#ifndef NAVMESHRANDOM_H
#define NAVMESHRANDOM_H

#include <random>
#include <vector>
#include "../math/DrawList.h"
#include "../geo/Point3.h"

#include "NavMeshLocation.h"

namespace NM {

	/**
	 * randomly pick points within the area of the nav-mesh.
	 * points are picked evenly:
	 * bigger triangles are used more often
	 *
	 */
	template <typename Tria> class NavMeshRandom {

		DrawList<size_t> lst;
		std::minstd_rand gen;
		std::uniform_real_distribution<float> dOnTriangle = std::uniform_real_distribution<float>(0.0f, 1.0f);
		std::vector<const Tria*> triangles;


		uint32_t nextSeed() {
			static uint32_t seed = 0;
			return ++seed;
		}

	public:

		/** ctor (const/non-const using T) */
		template <typename T> NavMeshRandom(const std::vector<T*>& srcTriangles) : lst(nextSeed()), gen(nextSeed()) {

			// almost always the same number?!
			gen();

			// construct a DrawList (probability = size[area] of the triangle
			// bigger triangles must be choosen more often
			for (size_t idx = 0; idx < srcTriangles.size(); ++idx) {
				this->triangles.push_back(srcTriangles[idx]);
				this->lst.add(idx, srcTriangles[idx]->getArea());
			}

		}

		/** draw a random point */
		NavMeshLocation<Tria> draw() {

			// pick a random triangle to draw from
			const size_t idx = lst.get();
			const Tria* tria = triangles[idx];

			while (true) {
				const float u = dOnTriangle(gen);
				const float v = dOnTriangle(gen);
				if ((u+v) > 1) {continue;}
				const Point3 pos = tria->getPoint(u,v); //tria->getA() + (tria.getAB() * u) + (tria.getAC() * v);
				return NavMeshLocation<Tria>(pos, tria);
			}

		}

	};

}

#endif // NAVMESHRANDOM_H