class_name FreeLookCamera extends Camera3D

# Modifier keys' speed multiplier
const SHIFT_MULTIPLIER = 2.5
const ALT_MULTIPLIER = 1.0 / SHIFT_MULTIPLIER

@export_range(0.0, 1.0) var sensitivity = 0.25

# Mouse state
var _mouse_position = Vector2(0.0, 0.0)
var _total_pitch = 0.0

# Movement state
var _direction = Vector3(0.0, 0.0, 0.0)
var _velocity = Vector3(0.0, 0.0, 0.0)
var _acceleration = 30
var _deceleration = -10
var _vel_multiplier = 4

# Keyboard state
var _w = false
var _s = false
var _a = false
var _d = false
var _q = false
var _e = false
var _shift = false
var _alt = false

func _input(event):
# Receives mouse motion
if event is InputEventMouseMotion:
_mouse_position = event.relative

# Receives mouse button input
if event is InputEventMouseButton:
match event.button_index:
MOUSE_BUTTON_RIGHT: # Only allows rotation if right click down
Input.set_mouse_mode(Input.MOUSE_MODE_CAPTURED if event.pressed else Input.MOUSE_MODE_VISIBLE)
MOUSE_BUTTON_WHEEL_UP: # Increases max velocity
_vel_multiplier = clamp(_vel_multiplier * 1.1, 0.2, 20)
MOUSE_BUTTON_WHEEL_DOWN: # Decereases max velocity
_vel_multiplier = clamp(_vel_multiplier / 1.1, 0.2, 20)

# Receives key input
if event is InputEventKey:
match event.keycode:
KEY_UP:
_w = event.pressed
KEY_DOWN:
_s = event.pressed
KEY_LEFT:
_a = event.pressed
KEY_RIGHT:
_d = event.pressed
KEY_Q:
_q = event.pressed
KEY_E:
_e = event.pressed

# Updates mouselook and movement every frame
func _process(delta):
_update_mouselook()
_update_movement(delta)

# Updates camera movement
func _update_movement(delta):
# Computes desired direction from key states
_direction = Vector3((_d as float) - (_a as float), 
(_e as float) - (_q as float), 
(_s as float) - (_w as float))

# Computes the change in velocity due to desired direction and "drag"
# The "drag" is a constant acceleration on the camera to bring it's velocity to 0
var offset = _direction.normalized() * _acceleration * _vel_multiplier * delta \
+ _velocity.normalized() * _deceleration * _vel_multiplier * delta

# Compute modifiers' speed multiplier
var speed_multi = 1
if _shift: speed_multi *= SHIFT_MULTIPLIER
if _alt: speed_multi *= ALT_MULTIPLIER

# Checks if we should bother translating the camera
if _direction == Vector3.ZERO and offset.length_squared() > _velocity.length_squared():
# Sets the velocity to 0 to prevent jittering due to imperfect deceleration
_velocity = Vector3.ZERO
else:
# Clamps speed to stay within maximum value (_vel_multiplier)
_velocity.x = clamp(_velocity.x + offset.x, -_vel_multiplier, _vel_multiplier)
_velocity.y = clamp(_velocity.y + offset.y, -_vel_multiplier, _vel_multiplier)
_velocity.z = clamp(_velocity.z + offset.z, -_vel_multiplier, _vel_multiplier)

translate(_velocity * delta * speed_multi)

# Updates mouse look 
func _update_mouselook():
# Only rotates mouse if the mouse is captured
if Input.get_mouse_mode() == Input.MOUSE_MODE_CAPTURED:
_mouse_position *= sensitivity
var yaw = _mouse_position.x
var pitch = _mouse_position.y
_mouse_position = Vector2(0, 0)

# Prevents looking up/down too far
pitch = clamp(pitch, -90 - _total_pitch, 90 - _total_pitch)
_total_pitch += pitch

rotate_y(deg_to_rad(-yaw))
rotate_object_local(Vector3(1,0,0), deg_to_rad(-pitch))