extends CharacterBody3D

## NS-23 path-follow; NS-24 idle. Details in `client/README.md` (movement, idle).
##
## Summary: Jolt, no interp; dual floor_max_angle; rim/straddle, bump lip escape.
## Snap upright after motion. Do not set global_transform in _process.
## Walk assist may run a second move_and_slide().

const MOVE_SPEED: float = 5.0
## Moving: floor angle for seams onto stepped QA bumps (~50°).
const FLOOR_MAX_ANGLE_MOVING_DEG: float = 50.0
## Idle: tighter angle to reduce vertex / vertical-face flicker (~35°).
const FLOOR_MAX_ANGLE_IDLE_DEG: float = 35.0
## Physics ticks to keep moving floor angle after walk goal clears (arrival).
const FLOOR_ANGLE_LOOSE_TICKS_AFTER_STOP: int = 96
const ARRIVE_EPS: float = 0.35
const VERT_ARRIVE_EPS: float = 0.055
const DIRECT_APPROACH_RADIUS: float = 0.85
## Hysteresis for nav-path column steering (see `_physics_process`). At exactly
## [member DIRECT_APPROACH_RADIUS] the old test flipped every frame: path nudges
## tangentially → [code]horiz_dist[/code] crosses the radius → direct vs path
## alternates → velocity sign flips (Jolt ping-pong while [code]has_goal[/code]).
const NAV_COLUMN_STEER_ENTER_DIST: float = 0.74
const NAV_COLUMN_STEER_EXIT_DIST: float = 0.97
## Hysteresis for [code]needs_vertical_routing[/code]: [code]feet_y[/code] wobbles with
## [code]move_and_slide[/code] on treads (~7 cm), so a single margin (see [member DESCEND_GOAL_Y_MARGIN])
## can flip path vs direct steering every tick → velocity sign ping-pong while [code]has_goal[/code].
const WALK_VERT_ROUTE_LATCH_ON_SEP: float = 0.10
const WALK_VERT_ROUTE_LATCH_OFF_SEP: float = 0.038
const FLOOR_SNAP_MOVING: float = 0.32
## Idle floor snap length (stronger to pin rim contacts).
const FLOOR_SNAP_IDLE: float = 0.11
## Below this floor-normal dot up, idle tick uses **moving** `floor_max_angle` (rim).
const IDLE_RIM_MIN_FLOOR_UP_DOT: float = 0.968
## Stable flat idle support: skip corrective idle motion when support is effectively level.
## 0.998 (~3.6°): 0.999 still saw open-floor HUD drift — Jolt [code]get_floor_normal()[/code] often
## reports ~0.9991–0.9992 on a flat box, so the old 0.999 gate rarely latched the idle anchor and
## [code]move_and_slide[/code] + rim/bump nudges kept nudging XZ.
const STABLE_IDLE_FLOOR_MIN_UP_DOT: float = 0.998
## While [member _idle_stable_latched], allow slightly tilted reported normals (tread/riser edge).
const STABLE_IDLE_FLOOR_HOLD_MIN_UP_DOT: float = 0.992
## Rare edge contacts can keep corrective nudges alive forever; budget them, then hold x/z.
const IDLE_MANUAL_CORRECTION_MAX_TICKS: int = 8
## Consecutive [code]raw_stable[/code] ticks required before first idle anchor latch (entry debounce).
const STABLE_IDLE_ENTER_STREAK_FRAMES: int = 2
## Consecutive unstable-idle physics ticks before leaving latched stable idle (thin tread lip).
const STABLE_IDLE_UNLATCH_TICKS: int = 10
## Horizontal nudge per tick for rim / straddle settle (**`_maybe_idle_rim_settle_nudge`**).
const IDLE_RIM_SETTLE_STEP: float = 0.004
## Used by tests and vertical routing checks (feet vs goal surface).
const DESCEND_GOAL_Y_MARGIN: float = 0.06
## Cap snap while dropping off a pad so Jolt cannot glue the capsule to the upper surface.
const DESCEND_LIP_SNAP_CAP: float = 0.1
## Y lift when blocked by wall-ish slide but nav goal is higher (stepped bumps).
const WALK_STEP_ASSIST_DELTA: float = 0.11
const WALK_STEP_ASSIST_COOLDOWN_TICKS: int = 8
## Floor-snap length while step-climbing. Small enough that it cannot reach the lower floor
## (~0.11 m away after the first lift) but large enough to catch the step surface once the
## capsule clears the face (~0.03 m away after the third lift for a 0.3 m step).
const WALK_STEP_ASSIST_SNAP: float = 0.09
## Do not step-assist when the goal surface is farther above the feet than this (meters).
## Matches [NavigationMesh] `agent_max_climb` in `main.tscn` so repeated lifts cannot bypass a
## two-level climb in one click (e.g. floor → **TerracePlatformB** violet deck at ~0.6 m — use
## **TerraceStepB** gold first, or a second click after standing on the step).
const WALK_STEP_ASSIST_MAX_SURFACE_DELTA: float = 0.35
## Ray below capsule feet while walking: if [method CharacterBody3D.is_on_floor] stays true off a
## ledge (snap + lip contacts), we still need gravity toward the lower floor — without re-applying
## gravity for every “goal below feet” tick on a whole upper deck (see [member _apply_walk_air_gravity]).
const WALK_SUPPORT_PROBE_DEPTH: float = 0.22
const WALK_SUPPORT_PROBE_MIN_UP_DOT: float = 0.42
## Only second-guess [code]is_on_floor()[/code] when the reported floor is fairly level (skip
## stair risers / seam normals where a down ray often hits vertical mesh).
const WALK_LEDGE_PROBE_MAX_FLOOR_UP_DOT: float = 0.92
## CapsuleShape3D in scene: height = 1.0 (cylinder portion), radius = 0.4.
## Total half-height from body origin to physical bottom = 0.5 + 0.4 = 0.9
## (`CAPSULE_HALF_HEIGHT + PLAYER_CAPSULE_RADIUS`).
## `CAPSULE_HALF_HEIGHT` alone (0.5) is the cylinder half; used only where that
## distinction matters (e.g. the descend-bypass feet estimate).
const CAPSULE_HALF_HEIGHT: float = 0.5
const BUMP_COLLISION_CONSTS_SCRIPT: Script = preload(
	"res://scripts/random_floor_bump_collision_constants.gd"
)
## Idle radial push per tick off bump lip / wall (meters; 120 Hz physics).
const IDLE_BUMP_ESCAPE_STEP: float = 0.014
## Player capsule radius; wall touch can happen past axis distance **`col_r`**.
const PLAYER_CAPSULE_RADIUS: float = 0.4
const DEBUG_IDLE_TRACE_DELTA_EPS: float = 0.0001
const DEBUG_IDLE_TRACE_HEARTBEAT_FRAMES: int = 60
const DEBUG_TRANSFORM_TRACE_DELTA_EPS: float = 0.000001
@export var debug_idle_trace: bool = false

var _has_walk_goal: bool = false
var _auth_walk_goal: Vector3 = Vector3.ZERO
var _floor_angle_loose_ticks: int = 0
var _step_assist_cooldown: int = 0
## True while the player is actively climbing a step; suppresses the normal large floor
## snap so it cannot pull the capsule back to the lower surface between assist cycles.
var _step_assist_active: bool = false
var _idle_anchor_active: bool = false
var _idle_anchor_xz: Vector2 = Vector2.ZERO
var _idle_anchor_y: float = 0.0
## Latched stable idle: stay on zero-vel + anchor through brief Jolt false negatives on treads.
var _idle_stable_latched: bool = false
var _idle_stable_unlatch_streak: int = 0
var _idle_stable_enter_streak: int = 0
var _idle_manual_correction_ticks: int = 0
var _debug_last_idle_xz: Vector2 = Vector2.INF
var _debug_idle_heartbeat: int = 0
var _debug_last_transform_xz: Vector2 = Vector2.INF
var _debug_trace_frame: int = 0
## True while we use [method _set_horizontal_velocity_from_nav_path_or_goal] for vertical routing.
var _walk_nav_column_steering: bool = false
## Schmitt latch for vertical routing (see [member WALK_VERT_ROUTE_LATCH_ON_SEP]).
var _walk_vert_route_latched: bool = false
@onready var _nav_agent: NavigationAgent3D = $NavigationAgent3D


func _ready() -> void:
	physics_interpolation_mode = Node.PHYSICS_INTERPOLATION_MODE_OFF
	_nav_agent.avoidance_enabled = false
	_nav_agent.set_target_position(global_position)
	floor_block_on_wall = true
	if debug_idle_trace:
		set_notify_transform(true)


func set_authoritative_nav_goal(world_pos: Vector3) -> void:
	_auth_walk_goal = world_pos
	_has_walk_goal = true
	_floor_angle_loose_ticks = 0
	_step_assist_active = false
	_idle_anchor_active = false
	_idle_manual_correction_ticks = 0
	_idle_stable_latched = false
	_idle_stable_unlatch_streak = 0
	_idle_stable_enter_streak = 0
	_walk_nav_column_steering = false
	_walk_vert_route_latched = false
	_nav_agent.set_target_position(world_pos)


func clear_nav_goal() -> void:
	velocity = Vector3.ZERO
	_has_walk_goal = false
	_floor_angle_loose_ticks = FLOOR_ANGLE_LOOSE_TICKS_AFTER_STOP
	_step_assist_active = false
	_idle_anchor_active = false
	_idle_manual_correction_ticks = 0
	_idle_stable_latched = false
	_idle_stable_unlatch_streak = 0
	_idle_stable_enter_streak = 0
	_walk_nav_column_steering = false
	_walk_vert_route_latched = false
	_nav_agent.set_target_position(global_position)


## Repath on a new nav map (e.g. after [NavigationRegion3D] rebake when geometry is removed).
## Rebaking can leave [NavigationAgent3D] on a stale map RID; rebind to the world's map first.
func sync_navigation_agent_after_map_rebuild(nav_region: NavigationRegion3D) -> void:
	var map_rid: RID = RID()
	var w3d := get_world_3d()
	if w3d != null:
		map_rid = w3d.navigation_map
	if map_rid == RID() and is_instance_valid(nav_region):
		map_rid = NavigationServer3D.region_get_map(nav_region.get_region_rid())
	if map_rid != RID():
		_nav_agent.set_navigation_map(map_rid)
	if _has_walk_goal:
		_nav_agent.set_target_position(_auth_walk_goal)
	else:
		_nav_agent.set_target_position(global_position)


func snap_to_server(world_pos: Vector3) -> void:
	# The server stores the surface Y of the last move target, not the capsule body-centre Y.
	# Clamping to the minimum standing height (total half = 0.9 m) prevents the player from
	# being placed underground (which, combined with a stale is_on_floor() returning true,
	# would skip all corrective move_and_slide() calls and leave the capsule stuck).
	var total_half: float = CAPSULE_HALF_HEIGHT + PLAYER_CAPSULE_RADIUS
	var settled := Vector3(world_pos.x, maxf(world_pos.y, total_half), world_pos.z)
	global_position = settled
	velocity = Vector3.ZERO
	_has_walk_goal = false
	# Force corrective idle ticks so Jolt resolves any residual physics state before walking.
	_floor_angle_loose_ticks = FLOOR_ANGLE_LOOSE_TICKS_AFTER_STOP
	_step_assist_cooldown = 0
	_step_assist_active = false
	_idle_anchor_active = false
	_idle_manual_correction_ticks = 0
	_idle_stable_latched = false
	_idle_stable_unlatch_streak = 0
	_idle_stable_enter_streak = 0
	_walk_nav_column_steering = false
	_walk_vert_route_latched = false
	_nav_agent.set_target_position(settled)
	reset_physics_interpolation()


## Returns true when the capsule has something to stand on **or** is pressing against a step face
## in the direction of travel.  `want_dir_xz` is the normalised horizontal goal direction.
## Using `is_on_wall()` as a blanket short-circuit was too broad: any floor-bump side-contact
## satisfied it, causing the assist to fire prematurely and then be unable to snap back.
func _step_assist_has_support(want_dir_xz: Vector3) -> bool:
	if is_on_floor():
		return true
	var w2 := Vector2(want_dir_xz.x, want_dir_xz.z)
	var have_dir: bool = w2.length_squared() > 1e-8
	if have_dir:
		w2 = w2.normalized()
	for i: int in get_slide_collision_count():
		var n: Vector3 = get_slide_collision(i).get_normal()
		if n.y > 0.35:
			return true  # upward-facing = floor support
		# Wall-ish contact opposing forward direction = step face immediately ahead.
		if have_dir and abs(n.y) < 0.52:
			var n2 := Vector2(n.x, n.z)
			if n2.length_squared() > 1e-8 and n2.normalized().dot(w2) < -0.2:
				return true
	return false


## True when a vertical-ish contact opposes motion toward the goal. Jolt often reports a wall
## via `is_on_wall()` + `get_wall_normal()` at box lips while slide normals are ambiguous; the
## old slide-only loop missed head-on climbs onto e.g. TerracePlatformA (teal pad).
func _step_assist_wallish_blocks(want_dir_xz: Vector3) -> bool:
	var w2 := Vector2(want_dir_xz.x, want_dir_xz.z)
	if w2.length_squared() < 1e-8:
		return false
	w2 = w2.normalized()
	if is_on_wall():
		var wn: Vector3 = get_wall_normal()
		var wnh := Vector2(wn.x, wn.z)
		if wnh.length_squared() > 1e-10:
			wnh = wnh.normalized()
			# Wall pushes back against forward (not parallel skimming along the face).
			if wnh.dot(w2) < -0.02:
				return true
	for i: int in get_slide_collision_count():
		var n: Vector3 = get_slide_collision(i).get_normal()
		if n.y > 0.52:
			continue
		var n2 := Vector2(n.x, n.z)
		if n2.length_squared() < 1e-8:
			continue
		n2 = n2.normalized()
		if n2.dot(w2) < -0.02:
			return true
	return false


func _step_assist_can_raise_by(dy: float) -> bool:
	if dy <= 0.0001:
		return false
	return not test_move(global_transform, Vector3(0.0, dy, 0.0), null, safe_margin)


func _try_walk_step_assist() -> bool:
	if not _has_walk_goal:
		return false
	# Use actual capsule bottom (cylindrical half-height + hemisphere radius) so the guard
	# triggers whenever the goal surface is meaningfully above the player's feet — not the
	# capsule centre, which sits ~0.9 m above the floor.
	var actual_feet_y: float = global_position.y - CAPSULE_HALF_HEIGHT - PLAYER_CAPSULE_RADIUS
	if _auth_walk_goal.y < actual_feet_y + 0.025:
		return false
	if _auth_walk_goal.y > actual_feet_y + WALK_STEP_ASSIST_MAX_SURFACE_DELTA:
		return false
	var pos: Vector3 = global_position
	var to_h: Vector3 = Vector3(_auth_walk_goal.x - pos.x, 0.0, _auth_walk_goal.z - pos.z)
	if to_h.length_squared() < 0.03:
		return false
	# Compute want direction before the support/blocking checks so both can use it.
	var want: Vector3 = to_h.normalized()
	if not _step_assist_wallish_blocks(want):
		return false
	if not _step_assist_has_support(want):
		return false
	# Target capsule centre once standing on the goal surface.
	var target_center_y: float = _auth_walk_goal.y + CAPSULE_HALF_HEIGHT + PLAYER_CAPSULE_RADIUS
	var lift: float = clampf(target_center_y - global_position.y, 0.0, WALK_STEP_ASSIST_DELTA)
	if lift <= 0.002 or not _step_assist_can_raise_by(lift):
		return false
	global_position.y += lift
	return true


func _after_walk_move_and_slide() -> void:
	if _step_assist_cooldown > 0:
		_step_assist_cooldown -= 1
	if _step_assist_cooldown > 0:
		return
	if _try_walk_step_assist():
		_step_assist_active = true
		_step_assist_cooldown = WALK_STEP_ASSIST_COOLDOWN_TICKS
		# Reduced snap so the lower floor (0.11 m below lifted capsule) is out of range.
		floor_snap_length = WALK_STEP_ASSIST_SNAP
		move_and_slide()


func _clear_step_assist_after_walk_move() -> void:
	if not _step_assist_active:
		return
	if is_on_floor() and not is_on_wall():
		_step_assist_active = false
	elif not is_on_floor() and get_slide_collision_count() == 0:
		_step_assist_active = false


func _set_horizontal_velocity_toward(
	point: Vector3, fallback_dir_xz: Vector3 = Vector3.ZERO
) -> void:
	var pos := global_position
	var dh: Vector3 = Vector3(point.x - pos.x, 0.0, point.z - pos.z)
	if dh.length_squared() < 1e-10:
		var fb2 := Vector2(fallback_dir_xz.x, fallback_dir_xz.z)
		if fb2.length_squared() > 1e-10:
			fb2 = fb2.normalized()
			dh = Vector3(fb2.x, 0.0, fb2.y)
		else:
			dh = Vector3(1.0, 0.0, 0.0)
	else:
		dh = dh.normalized()
	velocity = dh * MOVE_SPEED
	velocity.y = 0.0


func _walk_has_close_floor_probe_below() -> bool:
	var w3d := get_world_3d()
	if w3d == null:
		return true
	var space := w3d.direct_space_state
	var feet: Vector3 = global_position - Vector3(0.0, CAPSULE_HALF_HEIGHT + PLAYER_CAPSULE_RADIUS, 0.0)
	# Start slightly above the foot line so the ray is not born inside the deck collider after snap.
	var probe_from: Vector3 = feet + Vector3.UP * 0.04
	var probe_end: Vector3 = feet + Vector3.DOWN * WALK_SUPPORT_PROBE_DEPTH
	var q := PhysicsRayQueryParameters3D.create(probe_from, probe_end)
	q.collision_mask = collision_mask
	q.exclude = [get_rid()]
	var res: Dictionary = space.intersect_ray(q)
	if res.is_empty():
		return false
	if not res.has("normal"):
		return false
	var n: Vector3 = res["normal"]
	return n.dot(Vector3.UP) > WALK_SUPPORT_PROBE_MIN_UP_DOT


## Airborne walk ticks only. Do **not** add gravity just because the nav goal is below the
## feet — that stays true for the whole cross of a raised pad (e.g. TerracePlatformA / B)
## toward a floor click and poisons horizontal motion / slide resolution.
## Do apply gravity when [code]is_on_floor()[/code] is still true but there is no walkable surface
## within [member WALK_SUPPORT_PROBE_DEPTH] under the feet (ledge / void while moving).
func _apply_walk_air_gravity(delta: float) -> void:
	var apply_gravity: bool = not is_on_floor()
	if (
		not apply_gravity
		and _has_walk_goal
		and is_on_floor()
		and get_floor_normal().dot(Vector3.UP) > WALK_LEDGE_PROBE_MAX_FLOOR_UP_DOT
		and not _walk_has_close_floor_probe_below()
	):
		apply_gravity = true
	if apply_gravity:
		velocity += get_gravity() * delta


func _walk_floor_snap_length(feet_y: float, want_goal_h: Vector3) -> float:
	if _step_assist_active:
		return WALK_STEP_ASSIST_SNAP
	if _has_walk_goal:
		if want_goal_h.length_squared() > 1e-10:
			var want: Vector3 = want_goal_h.normalized()
			# Climb: cap snap only for a **meaningful** rise (not shallow tread-to-tread), or we
			# fight the approach stairs with snap ↔ assist oscillation.
			if _auth_walk_goal.y > feet_y + 0.12 and _step_assist_wallish_blocks(want):
				return WALK_STEP_ASSIST_SNAP
		if (
			_auth_walk_goal.y < feet_y - DESCEND_GOAL_Y_MARGIN
			and feet_y > _auth_walk_goal.y + 0.08
		):
			return minf(FLOOR_SNAP_MOVING, DESCEND_LIP_SNAP_CAP)
	return FLOOR_SNAP_MOVING


## Descend only: relax `floor_block_on_wall` when pressed against a vertical face so Jolt can
## slide off terrace lips. Never when the goal is above the feet (climb) — avoids platform-wide
## toggling that broke horizontal motion.
func _apply_floor_block_for_descend_at_wall(feet_y: float) -> void:
	floor_block_on_wall = true
	if not _has_walk_goal:
		return
	if _auth_walk_goal.y >= feet_y - DESCEND_GOAL_Y_MARGIN:
		return
	if is_on_wall():
		floor_block_on_wall = false
		return
	# Terrace lip: floor normal tilts off UP when straddling an internal edge (teal pad, etc.).
	if is_on_floor() and get_floor_normal().dot(Vector3.UP) < 0.992:
		floor_block_on_wall = false
		return
	for i: int in range(get_slide_collision_count()):
		var n: Vector3 = get_slide_collision(i).get_normal()
		if absf(n.y) < 0.58:
			floor_block_on_wall = false
			return


## When the authoritative goal shares XZ with the capsule (e.g. terrace above), horizontal
## `full_to_goal` is zero and steering must follow the baked path toward a ramp/step, not +X.
func _set_horizontal_velocity_from_nav_path_or_goal(fallback_goal_xz: Vector3) -> void:
	# Do **not** scan `get_current_navigation_path()` for the first point with
	# `dh.length_squared() > 0.0025` (5 cm). Jolt nudges the capsule across that radius every
	# physics tick → the chosen waypoint alternates → velocity sign flips 180° while
	# `needs_vertical_routing && _walk_nav_column_steering` (NEON-16 debug trace).
	if _nav_agent.is_navigation_finished():
		_set_horizontal_velocity_toward(_auth_walk_goal, fallback_goal_xz)
		return
	var next_pos: Vector3 = _nav_agent.get_next_path_position()
	var dh: Vector3 = Vector3(
		next_pos.x - global_position.x, 0.0, next_pos.z - global_position.z
	)
	if dh.length_squared() < 1e-8:
		_set_horizontal_velocity_toward(_auth_walk_goal, fallback_goal_xz)
	else:
		_set_horizontal_velocity_toward(next_pos, fallback_goal_xz)


static func capsule_feet_y(body_origin_y: float, capsule_half_height: float) -> float:
	return body_origin_y - capsule_half_height


static func vertical_arrival_error(
	goal_y: float, body_origin_y: float, capsule_half_height: float
) -> float:
	return absf(goal_y - capsule_feet_y(body_origin_y, capsule_half_height))


func _physics_idle_tick(delta: float) -> void:
	if is_on_floor():
		velocity = Vector3.ZERO
		floor_snap_length = FLOOR_SNAP_IDLE
	else:
		# Ledge / post-arrival hover: without gravity, vy stays 0 and FLOOR_SNAP_IDLE (0.11 m)
		# cannot reach the lower floor — the capsule idles in mid-air until a new walk goal runs.
		velocity.x = 0.0
		velocity.z = 0.0
		velocity += get_gravity() * delta
		floor_snap_length = FLOOR_SNAP_MOVING
	move_and_slide()


static func idle_slide_contacts_are_ridged(slide_normals: Array[Vector3]) -> bool:
	var upish := 0
	var wallish := 0
	for n: Vector3 in slide_normals:
		var ny: float = n.y
		if ny > 0.65:
			upish += 1
		# Steeper than ~70° from horizontal — shallow seam faces (ny≈0.4) are not “lip” walls.
		elif ny < 0.35:
			wallish += 1
	return upish >= 1 and wallish >= 1


static func idle_support_is_stable(
	on_floor: bool,
	floor_normal: Vector3,
	slide_normals: Array[Vector3],
	loose_ticks: int,
	min_flat_up_dot: float = STABLE_IDLE_FLOOR_MIN_UP_DOT,
) -> bool:
	if not on_floor:
		return false
	if floor_normal.dot(Vector3.UP) < min_flat_up_dot:
		return false
	# Post-stop **ridged** slides (tread + riser) used to force unstable idle for the entire
	# `loose_ticks` window even when the **floor** is level — e.g. idle on a flat approach tread
	# hugging a vertical face stayed in corrective `move_and_slide` ~0.8 s (HUD X/Y/Z noise).
	# Only demand rim settle when the reported floor is already shallow (lip straddle), not mere
	# proximity to a riser on an otherwise flat tread.
	if (
		loose_ticks > 0
		and idle_slide_contacts_are_ridged(slide_normals)
		and floor_normal.dot(Vector3.UP) < IDLE_RIM_MIN_FLOOR_UP_DOT
	):
		return false
	return true


func _current_slide_normals() -> Array[Vector3]:
	var normals: Array[Vector3] = []
	for i: int in get_slide_collision_count():
		normals.append(get_slide_collision(i).get_normal())
	return normals


func _stable_idle_support() -> bool:
	var min_dot: float = (
		STABLE_IDLE_FLOOR_HOLD_MIN_UP_DOT
		if _idle_stable_latched
		else STABLE_IDLE_FLOOR_MIN_UP_DOT
	)
	return idle_support_is_stable(
		is_on_floor(), get_floor_normal(), _current_slide_normals(), _floor_angle_loose_ticks, min_dot
	)


func _hold_idle_anchor() -> void:
	var pos := global_position
	if not _idle_anchor_active:
		_idle_anchor_xz = Vector2(pos.x, pos.z)
		_idle_anchor_y = pos.y
		_idle_anchor_active = true
		return
	global_position = Vector3(_idle_anchor_xz.x, _idle_anchor_y, _idle_anchor_xz.y)


func _debug_trace_idle_state(tag: String) -> void:
	if not debug_idle_trace or _has_walk_goal:
		_debug_idle_heartbeat = 0
		_debug_last_idle_xz = Vector2.INF
		return
	var pos_xz := Vector2(global_position.x, global_position.z)
	var should_log: bool = false
	if _debug_last_idle_xz == Vector2.INF:
		should_log = true
	elif pos_xz.distance_to(_debug_last_idle_xz) > DEBUG_IDLE_TRACE_DELTA_EPS:
		should_log = true
	elif _debug_idle_heartbeat >= DEBUG_IDLE_TRACE_HEARTBEAT_FRAMES:
		should_log = true
	if should_log:
		push_warning(
			(
				(
					"NEON-16 idle trace [%s] pos=%s vel=%s on_floor=%s loose=%d "
					+ "stable=%s anchor=%s anchor_xz=%s floor=%s slides=%s"
				)
				% [
					tag,
					global_position,
					velocity,
					is_on_floor(),
					_floor_angle_loose_ticks,
					_stable_idle_support(),
					_idle_anchor_active,
					_idle_anchor_xz,
					get_floor_normal(),
					_current_slide_normals(),
				]
			)
		)
		_debug_last_idle_xz = pos_xz
		_debug_idle_heartbeat = 0
	else:
		_debug_idle_heartbeat += 1


func _debug_trace_transform(tag: String) -> void:
	if not debug_idle_trace:
		return
	var pos_xz := Vector2(global_position.x, global_position.z)
	if (
		_debug_last_transform_xz != Vector2.INF
		and pos_xz.distance_to(_debug_last_transform_xz) < DEBUG_TRANSFORM_TRACE_DELTA_EPS
		and tag != "physics"
	):
		return
	var extra: String = ""
	if _has_walk_goal:
		var fy: float = capsule_feet_y(
			global_position.y, CAPSULE_HALF_HEIGHT + PLAYER_CAPSULE_RADIUS
		)
		var vsep: float = absf(_auth_walk_goal.y - fy)
		extra = (
			" feet_y=%s vert_sep=%.4f vlat=%s ncol=%s"
			% [fy, vsep, _walk_vert_route_latched, _walk_nav_column_steering]
		)
	print(
		(
			(
				"NEON-16 transform trace [%s] frame=%d pos=%s vel=%s has_goal=%s "
				+ "on_floor=%s loose=%d stable=%s anchor=%s anchor_xz=%s%s"
			)
			% [
				tag,
				_debug_trace_frame,
				global_position,
				velocity,
				_has_walk_goal,
				is_on_floor(),
				_floor_angle_loose_ticks,
				_stable_idle_support(),
				_idle_anchor_active,
				_idle_anchor_xz,
				extra,
			]
		)
	)
	_debug_last_transform_xz = pos_xz


func _notification(what: int) -> void:
	if what == NOTIFICATION_TRANSFORM_CHANGED:
		_debug_trace_transform("notify")


func _idle_ridged_floor_contacts() -> bool:
	return idle_slide_contacts_are_ridged(_current_slide_normals())


func _maybe_idle_rim_settle_nudge() -> bool:
	if get_slide_collision_count() < 1:
		return false
	var shallow_floor: bool = (
		is_on_floor() and get_floor_normal().dot(Vector3.UP) < IDLE_RIM_MIN_FLOOR_UP_DOT
	)
	if not shallow_floor and not _idle_ridged_floor_contacts():
		return false
	var h := Vector3.ZERO
	if shallow_floor:
		h = Vector3(get_floor_normal().x, 0.0, get_floor_normal().z)
	if h.length_squared() < 1e-12:
		for i: int in get_slide_collision_count():
			var n: Vector3 = get_slide_collision(i).get_normal()
			if n.y < 0.5:
				var nh: Vector3 = Vector3(n.x, 0.0, n.z)
				if nh.length_squared() > h.length_squared():
					h = nh
	if h.length_squared() < 1e-12:
		return false
	var step: Vector3 = -h.normalized() * IDLE_RIM_SETTLE_STEP
	if test_move(global_transform, step, null, safe_margin):
		return false
	global_position += step
	return true


func _maybe_idle_bump_proximity_escape() -> bool:
	var feet_y: float = global_position.y - CAPSULE_HALF_HEIGHT
	for node: Node in get_tree().get_nodes_in_group(
		BUMP_COLLISION_CONSTS_SCRIPT.RANDOM_FLOOR_BUMP_MESH_GROUP
	):
		if not node is MeshInstance3D:
			continue
		var mi := node as MeshInstance3D
		var mesh: Mesh = mi.mesh
		if not mesh is CylinderMesh:
			continue
		var cyl := mesh as CylinderMesh
		var c: Vector3 = mi.global_position
		var r_mesh: float = cyl.top_radius
		var h: float = cyl.height
		var col_r: float = minf(
			r_mesh + BUMP_COLLISION_CONSTS_SCRIPT.COLLISION_RADIUS_EXTRA,
			BUMP_COLLISION_CONSTS_SCRIPT.COLLISION_RADIUS_MAX
		)
		var dx: float = global_position.x - c.x
		var dz: float = global_position.z - c.z
		var d: float = sqrt(dx * dx + dz * dz)
		if d < 1e-5:
			continue
		var bottom_y: float = c.y - h * 0.5
		var top_y: float = c.y + h * 0.5
		if feet_y < bottom_y - 0.22 or feet_y > top_y + 0.4:
			continue
		var radial: Vector3 = Vector3(dx / d, 0.0, dz / d)
		var away: Vector3 = radial * IDLE_BUMP_ESCAPE_STEP
		var wall_band_outer: float = col_r + PLAYER_CAPSULE_RADIUS + 0.22
		var should_escape: bool = d > r_mesh * 0.9 and d < col_r + 0.32
		# On / above the disc, hugging the **visual** rim — step onto open slab.
		should_escape = (
			should_escape
			or (
				feet_y >= bottom_y - 0.06
				and feet_y <= top_y + 0.1
				and d >= r_mesh * 0.86
				and d <= r_mesh + 0.14
			)
		)
		# Beside vertical cylinder: axis distance may exceed **`col_r`** while capsule still touches wall.
		should_escape = (
			should_escape
			or (
				feet_y <= top_y + 0.14
				and d > r_mesh * 0.82
				and d < wall_band_outer
				and (is_on_wall() or _idle_ridged_floor_contacts())
			)
		)
		if not should_escape:
			continue
		if test_move(global_transform, away, null, safe_margin):
			return false
		global_position += away
		return true
	return false


func _apply_idle_manual_correction() -> bool:
	# Prefer explicit bump-rim escape over the generic shallow-floor settle so spawned
	# cylinder edges resolve radially off the lip instead of orbiting around it.
	if _maybe_idle_bump_proximity_escape():
		return true
	return _maybe_idle_rim_settle_nudge()


func _snap_capsule_upright() -> void:
	# TODO(NS-24 follow-on): With facing yaw, clear pitch/roll only; keep Y rotation.
	# Full **`Basis.IDENTITY`** would erase look direction.
	if global_transform.basis.orthonormalized().is_equal_approx(Basis.IDENTITY):
		return
	var p: Vector3 = global_position
	global_transform = Transform3D(Basis.IDENTITY, p)


func _physics_process(delta: float) -> void:
	_debug_trace_frame += 1
	# Do not tie wide floor angle to `_floor_angle_loose_ticks` alone: after a walk on **flat**
	# ground that still widened angle for ~0.8 s, `move_and_slide` + idle snap caused visible XZ
	# jitter. Use moving max angle only while walking or when idle support is shallow / ridged.
	var use_loose_floor_angle: bool = _has_walk_goal
	if not _has_walk_goal:
		var floor_up_dot: float = get_floor_normal().dot(Vector3.UP)
		var shallow_idle_floor: bool = is_on_floor() and floor_up_dot < IDLE_RIM_MIN_FLOOR_UP_DOT
		if shallow_idle_floor or _idle_ridged_floor_contacts():
			use_loose_floor_angle = true
	floor_max_angle = deg_to_rad(
		FLOOR_MAX_ANGLE_MOVING_DEG if use_loose_floor_angle else FLOOR_MAX_ANGLE_IDLE_DEG
	)
	if not _has_walk_goal:
		floor_block_on_wall = true
		var raw_stable: bool = _stable_idle_support()
		if raw_stable:
			_idle_stable_unlatch_streak = 0
			if not _idle_stable_latched:
				_idle_stable_enter_streak += 1
				if _idle_stable_enter_streak >= STABLE_IDLE_ENTER_STREAK_FRAMES:
					_idle_stable_latched = true
			else:
				_idle_stable_enter_streak = 0
		elif _idle_stable_latched:
			_idle_stable_unlatch_streak += 1
			if _idle_stable_unlatch_streak >= STABLE_IDLE_UNLATCH_TICKS:
				_idle_stable_latched = false
				_idle_stable_unlatch_streak = 0
				_idle_stable_enter_streak = 0
				_idle_anchor_active = false
		else:
			_idle_stable_enter_streak = 0
		if _idle_stable_latched:
			_idle_manual_correction_ticks = 0
			velocity = Vector3.ZERO
			floor_snap_length = FLOOR_SNAP_IDLE
			_hold_idle_anchor()
			_debug_trace_idle_state("stable")
			_debug_trace_transform("physics")
			_snap_capsule_upright()
			return
		if _idle_manual_correction_ticks >= IDLE_MANUAL_CORRECTION_MAX_TICKS:
			if is_on_floor():
				velocity = Vector3.ZERO
				floor_snap_length = FLOOR_SNAP_IDLE
				if _floor_angle_loose_ticks > 0:
					_floor_angle_loose_ticks -= 1
				_hold_idle_anchor()
				_debug_trace_idle_state("budgeted")
				_debug_trace_transform("physics")
				_snap_capsule_upright()
				return
			# Airborne: do not freeze XZ without a physics step — same mid-air hang as idle tick.
			_idle_anchor_active = false
			_physics_idle_tick(delta)
			if _floor_angle_loose_ticks > 0:
				_floor_angle_loose_ticks -= 1
			_debug_trace_idle_state("budgeted")
			_debug_trace_transform("physics")
			_snap_capsule_upright()
			return
		_idle_anchor_active = false
		_physics_idle_tick(delta)
		if _apply_idle_manual_correction():
			_idle_manual_correction_ticks += 1
		else:
			_idle_manual_correction_ticks = 0
		if _floor_angle_loose_ticks > 0:
			_floor_angle_loose_ticks -= 1
		_debug_trace_idle_state("corrective")
		_debug_trace_transform("physics")
		_snap_capsule_upright()
		return

	var full_to_goal: Vector3 = _auth_walk_goal - global_position
	var horiz_dist: float = Vector2(full_to_goal.x, full_to_goal.z).length()
	var want_goal_h: Vector3 = Vector3(full_to_goal.x, 0.0, full_to_goal.z)
	# Use actual capsule bottom (CAPSULE_HALF_HEIGHT + PLAYER_CAPSULE_RADIUS = 0.9) so that a
	# step-surface goal (e.g. Y=0.3) is never considered "arrived" while the player is still at
	# floor height. Using only CAPSULE_HALF_HEIGHT (0.5) gives code-feet at Y=0.4, which is too
	# close to step surfaces and causes premature arrival when Jolt nudges the body down to ~0.8
	# while the capsule hemisphere contacts the step edge.
	var vert_err: float = vertical_arrival_error(
		_auth_walk_goal.y, global_position.y, CAPSULE_HALF_HEIGHT + PLAYER_CAPSULE_RADIUS
	)
	if horiz_dist <= ARRIVE_EPS and vert_err <= VERT_ARRIVE_EPS:
		velocity = Vector3.ZERO
		_has_walk_goal = false
		floor_block_on_wall = true
		_floor_angle_loose_ticks = FLOOR_ANGLE_LOOSE_TICKS_AFTER_STOP
		_step_assist_active = false
		_idle_anchor_active = false
		_idle_manual_correction_ticks = 0
		_idle_stable_latched = false
		_idle_stable_unlatch_streak = 0
		_idle_stable_enter_streak = 0
		_walk_nav_column_steering = false
		_walk_vert_route_latched = false
		_nav_agent.set_target_position(global_position)
		_physics_idle_tick(delta)
		if _stable_idle_support():
			_idle_stable_latched = true
			_idle_stable_unlatch_streak = 0
			_idle_stable_enter_streak = 0
			_idle_manual_correction_ticks = 0
			velocity = Vector3.ZERO
			floor_snap_length = FLOOR_SNAP_IDLE
			_hold_idle_anchor()
			_debug_trace_idle_state("arrival_stable")
			_debug_trace_transform("physics")
			_snap_capsule_upright()
			return
		if _apply_idle_manual_correction():
			_idle_manual_correction_ticks += 1
		_debug_trace_transform("physics")
		_snap_capsule_upright()
		return

	_idle_manual_correction_ticks = 0

	var feet_y: float = capsule_feet_y(
		global_position.y, CAPSULE_HALF_HEIGHT + PLAYER_CAPSULE_RADIUS
	)
	_apply_floor_block_for_descend_at_wall(feet_y)

	# Horizontal motion toward the **authoritative** click target (XZ) by default. A **global**
	# `get_next_path_position()` steer regressed under Jolt / 120 Hz (“stuck” / slow advance).
	# Use the baked path only when vertical routing is latched **and** column hysteresis says so;
	# then **`_set_horizontal_velocity_from_nav_path_or_goal`** uses **`get_next_path_position()`**
	# (not a 5 cm path scan — that ping-ponged waypoints every tick).
	var vert_sep: float = absf(_auth_walk_goal.y - feet_y)
	if not _walk_vert_route_latched:
		if vert_sep > WALK_VERT_ROUTE_LATCH_ON_SEP:
			_walk_vert_route_latched = true
	else:
		if vert_sep < WALK_VERT_ROUTE_LATCH_OFF_SEP:
			_walk_vert_route_latched = false
	var needs_vertical_routing: bool = _walk_vert_route_latched
	if not needs_vertical_routing:
		_walk_nav_column_steering = false
	elif horiz_dist <= NAV_COLUMN_STEER_ENTER_DIST:
		_walk_nav_column_steering = true
	elif horiz_dist >= NAV_COLUMN_STEER_EXIT_DIST:
		_walk_nav_column_steering = false
	if needs_vertical_routing and _walk_nav_column_steering:
		_set_horizontal_velocity_from_nav_path_or_goal(want_goal_h)
	else:
		_set_horizontal_velocity_toward(_auth_walk_goal, want_goal_h)

	_apply_walk_air_gravity(delta)
	floor_snap_length = _walk_floor_snap_length(feet_y, want_goal_h)
	move_and_slide()
	_after_walk_move_and_slide()
	_clear_step_assist_after_walk_move()
	_debug_trace_transform("physics")
	_snap_capsule_upright()