/**************************************************************************/
/*  nav_map_builder_2d.cpp                                                */
/**************************************************************************/
/*                         This file is part of:                          */
/*                             GODOT ENGINE                               */
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
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#include "nav_map_builder_2d.h"

#include "../nav_link_2d.h"
#include "../nav_map_2d.h"
#include "../nav_region_2d.h"
#include "../triangle2.h"
#include "nav_map_iteration_2d.h"
#include "nav_region_iteration_2d.h"

using namespace Nav2D;

PointKey NavMapBuilder2D::get_point_key(const Vector2 &p_pos, const Vector2 &p_cell_size) {
	const int x = static_cast<int>(Math::floor(p_pos.x / p_cell_size.x));
	const int y = static_cast<int>(Math::floor(p_pos.y / p_cell_size.y));

	PointKey p;
	p.key = 0;
	p.x = x;
	p.y = y;
	return p;
}

void NavMapBuilder2D::build_navmap_iteration(NavMapIterationBuild2D &r_build) {
	PerformanceData &performance_data = r_build.performance_data;

	performance_data.pm_polygon_count = 0;
	performance_data.pm_edge_count = 0;
	performance_data.pm_edge_merge_count = 0;
	performance_data.pm_edge_connection_count = 0;
	performance_data.pm_edge_free_count = 0;

	_build_step_gather_region_polygons(r_build);

	_build_step_find_edge_connection_pairs(r_build);

	_build_step_merge_edge_connection_pairs(r_build);

	_build_step_edge_connection_margin_connections(r_build);

	_build_step_navlink_connections(r_build);

	_build_update_map_iteration(r_build);
}

void NavMapBuilder2D::_build_step_gather_region_polygons(NavMapIterationBuild2D &r_build) {
	PerformanceData &performance_data = r_build.performance_data;
	NavMapIteration2D *map_iteration = r_build.map_iteration;

	const LocalVector<Ref<NavRegionIteration2D>> &regions = map_iteration->region_iterations;
	HashMap<const NavBaseIteration2D *, LocalVector<Connection>> &region_external_connections = map_iteration->external_region_connections;

	map_iteration->navbases_polygons_external_connections.clear();

	// Remove regions connections.
	region_external_connections.clear();

	// Copy all region polygons in the map.
	int polygon_count = 0;
	for (const Ref<NavRegionIteration2D> &region : regions) {
		const uint32_t polygons_size = region->navmesh_polygons.size();
		polygon_count += polygons_size;

		region_external_connections[region.ptr()] = LocalVector<Connection>();
		map_iteration->navbases_polygons_external_connections[region.ptr()] = LocalVector<LocalVector<Connection>>();
		map_iteration->navbases_polygons_external_connections[region.ptr()].resize(polygons_size);
	}

	performance_data.pm_polygon_count = polygon_count;
	r_build.polygon_count = polygon_count;
}

void NavMapBuilder2D::_build_step_find_edge_connection_pairs(NavMapIterationBuild2D &r_build) {
	PerformanceData &performance_data = r_build.performance_data;
	NavMapIteration2D *map_iteration = r_build.map_iteration;
	int polygon_count = r_build.polygon_count;

	HashMap<EdgeKey, EdgeConnectionPair, EdgeKey> &connection_pairs_map = r_build.iter_connection_pairs_map;

	// Group all edges per key.
	connection_pairs_map.clear();
	connection_pairs_map.reserve(polygon_count);
	int free_edges_count = 0; // How many ConnectionPairs have only one Connection.

	for (const Ref<NavRegionIteration2D> &region : map_iteration->region_iterations) {
		for (const ConnectableEdge &connectable_edge : region->get_external_edges()) {
			const EdgeKey &ek = connectable_edge.ek;

			HashMap<EdgeKey, EdgeConnectionPair, EdgeKey>::Iterator pair_it = connection_pairs_map.find(ek);
			if (!pair_it) {
				pair_it = connection_pairs_map.insert(ek, EdgeConnectionPair());
				performance_data.pm_edge_count += 1;
				++free_edges_count;
			}
			EdgeConnectionPair &pair = pair_it->value;
			if (pair.size < 2) {
				// Add the polygon/edge tuple to this key.
				Connection new_connection;
				new_connection.polygon = &region->navmesh_polygons[connectable_edge.polygon_index];
				new_connection.pathway_start = connectable_edge.pathway_start;
				new_connection.pathway_end = connectable_edge.pathway_end;

				pair.connections[pair.size] = new_connection;
				++pair.size;
				if (pair.size == 2) {
					--free_edges_count;
				}

			} else {
				// The edge is already connected with another edge, skip.
				ERR_PRINT_ONCE("Navigation map synchronization error. Attempted to merge a navigation mesh polygon edge with another already-merged edge. This is usually caused by crossing edges, overlapping polygons, or a mismatch of the NavigationMesh / NavigationPolygon baked 'cell_size' and navigation map 'cell_size'. If you're certain none of above is the case, change 'navigation/3d/merge_rasterizer_cell_scale' to 0.001.");
			}
		}
	}

	r_build.free_edge_count = free_edges_count;
}

void NavMapBuilder2D::_build_step_merge_edge_connection_pairs(NavMapIterationBuild2D &r_build) {
	PerformanceData &performance_data = r_build.performance_data;

	HashMap<EdgeKey, EdgeConnectionPair, EdgeKey> &connection_pairs_map = r_build.iter_connection_pairs_map;
	LocalVector<Connection> &free_edges = r_build.iter_free_edges;
	int free_edges_count = r_build.free_edge_count;
	bool use_edge_connections = r_build.use_edge_connections;

	free_edges.clear();
	free_edges.reserve(free_edges_count);

	NavMapIteration2D *map_iteration = r_build.map_iteration;

	HashMap<const NavBaseIteration2D *, LocalVector<LocalVector<Nav2D::Connection>>> &navbases_polygons_external_connections = map_iteration->navbases_polygons_external_connections;

	for (const KeyValue<EdgeKey, EdgeConnectionPair> &pair_it : connection_pairs_map) {
		const EdgeConnectionPair &pair = pair_it.value;
		if (pair.size == 2) {
			// Connect edge that are shared in different polygons.
			const Connection &c1 = pair.connections[0];
			const Connection &c2 = pair.connections[1];

			navbases_polygons_external_connections[c1.polygon->owner][c1.polygon->id].push_back(c2);
			navbases_polygons_external_connections[c2.polygon->owner][c2.polygon->id].push_back(c1);
			performance_data.pm_edge_connection_count += 1;

		} else {
			CRASH_COND_MSG(pair.size != 1, vformat("Number of connection != 1. Found: %d", pair.size));
			if (use_edge_connections && pair.connections[0].polygon->owner->get_use_edge_connections()) {
				free_edges.push_back(pair.connections[0]);
			}
		}
	}
}

void NavMapBuilder2D::_build_step_edge_connection_margin_connections(NavMapIterationBuild2D &r_build) {
	PerformanceData &performance_data = r_build.performance_data;
	NavMapIteration2D *map_iteration = r_build.map_iteration;

	real_t edge_connection_margin = r_build.edge_connection_margin;

	LocalVector<Connection> &free_edges = r_build.iter_free_edges;
	HashMap<const NavBaseIteration2D *, LocalVector<Connection>> &region_external_connections = map_iteration->external_region_connections;

	HashMap<const NavBaseIteration2D *, LocalVector<LocalVector<Nav2D::Connection>>> &navbases_polygons_external_connections = map_iteration->navbases_polygons_external_connections;

	// Find the compatible near edges.
	//
	// Note:
	// Considering that the edges must be compatible (for obvious reasons)
	// to be connected, create new polygons to remove that small gap is
	// not really useful and would result in wasteful computation during
	// connection, integration and path finding.
	performance_data.pm_edge_free_count = free_edges.size();

	const real_t edge_connection_margin_squared = edge_connection_margin * edge_connection_margin;

	for (uint32_t i = 0; i < free_edges.size(); i++) {
		const Connection &free_edge = free_edges[i];
		const Vector2 &edge_p1 = free_edge.pathway_start;
		const Vector2 &edge_p2 = free_edge.pathway_end;

		for (uint32_t j = 0; j < free_edges.size(); j++) {
			const Connection &other_edge = free_edges[j];
			if (i == j || free_edge.polygon->owner == other_edge.polygon->owner) {
				continue;
			}

			const Vector2 &other_edge_p1 = other_edge.pathway_start;
			const Vector2 &other_edge_p2 = other_edge.pathway_end;

			// Compute the projection of the opposite edge on the current one
			Vector2 edge_vector = edge_p2 - edge_p1;
			real_t projected_p1_ratio = edge_vector.dot(other_edge_p1 - edge_p1) / (edge_vector.length_squared());
			real_t projected_p2_ratio = edge_vector.dot(other_edge_p2 - edge_p1) / (edge_vector.length_squared());
			if ((projected_p1_ratio < 0.0 && projected_p2_ratio < 0.0) || (projected_p1_ratio > 1.0 && projected_p2_ratio > 1.0)) {
				continue;
			}

			// Check if the two edges are close to each other enough and compute a pathway between the two regions.
			Vector2 self1 = edge_vector * CLAMP(projected_p1_ratio, 0.0, 1.0) + edge_p1;
			Vector2 other1;
			if (projected_p1_ratio >= 0.0 && projected_p1_ratio <= 1.0) {
				other1 = other_edge_p1;
			} else {
				other1 = other_edge_p1.lerp(other_edge_p2, (1.0 - projected_p1_ratio) / (projected_p2_ratio - projected_p1_ratio));
			}
			if (other1.distance_squared_to(self1) > edge_connection_margin_squared) {
				continue;
			}

			Vector2 self2 = edge_vector * CLAMP(projected_p2_ratio, 0.0, 1.0) + edge_p1;
			Vector2 other2;
			if (projected_p2_ratio >= 0.0 && projected_p2_ratio <= 1.0) {
				other2 = other_edge_p2;
			} else {
				other2 = other_edge_p1.lerp(other_edge_p2, (0.0 - projected_p1_ratio) / (projected_p2_ratio - projected_p1_ratio));
			}
			if (other2.distance_squared_to(self2) > edge_connection_margin_squared) {
				continue;
			}

			// The edges can now be connected.
			Connection new_connection = other_edge;
			new_connection.pathway_start = (self1 + other1) / 2.0;
			new_connection.pathway_end = (self2 + other2) / 2.0;
			//free_edge.polygon->connections.push_back(new_connection);

			// Add the connection to the region_connection map.
			region_external_connections[free_edge.polygon->owner].push_back(new_connection);
			navbases_polygons_external_connections[free_edge.polygon->owner][free_edge.polygon->id].push_back(new_connection);
			performance_data.pm_edge_connection_count += 1;
		}
	}
}

void NavMapBuilder2D::_build_step_navlink_connections(NavMapIterationBuild2D &r_build) {
	NavMapIteration2D *map_iteration = r_build.map_iteration;

	real_t link_connection_radius = r_build.link_connection_radius;

	const LocalVector<Ref<NavLinkIteration2D>> &links = map_iteration->link_iterations;

	int polygon_count = r_build.polygon_count;

	real_t link_connection_radius_sqr = link_connection_radius * link_connection_radius;

	HashMap<const NavBaseIteration2D *, LocalVector<LocalVector<Nav2D::Connection>>> &navbases_polygons_external_connections = map_iteration->navbases_polygons_external_connections;
	LocalVector<Nav2D::Polygon> &navlink_polygons = map_iteration->navlink_polygons;
	navlink_polygons.clear();
	navlink_polygons.resize(links.size());
	uint32_t navlink_index = 0;

	// Search for polygons within range of a nav link.
	for (const Ref<NavLinkIteration2D> &link : links) {
		polygon_count++;
		Polygon &new_polygon = navlink_polygons[navlink_index++];

		new_polygon.id = 0;
		new_polygon.owner = link.ptr();

		const Vector2 link_start_pos = link->get_start_position();
		const Vector2 link_end_pos = link->get_end_position();

		Polygon *closest_start_polygon = nullptr;
		real_t closest_start_sqr_dist = link_connection_radius_sqr;
		Vector2 closest_start_point;

		Polygon *closest_end_polygon = nullptr;
		real_t closest_end_sqr_dist = link_connection_radius_sqr;
		Vector2 closest_end_point;

		for (const Ref<NavRegionIteration2D> &region : map_iteration->region_iterations) {
			Rect2 region_bounds = region->get_bounds().grow(link_connection_radius);
			if (!region_bounds.has_point(link_start_pos) && !region_bounds.has_point(link_end_pos)) {
				continue;
			}

			for (Polygon &polyon : region->navmesh_polygons) {
				for (uint32_t point_id = 2; point_id < polyon.vertices.size(); point_id += 1) {
					const Triangle2 triangle(polyon.vertices[0], polyon.vertices[point_id - 1], polyon.vertices[point_id]);

					{
						const Vector2 start_point = triangle.get_closest_point_to(link_start_pos);
						const real_t sqr_dist = start_point.distance_squared_to(link_start_pos);

						// Pick the polygon that is within our radius and is closer than anything we've seen yet.
						if (sqr_dist < closest_start_sqr_dist) {
							closest_start_sqr_dist = sqr_dist;
							closest_start_point = start_point;
							closest_start_polygon = &polyon;
						}
					}

					{
						const Vector2 end_point = triangle.get_closest_point_to(link_end_pos);
						const real_t sqr_dist = end_point.distance_squared_to(link_end_pos);

						// Pick the polygon that is within our radius and is closer than anything we've seen yet.
						if (sqr_dist < closest_end_sqr_dist) {
							closest_end_sqr_dist = sqr_dist;
							closest_end_point = end_point;
							closest_end_polygon = &polyon;
						}
					}
				}
			}
		}

		// If we have both a start and end point, then create a synthetic polygon to route through.
		if (closest_start_polygon && closest_end_polygon) {
			new_polygon.vertices.resize(4);

			// Build a set of vertices that create a thin polygon going from the start to the end point.
			new_polygon.vertices[0] = closest_start_point;
			new_polygon.vertices[1] = closest_start_point;
			new_polygon.vertices[2] = closest_end_point;
			new_polygon.vertices[3] = closest_end_point;

			// Setup connections to go forward in the link.
			{
				Connection entry_connection;
				entry_connection.polygon = &new_polygon;
				entry_connection.edge = -1;
				entry_connection.pathway_start = new_polygon.vertices[0];
				entry_connection.pathway_end = new_polygon.vertices[1];
				navbases_polygons_external_connections[closest_start_polygon->owner][closest_start_polygon->id].push_back(entry_connection);

				Connection exit_connection;
				exit_connection.polygon = closest_end_polygon;
				exit_connection.edge = -1;
				exit_connection.pathway_start = new_polygon.vertices[2];
				exit_connection.pathway_end = new_polygon.vertices[3];
				navbases_polygons_external_connections[link.ptr()].push_back(LocalVector<Nav2D::Connection>());
				navbases_polygons_external_connections[link.ptr()][new_polygon.id].push_back(exit_connection);
			}

			// If the link is bi-directional, create connections from the end to the start.
			if (link->is_bidirectional()) {
				Connection entry_connection;
				entry_connection.polygon = &new_polygon;
				entry_connection.edge = -1;
				entry_connection.pathway_start = new_polygon.vertices[2];
				entry_connection.pathway_end = new_polygon.vertices[3];
				navbases_polygons_external_connections[closest_end_polygon->owner][closest_end_polygon->id].push_back(entry_connection);

				Connection exit_connection;
				exit_connection.polygon = closest_start_polygon;
				exit_connection.edge = -1;
				exit_connection.pathway_start = new_polygon.vertices[0];
				exit_connection.pathway_end = new_polygon.vertices[1];
				navbases_polygons_external_connections[link.ptr()].push_back(LocalVector<Nav2D::Connection>());
				navbases_polygons_external_connections[link.ptr()][new_polygon.id].push_back(exit_connection);
			}
		}
	}

	r_build.polygon_count = polygon_count;
}

void NavMapBuilder2D::_build_update_map_iteration(NavMapIterationBuild2D &r_build) {
	NavMapIteration2D *map_iteration = r_build.map_iteration;

	map_iteration->navmesh_polygon_count = r_build.polygon_count;

	uint32_t navmesh_polygon_count = r_build.polygon_count;
	uint32_t total_polygon_count = navmesh_polygon_count;

	map_iteration->path_query_slots_mutex.lock();
	for (NavMeshQueries2D::PathQuerySlot &p_path_query_slot : map_iteration->path_query_slots) {
		p_path_query_slot.traversable_polys.clear();
		p_path_query_slot.traversable_polys.reserve(navmesh_polygon_count * 0.25);
		p_path_query_slot.path_corridor.clear();

		p_path_query_slot.path_corridor.resize(total_polygon_count);

		p_path_query_slot.poly_to_id.clear();
		p_path_query_slot.poly_to_id.reserve(total_polygon_count);

		int polygon_id = 0;
		for (Ref<NavRegionIteration2D> &region : map_iteration->region_iterations) {
			for (const Polygon &polygon : region->navmesh_polygons) {
				p_path_query_slot.poly_to_id[&polygon] = polygon_id;
				polygon_id++;
			}
		}

		for (const Polygon &polygon : map_iteration->navlink_polygons) {
			p_path_query_slot.poly_to_id[&polygon] = polygon_id;
			polygon_id++;
		}

		DEV_ASSERT(p_path_query_slot.path_corridor.size() == p_path_query_slot.poly_to_id.size());
	}

	map_iteration->path_query_slots_mutex.unlock();
}