extends VehicleBody

const STEER_SPEED = 1.5
const STEER_LIMIT = 0.4

var steer_target = 0

export (float) var MAX_ENGINE_FORCE = 100.0
export (float) var MAX_BRAKE_FORCE = 50.0
export (float) var THROTTLE_POWER = 10000.0
export (float) var MAX_RPM_LOSS_PS = 3000.0

export (Array) var gear_ratios = [ 6, 5, 4, 3, 2, 1.0 ]
export (float) var reverse_ratio = -6.0
export (float) var final_drive = 3.38
export (float) var max_rpm = 7000
export (float) var min_rpm = 900
export (float) var gear_switch_time = 0.2
export (Curve) var power_curve

var clutch_position: float = 0.0
var rpm = 0
var gear = 1

var gear_timer = 0

onready var frwheel: VehicleWheel = $front_right
onready var flwheel: VehicleWheel = $front_left
onready var rrwheel: VehicleWheel = $rear_right
onready var rlwheel: VehicleWheel = $rear_left

var traction_wheels: Array

func _ready():
	for wheel in [frwheel, flwheel, rrwheel, rlwheel]:
		if wheel.use_as_traction:
			traction_wheels.append(wheel)

func _get_gear_ratio():
	if gear == 0:
		return 0
	elif gear == -1:
		return reverse_ratio
	else:
		return gear_ratios[gear - 1]

func _handle_gear_switch(delta: float):
	if gear_timer > 0:
		gear_timer = max(0, gear_timer - delta)
	elif clutch_position > 0.8:
		if Input.is_action_just_pressed("gear_up"):
			if gear + 1 <= gear_ratios.size():
				gear += 1
				gear_timer = gear_switch_time * (2 - clutch_position)
		if Input.is_action_just_pressed("gear_down"):
			if gear - 1 >= -1:
				gear -= 1
				gear_timer = gear_switch_time * (2 - clutch_position)

func _has_traction():
	for wheel in traction_wheels:
		if wheel.is_in_contact():
			return true
	return false

func _lerp_rpm(from, to, delta, factor):
	var new_val = lerp(from, to, factor)
	if abs(from - new_val) > MAX_RPM_LOSS_PS * delta:
		var new_factor = inverse_lerp(from, to, from - sign(from - new_val) * MAX_RPM_LOSS_PS * delta)
		new_val = lerp(from, to, new_factor)
	return new_val

func _physics_process(delta: float):
	clutch_position = Input.get_action_strength("clutch")
	_handle_gear_switch(delta)
	var throttle = Input.get_action_strength("throttle")

	var wheel_rpm = traction_wheels[0].get_rpm()
	var final_rpm = abs(wheel_rpm) * final_drive
	var transmission_rpm = final_rpm * abs(_get_gear_ratio())

	if gear != 0:
		rpm = lerp(rpm, transmission_rpm, delta * (1 - clutch_position))
		rpm = _lerp_rpm(rpm, min_rpm, delta, delta * clutch_position * 3)
	else:
		rpm = _lerp_rpm(rpm, min_rpm, delta, delta * 3)
	if _has_traction():
		rpm += throttle * delta * clutch_position * THROTTLE_POWER
	else:
		rpm += throttle * delta * THROTTLE_POWER
	rpm = clamp(rpm, 0, max_rpm)
	var rpm_factor = clamp(rpm / max_rpm, 0.0, 1.0)
	var power_factor = power_curve.interpolate_baked(rpm_factor)

	# Transfer to transmission
	var transmission_input = power_factor * (1 - clutch_position) * _get_gear_ratio()

	var final_input = transmission_input * final_drive

	brake = Input.get_action_strength("brake") * MAX_BRAKE_FORCE
	engine_force = throttle * final_input * MAX_ENGINE_FORCE

	var handbrake = Input.get_action_strength("handbrake")
	rrwheel.brake = handbrake * MAX_BRAKE_FORCE / 2
	rlwheel.brake = handbrake * MAX_BRAKE_FORCE / 2

	$Info.text = "Gear: %d, RPM: %.0f, TRPM: %.0f, Engine force: %.0f" % [ gear, rpm, transmission_rpm, engine_force ]

	steer_target = Input.get_action_strength("steer_left") - Input.get_action_strength("steer_right")
	steer_target *= STEER_LIMIT

	steering = move_toward(steering, steer_target, STEER_SPEED * delta)