1 files changed, 186 insertions, 0 deletions
diff --git a/src/crepe/system/AISystem.cpp b/src/crepe/system/AISystem.cpp
new file mode 100644
index 0000000..3c3fd93
--- /dev/null
+++ b/src/crepe/system/AISystem.cpp
@@ -0,0 +1,186 @@
+#include <algorithm>
+#include <cmath>
+
+#include "api/LoopTimer.h"
+#include "manager/ComponentManager.h"
+#include "manager/Mediator.h"
+
+#include "AISystem.h"
+
+using namespace crepe;
+
+void AISystem::fixed_update() {
+	const Mediator & mediator = this->mediator;
+	ComponentManager & mgr = mediator.component_manager;
+	LoopTimer & timer = mediator.timer;
+	RefVector<AI> ai_components = mgr.get_components_by_type<AI>();
+
+	//TODO: Use fixed loop dt (this is not available at master at the moment)
+	double dt = timer.get_delta_time();
+
+	// Loop through all AI components
+	for (AI & ai : ai_components) {
+		if (!ai.active) {
+			continue;
+		}
+
+		RefVector<Rigidbody> rigidbodies
+			= mgr.get_components_by_id<Rigidbody>(ai.game_object_id);
+		if (rigidbodies.empty()) {
+			throw std::runtime_error(
+				"AI component must be attached to a GameObject with a Rigidbody component");
+		}
+		Rigidbody & rigidbody = rigidbodies.front().get();
+		if (!rigidbody.active) {
+			continue;
+		}
+		if (rigidbody.data.mass <= 0) {
+			throw std::runtime_error("Mass must be greater than 0");
+		}
+
+		// Calculate the force to apply to the entity
+		vec2 force = this->calculate(ai, rigidbody);
+		// Calculate the acceleration (using the above calculated force)
+		vec2 acceleration = force / rigidbody.data.mass;
+		// Finally, update Rigidbody's velocity
+		rigidbody.data.linear_velocity += acceleration * dt;
+	}
+}
+
+vec2 AISystem::calculate(AI & ai, const Rigidbody & rigidbody) {
+	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();
+
+	vec2 force;
+
+	// Run all the behaviors that are on, and stop if the force gets too high
+	if (ai.on(AI::BehaviorTypeMask::FLEE)) {
+		vec2 force_to_add = this->flee(ai, rigidbody, transform);
+
+		if (!this->accumulate_force(ai, force, force_to_add)) {
+			return force;
+		}
+	}
+	if (ai.on(AI::BehaviorTypeMask::ARRIVE)) {
+		vec2 force_to_add = this->arrive(ai, rigidbody, transform);
+
+		if (!this->accumulate_force(ai, force, force_to_add)) {
+			return force;
+		}
+	}
+	if (ai.on(AI::BehaviorTypeMask::SEEK)) {
+		vec2 force_to_add = this->seek(ai, rigidbody, transform);
+
+		if (!this->accumulate_force(ai, force, force_to_add)) {
+			return force;
+		}
+	}
+	if (ai.on(AI::BehaviorTypeMask::PATH_FOLLOW)) {
+		vec2 force_to_add = this->path_follow(ai, rigidbody, transform);
+
+		if (!this->accumulate_force(ai, force, force_to_add)) {
+			return force;
+		}
+	}
+
+	return force;
+}
+
+bool AISystem::accumulate_force(const 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) {
+		// If the force is already at/above the max force, return false
+		return false;
+	}
+
+	float magnitude_to_add = force_to_add.length();
+	if (magnitude_to_add < magnitude_remaining) {
+		// If the force to add is less than the remaining force, add it
+		running_total += force_to_add;
+	} else {
+		// If the force to add is greater than the remaining force, add a fraction of it
+		force_to_add.normalize();
+		running_total += force_to_add * magnitude_remaining;
+	}
+
+	return true;
+}
+
+vec2 AISystem::seek(const AI & ai, const Rigidbody & rigidbody,
+					const Transform & transform) const {
+	// Calculate the desired velocity
+	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 Rigidbody & rigidbody,
+					const Transform & transform) const {
+	// Calculate the desired velocity if the entity is within the panic distance
+	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 Rigidbody & rigidbody,
+					  const Transform & transform) const {
+	// Calculate the desired velocity (taking into account the deceleration rate)
+	vec2 to_target = ai.arrive_target - transform.position;
+	float distance = to_target.length();
+	if (distance > 0.0f) {
+		if (ai.arrive_deceleration <= 0.0f) {
+			throw std::runtime_error("Deceleration rate must be greater than 0");
+		}
+
+		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 Rigidbody & rigidbody, const Transform & transform) {
+	if (ai.path.empty()) {
+		return vec2{0, 0};
+	}
+
+	// Get the target node
+	vec2 target = ai.path.at(ai.path_index);
+	// Calculate the force to apply to the entity
+	vec2 to_target = target - transform.position;
+	if (to_target.length_squared() > ai.path_node_distance * ai.path_node_distance) {
+		// If the entity is not close enough to the target node, seek it
+		ai.seek_target = target;
+		ai.arrive_target = target;
+	} else {
+		// If the entity is close enough to the target node, move to the next node
+		ai.path_index++;
+		if (ai.path_index >= ai.path.size()) {
+			if (ai.path_loop) {
+				// If the path is looping, reset the path index
+				ai.path_index = 0;
+			} else {
+				// If the path is not looping, arrive at the last node
+				ai.path_index = ai.path.size() - 1;
+				return this->arrive(ai, rigidbody, transform);
+			}
+		}
+	}
+
+	// Seek the target node
+	return this->seek(ai, rigidbody, transform);
+}