/* SPDX-License-Identifier: BSD-2-Clause */
/*
 * Copyright (C) 2019, Raspberry Pi Ltd
 *
 * histogram.h - histogram calculation interface
 */
#pragma once

#include <stdint.h>
#include <vector>
#include <cassert>

/*
 * A simple histogram class, for use in particular to find "quantiles" and
 * averages between "quantiles".
 */

namespace RPiController {

class Histogram
{
public:
	Histogram()
	{
		cumulative_.push_back(0);
	}

	template<typename T> Histogram(T *histogram, int num)
	{
		assert(num);
		cumulative_.reserve(num + 1);
		cumulative_.push_back(0);
		for (int i = 0; i < num; i++)
			cumulative_.push_back(cumulative_.back() +
					      histogram[i]);
	}
	uint32_t bins() const { return cumulative_.size() - 1; }
	uint64_t total() const { return cumulative_[cumulative_.size() - 1]; }
	/* Cumulative frequency up to a (fractional) point in a bin. */
	uint64_t cumulativeFreq(double bin) const;
	/* Return the mean value between two (fractional) bins. */
	double interBinMean(double binLo, double binHi) const;
	/*
	 * Return the (fractional) bin of the point q (0 <= q <= 1) through the
	 * histogram. Optionally provide limits to help.
	 */
	double quantile(double q, int first = -1, int last = -1) const;
	/* Return the average histogram bin value between the two quantiles. */
	double interQuantileMean(double qLo, double qHi) const;

private:
	std::vector<uint64_t> cumulative_;
};

} /* namespace RPiController */