// Jamcorder Shadertoy shim
// Simulates the mtSong* API with helper functions instead of real textures.
// For Shadertoy previews, route note lookups through:
//   mtSongVelocity(int timeSlice, int midiPitch)
//   mtSongChannelMask(int timeSlice, int midiPitch)
//   mtSongActive(int timeSlice, int midiPitch)

float mtTime = iTime;
float mtTimeDelta = iTimeDelta;
float mtSongSliceRate = 30.0;
ivec2 mtSongTextureSize = ivec2(1024, 256);
float mtSecondsVisible = 8.0;

const int MT_SONG_PITCH_COUNT = 128;
const float MT_SHIM_LOOP_SECONDS = 16.0;
const float MT_SHIM_STEP_SECONDS = 0.25;

int mtSongSliceCapacity()
{
    return max(1, mtSongTextureSize.y * max(1, mtSongTextureSize.x / MT_SONG_PITCH_COUNT));
}

float mtShimLoopTime(int timeSlice)
{
    float seconds = float(max(timeSlice, 0)) / mtSongSliceRate;
    return mod(seconds, MT_SHIM_LOOP_SECONDS);
}

int mtShimStepIndex(int timeSlice)
{
    return int(floor(mtShimLoopTime(timeSlice) / MT_SHIM_STEP_SECONDS));
}

float mtShimStepPhase(int timeSlice)
{
    return fract(mtShimLoopTime(timeSlice) / MT_SHIM_STEP_SECONDS);
}

int mtShimBarIndex(int timeSlice)
{
    return mtShimStepIndex(timeSlice) / 16;
}

int mtShimPitchClass(int midiPitch)
{
    return int(mod(float(midiPitch), 12.0));
}

bool mtShimPitchInChord(int midiPitch, int root, int quality)
{
    int pitchClass = mtShimPitchClass(midiPitch);
    int third = quality == 0 ? 4 : 3;
    return pitchClass == root
        || pitchClass == (root + third) % 12
        || pitchClass == (root + 7) % 12;
}

float mtShimVelocityAccent(int stepInBar)
{
    if (stepInBar == 0 || stepInBar == 8) return 1.0;
    if (stepInBar == 4 || stepInBar == 12) return 0.82;
    if (stepInBar % 2 == 0) return 0.72;
    return 0.58;
}

float mtSongVelocity(int timeSlice, int midiPitch)
{
    if (timeSlice < 0 || timeSlice >= mtSongSliceCapacity()) return 0.0;

    int step = mtShimStepIndex(timeSlice);
    int stepInBar = step % 16;
    int bar = mtShimBarIndex(timeSlice) % 4;
    float phase = mtShimStepPhase(timeSlice);
    int root = int[4](0, 5, 9, 7)[bar];
    int quality = int[4](0, 1, 1, 0)[bar];

    float velocity = 0.0;

    if (phase < 0.92 && midiPitch >= 33 && midiPitch <= 84 && mtShimPitchInChord(midiPitch, root, quality))
    {
        velocity = max(velocity, 84.0 * mtShimVelocityAccent(stepInBar));
    }

    if (phase < 0.62)
    {
        int bassPitch = int[4](36, 41, 45, 43)[bar];
        if (midiPitch == bassPitch && (stepInBar == 0 || stepInBar == 8))
        {
            velocity = max(velocity, 118.0);
        }
    }

    if (phase < 0.48)
    {
        int melody = int[8](72, 74, 76, 79, 81, 79, 76, 74)[step % 8] + int[4](0, -2, 2, 0)[bar];
        if (midiPitch == melody && stepInBar % 2 == 0)
        {
            velocity = max(velocity, 112.0);
        }
    }

    if (phase < 0.35)
    {
        int sparkle = 84 + (step % 4);
        if (midiPitch == sparkle && (stepInBar == 7 || stepInBar == 15))
        {
            velocity = max(velocity, 96.0);
        }
    }

    return velocity;
}

uint mtSongChannelMask(int timeSlice, int midiPitch)
{
    float velocity = mtSongVelocity(timeSlice, midiPitch);
    if (velocity <= 0.0) return 0u;

    int stepInBar = mtShimStepIndex(timeSlice) % 16;
    uint mask = 0u;

    if (midiPitch <= 48)
    {
        mask |= 1u << 1;
    }
    else
    {
        mask |= 1u << 0;
    }

    if (stepInBar == 7 || stepInBar == 15)
    {
        mask |= 1u << 4;
    }

    return mask;
}

bool mtSongActive(int timeSlice, int midiPitch)
{
    return mtSongChannelMask(timeSlice, midiPitch) != 0u;
}