#include "Delay.h"

namespace serum
{

void DelayUnit::prepare (double sampleRate, int)
{
    sr = sampleRate;
    const int maxDelay = (int) (sr * 2.1);   // 2.1 seconds
    delayL.assign ((size_t) maxDelay, 0.0f);
    delayR.assign ((size_t) maxDelay, 0.0f);
    reset();
}

void DelayUnit::reset()
{
    std::fill (delayL.begin(), delayL.end(), 0.0f);
    std::fill (delayR.begin(), delayR.end(), 0.0f);
    writePos = 0;
    dampL = dampR = 0.0f;
}

void DelayUnit::process (float* l, float* r, int numSamples, const float p[4])
{
    const int len = (int) delayL.size();
    if (len < 4)
        return;

    const double delaySamples = juce::jlimit (2.0, (double) len - 2.0, maps::delayToMs (p[0]) / 1000.0 * sr);
    const float  feedback = p[1] * 0.92f;
    const float  dampCoef = 1.0f - p[2] * 0.95f;      // 1 = no damping
    const float  pingpong = p[3];

    for (int i = 0; i < numSamples; ++i)
    {
        double readPos = writePos - delaySamples;
        if (readPos < 0.0) readPos += len;
        const int i0 = (int) readPos;
        const int i1 = (i0 + 1) % len;
        const float frac = (float) (readPos - std::floor (readPos));

        float dl = delayL[(size_t) i0] * (1.0f - frac) + delayL[(size_t) i1] * frac;
        float dr = delayR[(size_t) i0] * (1.0f - frac) + delayR[(size_t) i1] * frac;

        // Damping lowpass in the feedback path.
        dampL = dl * (1.0f - dampCoef) + dampL * dampCoef;
        dampR = dr * (1.0f - dampCoef) + dampR * dampCoef;

        // Ping-pong: cross-feed between channels.
        const float feedL = dampR * pingpong + dampL * (1.0f - pingpong);
        const float feedR = dampL * pingpong + dampR * (1.0f - pingpong);

        delayL[(size_t) writePos] = l[i] + feedL * feedback;
        delayR[(size_t) writePos] = r[i] + feedR * feedback;

        l[i] = dl;
        r[i] = dr;
        writePos = (writePos + 1) % len;
    }
}

} // namespace serum