extends ColorRect
## Drives the desaturation shader's `desaturation` uniform from nausea intensity.
##
## Nausea ramps desaturation from 0 (no effect) up to full grayscale at
## `max_at_intensity`. The uniform is smoothly faded toward its target.
## Attach to a full-screen ColorRect that uses `desaturation.gdshader`.

## Nausea intensity at (and above) which the screen is fully desaturated.
@export var max_at_intensity: float = 80.0
## How fast the shader uniform follows its target, per second.
@export var fade_speed: float = 2.0

var _target: float = 0.0
var _current: float = 0.0


func _ready() -> void:
	# Cover the whole viewport and never block input.
	mouse_filter = Control.MOUSE_FILTER_IGNORE
	set_anchors_preset(Control.PRESET_FULL_RECT)

	var sm: Node = null
	if is_inside_tree():
		sm = get_tree().root.get_node_or_null("SymptomManager")
	if sm == null:
		sm = SymptomManager
	if sm:
		sm.nausea_intensity_changed.connect(_on_nausea_changed)
		_set_target_from_intensity(sm.get_intensity(sm.NAUSEA))
		_current = _target
		_apply()


func _on_nausea_changed(value: float) -> void:
	_set_target_from_intensity(value)


func _set_target_from_intensity(intensity: float) -> void:
	_target = clampf(intensity / max_at_intensity, 0.0, 1.0)


func _process(delta: float) -> void:
	if is_equal_approx(_current, _target):
		return
	_current = move_toward(_current, _target, fade_speed * delta)
	_apply()


func _apply() -> void:
	if material is ShaderMaterial:
		(material as ShaderMaterial).set_shader_parameter("desaturation", _current)