scripts/studio/touch_camera.gd

extends Camera3D
##
## TouchCamera - lag-free mobile navigation for the 3D viewport (Step 3.1).
##
## Gesture map (configurable):
##   one finger drag      -> orbit (rotate around the focus point)
##   two finger pinch     -> dolly zoom
##   two finger drag      -> pan (move the focus point in screen space)
##   three finger drag    -> pan (alternative, larger screens)
##
## Design: raw InputEvent handling (not _input echo), one gesture re-evaluated
## per frame, no allocations in the hot path. Values are smoothed with an
## exponential filter so motion feels fluid even when touch sampling is jittery.
##

@export var orbit_speed: float = 0.4
@export var pan_speed: float = 0.6
@export var zoom_speed: float = 1.2
@export var min_distance: float = 0.5
@export var max_distance: float = 200.0
@export var smoothing: float = 18.0      # higher = snappier, lower = floatier

var focus: Vector3 = Vector3.ZERO
var _yaw: float = 0.6
var _pitch: float = -0.5
var _distance: float = 8.0

## When false, a single finger is reserved for sculpting/painting and only
## multi-finger gestures navigate. The UI flips this when a sculpt tool is on.
var one_finger_orbit: bool = true
var _painting := false
var _last_paint: Vector2 = Vector2.ZERO

# Smoothed targets
var _t_yaw: float = 0.6
var _t_pitch: float = -0.5
var _t_distance: float = 8.0
var _t_focus: Vector3 = Vector3.ZERO

# Touch bookkeeping
var _touches: Dictionary = {}            # index -> position
var _prev_centroid: Vector2 = Vector2.ZERO
var _prev_spread: float = 0.0
var _gesture_active := false


func _ready() -> void:
	_t_yaw = _yaw
	_t_pitch = _pitch
	_t_distance = _distance
	_t_focus = focus
	_apply_transform()


func _input(event: InputEvent) -> void:
	if event is InputEventScreenTouch:
		_handle_touch(event)
	elif event is InputEventScreenDrag:
		_handle_drag(event)


func _handle_touch(e: InputEventScreenTouch) -> void:
	if e.pressed:
		_touches[e.index] = e.position
		if e.index == 0 and not one_finger_orbit and _touches.size() == 1:
			_painting = true
			_last_paint = e.position
			StudioBus.stroke_begin.emit(_ray_center(e.position))
	else:
		_touches.erase(e.index)
		if e.index == 0 and _painting:
			_painting = false
			StudioBus.stroke_end.emit()
	if _touches.size() >= 2:
		_recompute_gesture_baseline()


func _handle_drag(e: InputEventScreenDrag) -> void:
	_touches[e.index] = e.position
	if _painting and e.index == 0 and not one_finger_orbit:
		var world := _ray_center(e.position)
		var prev_world := _ray_center(_last_paint)
		StudioBus.stroke_apply.emit(world, world - prev_world)
		_last_paint = e.position
		return
	var n := _touches.size()
	if n == 1:
		# Orbit
		var d := e.relative
		_t_yaw -= d.x * orbit_speed * 0.01
		_t_pitch = clampf(_t_pitch - d.y * orbit_speed * 0.01, -1.5, 1.5)
	elif n == 2:
		var pts := _touches.values()
		var centroid: Vector2 = (pts[0] + pts[1]) * 0.5
		var spread: float = (pts[0] as Vector2).distance_to(pts[1] as Vector2)
		if _prev_spread > 0.0:
			var dzoom := (spread - _prev_spread) * zoom_speed * 0.01
			_t_distance = clampf(_t_distance - dzoom, min_distance, max_distance)
		var dpan := centroid - _prev_centroid
		_apply_pan(dpan)
		_prev_centroid = centroid
		_prev_spread = spread
	elif n >= 3:
		var pts := _touches.values()
		var centroid := Vector2.ZERO
		for p in pts:
			centroid += p
		centroid /= float(pts.size())
		var dpan := centroid - _prev_centroid
		_apply_pan(dpan)
		_prev_centroid = centroid


func _recompute_gesture_baseline() -> void:
	var pts := _touches.values()
	if pts.size() >= 2:
		_prev_centroid = (pts[0] + pts[1]) * 0.5
		_prev_spread = (pts[0] as Vector2).distance_to(pts[1] as Vector2)


func _apply_pan(screen_delta: Vector2) -> void:
	# Pan along camera right/up, scaled by distance so it feels consistent at
	# any zoom level.
	var scale := _distance * pan_speed * 0.002
	var right := global_transform.basis.x
	var up := global_transform.basis.y
	_t_focus -= right * screen_delta.x * scale
	_t_focus += up * screen_delta.y * scale
	focus = _t_focus


func _process(delta: float) -> void:
	var t := 1.0 - exp(-smoothing * delta)
	_yaw = lerpf(_yaw, _t_yaw, t)
	_pitch = lerpf(_pitch, _t_pitch, t)
	_distance = lerpf(_distance, _t_distance, t)
	focus = focus.lerp(_t_focus, t)
	_apply_transform()


func _apply_transform() -> void:
	var offset := Vector3(
		cos(_pitch) * sin(_yaw),
		sin(_pitch),
		cos(_pitch) * cos(_yaw)
	) * _distance
	global_position = focus + offset
	look_at(focus, Vector3.UP)


## --- Public helpers ---------------------------------------------------------

func frame_aabb(box: AABB, margin: float = 1.6) -> void:
	_t_focus = box.get_center()
	focus = _t_focus
	var radius := maxf(0.5, box.size.length() * 0.5)
	_t_distance = clampf(radius * margin * 2.0, min_distance, max_distance)
	_distance = _t_distance


func set_focus(p: Vector3) -> void:
	_t_focus = p
	focus = p


func screen_to_ray(screen_pos: Vector2) -> Dictionary:
	return {
		"origin": project_ray_origin(screen_pos),
		"dir": project_ray_normal(screen_pos),
	}


## Ray-cast the viewport at a screen point against physics; returns the world
## hit (or a point in front of the camera if nothing is hit).
func _ray_center(screen_pos: Vector2) -> Vector3:
	var origin := project_ray_origin(screen_pos)
	var dir := project_ray_normal(screen_pos)
	var space := get_world_3d().direct_space_state
	var q := PhysicsRayQueryParameters3D.create(origin, origin + dir * 1000.0)
	var res := space.intersect_ray(q)
	if not res.is_empty():
		return res["position"]
	return origin + dir * _distance