# A specialized steering agent that updates itself every frame so the user does
# not have to using a KinematicBody2D
extends GSTSpecializedAgent
class_name GSTKinematicBody2DAgent


# SLIDE uses `move_and_slide`
# COLLIDE uses `move_and_collide`
# POSITION changes the `global_position` directly
enum MovementType { SLIDE, COLLIDE, POSITION }


# The KinematicBody2D to keep track of
var body: KinematicBody2D setget _set_body

# The type of movement the body executes
var movement_type: int

var _last_position: Vector2


func _init(body: KinematicBody2D, movement_type: int = MovementType.SLIDE) -> void:
	if not body.is_inside_tree():
		yield(body, "ready")
	
	self.body = body
	self.movement_type = movement_type
	
	body.get_tree().connect("physics_frame", self, "_on_SceneTree_physics_frame")


# Moves the agent's `body` by target `acceleration`.
# tags: virtual
func _apply_steering(acceleration: GSTTargetAcceleration, delta: float) -> void:
	_applied_steering = true
	match movement_type:
		MovementType.COLLIDE:
			_apply_collide_steering(acceleration.linear, delta)
		MovementType.SLIDE:
			_apply_sliding_steering(acceleration.linear)
		_:
			_apply_position_steering(acceleration.linear, delta)
	
	_apply_orientation_steering(acceleration.angular, delta)


func _apply_sliding_steering(accel: Vector3) -> void:
	var velocity := GSTUtils.to_vector2(linear_velocity + accel).clamped(linear_speed_max)
	if apply_linear_drag:
		velocity = velocity.linear_interpolate(Vector2.ZERO, linear_drag_percentage)
	velocity = body.move_and_slide(velocity)
	if calculate_velocities:
		linear_velocity = GSTUtils.to_vector3(velocity)


func _apply_collide_steering(accel: Vector3, delta: float) -> void:
	var velocity := GSTUtils.clampedv3(linear_velocity + accel, linear_speed_max)
	if apply_linear_drag:
		velocity = velocity.linear_interpolate(
				Vector3.ZERO,
				linear_drag_percentage
		)
	body.move_and_collide(GSTUtils.to_vector2(velocity) * delta)
	if calculate_velocities:
		linear_velocity = velocity


func _apply_position_steering(accel: Vector3, delta: float) -> void:
	var velocity := GSTUtils.clampedv3(linear_velocity + accel, linear_speed_max)
	if apply_linear_drag:
		velocity = velocity.linear_interpolate(
				Vector3.ZERO,
				linear_drag_percentage
		)
	body.global_position += GSTUtils.to_vector2(velocity) * delta
	if calculate_velocities:
		linear_velocity = velocity


func _apply_orientation_steering(angular_acceleration: float, delta: float) -> void:
	var velocity = angular_velocity + angular_acceleration
	if apply_angular_drag:
		velocity = lerp(velocity, 0, angular_drag_percentage)
	body.rotation += velocity * delta
	if calculate_velocities:
		angular_velocity = velocity


func _set_body(value: KinematicBody2D) -> void:
	body = value
	
	_last_position = body.global_position
	_last_orientation = body.rotation
	
	position = GSTUtils.to_vector3(_last_position)
	orientation = _last_orientation


func _on_SceneTree_physics_frame() -> void:
	var current_position: Vector2 = body.global_position
	var current_orientation: float = body.rotation
	
	position = GSTUtils.to_vector3(current_position)
	orientation = current_orientation
	
	if calculate_velocities:
		if _applied_steering:
			_applied_steering = false
		else:
			linear_velocity = GSTUtils.clampedv3(
				GSTUtils.to_vector3(_last_position - current_position),
				linear_speed_max
			)
			if apply_linear_drag:
				linear_velocity = linear_velocity.linear_interpolate(
					Vector3.ZERO,
					linear_drag_percentage
				)
			
			angular_velocity = clamp(
				_last_orientation - current_orientation,
				-angular_speed_max,
				angular_speed_max
			)
			
			if apply_angular_drag:
				angular_velocity = lerp(
					angular_velocity,
					0,
					angular_drag_percentage
			)
			
			_last_position = current_position
			_last_orientation = current_orientation