// Luanti
// SPDX-License-Identifier: LGPL-2.1-or-later
// Copyright (C) 2013 celeron55, Perttu Ahola <celeron55@gmail.com>

#include "collision.h"
#include <cmath>
#include "irr_aabb3d.h"
#include "mapblock.h"
#include "map.h"
#include "nodedef.h"
#include "gamedef.h"
#include "util/numeric.h"
#if CHECK_CLIENT_BUILD()
#include "client/clientenvironment.h"
#include "client/localplayer.h"
#endif
#include "serverenvironment.h"
#include "server/serveractiveobject.h"
#include "util/timetaker.h"
#include "profiler.h"
#include "object_properties.h"

#ifdef __FAST_MATH__
#warning "-ffast-math is known to cause bugs in collision code, do not use!"
#endif

bool g_collision_problems_encountered = false;

namespace {

//! NOTE: This struct is used for collision *candidates*. The effective
//!       collisions are forwarded to the struct `CollisionInfo`.
struct NearbyCollisionInfo {
	// node
	NearbyCollisionInfo(bool is_ul, int bouncy, v3s16 pos, const aabb3f &box) :
		obj(nullptr),
		box(box),
		position(pos),
		bouncy(bouncy),
		is_unloaded(is_ul)
	{}

	// object
	NearbyCollisionInfo(ActiveObject *obj, int bouncy, const aabb3f &box) :
		obj(obj),
		box(box),
		bouncy(bouncy)
	{}

	inline bool isObject() const { return obj != nullptr; }

	ActiveObject *obj;
	aabb3f box;
	v3s16 position;
	u8 bouncy;
	bool is_unloaded = false,
		is_step_up = false;
};

// Helper functions:
// Truncate floating point numbers to specified number of decimal places
// in order to move all the floating point error to one side of the correct value
inline f32 truncate(const f32 val, const f32 factor)
{
	return truncf(val * factor) / factor;
}

inline v3f truncate(const v3f vec, const f32 factor)
{
	return v3f(
		truncate(vec.X, factor),
		truncate(vec.Y, factor),
		truncate(vec.Z, factor)
	);
}

inline v3f rangelimv(const v3f vec, const f32 low, const f32 high)
{
	return v3f(
		rangelim(vec.X, low, high),
		rangelim(vec.Y, low, high),
		rangelim(vec.Z, low, high)
	);
}
}

// 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.
CollisionAxis axisAlignedCollision(
		const aabb3f &staticbox, const aabb3f &movingbox,
		const v3f speed, f32 *dtime)
{
	//TimeTaker tt("axisAlignedCollision");

	aabb3f relbox(
			(movingbox.MaxEdge.X - movingbox.MinEdge.X) + (staticbox.MaxEdge.X - staticbox.MinEdge.X),						// sum of the widths
			(movingbox.MaxEdge.Y - movingbox.MinEdge.Y) + (staticbox.MaxEdge.Y - staticbox.MinEdge.Y),
			(movingbox.MaxEdge.Z - movingbox.MinEdge.Z) + (staticbox.MaxEdge.Z - staticbox.MinEdge.Z),
			std::max(movingbox.MaxEdge.X, staticbox.MaxEdge.X) - std::min(movingbox.MinEdge.X, staticbox.MinEdge.X),	//outer bounding 'box' dimensions
			std::max(movingbox.MaxEdge.Y, staticbox.MaxEdge.Y) - std::min(movingbox.MinEdge.Y, staticbox.MinEdge.Y),
			std::max(movingbox.MaxEdge.Z, staticbox.MaxEdge.Z) - std::min(movingbox.MinEdge.Z, staticbox.MinEdge.Z)
	);

	const f32 dtime_max = *dtime;
	f32 inner_margin;		// the distance of clipping recovery
	f32 distance;
	f32 time;


	if (speed.Y) {
		distance = relbox.MaxEdge.Y - relbox.MinEdge.Y;
		// FIXME: The dtime calculation is inaccurate without acceleration information.
		// Exact formula: `dtime = (-vel ± sqrt(vel² + 2 * acc * distance)) / acc`
		*dtime = distance / std::abs(speed.Y);
		time = std::max(*dtime, 0.0f);

		if (*dtime <= dtime_max) {
			inner_margin = std::max(-0.5f * (staticbox.MaxEdge.Y - staticbox.MinEdge.Y), -2.0f);

			if ((speed.Y > 0 && staticbox.MinEdge.Y - movingbox.MaxEdge.Y > inner_margin) ||
				(speed.Y < 0 && movingbox.MinEdge.Y - staticbox.MaxEdge.Y > inner_margin)) {
				if (
					(std::max(movingbox.MaxEdge.X + speed.X * time, staticbox.MaxEdge.X)
						- std::min(movingbox.MinEdge.X + speed.X * time, staticbox.MinEdge.X)
						- relbox.MinEdge.X < 0) &&
						(std::max(movingbox.MaxEdge.Z + speed.Z * time, staticbox.MaxEdge.Z)
							- std::min(movingbox.MinEdge.Z + speed.Z * time, staticbox.MinEdge.Z)
							- relbox.MinEdge.Z < 0)
					)
					return COLLISION_AXIS_Y;
			}
		}
		else {
			return COLLISION_AXIS_NONE;
		}
	}

	// NO else if here

	if (speed.X) {
		distance = relbox.MaxEdge.X - relbox.MinEdge.X;
		*dtime = distance / std::abs(speed.X);
		time = std::max(*dtime, 0.0f);

		if (*dtime <= dtime_max) {
			inner_margin = std::max(-0.5f * (staticbox.MaxEdge.X - staticbox.MinEdge.X), -2.0f);

			if ((speed.X > 0 && staticbox.MinEdge.X - movingbox.MaxEdge.X > inner_margin) ||
				(speed.X < 0 && movingbox.MinEdge.X - staticbox.MaxEdge.X > inner_margin)) {
				if (
					(std::max(movingbox.MaxEdge.Y + speed.Y * time, staticbox.MaxEdge.Y)
						- std::min(movingbox.MinEdge.Y + speed.Y * time, staticbox.MinEdge.Y)
						- relbox.MinEdge.Y < 0) &&
						(std::max(movingbox.MaxEdge.Z + speed.Z * time, staticbox.MaxEdge.Z)
							- std::min(movingbox.MinEdge.Z + speed.Z * time, staticbox.MinEdge.Z)
							- relbox.MinEdge.Z < 0)
					)
					return COLLISION_AXIS_X;
			}
		} else {
			return COLLISION_AXIS_NONE;
		}
	}

	// NO else if here

	if (speed.Z) {
		distance = relbox.MaxEdge.Z - relbox.MinEdge.Z;
		*dtime = distance / std::abs(speed.Z);
		time = std::max(*dtime, 0.0f);

		if (*dtime <= dtime_max) {
			inner_margin = std::max(-0.5f * (staticbox.MaxEdge.Z - staticbox.MinEdge.Z), -2.0f);

			if ((speed.Z > 0 && staticbox.MinEdge.Z - movingbox.MaxEdge.Z > inner_margin) ||
				(speed.Z < 0 && movingbox.MinEdge.Z - staticbox.MaxEdge.Z > inner_margin)) {
				if (
					(std::max(movingbox.MaxEdge.X + speed.X * time, staticbox.MaxEdge.X)
						- std::min(movingbox.MinEdge.X + speed.X * time, staticbox.MinEdge.X)
						- relbox.MinEdge.X < 0) &&
						(std::max(movingbox.MaxEdge.Y + speed.Y * time, staticbox.MaxEdge.Y)
							- std::min(movingbox.MinEdge.Y + speed.Y * time, staticbox.MinEdge.Y)
							- relbox.MinEdge.Y < 0)
					)
					return COLLISION_AXIS_Z;
			}
		}
	}

	return COLLISION_AXIS_NONE;
}

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

	assert(y_increase >= 0);	// pre-condition

	for (const auto &it : cinfo) {
		const aabb3f &staticbox = it.box;
		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;
}

static bool add_area_node_boxes(const v3s16 min, const v3s16 max, IGameDef *gamedef,
		Environment *env, std::vector<NearbyCollisionInfo> &cinfo)
{
	const auto *nodedef = gamedef->getNodeDefManager();
	bool any_position_valid = false;

	thread_local std::vector<aabb3f> nodeboxes;
	Map *map = &env->getMap();

	const bool air_walkable = nodedef->get(CONTENT_AIR).walkable;

	v3s16 last_bp(S16_MAX);
	MapBlock *last_block = nullptr;

	// Note: as the area used here is usually small, iterating entire blocks
	// would actually be slower by factor of 10.

	v3s16 p;
	for (p.Z = min.Z; p.Z <= max.Z; p.Z++)
	for (p.Y = min.Y; p.Y <= max.Y; p.Y++)
	for (p.X = min.X; p.X <= max.X; p.X++) {
		v3s16 bp, relp;
		getNodeBlockPosWithOffset(p, bp, relp);
		if (bp != last_bp) {
			last_block = map->getBlockNoCreateNoEx(bp);
			last_bp = bp;
		}
		MapBlock *const block = last_block;

		if (!block) {
			// Since we iterate with node precision we can only safely skip
			// ahead in the "innermost" axis of the MapBlock (X).
			// This still worth it as it reduces the number of nodes to look at
			// and entries in `cinfo`.
			v3s16 rowend(bp.X * MAP_BLOCKSIZE + MAP_BLOCKSIZE - 1, p.Y, p.Z);
			aabb3f box = getNodeBox(p, BS);
			box.addInternalBox(getNodeBox(rowend, BS));
			// Collide with unloaded block
			cinfo.emplace_back(true, 0, p, box);
			p.X = rowend.X;
			continue;
		}

		if (!air_walkable && block->isAir()) {
			// Skip ahead if air, like above
			any_position_valid = true;
			p.X = bp.X * MAP_BLOCKSIZE + MAP_BLOCKSIZE - 1;
			continue;
		}

		const MapNode n = block->getNodeNoCheck(relp);

		if (n.getContent() != CONTENT_IGNORE) {
			any_position_valid = true;
			const ContentFeatures &f = nodedef->get(n);

			if (!f.walkable)
				continue;

			// Negative bouncy may have a meaning, but we need +value here.
			int n_bouncy_value = abs(itemgroup_get(f.groups, "bouncy"));

			u8 neighbors = n.getNeighbors(p, map);

			nodeboxes.clear();
			n.getCollisionBoxes(nodedef, &nodeboxes, neighbors);

			v3f posf = intToFloat(p, BS);
			for (auto box : nodeboxes) {
				box.MinEdge += posf;
				box.MaxEdge += posf;
				cinfo.emplace_back(false, n_bouncy_value, p, box);
			}
		} else {
			// Collide with loaded CONTENT_IGNORE nodes
			aabb3f box = getNodeBox(p, BS);
			cinfo.emplace_back(true, 0, p, box);
		}
	}

	return any_position_valid;
}

static void add_object_boxes(Environment *env,
		const aabb3f &box_0, f32 dtime,
		const v3f pos_f, const v3f speed_f, ActiveObject *self,
		std::vector<NearbyCollisionInfo> &cinfo)
{
	auto process_object = [&cinfo] (ActiveObject *object) {
		if (object && object->collideWithObjects()) {
			aabb3f box{{0.0f, 0.0f, 0.0f}};
			if (object->getCollisionBox(&box))
				cinfo.emplace_back(object, 0, box);
		}
	};

	constexpr f32 tolerance = 1.5f * BS;

#if CHECK_CLIENT_BUILD()
	ClientEnvironment *c_env = dynamic_cast<ClientEnvironment*>(env);
	if (c_env) {
		// Calculate distance by speed, add own extent and tolerance
		const f32 distance = speed_f.getLength() * dtime +
				box_0.getExtent().getLength() + tolerance;
		std::vector<DistanceSortedActiveObject> clientobjects;
		c_env->getActiveObjects(pos_f, distance, clientobjects);

		for (auto &clientobject : clientobjects) {
			// Do collide with everything but itself and children
			if (!self || (self != clientobject.obj &&
					self != clientobject.obj->getParent())) {
				process_object(clientobject.obj);
			}
		}

		// add collision with local player
		LocalPlayer *lplayer = c_env->getLocalPlayer();
		auto *obj = (ClientActiveObject*) lplayer->getCAO();
		if (!self || (self != obj && self != obj->getParent())) {
			aabb3f lplayer_collisionbox = lplayer->getCollisionbox();
			v3f lplayer_pos = lplayer->getPosition();
			lplayer_collisionbox.MinEdge += lplayer_pos;
			lplayer_collisionbox.MaxEdge += lplayer_pos;
			cinfo.emplace_back(obj, 0, lplayer_collisionbox);
		}
	}
	else
#endif
	{
		ServerEnvironment *s_env = dynamic_cast<ServerEnvironment*>(env);
		if (s_env) {
			// search for objects which are not us and not our children.
			// we directly process the object in this callback to avoid useless
			// looping afterwards.
			auto include_obj_cb = [self, &process_object] (ServerActiveObject *obj) {
				if (!obj->isGone() &&
					(!self || (self != obj && self != obj->getParent()))) {
					process_object(obj);
				}
				return false;
			};

			// Calculate distance by speed, add own extent and tolerance
			const v3f movement = speed_f * dtime;
			const v3f min = pos_f + box_0.MinEdge - v3f(tolerance) + componentwise_min(movement, v3f());
			const v3f max = pos_f + box_0.MaxEdge + v3f(tolerance) + componentwise_max(movement, v3f());

			// nothing is put into this vector
			std::vector<ServerActiveObject*> s_objects;
			s_env->getObjectsInArea(s_objects, aabb3f(min, max), include_obj_cb);
		}
	}
}

template <float v3f::*AX>
inline void collide_with(const aabb3f &box_mov, const aabb3f &box_stat,
	v3f *pos_f, v3f *speed_f, v3f *accel_f, const v3f &aspeed_f, float bounce)
{
	const float speed = aspeed_f.*AX;

	if (speed) {
		// Set the position along the axis of collision to exactly where the box collided.
		// This gets rid of nasty floating point errors introduced by calculating
		// the collision position based on 'nearest_dtime' and average velocity.
		pos_f->*AX = speed < 0.0f
			? (box_stat.MaxEdge.*AX - box_mov.MinEdge.*AX)
			: (box_stat.MinEdge.*AX - box_mov.MaxEdge.*AX);
	}

	if (bounce < -1e-4f && fabsf(speed) > BS * 3.0f) {
		speed_f->*AX *= bounce;
	} else {
		speed_f->*AX = 0;
		accel_f->*AX = 0; // avoid colliding in the next iterations
	}
}

#define PROFILER_NAME(text) (dynamic_cast<ServerEnvironment*>(env) ? ("Server: " text) : ("Client: " text))

CollisionMoveResult collisionMoveSimple(Environment *env, IGameDef *gamedef,
		const aabb3f &box_0,
		f32 stepheight, f32 dtime,
		v3f *pos_f, v3f *speed_f,
		v3f accel_f, ActiveObject *self,
		bool collide_with_objects,
		StepUpMode step_up_mode)
{
	static bool time_notification_done = false;

	ScopeProfiler sp(g_profiler, PROFILER_NAME("collisionMoveSimple()"), SPT_AVG, PRECISION_MICRO);

	CollisionMoveResult result;

	// Assume no collisions when no velocity and no acceleration
	if (*speed_f == v3f() && accel_f == v3f())
		return result;

	/*
		Calculate new velocity
	*/
	if (dtime > DTIME_LIMIT) {
		if (!time_notification_done) {
			time_notification_done = true;
			warningstream << "collisionMoveSimple: maximum step interval exceeded,"
					" lost movement details!"<<std::endl;
		}
		g_collision_problems_encountered = true;
		dtime = DTIME_LIMIT;
	} else {
		time_notification_done = false;
	}

	// Average speed
	v3f aspeed_f = *speed_f + accel_f * 0.5f * dtime;
	// Limit speed for avoiding hangs
	aspeed_f = truncate(rangelimv(aspeed_f, -5000.0f, 5000.0f), 10000.0f);

	// Collect node boxes in movement range

	// cached allocation
	thread_local std::vector<NearbyCollisionInfo> cinfo;
	cinfo.clear();
	{
		// Movement if no collisions
		v3f newpos_f = *pos_f + aspeed_f * dtime;
		v3f minpos_f(
			MYMIN(pos_f->X, newpos_f.X),
			MYMIN(pos_f->Y, newpos_f.Y) + 0.01f * BS, // bias rounding, player often at +/-n.5
			MYMIN(pos_f->Z, newpos_f.Z)
		);
		v3f maxpos_f(
			MYMAX(pos_f->X, newpos_f.X),
			MYMAX(pos_f->Y, newpos_f.Y),
			MYMAX(pos_f->Z, newpos_f.Z)
		);
		v3s16 min = floatToInt(minpos_f + box_0.MinEdge, BS) - v3s16(1, 1, 1);
		v3s16 max = floatToInt(maxpos_f + box_0.MaxEdge, BS) + v3s16(1, 1, 1);

		bool any_position_valid = add_area_node_boxes(min, max, gamedef, env, cinfo);

		// Do not move if world has not loaded yet, since custom node boxes
		// are not available for collision detection.
		// This also intentionally occurs in the case of the object being positioned
		// solely on loaded CONTENT_IGNORE nodes, no matter where they come from.
		if (!any_position_valid) {
			*speed_f = v3f(0, 0, 0);
			return result;
		}
	}

	// Collect object boxes in movement range
	if (collide_with_objects) {
		add_object_boxes(env, box_0, dtime, *pos_f, aspeed_f, self, cinfo);
	}

	// Collision detection
	for (int loopcount = 0;; loopcount++) {
		if (loopcount >= 100) {
			warningstream << "collisionMoveSimple: Loop count exceeded, aborting to avoid infinite loop" << std::endl;
			g_collision_problems_encountered = true;
			break;
		}

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

		CollisionAxis nearest_collided = COLLISION_AXIS_NONE;
		f32 nearest_dtime = dtime;
		int nearest_boxindex = -1;

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

			// Find nearest collision of the two boxes (raytracing-like)
			f32 dtime_tmp = nearest_dtime;
			CollisionAxis collided = axisAlignedCollision(box_info.box,
					movingbox, aspeed_f, &dtime_tmp);
			if (collided == -1 || dtime_tmp >= nearest_dtime)
				continue;

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

		if (nearest_collided == COLLISION_AXIS_NONE) {
			// No collision with any collision box.
			*pos_f += aspeed_f * dtime;
			// Final speed:
			*speed_f += accel_f * dtime;
			// Limit speed for avoiding hangs
			*speed_f = truncate(rangelimv(*speed_f, -5000.0f, 5000.0f), 10000.0f);
			break;
		}
		// Otherwise, a collision occurred.
		NearbyCollisionInfo &nearest_info = cinfo[nearest_boxindex];
		const aabb3f& cbox = nearest_info.box;

		//movingbox except moved to the horizontal position it would be after step up
		bool step_up = false;
		if (nearest_collided != COLLISION_AXIS_Y) {
			aabb3f stepbox = movingbox;
			// Look slightly ahead  for checking the height when stepping
			// to ensure we also check above the node we collided with
			// otherwise, might allow glitches such as a stack of stairs
			float extra_dtime = nearest_dtime + 0.1f * fabsf(dtime - nearest_dtime);
			stepbox.MinEdge.X += aspeed_f.X * extra_dtime;
			stepbox.MinEdge.Z += aspeed_f.Z * extra_dtime;
			stepbox.MaxEdge.X += aspeed_f.X * extra_dtime;
			stepbox.MaxEdge.Z += aspeed_f.Z * extra_dtime;
			// Check for stairs.
			step_up = (movingbox.MinEdge.Y < cbox.MaxEdge.Y) &&
				(movingbox.MinEdge.Y + stepheight > cbox.MaxEdge.Y) &&
				(!wouldCollideWithCeiling(cinfo, stepbox,
						cbox.MaxEdge.Y - movingbox.MinEdge.Y,
						0));
		}

		// Get bounce multiplier
		float bounce = -(float)nearest_info.bouncy / 100.0f;

		// Move to the point of collision and reduce dtime by nearest_dtime
		if (nearest_dtime < 0) {
			// This largely means an "instant" collision, e.g., intersecting with the floor.
			//   For `step_up == false`: Position is corrected by `collide_with`
			//   For `step_up == true`:  Position is set by the step-up handler below.
		} else if (nearest_dtime > 0) {
			// updated average speed for the sub-interval up to nearest_dtime
			aspeed_f = *speed_f + accel_f * 0.5f * nearest_dtime;
			*pos_f += aspeed_f * nearest_dtime;
			// Speed at (approximated) collision:
			*speed_f += accel_f * nearest_dtime;
			// Limit speed for avoiding hangs
			*speed_f = truncate(rangelimv(*speed_f, -5000.0f, 5000.0f), 10000.0f);
			dtime -= nearest_dtime;
		}

		const v3f old_speed_f = *speed_f;

		// Set the speed component that caused the collision to zero
		if (step_up && (step_up_mode == StepUpMode::LEGACY ||
				(step_up_mode == StepUpMode::FLOATY && speed_f->Y <= 0.0f) ||
				(step_up_mode == StepUpMode::RIGID && speed_f->Y == 0.0f))) {
			// Special case: Handle stairs
			nearest_info.is_step_up = true;
		} else if (nearest_collided == COLLISION_AXIS_X) {
			collide_with<&v3f::X>(box_0, cbox, pos_f, speed_f, &accel_f, aspeed_f, bounce);
		} else if (nearest_collided == COLLISION_AXIS_Y) {
			collide_with<&v3f::Y>(box_0, cbox, pos_f, speed_f, &accel_f, aspeed_f, bounce);

			if (accel_f.Y == 0 && aspeed_f.Y < 0.0f) {
				// Collided with ground. Update relevant variables.
				result.touching_ground = true;
				result.standing_on_object = nearest_info.isObject();
			}
		} else {
			assert(nearest_collided == COLLISION_AXIS_Z);
			collide_with<&v3f::Z>(box_0, cbox, pos_f, speed_f, &accel_f, aspeed_f, bounce);
		}

		if (!nearest_info.is_unloaded && !step_up) {
			CollisionInfo info;
			info.axis = nearest_collided;
			info.type = nearest_info.isObject() ? COLLISION_OBJECT : COLLISION_NODE;
			info.node_p = nearest_info.position;
			info.object = nearest_info.obj;
			info.new_pos = *pos_f;
			info.old_speed = old_speed_f;
			info.new_speed = *speed_f;
			result.collisions.push_back(info);
		}

		if (dtime < BS * 1e-10f)
			break;

		// Speed for finding the next collision
		aspeed_f = *speed_f + accel_f * 0.5f * dtime;
		// Limit speed for avoiding hangs
		aspeed_f = truncate(rangelimv(aspeed_f, -5000.0f, 5000.0f), 10000.0f);
	}

	/*
		Final touches: Step up stairs and ground detection (compat).
	*/
	aabb3f mbox = box_0;
	mbox.MinEdge += *pos_f;
	mbox.MaxEdge += *pos_f;
	for (const auto &box_info : cinfo) {
		const aabb3f &sbox = box_info.box;

		/*
			`step_up == true` requires the object to intersect with the static box.
			Hence, check whether that is still the case.

			For compatibility reasons (ground detection), only X-Z are checked here.
		*/

		if (sbox.MaxEdge.X > mbox.MinEdge.X && sbox.MinEdge.X < mbox.MaxEdge.X &&
				sbox.MaxEdge.Z > mbox.MinEdge.Z &&
				sbox.MinEdge.Z < mbox.MaxEdge.Z) {

			// Only allow stepping up, not down (if there are multiple collisions).
			// These conditions are almost identical to `mbox.intersectsWithBox(sbox)`.
			if (box_info.is_step_up && sbox.MaxEdge.Y > mbox.MinEdge.Y) {
				pos_f->Y = sbox.MaxEdge.Y - box_0.MinEdge.Y;
				mbox = box_0;
				mbox.MinEdge += *pos_f;
				mbox.MaxEdge += *pos_f;
			}
			if (std::fabs(sbox.MaxEdge.Y - mbox.MinEdge.Y) < 0.05f) {
				// This code is technically only required if `box_info.is_step_up == true`.
				// However, players rely on this check/condition to climb stairs faster. See PR #10587.
				result.touching_ground = true;
				result.standing_on_object = box_info.isObject();
			}
		}
	}

	result.collides = !result.collisions.empty();
	return result;
}

bool collision_check_intersection(Environment *env, IGameDef *gamedef,
		const aabb3f &box_0, const v3f &pos_f, ActiveObject *self,
		bool collide_with_objects)
{
	ScopeProfiler sp(g_profiler, PROFILER_NAME("collision_check_intersection()"), SPT_AVG, PRECISION_MICRO);

	std::vector<NearbyCollisionInfo> cinfo;
	{
		v3s16 min = floatToInt(pos_f + box_0.MinEdge, BS) - v3s16(1, 1, 1);
		v3s16 max = floatToInt(pos_f + box_0.MaxEdge, BS) + v3s16(1, 1, 1);

		bool any_position_valid = add_area_node_boxes(min, max, gamedef, env, cinfo);

		if (!any_position_valid) {
			return true;
		}
	}

	if (collide_with_objects) {
		v3f speed;
		add_object_boxes(env, box_0, 0, pos_f, speed, self, cinfo);
	}

	/*
		Collision detection
	*/
	aabb3f checkbox = box_0;
	// aabbox3d::intersectsWithBox(box) returns true when the faces are touching perfectly.
	// However, we do not want a true-ish return value in that case. Add some tolerance.
	checkbox.MinEdge += pos_f + (0.1f * BS);
	checkbox.MaxEdge += pos_f - (0.1f * BS);

	/*
		Go through every node and object box
	*/
	for (const NearbyCollisionInfo &box_info : cinfo) {
		if (box_info.box.intersectsWithBox(checkbox))
			return true;
	}

	return false;
}