4 files changed, 198 insertions, 1 deletions

diff --git a/src/crepe/system/AISystem.cpp b/src/crepe/system/AISystem.cpp
new file mode 100644
index 0000000..55dc14c
--- /dev/null
+++ b/src/crepe/system/AISystem.cpp
@@ -0,0 +1,170 @@
+#include <algorithm>
+#include <cmath>
+
+#include "api/LoopTimer.h"
+#include "api/Rigidbody.h"
+#include "api/Transform.h"
+#include "manager/ComponentManager.h"
+#include "manager/Mediator.h"
+
+#include "AISystem.h"
+#include "types.h"
+
+using namespace crepe;
+
+void AISystem::update() {
+	const Mediator & mediator = this->mediator;
+	ComponentManager & mgr = mediator.component_manager;
+	RefVector<AI> ai_components = mgr.get_components_by_type<AI>();
+
+	double dt = LoopTimer::get_instance().get_delta_time();
+
+	for (AI & ai : ai_components) {
+		RefVector<Rigidbody> rigidbodies
+			= mgr.get_components_by_id<Rigidbody>(ai.game_object_id);
+		Rigidbody & rigidbody = rigidbodies.front().get();
+
+		vec2 force = this->calculate(ai);
+		vec2 acceleration = force / rigidbody.data.mass;
+		rigidbody.data.linear_velocity += acceleration * dt;
+	}
+}
+
+vec2 AISystem::calculate(AI & ai) {
+	vec2 force;
+
+	if (ai.on(AI::BehaviorType::FLEE)) {
+		vec2 force_to_add = this->flee(ai);
+
+		if (!this->accumulate_force(ai, force, force_to_add)) {
+			return force;
+		}
+	}
+	if (ai.on(AI::BehaviorType::ARRIVE)) {
+		vec2 force_to_add = this->arrive(ai);
+
+		if (!this->accumulate_force(ai, force, force_to_add)) {
+			return force;
+		}
+	}
+	if (ai.on(AI::BehaviorType::SEEK)) {
+		vec2 force_to_add = this->seek(ai);
+
+		if (!this->accumulate_force(ai, force, force_to_add)) {
+			return force;
+		}
+	}
+	if (ai.on(AI::BehaviorType::PATH_FOLLOW)) {
+		vec2 force_to_add = this->path_follow(ai);
+
+		if (!this->accumulate_force(ai, force, force_to_add)) {
+			return force;
+		}
+	}
+
+	return force;
+}
+
+bool AISystem::accumulate_force(AI & ai, vec2 & running_total, vec2 force_to_add) {
+	float magnitude = running_total.length();
+	float magnitude_remaining = ai.max_force - magnitude;
+
+	if (magnitude_remaining <= 0.0f) {
+		return false;
+	}
+
+	float magnitude_to_add = force_to_add.length();
+	if (magnitude_to_add < magnitude_remaining) {
+		running_total += force_to_add;
+	} else {
+		force_to_add.normalize();
+		running_total += force_to_add * magnitude_remaining;
+	}
+
+	return true;
+}
+
+vec2 AISystem::seek(const AI & ai) {
+	const Mediator & mediator = this->mediator;
+	ComponentManager & mgr = mediator.component_manager;
+	RefVector<Transform> transforms = mgr.get_components_by_id<Transform>(ai.game_object_id);
+	Transform & transform = transforms.front().get();
+	RefVector<Rigidbody> rigidbodies = mgr.get_components_by_id<Rigidbody>(ai.game_object_id);
+	Rigidbody & rigidbody = rigidbodies.front().get();
+
+	vec2 desired_velocity = ai.seek_target - transform.position;
+	desired_velocity.normalize();
+	desired_velocity *= rigidbody.data.max_linear_velocity;
+
+	return desired_velocity - rigidbody.data.linear_velocity;
+}
+
+vec2 AISystem::flee(const AI & ai) {
+	const Mediator & mediator = this->mediator;
+	ComponentManager & mgr = mediator.component_manager;
+	RefVector<Transform> transforms = mgr.get_components_by_id<Transform>(ai.game_object_id);
+	Transform & transform = transforms.front().get();
+	RefVector<Rigidbody> rigidbodies = mgr.get_components_by_id<Rigidbody>(ai.game_object_id);
+	Rigidbody & rigidbody = rigidbodies.front().get();
+
+	vec2 desired_velocity = transform.position - ai.flee_target;
+	if (desired_velocity.length_squared() > ai.square_flee_panic_distance) {
+		return vec2{0, 0};
+	}
+
+	desired_velocity.normalize();
+	desired_velocity *= rigidbody.data.max_linear_velocity;
+
+	return desired_velocity - rigidbody.data.linear_velocity;
+}
+
+vec2 AISystem::arrive(const AI & ai) {
+	const Mediator & mediator = this->mediator;
+	ComponentManager & mgr = mediator.component_manager;
+	RefVector<Transform> transforms = mgr.get_components_by_id<Transform>(ai.game_object_id);
+	Transform & transform = transforms.front().get();
+	RefVector<Rigidbody> rigidbodies = mgr.get_components_by_id<Rigidbody>(ai.game_object_id);
+	Rigidbody & rigidbody = rigidbodies.front().get();
+
+	vec2 to_target = ai.seek_target - transform.position;
+	float distance = to_target.length();
+	if (distance > 0.0f) {
+		float speed = distance / ai.arrive_deceleration;
+		speed = std::min(speed, rigidbody.data.max_linear_velocity.length());
+		vec2 desired_velocity = to_target * (speed / distance);
+
+		return desired_velocity - rigidbody.data.linear_velocity;
+	}
+
+	return vec2{0, 0};
+}
+
+vec2 AISystem::path_follow(AI & ai) {
+	const Mediator & mediator = this->mediator;
+	ComponentManager & mgr = mediator.component_manager;
+	RefVector<Transform> transforms = mgr.get_components_by_id<Transform>(ai.game_object_id);
+	Transform & transform = transforms.front().get();
+	RefVector<Rigidbody> rigidbodies = mgr.get_components_by_id<Rigidbody>(ai.game_object_id);
+	Rigidbody & rigidbody = rigidbodies.front().get();
+
+	if (ai.path.empty()) {
+		return vec2{0, 0};
+	}
+
+	vec2 to_target = ai.path.at(ai.path_index) - transform.position;
+	if (to_target.length_squared() > ai.path_node_distance * ai.path_node_distance) {
+		ai.seek_target = ai.path.at(ai.path_index);
+	} else {
+		ai.path_index++;
+		if (ai.path_index >= ai.path.size()) {
+			if (ai.path_loop) {
+				ai.path_index = 0;
+			} else {
+				ai.path_index = ai.path.size() - 1;
+				return this->arrive(ai);
+			}
+		}
+	}
+
+	return this->seek(ai);
+}
diff --git a/src/crepe/system/AISystem.h b/src/crepe/system/AISystem.h
new file mode 100644
index 0000000..27861d9
--- /dev/null
+++ b/src/crepe/system/AISystem.h
@@ -0,0 +1,26 @@
+#pragma once
+
+#include "api/AI.h"
+
+#include "System.h"
+#include "types.h"
+
+namespace crepe {
+
+class AISystem : public System {
+public:
+	using System::System;
+
+	void update() override;
+
+private:
+	vec2 calculate(AI & ai);
+	bool accumulate_force(AI & ai, vec2 & running_total, vec2 force_to_add);
+
+	vec2 seek(const AI & ai);
+	vec2 flee(const AI & ai);
+	vec2 arrive(const AI & ai);
+	vec2 path_follow(AI & ai);
+};
+
+} // namespace crepe
diff --git a/src/crepe/system/CMakeLists.txt b/src/crepe/system/CMakeLists.txt
index 95f6e33..7de5198 100644
--- a/src/crepe/system/CMakeLists.txt
+++ b/src/crepe/system/CMakeLists.txt
@@ -7,6 +7,7 @@ target_sources(crepe PUBLIC
 	RenderSystem.cpp
 	AnimatorSystem.cpp
 	InputSystem.cpp
+	AISystem.cpp
 )
 
 target_sources(crepe PUBLIC FILE_SET HEADERS FILES
@@ -17,4 +18,5 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	RenderSystem.h
 	AnimatorSystem.h
 	InputSystem.h
+	AISystem.h
 )
diff --git a/src/crepe/system/CollisionSystem.cpp b/src/crepe/system/CollisionSystem.cpp
index 44a0431..0483693 100644
--- a/src/crepe/system/CollisionSystem.cpp
+++ b/src/crepe/system/CollisionSystem.cpp
@@ -290,7 +290,6 @@ vec2 CollisionSystem::get_circle_box_resolution(const CircleCollider & circle_co
 
 	// Compute penetration depth
 	float penetration_depth = circle_collider.radius - distance;
-
 	// Compute the resolution vector
 	vec2 resolution = collision_normal * penetration_depth;