extends CharacterBody3D

## NS-23: Nav waypoints + stored server goal for arrival.
## NS-19: bump collision is one convex frustum (plateau + slopes); no autostep.

const MOVE_SPEED: float = 5.0
const ARRIVE_EPS: float = 0.35
const VERT_ARRIVE_EPS: float = 0.16
const MAX_CLIMB_SPEED: float = 2.6
const MAX_DESCENT_SPEED: float = 2.2
const DIRECT_APPROACH_RADIUS: float = 0.85

var _has_walk_goal: bool = false
var _auth_walk_goal: Vector3 = Vector3.ZERO

@onready var _nav_agent: NavigationAgent3D = $NavigationAgent3D


func _ready() -> void:
	_nav_agent.set_target_position(global_position)


func set_authoritative_nav_goal(world_pos: Vector3) -> void:
	_auth_walk_goal = world_pos
	_has_walk_goal = true
	_nav_agent.set_target_position(world_pos)


func clear_nav_goal() -> void:
	velocity = Vector3.ZERO
	_has_walk_goal = false
	_nav_agent.set_target_position(global_position)


func snap_to_server(world_pos: Vector3) -> void:
	global_position = world_pos
	velocity = Vector3.ZERO
	_has_walk_goal = false
	_nav_agent.set_target_position(world_pos)


func _steer_toward_world_point(point: Vector3) -> void:
	var pos := global_position
	var delta_h: Vector3 = Vector3(point.x - pos.x, 0.0, point.z - pos.z)
	# Full 3D toward a waypoint that is mostly *below* (same xz, on the slope) while standing on
	# the plateau yields almost no horizontal speed, so you never reach the rim. Nav in xz + floor
	# slide handles ramps and departure from bump tops.
	if delta_h.length_squared() > 1e-8:
		velocity = delta_h.normalized() * MOVE_SPEED
		return
	var dy: float = point.y - pos.y
	if dy > 0.08:
		var delta: Vector3 = point - pos
		if delta.length_squared() < 1e-8:
			velocity = Vector3.ZERO
			return
		var desired: Vector3 = delta.normalized() * MOVE_SPEED
		desired.y = clampf(desired.y, -MAX_DESCENT_SPEED, MAX_CLIMB_SPEED)
		velocity = desired
	else:
		velocity = Vector3.ZERO


func _physics_process(_delta: float) -> void:
	if not _has_walk_goal:
		velocity = Vector3.ZERO
		move_and_slide()
		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 vert_err: float = absf(full_to_goal.y)
	if horiz_dist <= ARRIVE_EPS and vert_err <= VERT_ARRIVE_EPS:
		velocity = Vector3.ZERO
		_has_walk_goal = false
		_nav_agent.set_target_position(global_position)
		move_and_slide()
		return

	var nav_map: RID = _nav_agent.get_navigation_map()
	if NavigationServer3D.map_get_iteration_id(nav_map) == 0:
		_steer_toward_world_point(_auth_walk_goal)
		move_and_slide()
		return

	if horiz_dist <= DIRECT_APPROACH_RADIUS:
		_steer_toward_world_point(_auth_walk_goal)
	else:
		var next_path_position: Vector3 = _nav_agent.get_next_path_position()
		var to_next_h: Vector3 = Vector3(
			next_path_position.x - global_position.x, 0.0, next_path_position.z - global_position.z
		)
		if to_next_h.length_squared() > 0.0025:
			_steer_toward_world_point(next_path_position)
		else:
			_steer_toward_world_point(_auth_walk_goal)

	move_and_slide()