SDL_Minigame/src/CollisionHandler.cpp

#include "CollisionHandler.h"

#include "ColliderComponent.h"
#include "Constants.h"
#include "Entity.h"
#include "Manager.h"
#include "Vector2D.h"

#include <SDL3/SDL_rect.h>
#include <bitset>
#include <cstdio>
#include <memory>

IntersectionBitSet CollisionHandler::getIntersection(Entity* entityA, Entity* entityB, Vector2D posModA, Vector2D posModB)
{
	if (!entityA->hasComponent<ColliderComponent>() ||
		!entityB->hasComponent<ColliderComponent>())
		return std::bitset<DIRECTION_C>();

	SDL_Rect colliderA = entityA->getComponent<ColliderComponent>().collider;
	SDL_Rect colliderB = entityB->getComponent<ColliderComponent>().collider;

	colliderA.x += posModA.x;
	colliderA.y += posModA.y;

	colliderB.x += posModB.x;
	colliderB.y += posModB.y;

	if (!SDL_HasRectIntersection(
		&colliderA,
		&colliderB))
		return std::bitset<DIRECTION_C>();

	std::bitset<DIRECTION_C> intersections;

	// checks all 4 directions to allow checking full overlap
	if (colliderA.x < colliderB.x + colliderB.w &&
		colliderA.x > colliderB.x) {
		intersections.set((size_t) Direction::LEFT);
	}

	if (colliderA.x + colliderA.w < colliderB.x + colliderB.w &&
		colliderA.x + colliderA.w > colliderB.x) {
		intersections.set((size_t) Direction::RIGHT);
	}

	if (colliderA.y < colliderB.y + colliderB.h &&
		colliderA.y > colliderB.y)
		intersections.set((size_t) Direction::UP);

	if (colliderA.y + colliderA.h < colliderB.y + colliderB.h &&
		colliderA.y + colliderA.h > colliderB.y)
		intersections.set((size_t) Direction::DOWN);

	return intersections;
}

IntersectionBitSet CollisionHandler::getIntersectionWithBounds(Entity* entity, Vector2D posMod) 
{
	if (!entity->hasComponent<ColliderComponent>())
		return std::bitset<DIRECTION_C>();

	SDL_Rect* collider = &entity->getComponent<ColliderComponent>().collider;

	std::bitset<DIRECTION_C> intersections;

	// all 4 directions and both sides to allow checking for fully out of bounds
	if (collider->x + posMod.x < 0 ||
		collider->x + posMod.x > SCREEN_SIZE_WIDTH) {
		intersections.set((size_t) Direction::LEFT);
	}

	if (collider->x + collider->w + posMod.x < 0 ||
		collider->x + collider->w + posMod.x > SCREEN_SIZE_WIDTH)
		intersections.set((size_t) Direction::RIGHT);

	if (collider->y + posMod.y < 0 ||
		collider->y + posMod.y > SCREEN_SIZE_HEIGHT)
		intersections.set((size_t) Direction::UP);

	if (collider->y + collider->h + posMod.y < 0 ||
		collider->y + collider->h + posMod.y > SCREEN_SIZE_HEIGHT)
		intersections.set((size_t) Direction::DOWN);

	return intersections;
}

std::vector<ColliderComponent*> CollisionHandler::getColliders(
	std::initializer_list<Entity::GroupLabel> const& groupLabels,
	std::initializer_list<Entity*> const& excludedEntities) 
{
	std::vector<ColliderComponent*> colliders;

	std::bitset<MAX_GROUPS> groupBitSet;
	for (auto& groupLabel : groupLabels) {
		groupBitSet.set((size_t) groupLabel);
	}

	for (auto& entity : manager.getAll()) {
		if ((groupBitSet & entity->getGroupBitSet()).none())
			continue;
		if (std::ranges::find(excludedEntities, entity) != excludedEntities.end())
    		continue;
		if (!entity->hasComponent<ColliderComponent>())
			continue;
		colliders.emplace_back(&entity->getComponent<ColliderComponent>());
	}

	return colliders;
}

/*!
 * 
 * \details Refer to getAnyIntersection() for more details
 * \return A bitset of intersections, describing the directions of intersection. Position `Direction` in bitset true if edge in that direction collides
 * \see Direction
 * \see IntersectionBitSet
 * \snippet CollisionHandler.h IntersectionBitSet
 * \details Example usage for IntersectionBitSet (TransformComponent::update()):
 * \snippet{trimleft} TransformComponent.cpp getAnyIntersection example code
 * 
 */
template<>
IntersectionBitSet CollisionHandler::getAnyIntersection<IntersectionBitSet>(
	Entity* entity,
	Vector2D posMod,
	std::initializer_list<Entity::GroupLabel> const& groupLabels,
	std::initializer_list<Entity*> const& excludedEntities)
{
	if (!entity->hasComponent<ColliderComponent>()) return std::bitset<DIRECTION_C>();
	IntersectionBitSet intersections;
	for (auto& collider : getColliders(groupLabels, excludedEntities)) {
   		intersections |= getIntersection(entity, collider->entity, posMod);
	}
	return intersections;
};

/*!
 * 
 * \details Refer to getAnyIntersection() for more details
 * \return The first entity with collision found
 * \see Entity
 * 
 */
template<>
Entity* CollisionHandler::getAnyIntersection<Entity*>(
	Entity* entity,
	Vector2D posMod,
	std::initializer_list<Entity::GroupLabel> const& groupLabels,
	std::initializer_list<Entity*> const& excludedEntities)
{
	if (!entity->hasComponent<ColliderComponent>()) return nullptr;
	for (auto& collider : getColliders(groupLabels, excludedEntities)) {
		SDL_Rect rect = entity->getComponent<ColliderComponent>().collider + posMod;
   	    if (SDL_HasRectIntersection(&rect, &collider->collider)) {
   	    	return collider->entity;
   	    }
	}
	return nullptr;
};

/*!
 * 
 * \details Refer to getAnyIntersection() for more details
 * \return True if any collision was found, otherwise false
 * 
 */
template<>
bool CollisionHandler::getAnyIntersection<bool>(
	Entity* entity,
	Vector2D posMod,
	std::initializer_list<Entity::GroupLabel> const& groupLabels,
	std::initializer_list<Entity*> const& excludedEntities)
{
	if (!entity->hasComponent<ColliderComponent>()) return false;
	for (auto& collider : getColliders(groupLabels, excludedEntities)) {
		SDL_Rect rect = entity->getComponent<ColliderComponent>().collider + posMod;
   	    if (SDL_HasRectIntersection(&rect, &collider->collider)) {
   	    	return true;
   	    }
	}
	return false;
};