/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Rubber Band Library
    An audio time-stretching and pitch-shifting library.
    Copyright 2007-2022 Particular Programs Ltd.

    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 2 of the
    License, or (at your option) any later version.  See the file
    COPYING included with this distribution for more information.

    Alternatively, if you have a valid commercial licence for the
    Rubber Band Library obtained by agreement with the copyright
    holders, you may redistribute and/or modify it under the terms
    described in that licence.

    If you wish to distribute code using the Rubber Band Library
    under terms other than those of the GNU General Public License,
    you must obtain a valid commercial licence before doing so.
*/

#ifndef RUBBERBAND_PEAK_H
#define RUBBERBAND_PEAK_H

#include <vector>

namespace RubberBand
{

template <typename T>
class Peak
{
public:
    Peak(int n) :
        m_n(n),
        m_locations(n, 0) { }

    // Find the nearest peak to each bin, and optionally the next
    // highest peak above each bin, within an array v, where a peak is
    // a value greater than the p nearest neighbours on each side. The
    // array must have length n where n is the size passed the the
    // constructor.
    void findNearestAndNextPeaks(const T *const v,
                                 int p,
                                 int *nearest,
                                 int *next = nullptr)
    {
        findNearestAndNextPeaks(v, 0, m_n, p, nearest, next);
    }

    // As above but consider only the range of size rangeCount from
    // index rangeStart. Write rangeCount results into nearest and
    // optionally next, starting to write at index rangeStart - so
    // these arrays must have the full length even if rangeCount is
    // shorter. Leave the rest of nearest and/or next unmodified.
    void findNearestAndNextPeaks(const T *const v,
                                 int rangeStart,
                                 int rangeCount,
                                 int p,
                                 int *nearest,
                                 int *next = nullptr)
    {
        int nPeaks = 0;
        int n = rangeStart + rangeCount;

        for (int i = rangeStart; i < n; ++i) {
            T x = v[i];
            bool good = true;
            for (int k = i - p; k <= i + p; ++k) {
                if (k < rangeStart || k == i) continue;
                if (k >= n) break;
                if (k < i && x <= v[k]) {
                    good = false;
                    break;
                }
                if (k > i && x < v[k]) {
                    good = false;
                    break;
                }
            }
            if (good) {
                m_locations[nPeaks++] = i;
            }
        }

        int pp = rangeStart - 1;
        for (int i = rangeStart, j = 0; i < n; ++i) {
            int np = i;
            if (j < nPeaks) {
                np = m_locations[j];
            }
            if (next) {
                if (pp == i) {
                    next[i] = i;
                } else {
                    next[i] = np;
                }
            }
            if (nearest) {
                if (j == 0) {
                    nearest[i] = np;
                } else {
                    if (np - i < i - pp) {
                        nearest[i] = np;
                    } else {
                        nearest[i] = pp;
                    }
                }
            }
            while (j < nPeaks && m_locations[j] <= i) {
                pp = np;
                ++j;
            }
        }
    }

protected:
    int m_n;
    std::vector<int> m_locations;
};


}

#endif