#include <stdint.h>
#include <cstdio>

#include "ardour/interpolation.h"

using namespace ARDOUR;


nframes_t
LinearInterpolation::interpolate (int channel, nframes_t nframes, Sample *input, Sample *output)
{
	// index in the input buffers
	nframes_t   i = 0;

	double acceleration;
	double distance = 0.0;

	if (_speed != _target_speed) {
		acceleration = _target_speed - _speed;
	} else {
		acceleration = 0.0;
	}

	distance = phase[channel];
	for (nframes_t outsample = 0; outsample < nframes; ++outsample) {
		i = floor(distance);
		Sample fractional_phase_part = distance - i;
		if (fractional_phase_part >= 1.0) {
			fractional_phase_part -= 1.0;
			i++;
		}

		if (input && output) {
		// Linearly interpolate into the output buffer
			output[outsample] =
				input[i] * (1.0f - fractional_phase_part) +
				input[i+1] * fractional_phase_part;
		}
		distance += _speed + acceleration;
	}

	i = floor(distance);
	phase[channel] = distance - floor(distance);

	return i;
}

nframes_t
CubicInterpolation::interpolate (int channel, nframes_t nframes, Sample *input, Sample *output)
{
    // index in the input buffers
    nframes_t   i = 0;

    double acceleration;
    double distance = 0.0;

    if (_speed != _target_speed) {
        acceleration = _target_speed - _speed;
    } else {
        acceleration = 0.0;
    }

    distance = phase[channel];

    if (nframes < 3) {
	    /* no interpolation possible */

	    for (i = 0; i < nframes; ++i) {
		    output[i] = input[i];
	    }

	    return nframes;
    }

    /* keep this condition out of the inner loop */
    
    if (input && output) {

	    Sample inm1;
	    
	    if (floor (distance) == 0.0) {
		    /* best guess for the fake point we have to add to be able to interpolate at i == 0: 
		       .... maintain slope of first actual segment ...
		    */
		    inm1 = input[i] - (input[i+1] - input[i]);
	    } else {
		    inm1 = input[i-1];
	    }

	    for (nframes_t outsample = 0; outsample < nframes; ++outsample) {

		    float f = floor (distance);
		    float fractional_phase_part = distance - f;

		    /* get the index into the input we should start with */

		    i = lrintf (f);

		    /* fractional_phase_part only reaches 1.0 thanks to float imprecision. In theory
		       it should always be < 1.0. If it ever >= 1.0, then bump the index we use
		       and back it off. This is the point where we "skip" an entire sample in the
		       input, because the phase part has accumulated so much error that we should
		       really be closer to the next sample. or something like that ...
		    */

		    if (fractional_phase_part >= 1.0) {
			    fractional_phase_part -= 1.0;
			    ++i;
		    } 

		    // Cubically interpolate into the output buffer: keep this inlined for speed and rely on compiler
		    // optimization to take care of the rest
		    // shamelessly ripped from Steve Harris' swh-plugins (ladspa-util.h)

		    output[outsample] = input[i] + 0.5f * fractional_phase_part * (input[i+1] - inm1 +
							  fractional_phase_part * (4.0f * input[i+1] + 2.0f * inm1 - 5.0f * input[i] - input[i+2] +
								fractional_phase_part * (3.0f * (input[i] - input[i+1]) - inm1 + input[i+2])));

		    distance += _speed + acceleration;
		    inm1 = input[i];
	    }

    } else {

	    /* not sure that this is ever utilized - it implies that one of the input/output buffers is missing */

	    for (nframes_t outsample = 0; outsample < nframes; ++outsample) {
		    distance += _speed + acceleration;
	    }
    }

    i = floor(distance);
    phase[channel] = distance - floor(distance);

    return i;
}
