/*
 * © Copyright 2014 – Urheberrechtshinweis
 * Alle Rechte vorbehalten / All Rights Reserved
 *
 * Programmcode ist urheberrechtlich geschuetzt.
 * Das Urheberrecht liegt, soweit nicht ausdruecklich anders gekennzeichnet, bei Frank Ebner.
 * Keine Verwendung ohne explizite Genehmigung.
 * (vgl. § 106 ff UrhG / § 97 UrhG)
 */

#ifndef MOVINGAVERAGETS_H
#define MOVINGAVERAGETS_H

#include <vector>
#include "../data/Timestamp.h"
#include <algorithm>
#include "KahanSum.h"

template <typename T> class MovingAverageTS {

private:

	/** timestamp -> value combination */
	struct Entry {
		Timestamp ts;
		T value;
		Entry(const Timestamp ts, const T& value) : ts(ts), value(value) {;}
	};

	/** the regional window to use */
	Timestamp window;

	/** the value history for the window-size */
	std::vector<Entry> history;

	const T zero;

	/** current sum */
	T sum;

	/** more exact running summation of many values */
	KahanSum<T> kSum;

public:


	/** ctor with the window-size to use */
	MovingAverageTS(const Timestamp window, const T zeroElement) : window(window), zero(zeroElement), sum(zeroElement), kSum(zeroElement) {

	}

	/** add a new entry */
	void add(const Timestamp ts, const T& data) {

		// append to history
		history.push_back(Entry(ts, data));

		// adjust sum
		sum += data;
		kSum += data;

		// remove too-old history entries
		const Timestamp oldest = ts - window;
		while(history.front().ts < oldest) {

			// adjust sum
			sum -= history.front().value;
			kSum -= history.front().value;

			// remove from history
			history.erase(history.begin());

		}

	}

	/** get the current average (with increasing error due to float sum!) */
	T getOldAPX() const {
		return sum / history.size();
	}

	/** get the current average */
	T get() const {
		return kSum.get() / history.size();
	}

//	T get() const {

//		T sum = zero;
//		volatile T comp = zero;
//		for (const auto e : history) {
//			T inp = e.value;
//			T y = inp - comp;
//			T t = sum + y;
//			comp = (t-sum) - y;
//			sum = t;
//		}

//		return sum / history.size();

//	}

};

#endif // MOVINGAVERAGETS_H