extends CharacterBody3D

# Settings to control the character
@export var rotation_speed : float = 1.0
@export var movement_speed : float = 5.0
@export var movement_acceleration : float = 5.0

# Get the gravity from the project settings to be synced with RigidBody nodes.
var gravity = ProjectSettings.get_setting("physics/3d/default_gravity")

# Helper variables to keep our code readable
@onready var origin_node : XROrigin3D = $XROrigin3D
@onready var camera_node : XRCamera3D = $XROrigin3D/XRCamera3D
@onready var neck_position_node : Node3D = $XROrigin3D/XRCamera3D/Neck
@onready var black_out : Node3D = $XROrigin3D/XRCamera3D/BlackOut

# `recenter` is called when the user has requested their view to be recentered.
# The code here assumes the player has walked into an area they shouldn't be
# and we return the player back to the character body.
# But other strategies can be applied here as well such as returning the player
# to a starting position or a checkpoint.
func recenter():
	# Calculate where our camera should be, we start with our global transform
	var new_camera_transform : Transform3D = global_transform

	# Set to the height of our neck joint
	new_camera_transform.origin.y = neck_position_node.global_position.y

	# Apply transform our our next position to get our desired camera transform
	new_camera_transform = new_camera_transform * neck_position_node.transform.inverse()

	# Remove tilt from camera transform
	var camera_transform : Transform3D = camera_node.transform
	var forward_dir : Vector3 = camera_transform.basis.z
	forward_dir.y = 0.0
	camera_transform = camera_transform.looking_at(camera_transform.origin + forward_dir.normalized(), Vector3.UP, true)

	# Update our XR location
	origin_node.global_transform = new_camera_transform * camera_transform.inverse()

# `_get_movement_input` returns our move input by querying the move action on each controller
func _get_movement_input() -> Vector2:
	var movement : Vector2 = Vector2()

	# If move is not bound to one of our controllers,
	# that controller will return a Vector2(0.0, 0.0)
	movement += $XROrigin3D/LeftHand.get_vector2("move")
	movement += $XROrigin3D/RightHand.get_vector2("move")

	return movement

# `_process_on_physical_movement` handles the physical movement of the player
# adjusting our character body position to "catch up to" the player.
# If the character body encounters an obstruction our view will black out
# and we will stop further character movement until the player physically
# moves back.
func _process_on_physical_movement(delta) -> bool:
	# Remember our current velocity, we'll apply that later
	var current_velocity = velocity

	# Start by rotating the player to face the same way our real player is
	var camera_basis: Basis = origin_node.transform.basis * camera_node.transform.basis
	var forward: Vector2 = Vector2(camera_basis.z.x, camera_basis.z.z)
	var angle: float = forward.angle_to(Vector2(0.0, 1.0))

	# Rotate our character body
	transform.basis = transform.basis.rotated(Vector3.UP, angle)

	# Reverse this rotation our origin node
	origin_node.transform = Transform3D().rotated(Vector3.UP, -angle) * origin_node.transform

	# Now apply movement, first move our player body to the right location
	var org_player_body: Vector3 = global_transform.origin
	var player_body_location: Vector3 = origin_node.transform * camera_node.transform * neck_position_node.transform.origin
	player_body_location.y = 0.0
	player_body_location = global_transform * player_body_location

	velocity = (player_body_location - org_player_body) / delta
	move_and_slide()

	# Now move our XROrigin back
	var delta_movement = global_transform.origin - org_player_body
	origin_node.global_transform.origin -= delta_movement

	# Negate any height change in local space due to player hitting ramps etc.
	origin_node.transform.origin.y = 0.0

	# Return our value
	velocity = current_velocity

	# Check if we managed to move where we wanted to
	var location_offset = (player_body_location - global_transform.origin).length()
	if location_offset > 0.1:
		# We couldn't go where we wanted to, black out our screen
		black_out.fade = clamp((location_offset - 0.1) / 0.1, 0.0, 1.0)

		return true
	else:
		black_out.fade = 0.0
		return false

# `_process_movement_on_input` handles movement through controller input.
# We first handle rotating the player and then apply movement.
# We also apply the effects of gravity at this point.
func _process_movement_on_input(is_colliding, delta):
	if !is_colliding:
		# Only handle input if we've not physically moved somewhere we shouldn't.
		var movement_input = _get_movement_input()

		# First handle rotation, to keep this example simple we are implementing
		# "smooth" rotation here. This can lead to motion sickness.
		# Adding a comfort option with "stepped" rotation is good practice but
		# falls outside of the scope of this demonstration.
		rotation.y += -movement_input.x * delta * rotation_speed

		# Now handle forward/backwards movement.
		# Straffing can be added by using the movement_input.x input
		# and using a different input for rotational control.
		# Straffing is more prone to motion sickness.
		var direction = global_transform.basis * Vector3(0.0, 0.0, -movement_input.y) * movement_speed
		if direction:
			velocity.x = move_toward(velocity.x, direction.x, delta * movement_acceleration)
			velocity.z = move_toward(velocity.z, direction.z, delta * movement_acceleration)
		else:
			velocity.x = move_toward(velocity.x, 0, delta * movement_acceleration)
			velocity.z = move_toward(velocity.z, 0, delta * movement_acceleration)

	# Always handle gravity
	velocity.y -= gravity * delta

	move_and_slide()

# _physics_process handles our player movement.
func _physics_process(delta):
	var is_colliding = _process_on_physical_movement(delta)
	_process_movement_on_input(is_colliding, delta)