#ifndef NAVMESHWALKRANDOM_H
#define NAVMESHWALKRANDOM_H


#include "../NavMesh.h"
#include "../NavMeshLocation.h"
#include "../../geo/Heading.h"

#include "NavMeshSub.h"
#include "NavMeshWalkParams.h"
#include "NavMeshWalkEval.h"

namespace NM {

	/**
	 * pick a truely random destination within the reachable area
	 * weight this area (evaluators)
	 * repeat this several times to find a robus destination
	 */
	template <typename Tria> class NavMeshWalkRandom {

	private:

		const NavMesh<Tria>& mesh;

		std::vector<NavMeshWalkEval<Tria>*> evals;

	public:

		struct ResultEntry {
			NavMeshLocation<Tria> location;
			Heading heading;
			double probability;
			ResultEntry() : heading(0) {;}
		};

		struct ResultList : std::vector<ResultEntry> {};

	public:

		/** ctor */
		NavMeshWalkRandom(const NavMesh<Tria>& mesh) : mesh(mesh) {

		}

		/** add a new evaluator to the walker */
		void addEvaluator(NavMeshWalkEval<Tria>* eval) {
			this->evals.push_back(eval);
		}

		ResultEntry getOne(const NavMeshWalkParams<Tria>& params) const {

			// sanity checks
			params.check();

			ResultEntry res;
			res.probability = 0;

			// to-be-walked distance;
			const float toBeWalkedDist = params.getToBeWalkedDistance();
			const float toBeWalkedDistSafe = 1.0 + toBeWalkedDist * 1.1;

			// construct reachable region
			const NavMeshSub<Tria> reachable(params.start, toBeWalkedDistSafe);

			NavMeshRandom<Tria> rnd = reachable.getRandom();
			NavMeshPotentialWalk<Tria> pwalk(params);

			// improve quality (the higher, the better)
			for (int i = 0; i < 50; ++i) {

				PERF_REGION(1, "NavMeshWalkRandom::SampleLoop");

				// draw a random destination
				// is this destination within the reachable area? (triangles might be larger!)
				pwalk.end = rnd.draw();
				if (pwalk.end.pos.getDistance(params.start.pos) > toBeWalkedDistSafe) {
					--i; continue;
				}

				// calculate the probability for this destination
				const double p = eval(pwalk);

				// better?
				if (p > res.probability) {
					res.location = pwalk.end;
					res.probability = p;
				}

			}

			// destination is known. update the heading
			res.heading = Heading(params.start.pos.xy(), res.location.pos.xy());
			return res;

		}

		ResultList getMany(const NavMeshWalkParams<Tria>& params) const {

			// sanity checks
			params.check();

			ResultList res;

			// to-be-walked distance;
			const float toBeWalkedDist = params.getToBeWalkedDistance();
			const float toBeWalkedDistSafe = 1.0 + toBeWalkedDist * 1.1;

			// construct reachable region
			const NavMeshSub<Tria> reachable(params.start, toBeWalkedDistSafe);

			NavMeshRandom<Tria> rnd = reachable.getRandom();
			NavMeshPotentialWalk<Tria> pwalk(params);

			// improve quality (the higher, the better)
			for (int i = 0; i < 50; ++i) {

				PERF_REGION(1, "NavMeshWalkRandom::SampleLoop");

				pwalk.end = rnd.drawWithin(params.start.pos, toBeWalkedDistSafe);

				// calculate the probability for this destination
				const double p = eval(pwalk);

				ResultEntry re;
				re.heading = Heading(params.start.pos.xy(), pwalk.end.pos.xy());
				re.location = pwalk.end;
				re.probability = p;
				res.push_back(re);

			}

			return res;

		}

		double eval(const NM::NavMeshPotentialWalk<Tria>& pwalk) const {
			PERF_REGION(2, "NavMeshWalkRandom::EvalLoop");
			double p = 1.0;
			for (const NavMeshWalkEval<Tria>* eval : evals) {
				const double p1 = eval->getProbability(pwalk);
				p *= p1;
			}
			return p;
		}


	};

}

#endif // NAVMESHWALKRANDOM_H