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#pragma once
#include <vector>
#include <variant>
#include <optional>
#include "api/Rigidbody.h"
#include "api/Transform.h"
#include "api/BoxCollider.h"
#include "api/CircleCollider.h"
#include "api/Vector2.h"
#include "Collider.h"
#include "System.h"
namespace crepe {
//! A system responsible for detecting and handling collisions between colliders.
class CollisionSystem : public System {
public:
using System::System;
private:
//! A variant type that can hold either a BoxCollider or a CircleCollider.
using collider_variant = std::variant<std::reference_wrapper<BoxCollider>, std::reference_wrapper<CircleCollider>>;
//! Enum representing the types of collider pairs for collision detection.
enum class CollisionInternalType {
BOX_BOX,
CIRCLE_CIRCLE,
BOX_CIRCLE,
CIRCLE_BOX,
};
/**
* \brief A structure to store the collision data of a single collider.
*
* This structure stores the collider type, its associated transform, and its rigidbody.
*/
struct CollisionInternal {
//! Store either BoxCollider or CircleCollider
collider_variant& collider;
Transform& transform;
Rigidbody& rigidbody;
};
//! Enum representing movement directions during collision resolution.
enum class Direction {
//! No movement required.
NONE,
//! Movement in the X direction.
X_DIRECTION,
//! Movement in the Y direction.
Y_DIRECTION,
//! Movement in both X and Y directions.
BOTH
};
public:
/**
* \brief Structure representing detailed collision information between two colliders.
*
* Includes information about the colliding objects and the resolution data for handling the collision.
*/
struct CollisionInfo{
Collider& first_collider;
Transform& first_transform;
Rigidbody& first_rigidbody;
Collider& second_collider;
Transform& second_transform;
Rigidbody& second_rigidbody;
//! The resolution vector for the collision.
vec2 resolution;
//! The direction of movement for resolving the collision.
Direction resolution_direction = Direction::NONE;
};
public:
//! Updates the collision system by checking for collisions between colliders and handling them.
void update() override;
private:
/**
* \brief Determines the type of collider pair from two colliders.
*
* Uses std::holds_alternative to identify the types of the provided colliders.
*
* \param collider1 First collider variant (BoxCollider or CircleCollider).
* \param collider2 Second collider variant (BoxCollider or CircleCollider).
* \return The combined type of the two colliders.
*/
CollisionInternalType check_collider_type(const collider_variant& collider1,const collider_variant& collider2);
/**
* \brief Calculates the current position of a collider.
*
* Combines the Collider offset, Transform position, and Rigidbody offset to compute the position of the collider.
*
* \param collider_offset The offset of the collider.
* \param transform The Transform of the associated game object.
* \param rigidbody The Rigidbody of the associated game object.
* \return The calculated position of the collider.
*/
vec2 current_position(vec2 collider_offset, const Transform& transform, const Rigidbody& rigidbody);
private:
/**
* \brief Handles collision resolution between two colliders.
*
* Processes collision data and adjusts objects to resolve collisions and/or calls the user oncollision script function.
*
* \param data1 Collision data for the first collider.
* \param data2 Collision data for the second collider.
*/
void collision_handler_request(CollisionInternal& data1,CollisionInternal& data2);
/**
* \brief Resolves collision between two colliders and calculates the movement required.
*
* Determines the displacement and direction needed to separate colliders based on their types.
*
* \param data1 Collision data for the first collider.
* \param data2 Collision data for the second collider.
* \param type The type of collider pair.
* \return A pair containing the resolution vector and direction for the first collider.
*/
std::pair<vec2,Direction> collision_handler(CollisionInternal& data1,CollisionInternal& data2 ,CollisionInternalType type);
/**
* \brief Calculates the resolution vector for two BoxColliders.
*
* Computes the displacement required to separate two overlapping BoxColliders.
*
* \param box_collider1 The first BoxCollider.
* \param box_collider2 The second BoxCollider.
* \param position1 The position of the first BoxCollider.
* \param position2 The position of the second BoxCollider.
* \return The resolution vector for the first BoxCollider.
*/
vec2 box_box_resolution(const BoxCollider& box_collider1,const BoxCollider& box_collider2,vec2 position1,vec2 position2);
/**
* \brief Determines the appropriate collision handler for a collision.
*
* Decides the correct resolution process based on the dynamic or static nature of the colliders involved.
*
* \param info Collision information containing data about both colliders.
*/
void determine_collision_handler(CollisionInfo& info);
/**
* \brief Handles collisions involving static objects.
*
* Resolves collisions by adjusting positions and modifying velocities if bounce is enabled.
*
* \param info Collision information containing data about both colliders.
*/
void static_collision_handler(CollisionInfo& info);
private:
/**
* \brief Checks for collisions between colliders.
*
* Identifies collisions and generates pairs of colliding objects for further processing.
*
* \param colliders A collection of all active colliders.
* \return A list of collision pairs with their associated data.
*/
std::vector<std::pair<CollisionInternal,CollisionInternal>> check_collisions(std::vector<collider_variant> & colliders);
/**
* \brief Checks for collision between two colliders.
*
* Calls the appropriate collision detection function based on the collider types.
*
* \param first_info Collision data for the first collider.
* \param second_info Collision data for the second collider.
* \param type The type of collider pair.
* \return True if a collision is detected, otherwise false.
*/
bool check_collision(const CollisionInternal& first_info,const CollisionInternal& second_info, CollisionInternalType type);
/**
* \brief Retrieves the active Transform and Rigidbody components for a given game object.
*
* This function looks up the Transform and Rigidbody components associated with the specified
* game object ID. It checks if both components are present and active. If both are found
* to be active, they are returned wrapped in reference wrappers; otherwise, an empty
* optional is returned.
*
* \param game_object_id The ID of the game object for which to retrieve the components.
*
* \return A std::optional containing a pair of reference wrappers to the active Transform
* and Rigidbody components, or std::nullopt if either component is not found
* or not active.
*/
std::optional<std::pair<std::reference_wrapper<Transform>, std::reference_wrapper<Rigidbody>>> get_active_transform_and_rigidbody(game_object_id_t game_object_id);
/**
* \brief Detects collisions between two BoxColliders.
*
* \param box1 The first BoxCollider.
* \param box2 The second BoxCollider.
* \param transform1 Transform of the first object.
* \param transform2 Transform of the second object.
* \param rigidbody1 Rigidbody of the first object.
* \param rigidbody2 Rigidbody of the second object.
* \return True if a collision is detected, otherwise false.
*/
bool check_box_box_collision(const BoxCollider& box1, const BoxCollider& box2, const Transform& transform1, const Transform& transform2, const Rigidbody& rigidbody1, const Rigidbody& rigidbody2);
/**
* \brief Check collision for box on circle collider
*
* \param box1 The BoxCollider
* \param circle2 The CircleCollider
* \param transform1 Transform of the first object.
* \param transform2 Transform of the second object.
* \param rigidbody1 Rigidbody of the first object.
* \param rigidbody2 Rigidbody of the second object.
* \return True if a collision is detected, otherwise false.
*/
bool check_box_circle_collision(const BoxCollider& box1, const CircleCollider& circle2, const Transform& transform1, const Transform& transform2, const Rigidbody& rigidbody1, const Rigidbody& rigidbody2);
/**
* \brief Check collision for circle on circle collider
*
* \param circle1 First CircleCollider
* \param circle2 Second CircleCollider
* \param transform1 Transform of the first object.
* \param transform2 Transform of the second object.
* \param rigidbody1 Rigidbody of the first object.
* \param rigidbody2 Rigidbody of the second object.
* \return True if a collision is detected, otherwise false.
*
* \return status of collision
*/
bool check_circle_circle_collision(const CircleCollider& circle1, const CircleCollider& circle2, const Transform& transform1, const Transform& transform2, const Rigidbody& rigidbody1, const Rigidbody& rigidbody2);
};
} // namespace crepe
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