# Instant scene change
get_tree().change_scene_to_file("res://levels/level_2.tscn")

# Or with packed scene
var next_scene := load("res://levels/level_2.tscn")
get_tree().change_scene_to_packed(next_scene)

# scene_transitioner.gd (AutoLoad)
extends CanvasLayer

signal transition_finished

func change_scene(scene_path: String) -> void:
    # Fade out
    $AnimationPlayer.play("fade_out")
    await $AnimationPlayer.animation_finished
    
    # Change scene
    get_tree().change_scene_to_file(scene_path)
    
    # Fade in
    $AnimationPlayer.play("fade_in")
    await $AnimationPlayer.animation_finished
    
    transition_finished.emit()

# Usage:
SceneTransitioner.change_scene("res://levels/level_2.tscn")
await SceneTransitioner.transition_finished

extends Node

var loading_status: int = 0
var progress := []

func load_scene_async(path: String) -> void:
    ResourceLoader.load_threaded_request(path)
    
    while true:
        loading_status = ResourceLoader.load_threaded_get_status(
            path,
            progress
        )
        
        if loading_status == ResourceLoader.THREAD_LOAD_LOADED:
            var scene := ResourceLoader.load_threaded_get(path)
            get_tree().change_scene_to_packed(scene)
            break
        
        # Update loading bar
        print("Loading: ", progress[0] * 100, "%")
        await get_tree().process_frame

# loading_screen.gd
extends Control

@onready var progress_bar: ProgressBar = $ProgressBar

func load_scene(path: String) -> void:
    show()
    ResourceLoader.load_threaded_request(path)
    
    var progress := []
    var status: int
    
    while true:
        status = ResourceLoader.load_threaded_get_status(path, progress)
        
        if status == ResourceLoader.THREAD_LOAD_LOADED:
            var scene := ResourceLoader.load_threaded_get(path)
            get_tree().change_scene_to_packed(scene)
            break
        elif status == ResourceLoader.THREAD_LOAD_FAILED:
            push_error("Failed to load scene: " + path)
            break
        
        progress_bar.value = progress[0] * 100
        await get_tree().process_frame
    
    hide()

# Spawn enemy at runtime
const ENEMY_SCENE := preload("res://enemies/goblin.tscn")

func spawn_enemy(position: Vector2) -> void:
    var enemy := ENEMY_SCENE.instantiate()
    enemy.global_position = position
    add_child(enemy)

# Keep track of spawned enemies
var active_enemies: Array[Node] = []

func spawn_enemy(pos: Vector2) -> void:
    var enemy := ENEMY_SCENE.instantiate()
    enemy.global_position = pos
    add_child(enemy)
    active_enemies.append(enemy)
    
    # Clean up when enemy dies
    enemy.tree_exited.connect(
        func(): active_enemies.erase(enemy)
    )

func clear_all_enemies() -> void:
    for enemy in active_enemies:
        enemy.queue_free()
    active_enemies.clear()

# Load UI as sub-scene
@onready var ui := preload("res://ui/game_ui.tscn").instantiate()

func _ready() -> void:
    add_child(ui)

# Keep scene loaded when changing scenes
var persistent_scene: Node

func make_persistent(scene: Node) -> void:
    persistent_scene = scene
    scene.get_parent().remove_child(scene)
    get_tree().root.add_child(scene)

func restore_persistent() -> void:
    if persistent_scene:
        get_tree().root.remove_child(persistent_scene)
        add_child(persistent_scene)

# Restart level
get_tree().reload_current_scene()

# Cache frequently used scenes
var scene_cache: Dictionary = {}

func get_cached_scene(path: String) -> PackedScene:
    if not scene_cache.has(path):
        scene_cache[path] = load(path)
    return scene_cache[path]

# Usage:
var enemy := get_cached_scene("res://enemies/goblin.tscn").instantiate()

# Centralized scene management
# All transitions go through one system
# Consistent fade effects

# ✅ Good - preload at compile time
const BULLET := preload("res://projectiles/bullet.tscn")

# ❌ Bad - load at runtime
var bullet := load("res://projectiles/bullet.tscn")

func change_level() -> void:
    # Clear timers, tweens, etc.
    for timer in get_tree().get_nodes_in_group("timers"):
        timer.stop()
    
    SceneTransitioner.change_scene("res://levels/next.tscn")

func load_scene_safe(path: String) -> bool:
    if not ResourceLoader.exists(path):
        push_error("Scene not found: " + path)
        return false
    
    get_tree().change_scene_to_file(path)
    return true