class_name Boat
extends FloatingBody

## All force values are per-kilogram (they get multiplied by mass), so the
## boat handles the same if you change its mass later.
@export var engine_power := 12.0        # forward thrust, m/s² at full throttle
@export var reverse_ratio := 0.4        # reverse is weaker, like a real prop
@export var throttle_response := 1.5    # how fast the engine spools up/down
@export var rudder_strength := 2.5      # turning torque at speed
@export var keel_grip := 3.0            # resistance to sliding sideways

var desired_throttle := 0.0
var throttle := 0.0


func _physics_process(delta: float) -> void:
	super(delta)

	if Input.is_action_pressed("throttle_increase"):
		desired_throttle = move_toward(desired_throttle, 1, 0.005)
	elif Input.is_action_pressed("throttle_decrease"):
		desired_throttle = move_toward(desired_throttle, -1, 0.006)
	elif Input.is_action_pressed("throttle_stop"):
		desired_throttle = 0.0
	
	throttle = move_toward(throttle, desired_throttle, throttle_response * delta)

	if submerged_ratio <= 0.0:
		return   # airborne: no thrust, no rudder, no keel

	# boat's forward direction, flattened onto the water plane
	var forward := -global_basis.z
	forward.y = 0.0
	forward = forward.normalized()

	# --- engine ---
	var power := engine_power * (reverse_ratio if throttle < 0.0 else 1.0)
	apply_central_force(forward * throttle * power * mass * submerged_ratio)

	# --- rudder: only bites when water flows past it ---
	var steer_input := Input.get_axis("rudder_right", "rudder_left")
	var forward_speed := linear_velocity.dot(forward)
	var rudder_bite := clampf(forward_speed / 3.0, -1.0, 1.0)
	apply_torque(Vector3.UP * steer_input * rudder_strength * rudder_bite * mass * submerged_ratio)

	# --- keel: kill sideways sliding ---
	var right := global_basis.x
	right.y = 0.0
	right = right.normalized()
	var lateral_speed := linear_velocity.dot(right)
	apply_central_force(-right * lateral_speed * keel_grip * mass * submerged_ratio)