/************************************************************************
* Minetest-c55
* Copyright (C) 2013 celeron55, Perttu Ahola <celeron55@gmail.com>
*
* collision.cpp
* voxelands - 3d voxel world sandbox game
* Copyright (C) Lisa 'darkrose' Milne 2014 <lisa@ltmnet.com>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program.  If not, see <http://www.gnu.org/licenses/>
*
* License updated from GPLv2 or later to GPLv3 or later by Lisa Milne
* for Voxelands.
************************************************************************/

#include "collision.h"
#include "mapblock.h"
#include "map.h"
#include "log.h"
#include "main.h" // g_profiler
#include "profiler.h"
#include "content_mapnode.h"

// Helper function:
// Checks for collision of a moving aabbox with a static aabbox
// Returns -1 if no collision, 0 if X collision, 1 if Y collision, 2 if Z collision
// The time after which the collision occurs is stored in dtime.
int axisAlignedCollision(
		const aabb3f &staticbox, const aabb3f &movingbox,
		const v3f &speed, f32 d, f32 &dtime)
{
	//TimeTaker tt("axisAlignedCollision");

	f32 xsize = (staticbox.MaxEdge.X - staticbox.MinEdge.X);
	f32 ysize = (staticbox.MaxEdge.Y - staticbox.MinEdge.Y);
	f32 zsize = (staticbox.MaxEdge.Z - staticbox.MinEdge.Z);

	aabb3f relbox(
			movingbox.MinEdge.X - staticbox.MinEdge.X,
			movingbox.MinEdge.Y - staticbox.MinEdge.Y,
			movingbox.MinEdge.Z - staticbox.MinEdge.Z,
			movingbox.MaxEdge.X - staticbox.MinEdge.X,
			movingbox.MaxEdge.Y - staticbox.MinEdge.Y,
			movingbox.MaxEdge.Z - staticbox.MinEdge.Z
	);

	if(speed.X > 0) // Check for collision with X- plane
	{
		if(relbox.MaxEdge.X <= d)
		{
			dtime = - relbox.MaxEdge.X / speed.X;
			if((relbox.MinEdge.Y + speed.Y * dtime < ysize) &&
					(relbox.MaxEdge.Y + speed.Y * dtime > 0) &&
					(relbox.MinEdge.Z + speed.Z * dtime < zsize) &&
					(relbox.MaxEdge.Z + speed.Z * dtime > 0))
				return 0;
		}
		else if(relbox.MinEdge.X > xsize)
		{
			return -1;
		}
	}
	else if(speed.X < 0) // Check for collision with X+ plane
	{
		if(relbox.MinEdge.X >= xsize - d)
		{
			dtime = (xsize - relbox.MinEdge.X) / speed.X;
			if((relbox.MinEdge.Y + speed.Y * dtime < ysize) &&
					(relbox.MaxEdge.Y + speed.Y * dtime > 0) &&
					(relbox.MinEdge.Z + speed.Z * dtime < zsize) &&
					(relbox.MaxEdge.Z + speed.Z * dtime > 0))
				return 0;
		}
		else if(relbox.MaxEdge.X < 0)
		{
			return -1;
		}
	}

	// NO else if here

	if(speed.Y > 0) // Check for collision with Y- plane
	{
		if(relbox.MaxEdge.Y <= d)
		{
			dtime = - relbox.MaxEdge.Y / speed.Y;
			if((relbox.MinEdge.X + speed.X * dtime < xsize) &&
					(relbox.MaxEdge.X + speed.X * dtime > 0) &&
					(relbox.MinEdge.Z + speed.Z * dtime < zsize) &&
					(relbox.MaxEdge.Z + speed.Z * dtime > 0))
				return 1;
		}
		else if(relbox.MinEdge.Y > ysize)
		{
			return -1;
		}
	}
	else if(speed.Y < 0) // Check for collision with Y+ plane
	{
		if(relbox.MinEdge.Y >= ysize - d)
		{
			dtime = (ysize - relbox.MinEdge.Y) / speed.Y;
			if((relbox.MinEdge.X + speed.X * dtime < xsize) &&
					(relbox.MaxEdge.X + speed.X * dtime > 0) &&
					(relbox.MinEdge.Z + speed.Z * dtime < zsize) &&
					(relbox.MaxEdge.Z + speed.Z * dtime > 0))
				return 1;
		}
		else if(relbox.MaxEdge.Y < 0)
		{
			return -1;
		}
	}

	// NO else if here

	if(speed.Z > 0) // Check for collision with Z- plane
	{
		if(relbox.MaxEdge.Z <= d)
		{
			dtime = - relbox.MaxEdge.Z / speed.Z;
			if((relbox.MinEdge.X + speed.X * dtime < xsize) &&
					(relbox.MaxEdge.X + speed.X * dtime > 0) &&
					(relbox.MinEdge.Y + speed.Y * dtime < ysize) &&
					(relbox.MaxEdge.Y + speed.Y * dtime > 0))
				return 2;
		}
		//else if(relbox.MinEdge.Z > zsize)
		//{
		//	return -1;
		//}
	}
	else if(speed.Z < 0) // Check for collision with Z+ plane
	{
		if(relbox.MinEdge.Z >= zsize - d)
		{
			dtime = (zsize - relbox.MinEdge.Z) / speed.Z;
			if((relbox.MinEdge.X + speed.X * dtime < xsize) &&
					(relbox.MaxEdge.X + speed.X * dtime > 0) &&
					(relbox.MinEdge.Y + speed.Y * dtime < ysize) &&
					(relbox.MaxEdge.Y + speed.Y * dtime > 0))
				return 2;
		}
		//else if(relbox.MaxEdge.Z < 0)
		//{
		//	return -1;
		//}
	}

	return -1;
}

// Helper function:
// Checks if moving the movingbox up by the given distance would hit a ceiling.
bool wouldCollideWithCeiling(
		const std::vector<aabb3f> &staticboxes,
		const aabb3f &movingbox,
		f32 y_increase, f32 d)
{
	//TimeTaker tt("wouldCollideWithCeiling");

	assert(y_increase >= 0);

	for(std::vector<aabb3f>::const_iterator
			i = staticboxes.begin();
			i != staticboxes.end(); i++)
	{
		const aabb3f& staticbox = *i;
		if((movingbox.MaxEdge.Y - d <= staticbox.MinEdge.Y) &&
				(movingbox.MaxEdge.Y + y_increase > staticbox.MinEdge.Y) &&
				(movingbox.MinEdge.X < staticbox.MaxEdge.X) &&
				(movingbox.MaxEdge.X > staticbox.MinEdge.X) &&
				(movingbox.MinEdge.Z < staticbox.MaxEdge.Z) &&
				(movingbox.MaxEdge.Z > staticbox.MinEdge.Z))
			return true;
	}

	return false;
}

collisionMoveResult collisionMoveSimple(Map *map,
		f32 pos_max_d, const aabb3f &box_0,
		f32 stepheight, f32 dtime,
		v3f &pos_f, v3f &speed_f, v3f &accel_f)
{
	//TimeTaker tt("collisionMoveSimple");
	    ScopeProfiler sp(g_profiler, "collisionMoveSimple avg", SPT_AVG);

	collisionMoveResult result;

	/*
	Calculate new velocity
	*/
	if( dtime > 0.5 ) {
		infostream<<"collisionMoveSimple: WARNING: maximum step interval exceeded, lost movement details!"<<std::endl;
		dtime = 0.5;
	}
	speed_f += accel_f * dtime;

	// If there is no speed, there are no collisions
	if(speed_f.getLength() == 0)
		return result;

	// Limit speed for avoiding hangs
	speed_f.Y=rangelim(speed_f.Y,-5000,5000);
	speed_f.X=rangelim(speed_f.X,-5000,5000);
	speed_f.Z=rangelim(speed_f.Z,-5000,5000);

	/*
	Collect node boxes in movement range
	*/
	std::vector<aabb3f> cboxes;
	std::vector<bool> is_unloaded;
	std::vector<bool> is_step_up;
	std::vector<bool> is_object;
	std::vector<v3s16> node_positions;
	{
		//TimeTaker tt2("collisionMoveSimple collect boxes");
		    ScopeProfiler sp(g_profiler, "collisionMoveSimple collect boxes avg", SPT_AVG);

		v3s16 oldpos_i = floatToInt(pos_f, BS);
		v3s16 newpos_i = floatToInt(pos_f + speed_f * dtime, BS);
		s16 min_x = MYMIN(oldpos_i.X, newpos_i.X) + (box_0.MinEdge.X / BS) - 1;
		s16 min_y = MYMIN(oldpos_i.Y, newpos_i.Y) + (box_0.MinEdge.Y / BS) - 1;
		s16 min_z = MYMIN(oldpos_i.Z, newpos_i.Z) + (box_0.MinEdge.Z / BS) - 1;
		s16 max_x = MYMAX(oldpos_i.X, newpos_i.X) + (box_0.MaxEdge.X / BS) + 1;
		s16 max_y = MYMAX(oldpos_i.Y, newpos_i.Y) + (box_0.MaxEdge.Y / BS) + 1;
		s16 max_z = MYMAX(oldpos_i.Z, newpos_i.Z) + (box_0.MaxEdge.Z / BS) + 1;

		for(s16 x = min_x; x <= max_x; x++)
		for(s16 y = min_y; y <= max_y; y++)
		for(s16 z = min_z; z <= max_z; z++)
		{
			v3s16 p(x,y,z);
			bool pos_ok;
			// Object collides into walkable nodes
			MapNode n = map->getNodeNoEx(p,&pos_ok);
			if (!pos_ok) {
				// Collide with unloaded nodes
				aabb3f box = getNodeBox(p, BS);
				cboxes.push_back(box);
				is_unloaded.push_back(true);
				is_step_up.push_back(false);
				node_positions.push_back(p);
				is_object.push_back(false);
				continue;
			}
			const ContentFeatures &f = content_features(n);
			if(f.walkable == false)
				continue;

			std::vector<NodeBox> nodeboxes = f.getNodeBoxes(n);

#ifndef SERVER
			if (f.draw_type == CDT_FENCELIKE || f.draw_type == CDT_WALLLIKE) {
				static const int boxcheck[4][2] = {
					{0,2},
					{0,3},
					{1,2},
					{1,3}
				};
				nodeboxes = content_features(CONTENT_STONE_WALL).getNodeBoxes(n);
				int bps = ((nodeboxes.size()-2)/4); // boxes per section
				u8 np = 1;
				{
					aabb3f box = nodeboxes[0].m_box;
					box.MinEdge += v3f(x, y, z)*BS;
					if (f.jumpable == false)
						box.MaxEdge.Y = 1.0*BS;
					box.MaxEdge += v3f(x, y, z)*BS;
					cboxes.push_back(box);
					is_unloaded.push_back(false);
					is_step_up.push_back(false);
					node_positions.push_back(p);
					is_object.push_back(false);
				}
				for (int k=0; k<8; k++) {
					if ((n.param2&(np<<k)) == 0)
						continue;
					if (k > 3) {
						for (int j=0; j<2; j++) {
							for (int i=0; i<bps; i++) {
								aabb3f box = nodeboxes[i+2+(bps*boxcheck[k%4][j])].m_box;
								box.MinEdge += v3f(x, y, z)*BS;
								if (f.jumpable == false)
									box.MaxEdge.Y = 1.0*BS;
								box.MaxEdge += v3f(x, y, z)*BS;
								cboxes.push_back(box);
								is_unloaded.push_back(false);
								is_step_up.push_back(false);
								node_positions.push_back(p);
								is_object.push_back(false);
							}
						}
					}else{
						for (int i=0; i<bps; i++) {
							aabb3f box = nodeboxes[i+2+(bps*(k%4))].m_box;
							box.MinEdge += v3f(x, y, z)*BS;
							if (f.jumpable == false)
								box.MaxEdge.Y = 1.0*BS;
							box.MaxEdge += v3f(x, y, z)*BS;
							cboxes.push_back(box);
							is_unloaded.push_back(false);
							is_step_up.push_back(false);
							node_positions.push_back(p);
							is_object.push_back(false);
						}
					}
				}
				nodeboxes.clear();
			}else
#endif
			{
				/* TODO: obb for rotated nodeboxes */
				for (std::vector<NodeBox>::iterator i = nodeboxes.begin(); i != nodeboxes.end(); i++) {
					aabb3f box = (*i).m_box;
					box.MinEdge += v3f(x, y, z)*BS;
					if (f.jumpable == false)
						box.MaxEdge.Y = 1.0*BS;
					box.MaxEdge += v3f(x, y, z)*BS;
					cboxes.push_back(box);
					is_unloaded.push_back(false);
					is_step_up.push_back(false);
					node_positions.push_back(p);
					is_object.push_back(false);
				}
				nodeboxes.clear();
			}
		}
	} // tt2

	assert(cboxes.size() == is_unloaded.size());
	assert(cboxes.size() == is_step_up.size());
	assert(cboxes.size() == node_positions.size());
	assert(cboxes.size() == is_object.size());

	/*
	Collision detection
	*/

	/*
	Collision uncertainty radius
	Make it a bit larger than the maximum distance of movement
	*/
	f32 d = pos_max_d * 1.1;
	// A fairly large value in here makes moving smoother
	//f32 d = 0.15*BS;

	// This should always apply, otherwise there are glitches
	assert(d > pos_max_d);

	int loopcount = 0;

	while(dtime > BS*1e-10)
	{
		//TimeTaker tt3("collisionMoveSimple dtime loop");
			ScopeProfiler sp(g_profiler, "collisionMoveSimple dtime loop avg", SPT_AVG);

		// Avoid infinite loop
		loopcount++;
		if(loopcount >= 100)
		{
			infostream<<"collisionMoveSimple: WARNING: Loop count exceeded, aborting to avoid infiniite loop"<<std::endl;
			dtime = 0;
			break;
		}

		aabb3f movingbox = box_0;
		movingbox.MinEdge += pos_f;
		movingbox.MaxEdge += pos_f;

		int nearest_collided = -1;
		f32 nearest_dtime = dtime;
		u32 nearest_boxindex = -1;

		/*
		Go through every nodebox, find nearest collision
		*/
		for(u32 boxindex = 0; boxindex < cboxes.size(); boxindex++)
		{
			// Ignore if already stepped up this nodebox.
			if(is_step_up[boxindex])
				continue;

			// Find nearest collision of the two boxes (raytracing-like)
			f32 dtime_tmp;
			int collided = axisAlignedCollision(
			cboxes[boxindex], movingbox, speed_f, d, dtime_tmp);

			if(collided == -1 || dtime_tmp >= nearest_dtime)
				continue;

			nearest_dtime = dtime_tmp;
			nearest_collided = collided;
			nearest_boxindex = boxindex;
		}

		if(nearest_collided == -1)
		{
			// No collision with any collision box.
			pos_f += speed_f * dtime;
			dtime = 0; // Set to 0 to avoid "infinite" loop due to small FP numbers
		}
		else
		{
			// Otherwise, a collision occurred.

			const aabb3f& cbox = cboxes[nearest_boxindex];

			// Check for stairs.
			bool step_up = (nearest_collided != 1) && // must not be Y direction
			(movingbox.MinEdge.Y < cbox.MaxEdge.Y) &&
			(movingbox.MinEdge.Y + stepheight > cbox.MaxEdge.Y) &&
			(!wouldCollideWithCeiling(cboxes, movingbox,
			cbox.MaxEdge.Y - movingbox.MinEdge.Y,
			d));

			// Move to the point of collision and reduce dtime by nearest_dtime
			if(nearest_dtime < 0)
			{
				// Handle negative nearest_dtime (can be caused by the d allowance)
				if(!step_up)
				{
					if(nearest_collided == 0)
						pos_f.X += speed_f.X * nearest_dtime;
					if(nearest_collided == 1)
						pos_f.Y += speed_f.Y * nearest_dtime;
					if(nearest_collided == 2)
						pos_f.Z += speed_f.Z * nearest_dtime;
				}
			}
			else
			{
				pos_f += speed_f * nearest_dtime;
				dtime -= nearest_dtime;
			}

			bool is_collision = true;
			if(is_unloaded[nearest_boxindex])
				is_collision = false;

			CollisionInfo info;
			info.node_p = node_positions[nearest_boxindex];
			info.old_speed = speed_f;

			// Set the speed component that caused the collision to zero
			if(step_up)
			{
				// Special case: Handle stairs
				is_step_up[nearest_boxindex] = true;
				is_collision = false;
			}
			else if(nearest_collided == 0) // X
			{
				speed_f.X = 0;
				result.collides = true;
				result.collides_xz = true;
			}
			else if(nearest_collided == 1) // Y
			{
				speed_f.Y = 0;
				result.collides = true;
			}
			else if(nearest_collided == 2) // Z
			{
				speed_f.Z = 0;
				result.collides = true;
				result.collides_xz = true;
			}

			info.new_speed = speed_f;
			if(info.new_speed.getDistanceFrom(info.old_speed) < 0.1*BS)
				is_collision = false;

			if(is_collision){
				result.collisions.push_back(info);
			}
		}
	}

	/*
	Final touches: Check if standing on ground, step up stairs.
	*/
	aabb3f box = box_0;
	box.MinEdge += pos_f;
	box.MaxEdge += pos_f;
	for(u32 boxindex = 0; boxindex < cboxes.size(); boxindex++)
	{
		const aabb3f& cbox = cboxes[boxindex];

		/*
		See if the object is touching ground.

		Object touches ground if object's minimum Y is near node's
		maximum Y and object's X-Z-area overlaps with the node's
		X-Z-area.

		Use 0.15*BS so that it is easier to get on a node.
		*/
		if(
		cbox.MaxEdge.X-d > box.MinEdge.X &&
		cbox.MinEdge.X+d < box.MaxEdge.X &&
		cbox.MaxEdge.Z-d > box.MinEdge.Z &&
		cbox.MinEdge.Z+d < box.MaxEdge.Z
		){
			if(is_step_up[boxindex])
			{
				pos_f.Y += (cbox.MaxEdge.Y - box.MinEdge.Y);
				box = box_0;
				box.MinEdge += pos_f;
				box.MaxEdge += pos_f;
			}
			if(fabs(cbox.MaxEdge.Y-box.MinEdge.Y) < 0.15*BS)
			{
				result.touching_ground = true;
				if(is_unloaded[boxindex])
					result.standing_on_unloaded = true;
			}
		}
	}

	return result;
}
