1 files changed, 389 insertions, 1 deletions

diff --git a/src/crepe/system/CollisionSystem.cpp b/src/crepe/system/CollisionSystem.cpp
index c74ca1d..e0c6d03 100644
--- a/src/crepe/system/CollisionSystem.cpp
+++ b/src/crepe/system/CollisionSystem.cpp
@@ -1,5 +1,393 @@
+#include <cmath>
+#include <algorithm>
+#include <cstddef>
+#include <functional>
+#include <utility>
+#include <variant>
+#include <optional>
+
+#include "api/Event.h"
+#include "api/EventManager.h"
+#include "api/BoxCollider.h"
+#include "api/CircleCollider.h"
+#include "api/Vector2.h"
+#include "api/Rigidbody.h"
+#include "api/Transform.h"
+
+#include "ComponentManager.h"
 #include "CollisionSystem.h"
+#include "Collider.h"
+#include "types.h"
+#include "util/OptionalRef.h"
 
 using namespace crepe;
 
-void CollisionSystem::update() {}
+void CollisionSystem::update() {
+	// Get collider components and keep them seperate
+	ComponentManager & mgr = this->component_manager;
+	std::vector<std::reference_wrapper<BoxCollider>> boxcolliders	= mgr.get_components_by_type<BoxCollider>();
+	std::vector<std::reference_wrapper<CircleCollider>> circlecolliders	= mgr.get_components_by_type<CircleCollider>();
+
+	std::vector<collider_variant> all_colliders;
+	// Add BoxCollider references
+	for (auto& box : boxcolliders) {
+			all_colliders.push_back(collider_variant{box});
+	}
+
+	// Add CircleCollider references
+	for (auto& circle : circlecolliders) {
+			all_colliders.push_back(collider_variant{circle});
+	}
+	
+	// Check between all colliders if there is a collision
+	std::vector<std::pair<CollisionInternal,CollisionInternal>> collided = check_collisions(all_colliders);
+
+	// For both objects call the collision handler 
+	for (auto& collision_pair : collided) {
+		collision_handler_request(collision_pair.first,collision_pair.second);
+		collision_handler_request(collision_pair.second,collision_pair.first);
+	}
+}
+
+void CollisionSystem::collision_handler_request(CollisionInternal& data1,CollisionInternal& data2){
+
+	CollisionInternalType type = check_collider_type(data1.collider,data2.collider);
+	std::pair<vec2,CollisionSystem::Direction> resolution_data = collision_handler(data1,data2,type);
+
+	OptionalRef<Collider> collider1;
+	OptionalRef<Collider> collider2;
+	switch (type) {
+		case CollisionInternalType::BOX_BOX:{
+			collider1 = std::get<std::reference_wrapper<BoxCollider>>(data1.collider);
+			collider2 = std::get<std::reference_wrapper<BoxCollider>>(data2.collider);
+			break;
+		}
+		case CollisionInternalType::BOX_CIRCLE:{
+			collider1 = std::get<std::reference_wrapper<BoxCollider>>(data1.collider);
+			collider2 = std::get<std::reference_wrapper<CircleCollider>>(data2.collider);
+			break;
+		}
+		case CollisionInternalType::CIRCLE_BOX:{
+			collider1 = std::get<std::reference_wrapper<CircleCollider>>(data1.collider);
+			collider2 = std::get<std::reference_wrapper<BoxCollider>>(data2.collider);
+			break;
+		}
+		case CollisionInternalType::CIRCLE_CIRCLE:{
+			collider1 = std::get<std::reference_wrapper<CircleCollider>>(data1.collider);
+			collider2 = std::get<std::reference_wrapper<CircleCollider>>(data2.collider);
+			break;
+		}
+	}
+	
+	// collision info
+	crepe::CollisionSystem::CollisionInfo collision_info{
+						.first_collider = collider1,
+						.first_transform = data1.transform,
+						.first_rigidbody = data1.rigidbody,
+						.second_collider = collider2,
+						.second_transform = data2.transform,
+						.second_rigidbody = data2.rigidbody,
+						.resolution = resolution_data.first,
+						.resolution_direction = resolution_data.second,
+        };
+
+	// Determine if static needs to be called
+	determine_collision_handler(collision_info);	
+}
+
+
+std::pair<vec2,CollisionSystem::Direction> CollisionSystem::collision_handler(CollisionInternal& data1,CollisionInternal& data2,CollisionInternalType type) {
+	vec2 move_back;
+	switch (type) {
+		case CollisionInternalType::BOX_BOX:	{
+			const BoxCollider & collider1 = std::get<std::reference_wrapper<BoxCollider>>(data1.collider);
+			const BoxCollider & collider2 = std::get<std::reference_wrapper<BoxCollider>>(data2.collider);
+			vec2 collider_pos1 = current_position(collider1.offset, data1.transform, data1.rigidbody);
+			vec2 collider_pos2 = current_position(collider2.offset, data2.transform, data2.rigidbody);
+			move_back = box_box_resolution(collider1,collider2,collider_pos1,collider_pos2);
+		}
+		case CollisionInternalType::BOX_CIRCLE: {
+		
+		}
+		case CollisionInternalType::CIRCLE_CIRCLE:	{
+		
+		}
+		case CollisionInternalType::CIRCLE_BOX:	{
+		
+		}
+	}
+
+	Direction move_back_direction = Direction::NONE;
+	if(move_back.x != 0 && move_back.y > 0) {
+		move_back_direction = Direction::BOTH;
+	} else if (move_back.x != 0) {
+		move_back_direction = Direction::X_DIRECTION;
+		if(data1.rigidbody.data.linear_velocity.y != 0)	
+		move_back.y = data1.rigidbody.data.linear_velocity.y * (move_back.x/data1.rigidbody.data.linear_velocity.x);
+	} else if (move_back.y != 0) {
+		move_back_direction = Direction::Y_DIRECTION;
+		if(data1.rigidbody.data.linear_velocity.x != 0) 
+		move_back.x = data1.rigidbody.data.linear_velocity.x * (move_back.y/data1.rigidbody.data.linear_velocity.y);
+	}
+
+	return {move_back,move_back_direction};
+}
+
+vec2 CollisionSystem::box_box_resolution(const BoxCollider& box_collider1,const BoxCollider& box_collider2,vec2 final_position1,vec2 final_position2)
+{
+	vec2 resolution; // Default resolution vector
+	vec2 delta = final_position2 - final_position1;
+
+	// Compute half-dimensions of the boxes
+	float half_width1 = box_collider1.width / 2.0;
+	float half_height1 = box_collider1.height / 2.0;
+	float half_width2 = box_collider2.width / 2.0;
+	float half_height2 = box_collider2.height / 2.0;
+
+	// Calculate overlaps along X and Y axes
+	float overlap_x = (half_width1 + half_width2) - std::abs(delta.x);
+	float overlap_y = (half_height1 + half_height2) - std::abs(delta.y);
+
+	// Check if there is a collision
+	if (overlap_x > 0 && overlap_y > 0) {//should always be true check if this can be removed
+		// Determine the direction of resolution
+		if (overlap_x < overlap_y) {
+			// Resolve along the X-axis (smallest overlap)
+			resolution.x = (delta.x > 0) ? -overlap_x : overlap_x;
+		} else if (overlap_y < overlap_x) {
+			// Resolve along the Y-axis (smallest overlap)
+			resolution.y = (delta.y > 0) ? -overlap_y : overlap_y;
+		} else {
+			// Equal overlap, resolve both directions with preference
+			resolution.x = (delta.x > 0) ? -overlap_x : overlap_x;
+			resolution.y = (delta.y > 0) ? -overlap_y : overlap_y;
+		}
+	}
+
+	return resolution;
+}
+
+void CollisionSystem::determine_collision_handler(CollisionInfo& info){
+	// Check rigidbody type for static
+	if(info.first_rigidbody.data.body_type != Rigidbody::BodyType::STATIC)
+	{
+		// If second body is static perform the static collision handler in this system
+		if(info.second_rigidbody.data.body_type == Rigidbody::BodyType::STATIC){
+			static_collision_handler(info);
+		}; 
+		// Call collision event for user
+		CollisionEvent data(info);
+		EventManager::get_instance().trigger_event<CollisionEvent>(data, info.first_collider.game_object_id);
+	}		
+}
+
+void CollisionSystem::static_collision_handler(CollisionInfo& info){
+	// Move object back using calculate move back value 
+	info.first_transform.position += info.resolution;
+
+	// If bounce is enabled mirror velocity
+	if(info.first_rigidbody.data.bounce) {
+		if(info.resolution_direction == Direction::BOTH)
+		{
+			info.first_rigidbody.data.linear_velocity.y = -info.first_rigidbody.data.linear_velocity.y * info.first_rigidbody.data.elastisity;
+			info.first_rigidbody.data.linear_velocity.x = -info.first_rigidbody.data.linear_velocity.x * info.first_rigidbody.data.elastisity;
+		}
+		else if(info.resolution_direction == Direction::Y_DIRECTION) {
+			info.first_rigidbody.data.linear_velocity.y = -info.first_rigidbody.data.linear_velocity.y * info.first_rigidbody.data.elastisity;
+		}
+		else if(info.resolution_direction == Direction::X_DIRECTION){
+			info.first_rigidbody.data.linear_velocity.x = -info.first_rigidbody.data.linear_velocity.x * info.first_rigidbody.data.elastisity;
+		}
+	}
+	// Stop movement if bounce is disabled
+	else {
+		info.first_rigidbody.data.linear_velocity = {0,0};
+	}
+}
+
+std::vector<std::pair<CollisionSystem::CollisionInternal,CollisionSystem::CollisionInternal>> CollisionSystem::check_collisions(std::vector<collider_variant> & colliders) {
+	
+	
+	// TODO:
+	// If no colliders skip
+	// Check if colliders has rigidbody if not skip
+
+	// TODO:
+	// If amount is higer than lets say 16 for now use quadtree otwerwise skip
+	// Quadtree code
+	// Quadtree is placed over the input vector
+
+	std::vector<std::pair<CollisionInternal,CollisionInternal>> collisions_ret;
+	for (size_t i = 0; i < colliders.size(); ++i) {
+    std::visit([&](auto& inner_collider_ref) {
+			if (!inner_collider_ref.get().active) return;
+			auto inner_components = get_active_transform_and_rigidbody(inner_collider_ref.get().game_object_id);
+			if (!inner_components) return;
+			for (size_t j = i + 1; j < colliders.size(); ++j) {
+				std::visit([&](auto& outer_collider_ref) { 
+					if (!outer_collider_ref.get().active) return;
+					if (inner_collider_ref.get().game_object_id == outer_collider_ref.get().game_object_id) return;
+					auto outer_components = get_active_transform_and_rigidbody(outer_collider_ref.get().game_object_id);
+					if (!outer_components) return;
+					CollisionInternalType type = check_collider_type(colliders[i],colliders[j]);
+					if(!check_collision({
+															.collider = colliders[i],
+															.transform = inner_components->first,
+															.rigidbody = inner_components->second,
+															},
+															{
+															.collider = colliders[j],
+															.transform = outer_components->first,
+															.rigidbody = outer_components->second,
+															},
+															type)) return;
+					collisions_ret.emplace_back(
+                        CollisionInternal{colliders[i], inner_components->first.get(), inner_components->second.get()},
+                        CollisionInternal{colliders[j], outer_components->first.get(), outer_components->second.get()}
+                    );
+				}, colliders[j]);
+			}
+    }, colliders[i]);
+	}
+	
+	return collisions_ret;
+}
+
+std::optional<std::pair<std::reference_wrapper<Transform>, std::reference_wrapper<Rigidbody>>>
+CollisionSystem::get_active_transform_and_rigidbody(game_object_id_t game_object_id) {
+    RefVector<Transform> transforms = this->component_manager.get_components_by_id<Transform>(game_object_id);
+    if (transforms.empty()) return std::nullopt;
+
+    RefVector<Rigidbody> rigidbodies = this->component_manager.get_components_by_id<Rigidbody>(game_object_id);
+    if (rigidbodies.empty()) return std::nullopt;
+
+    Transform& transform = transforms.front().get();
+    if (!transform.active) return std::nullopt;
+
+    Rigidbody& rigidbody = rigidbodies.front().get();
+    if (!rigidbody.active) return std::nullopt;
+
+    // Return the active components
+    return std::make_pair(std::ref(transform), std::ref(rigidbody));
+}
+
+CollisionSystem::CollisionInternalType CollisionSystem::check_collider_type(const collider_variant& collider1,const collider_variant& collider2){
+	if(std::holds_alternative<std::reference_wrapper<CircleCollider>>(collider1)){
+		if(std::holds_alternative<std::reference_wrapper<CircleCollider>>(collider2))
+		{
+			return CollisionInternalType::CIRCLE_CIRCLE;
+		}
+		else {
+			return CollisionInternalType::CIRCLE_BOX;
+		}
+	}
+	else {
+		if(std::holds_alternative<std::reference_wrapper<CircleCollider>>(collider2))
+		{
+			return CollisionInternalType::BOX_CIRCLE;
+		}
+		else {
+			return CollisionInternalType::BOX_BOX;
+		}
+	}
+}
+
+bool CollisionSystem::check_collision(const CollisionInternal& first_info,const CollisionInternal& second_info, CollisionInternalType type){
+	switch (type) {
+		case CollisionInternalType::BOX_BOX:	{
+			const BoxCollider & box_collider1 = std::get<std::reference_wrapper<BoxCollider>>(first_info.collider);
+			const BoxCollider & box_collider2 = std::get<std::reference_wrapper<BoxCollider>>(second_info.collider);
+			return check_box_box_collision(box_collider1,box_collider2,first_info.transform,second_info.transform,second_info.rigidbody,second_info.rigidbody);
+		}
+		case CollisionInternalType::BOX_CIRCLE: {
+			const BoxCollider & box_collider = std::get<std::reference_wrapper<BoxCollider>>(first_info.collider);
+			const CircleCollider & circle_collider = std::get<std::reference_wrapper<CircleCollider>>(second_info.collider);
+			return check_box_circle_collision(box_collider,circle_collider,first_info.transform,second_info.transform,second_info.rigidbody,second_info.rigidbody);
+		}
+		case CollisionInternalType::CIRCLE_CIRCLE:	{
+			const CircleCollider & circle_collider1 = std::get<std::reference_wrapper<CircleCollider>>(first_info.collider);
+			const CircleCollider & circle_collider2 = std::get<std::reference_wrapper<CircleCollider>>(second_info.collider);
+			return check_circle_circle_collision(circle_collider1,circle_collider2,first_info.transform,second_info.transform,second_info.rigidbody,second_info.rigidbody);
+		}
+		case CollisionInternalType::CIRCLE_BOX:	{
+			const CircleCollider & circle_collider = std::get<std::reference_wrapper<CircleCollider>>(first_info.collider);
+			const BoxCollider & box_collider = std::get<std::reference_wrapper<BoxCollider>>(second_info.collider);
+			return check_box_circle_collision(box_collider,circle_collider,first_info.transform,second_info.transform,second_info.rigidbody,second_info.rigidbody);
+		}
+	}
+	return false;
+}
+
+
+bool CollisionSystem::check_box_box_collision(const BoxCollider& box1, const BoxCollider& box2, const Transform& transform1, const Transform& transform2, const Rigidbody& rigidbody1, const Rigidbody& rigidbody2)
+{
+	// Get current positions of colliders
+	vec2 final_position1 = current_position(box1.offset,transform1,rigidbody1);
+	vec2 final_position2 = current_position(box2.offset,transform2,rigidbody2);
+
+	// Calculate half-extents (half width and half height)
+	float half_width1 = box1.width / 2.0;
+	float half_height1 = box1.height / 2.0;
+	float half_width2 = box2.width / 2.0;
+	float half_height2 = box2.height / 2.0;
+
+	// Check if the boxes overlap along the X and Y axes
+	return (final_position1.x + half_width1 > final_position2.x - half_width2 &&  // not left
+        final_position1.x - half_width1 < final_position2.x + half_width2 &&  // not right
+        final_position1.y + half_height1 > final_position2.y - half_height2 && // not above
+        final_position1.y - half_height1 < final_position2.y + half_height2);  // not below
+}
+
+bool CollisionSystem::check_box_circle_collision(const BoxCollider& box1, const CircleCollider& circle2, const Transform& transform1, const Transform& transform2, const Rigidbody& rigidbody1, const Rigidbody& rigidbody2) {
+	// Get current positions of colliders
+	vec2 final_position1 = current_position(box1.offset, transform1, rigidbody1);
+	vec2 final_position2 = current_position(circle2.offset, transform2, rigidbody2);
+
+	// Calculate box half-extents
+	float half_width = box1.width / 2.0;
+	float half_height = box1.height / 2.0;
+
+	// Find the closest point on the box to the circle's center
+	float closest_x = std::max(final_position1.x - half_width, std::min(final_position2.x, final_position1.x + half_width));
+	float closest_y = std::max(final_position1.y - half_height, std::min(final_position2.y, final_position1.y + half_height));
+
+	// Calculate the distance squared between the circle's center and the closest point on the box
+	float distance_x = final_position2.x - closest_x;
+	float distance_y = final_position2.y - closest_y;
+	float distance_squared = distance_x * distance_x + distance_y * distance_y;
+
+	// Compare distance squared with the square of the circle's radius
+	return distance_squared <= circle2.radius * circle2.radius;
+}
+
+bool CollisionSystem::check_circle_circle_collision(const CircleCollider& circle1, const CircleCollider& circle2, const Transform& transform1, const Transform& transform2, const Rigidbody& rigidbody1, const Rigidbody& rigidbody2) {
+	// Get current positions of colliders
+	vec2 final_position1 = current_position(circle1.offset,transform1,rigidbody1);
+	vec2 final_position2 = current_position(circle2.offset,transform2,rigidbody2);
+
+	float distance_x = final_position1.x - final_position2.x;
+	float distance_y = final_position1.y - final_position2.y;
+	float distance_squared = distance_x * distance_x + distance_y * distance_y;
+
+	// Calculate the sum of the radii
+	float radius_sum = circle1.radius + circle2.radius;
+
+	// Check if the distance between the centers is less than or equal to the sum of the radii
+	return distance_squared <= radius_sum * radius_sum;
+}
+
+vec2 CollisionSystem::current_position(vec2 collider_offset, const Transform& transform, const Rigidbody& rigidbody) {
+	// Get the rotation in radians
+	float radians1 = transform.rotation * (M_PI / 180.0);
+
+	// Calculate total offset with scale
+	vec2 total_offset = (rigidbody.data.offset + collider_offset) * transform.scale;
+
+	// Rotate
+	float rotated_total_offset_x1 = total_offset.x * cos(radians1) - total_offset.y * sin(radians1);
+	float rotated_total_offset_y1 = total_offset.x * sin(radians1) + total_offset.y * cos(radians1);
+
+	// Final positions considering scaling and rotation
+	return(transform.position + vec2(rotated_total_offset_x1, rotated_total_offset_y1));
+
+}