/*
 * © 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 LUT_H
#define LUT_H

#include <vector>
#include "../Math.h"
#include "../DrawList.h"

namespace Distribution {

	template <typename Scalar> class LUT {

	private:

		Scalar min;
		Scalar max;
		Scalar diff;

		/** number of samples between min and max */
		int numSamples;

		/** the look-up-table */
		std::vector<Scalar> samples;


	public:

		/** ctor */
		template <typename Distribution> LUT(const Distribution dist, const Scalar min, const Scalar max, const int numSamples) :
			min(min), max(max), diff(max-min), numSamples(numSamples) {

			buildLUT(dist);

		}

		/** get the probability of val from the LUT */
		Scalar getProbability(const Scalar val) const {
			int idx = ((val - min) * numSamples / diff);
			idx = Math::clamp(0, numSamples-1, idx);
			return samples[idx];
		}

		/** get a DrawList for this LUT to draw random values out of it */
		DrawList<Scalar> getDrawList() {
			DrawList<Scalar> dl;
			for (int idx = 0; idx < (int) samples.size(); ++idx) {
				const Scalar val = idxToVal(idx);
				const Scalar prob = samples[idx];
				dl.add(val, prob);
			}
			return dl;
		}

protected:

		/** convert value [min:max] to index [0:numSamples] */
		inline int valToIdx(const Scalar val) const {
			return ((val - min) * numSamples / diff);
		}

		/** convert index [0:numSamples] to value [min:max] */
		inline Scalar idxToVal(const int idx) const {
			return min + (idx * diff / numSamples);
		}

	private:

		/** build the look-up-table */
		template <typename Distribution> void buildLUT(const Distribution dist) {

			samples.resize(numSamples);
			for (int idx = 0; idx < numSamples; ++idx) {
				const Scalar val = min + (idx * diff / numSamples);
				samples[idx] = dist.getProbability(val);
			}

		}

	};

}

#endif // LUT_H