr uint CubicPhaseDiffMask{CubicPhaseDiffOne - 1u};

inline float32x4_t set_f4(float l0, float l1, float l2, float l3)
{
    float32x4_t ret{vmovq_n_f32(l0)};
    ret = vsetq_lane_f32(l1, ret, 1);
    ret = vsetq_lane_f32(l2, ret, 2);
    ret = vsetq_lane_f32(l3, ret, 3);
    return ret;
}

inline void ApplyCoeffs(float2 *RESTRICT Values, const size_t IrSize, const ConstHrirSpan Coeffs,
    const float left, const float right)
{
    float32x4_t leftright4;
    {
        float32x2_t leftright2{vmov_n_f32(left)};
        leftright2 = vset_lane_f32(right, leftright2, 1);
        leftright4 = vcombine_f32(leftright2, leftright2);
    }

    ASSUME(IrSize >= MinIrLength);
    for(size_t c{0};c < IrSize;c += 2)
    {
        float32x4_t vals = vld1q_f32(&Values[c][0]);
        float32x4_t coefs = vld1q_f32(&Coeffs[c][0]);

        vals = vmlaq_f32(vals, coefs, leftright4);

        vst1q_f32(&Values[c][0], vals);
    }
}

force_inline void MixLine(const al::span<const float> InSamples, float *RESTRICT dst,
    float &CurrentGain, const float TargetGain, const float delta, const size_t min_len,
    const size_t aligned_len, size_t Counter)
{
    float gain{CurrentGain};
    const float step{(TargetGain-gain) * delta};

    size_t pos{0};
    if(!(std::abs(step) > std::numeric_limits<float>::epsilon()))
        gain = TargetGain;
    else
    {
        float step_count{0.0f};
        /* Mix with applying gain steps in aligned multiples of 4. */
        if(size_t todo{min_len >> 2})
        {
            const float32x4_t four4{vdupq_n_f32(4.0f)};
            const float32x4_t step4{vdupq_n_f32(step)};
            const float32x4_t gain4{vdupq_n_f32(gain)};
            float32x4_t step_count4{vdupq_n_f32(0.0f)};
            step_count4 = vsetq_lane_f32(1.0f, step_count4, 1);
            step_count4 = vsetq_lane_f32(2.0f, step_count4, 2);
            step_count4 = vsetq_lane_f32(3.0f, step_count4, 3);

            do {
                const float32x4_t val4 = vld1q_f32(&InSamples[pos]);
                float32x4_t dry4 = vld1q_f32(&dst[pos]);
                dry4 = vmlaq_f32(dry4, val4, vmlaq_f32(gain4, step4, step_count4));
                step_count4 = vaddq_f32(step_count4, four4);
                vst1q_f32(&dst[pos], dry4);
                pos += 4;
            } while(--todo);
            /* NOTE: step_count4 now represents the next four counts after the
             * last four mixed samples, so the lowest element represents the
             * next step count to apply.
             */
            step_count = vgetq_lane_f32(step_count4, 0);
        }
        /* Mix with applying left over gain steps that aren't aligned multiples of 4. */
        for(size_t leftover{min_len&3};leftover;++pos,--leftover)
        {
            dst[pos] += InSamples[pos] * (gain + step*step_count);
            step_count += 1.0f;
        }
        if(pos == Counter)
            gain = TargetGain;
        else
            gain += step*step_count;

        /* Mix until pos is aligned with 4 or the mix is done. */
        for(size_t leftover{aligned_len&3};leftover;++pos,--leftover)
            dst[pos] += InSamples[pos] * gain;
    }
    CurrentGain = gain;

    if(!(std::abs(gain) > GainSilenceThreshold))
        return;
    if(size_t todo{(InSamples.size()-pos) >> 2})
    {
        const float32x4_t gain4 = vdupq_n_f32(gain);
        do {
            const float32x4_t val4 = vld1q_f32(&InSamples[pos]);
            float32x4_t dry4 = vld1q_f32(&dst[pos]);
            dry4 = vmlaq_f32(dry4, val4, gain4);
            vst1q_f32(&dst[pos], dry4);
            pos += 4;
        } while(--todo);
    }
    for(size_t leftover{(InSamples.size()-pos)&3};leftover;++pos,--leftover)
        dst[pos] += InSamples[pos] * gain;
}

} // namespace

template<>
void Resample_<LerpTag,NEONTag>(const InterpState*, const float *RESTRICT src, uint frac,
    const uint increment, const al::span<float> dst)
{
    ASSUME(frac < MixerFracOne);

    const int32x4_t increment4 = vdupq_n_s32(static_cast<int>(increment*4));
    const float32x4_t fracOne4 = vdupq_n_f32(1.0f/MixerFracOne);
    const int32x4_t fracMask4 = vdupq_n_s32(MixerFracMask);

    alignas(16) std::array<uint,4> pos_, frac_;
    InitPosArrays(frac, increment, al::span{frac_}, al::span{pos_});
    int32x4_t frac4 = vld1q_s32(reinterpret_cast<int*>(frac_.data()));
    int32x4_t pos4 = vld1q_s32(reinterpret_cast<int*>(pos_.data()));

    auto dst_iter = dst.begin();
    for(size_t todo{dst.size()>>2};todo;--todo)
    {
        const int pos0{vgetq_lane_s32(pos4, 0)};
        const int pos1{vgetq_lane_s32(pos4, 1)};
        const int pos2{vgetq_lane_s32(pos4, 2)};
        const int pos3{vgetq_lane_s32(pos4, 3)};
        const float32x4_t val1{set_f4(src[pos0], src[pos1], src[pos2], src[pos3])};
        const float32x4_t val2{set_f4(src[pos0+1], src[pos1+1], src[pos2+1], src[pos3+1])};

        /* val1 + (val2-val1)*mu */
        const float32x4_t r0{vsubq_f32(val2, val1)};
        const float32x4_t mu{vmulq_f32(vcvtq_f32_s32(frac4), fracOne4)};
        const float32x4_t out{vmlaq_f32(val1, mu, r0)};

        vst1q_f32(dst_iter, out);
        dst_iter += 4;

        frac4 = vaddq_s32(frac4, increment4);
        pos4 = vaddq_s32(pos4, vshrq_n_s32(frac4, MixerFracBits));
        frac4 = vandq_s32(frac4, fracMask4);
    }

    if(size_t todo{dst.size()&3})
    {
        src += static_cast<uint>(vgetq_lane_s32(pos4, 0));
        frac = static_cast<uint>(vgetq_lane_s32(frac4, 0));

        do {
            *(dst_iter++) = lerpf(src[0], src[1], static_cast<float>(frac) * (1.0f/MixerFracOne));

            frac += increment;
            src  += frac>>MixerFracBits;
            frac &= MixerFracMask;
        } while(--todo);
    }
}

template<>
void Resample_<CubicTag,NEONTag>(const InterpState *state, const float *RESTRICT src, uint frac,
    const uint increment, const al::span<float> dst)
{
    ASSUME(frac < MixerFracOne);

    const auto *RESTRICT filter = al::assume_aligned<16>(std::get<CubicState>(*state).filter);

    src -= 1;
    for(float &out_sample : dst)
    {
        const uint pi{frac >> CubicPhaseDiffBits};
        const float pf{static_cast<float>(frac&CubicPhaseDiffMask) * (1.0f/CubicPhaseDiffOne)};
        const float32x4_t pf4{vdupq_n_f32(pf)};

        /* Apply the phase interpolated filter. */

        /* f = fil + pf*phd */
        const float32x4_t f4 = vmlaq_f32(vld1q_f32(filter[pi].mCoeffs.data()), pf4,
            vld1q_f32(filter[pi].mDeltas.data()));
        /* r = f*src */
        float32x4_t r4{vmulq_f32(f4, vld1q_f32(src))};

        r4 = vaddq_f32(r4, vrev64q_f32(r4));
        out_sample = vget_lane_f32(vadd_f32(vget_low_f32(r4), vget_high_f32(r4)), 0);

        frac += increment;
        src  += frac>>MixerFracBits;
        frac &= MixerFracMask;
    }
}

template<>
void Resample_<BSincTag,NEONTag>(const InterpState *state, const float *RESTRICT src, uint frac,
    const uint increment, const al::span<float> dst)
{
    const auto &bsinc = std::get<BsincState>(*state);
    const float *const filter{bsinc.filter};
    const float32x4_t sf4{vdupq_n_f32(bsinc.sf)};
    const size_t m{bsinc.m};
    ASSUME(m > 0);
    ASSUME(frac < MixerFracOne);

    src -= bsinc.l;
    for(float &out_sample : dst)
    {
        // Calculate the phase index and factor.
        const uint pi{frac >> BSincPhaseDiffBits};
        const float pf{static_cast<float>(frac&BSincPhaseDiffMask) * (1.0f/BSincPhaseDiffOne)};

        // Apply the scale and phase interpolated filter.
        float32x4_t r4{vdupq_n_f32(0.0f)};
        {
            const float32x4_t pf4{vdupq_n_f32(pf)};
            const float *RESTRICT fil{filter + m*pi*2_uz};
            const float *RESTRICT phd{fil + m};
            const float *RESTRICT scd{fil + BSincPhaseCount*2_uz*m};
            const float *RESTRICT spd{scd + m};
            size_t td{m >> 2};
            size_t j{0u};

            do {
                /* f = ((fil + sf*scd) + pf*(phd + sf*spd)) */
                const float32x4_t f4 = vmlaq_f32(
                    vmlaq_f32(vld1q_f32(&fil[j]), sf4, vld1q_f32(&scd[j])),
                    pf4, vmlaq_f32(vld1q_f32(&phd[j]), sf4, vld1q_f32(&spd[j])));
                /* r += f*src */
                r4 = vmlaq_f32(r4, f4, vld1q_f32(&src[j]));
                j += 4;
            } while(--td);
        }
        r4 = vaddq_f32(r4, vrev64q_f32(r4));
        out_sample = vget_lane_f32(vadd_f32(vget_low_f32(r4), vget_high_f32(r4)), 0);

        frac += increment;
        src  += frac>>MixerFracBits;
        frac &= MixerFracMask;
    }
}

template<>
void Resample_<FastBSincTag,NEONTag>(const InterpState *state, const float *RESTRICT src,
    uint frac, const uint increment, const al::span<float> dst)
{
    const auto &bsinc = std::get<BsincState>(*state);
    const float *const filter{bsinc.filter};
    const size_t m{bsinc.m};
    ASSUME(m > 0);
    ASSUME(frac < MixerFracOne);

    src -= bsinc.l;
    for(float &out_sample : dst)
    {
        // Calculate the phase index and factor.
        const uint pi{frac >> BSincPhaseDiffBits};
        const float pf{static_cast<float>(frac&BSincPhaseDiffMask) * (1.0f/BSincPhaseDiffOne)};

        // Apply the phase interpolated filter.
        float32x4_t r4{vdupq_n_f32(0.0f)};
        {
            const float32x4_t pf4{vdupq_n_f32(pf)};
            const float *RESTRICT fil{filter + m*pi*2_uz};
            const float *RESTRICT phd{fil + m};
            size_t td{m >> 2};
            size_t j{0u};

            do {
                /* f = fil + pf*phd */
                const float32x4_t f4 = vmlaq_f32(vld1q_f32(&fil[j]), pf4, vld1q_f32(&phd[j]));
                /* r += f*src */
                r4 = vmlaq_f32(r4, f4, vld1q_f32(&src[j]));
                j += 4;
            } while(--td);
        }
        r4 = vaddq_f32(r4, vrev64q_f32(r4));
        out_sample = vget_lane_f32(vadd_f32(vget_low_f32(r4), vget_high_f32(r4)), 0);

        frac += increment;
        src  += frac>>MixerFracBits;
        frac &= MixerFracMask;
    }
}


template<>
void MixHrtf_<NEONTag>(const float *InSamples, float2 *AccumSamples, const uint IrSize,
    const MixHrtfFilter *hrtfparams, const size_t BufferSize)
{ MixHrtfBase<ApplyCoeffs>(InSamples, AccumSamples, IrSize, hrtfparams, BufferSize); }

template<>
void MixHrtfBlend_<NEONTag>(const float *InSamples, float2 *AccumSamples, const uint IrSize,
    const HrtfFilter *oldparams, const MixHrtfFilter *newparams, const size_t BufferSize)
{
    MixHrtfBlendBase<ApplyCoeffs>(InSamples, AccumSamples, IrSize, oldparams, newparams,
        BufferSize);
}

template<>
void MixDirectHrtf_<NEONTag>(const FloatBufferSpan LeftOut, const FloatBufferSpan RightOut,
    const al::span<const FloatBufferLine> InSamples, float2 *AccumSamples,
    float *TempBuf, HrtfChannelState *ChanState, const size_t IrSize, const size_t BufferSize)
{
    MixDirectHrtfBase<ApplyCoeffs>(LeftOut, RightOut, InSamples, AccumSamples, TempBuf, ChanState,
        IrSize, BufferSize);
}


template<>
void Mix_<NEONTag>(const al::span<const float> InSamples, const al::span<FloatBufferLine> OutBuffer,
    float *CurrentGains, const float *TargetGains, const size_t Counter, const size_t OutPos)
{
    const float delta{(Counter > 0) ? 1.0f / static_cast<float>(Counter) : 0.0f};
    const auto min_len = minz(Counter, InSamples.size());
    const auto aligned_len = minz((min_len+3) & ~3_uz, InSamples.size()) - min_len;

    for(FloatBufferLine &output : OutBuffer)
        MixLine(InSamples, al::assume_aligned<16>(output.data()+OutPos), *CurrentGains++,
            *TargetGains++, delta, min_len, aligned_len, Counter);
}

template<>
void Mix_<NEONTag>(const al::span<const float> InSamples, float *OutBuffer, float &CurrentGain,
    const float TargetGain, const size_t Counter)
{
    const float delta{(Counter > 0) ? 1.0f / static_cast<float>(Counter) : 0.0f};
    const auto min_len = minz(Counter, InSamples.size());
    const auto aligned_len = minz((min_len+3) & ~3_uz, InSamples.size()) - min_len;

    MixLine(InSamples, al::assume_aligned<16>(OutBuffer), CurrentGain, TargetGain, delta, min_len,
        aligned_len, Counter);
}