/*************************************************************************/
/*  nav_region.cpp                                                       */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
/*                      https://godotengine.org                          */
/*************************************************************************/
/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
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/*************************************************************************/

#include "nav_region.h"

#include "nav_map.h"

/**
	@author AndreaCatania
*/

NavRegion::NavRegion() :
		map(NULL),
		polygons_dirty(true) {
}

void NavRegion::set_map(NavMap *p_map) {
	map = p_map;
	polygons_dirty = true;
}

void NavRegion::set_transform(Transform p_transform) {
	transform = p_transform;
	polygons_dirty = true;
}

void NavRegion::set_mesh(Ref<NavigationMesh> p_mesh) {
	mesh = p_mesh;
	polygons_dirty = true;
}

bool NavRegion::sync() {
	bool something_changed = polygons_dirty /* || something_dirty? */;

	update_polygons();

	return something_changed;
}

void NavRegion::update_polygons() {
	if (!polygons_dirty) {
		return;
	}
	polygons.clear();
	polygons_dirty = false;

	if (map == NULL) {
		return;
	}

	if (mesh.is_null())
		return;

	PoolVector<Vector3> vertices = mesh->get_vertices();
	int len = vertices.size();
	if (len == 0)
		return;

	PoolVector<Vector3>::Read vertices_r = vertices.read();

	polygons.resize(mesh->get_polygon_count());

	// Build
	for (size_t i(0); i < polygons.size(); i++) {
		gd::Polygon &p = polygons[i];
		p.owner = this;

		Vector<int> mesh_poly = mesh->get_polygon(i);
		const int *indices = mesh_poly.ptr();
		bool valid(true);
		p.points.resize(mesh_poly.size());
		p.edges.resize(mesh_poly.size());

		Vector3 center;
		float sum(0);

		for (int j(0); j < mesh_poly.size(); j++) {
			int idx = indices[j];
			if (idx < 0 || idx >= len) {
				valid = false;
				break;
			}

			Vector3 point_position = transform.xform(vertices_r[idx]);
			p.points[j].pos = point_position;
			p.points[j].key = map->get_point_key(point_position);

			center += point_position; // Composing the center of the polygon

			if (j >= 2) {
				Vector3 epa = transform.xform(vertices_r[indices[j - 2]]);
				Vector3 epb = transform.xform(vertices_r[indices[j - 1]]);

				sum += map->get_up().dot((epb - epa).cross(point_position - epa));
			}
		}

		if (!valid) {
			ERR_BREAK_MSG(!valid, "The navigation mesh set in this region is not valid!");
		}

		p.clockwise = sum > 0;
		if (mesh_poly.size() != 0) {
			p.center = center / float(mesh_poly.size());
		}
	}
}