#ifndef NAVMESHRANDOM_H
#define NAVMESHRANDOM_H

#include <random>
#include <vector>
#include "../math/DrawList.h"
#include "../geo/Point3.h"
#include "../misc/PerfCheck.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::uniform_real_distribution<float> dHeading = std::uniform_real_distribution<float>(0, M_PI*2);
		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()) {

			// 1st = almost always the same number?!
			gen(); 	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() {

			PERF_REGION(3, "NavMeshRandom::draw()");

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

			// get random (u,v) on triangle
			float u = dOnTriangle(gen);
			float v = dOnTriangle(gen);

			// if the (u,v) is outside of the triangle, mirror it so its inside the triangle again
			if ((u+v) > 1) {
				u = 1.0f - u;
				v = 1.0f - v;
			}

			// done
			const Point3 pos = tria->getPoint(u,v); //tria->getA() + (tria.getAB() * u) + (tria.getAC() * v);
			return NavMeshLocation<Tria>(pos, tria);

		}

		/** draw a random location within the given radius */
		NavMeshLocation<Tria> drawWithin(const Point3 center, const float radius) {

			std::uniform_real_distribution<float> dDistance(0.001, radius);

			while(true) {
				const float head = dHeading(gen);
				const float dist = dDistance(gen);

				const float ox = std::cos(head) * dist;
				const float oy = std::sin(head) * dist;

				// 2D destination (ignore z)
				const Point2 dst(center.x + ox, center.y + oy);

				for (const Tria* t : triangles) {

					// if triangle contains 2D position
					if (t->contains(dst)) {

						// convert it to a 3D position
						const Point3 p3 = t->toPoint3(dst);
						const NavMeshLocation<Tria> loc(p3, t);
						return loc;

					}
				}

			}

		}

	};

}

#endif // NAVMESHRANDOM_H