/*
   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "ModeFilter.h"

// Constructor
template <class T, uint8_t FILTER_SIZE>
ModeFilter<T,FILTER_SIZE>::ModeFilter(uint8_t return_element) :
    FilterWithBuffer<T,FILTER_SIZE>(),
    _return_element(return_element),
    drop_high_sample(true)
{
    // ensure we have a valid return_nth_element value.  if not, revert to median
    if ( _return_element >= FILTER_SIZE ) {
        _return_element = FILTER_SIZE / 2;
    }
}

// Public Methods //////////////////////////////////////////////////////////////

template <class T, uint8_t FILTER_SIZE>
T ModeFilter<T,FILTER_SIZE>::apply(T sample)
{
    // insert the new items into the samples buffer
    isort(sample, drop_high_sample);

    // next time drop from the other end of the sample buffer
    drop_high_sample = !drop_high_sample;

    // return results
    if (FilterWithBuffer<T,FILTER_SIZE>::sample_index < FILTER_SIZE ) {
        // middle sample if buffer is not yet full
        return _output = FilterWithBuffer<T,FILTER_SIZE>::samples[(FilterWithBuffer<T,FILTER_SIZE>::sample_index / 2)];
    } else {
        // return element specified by user in constructor
        return _output = FilterWithBuffer<T,FILTER_SIZE>::samples[_return_element];
    }
}

//
// insertion sort - takes a new sample and pushes it into the sample array
//                  drops either the highest or lowest sample depending on the 'drop_high_sample' parameter
//
template <class T, uint8_t FILTER_SIZE>
void ModeFilter<T,FILTER_SIZE>::isort(T new_sample, bool drop_high)
{
    int8_t        i;

    // if the buffer isn't full simply increase the #items in the buffer (i.e. sample_index)
    // the rest is the same as dropping the high sample
    if ( FilterWithBuffer<T,FILTER_SIZE>::sample_index < FILTER_SIZE ) {
        FilterWithBuffer<T,FILTER_SIZE>::sample_index++;
        drop_high = true;
    }

    if ( drop_high ) {     // drop highest sample from the buffer to make room for our new sample

        // start from top. Note: sample_index always points to the next open space so we start from sample_index-1
        i = FilterWithBuffer<T,FILTER_SIZE>::sample_index-1;

        // if the next element is higher than our new sample, push it up one position
        while (i > 0 && FilterWithBuffer<T,FILTER_SIZE>::samples[i-1] > new_sample) {
            FilterWithBuffer<T,FILTER_SIZE>::samples[i] = FilterWithBuffer<T,FILTER_SIZE>::samples[i-1];
            i--;
        }

        // add our new sample to the buffer
        FilterWithBuffer<T,FILTER_SIZE>::samples[i] = new_sample;

    } else {    // drop lowest sample from the buffer to make room for our new sample

        // start from the bottom
        i = 0;

        // if the element is lower than our new sample, push it down one position
        while ( i < FilterWithBuffer<T,FILTER_SIZE>::sample_index-1 && FilterWithBuffer<T,FILTER_SIZE>::samples[i+1] < new_sample ) {
            FilterWithBuffer<T,FILTER_SIZE>::samples[i] = FilterWithBuffer<T,FILTER_SIZE>::samples[i+1];
            i++;
        }

        // add our new sample to the buffer
        FilterWithBuffer<T,FILTER_SIZE>::samples[i] = new_sample;
    }
}

// instantiate required implementations
template class ModeFilter<float,5>;
template class ModeFilter<int16_t,5>;