game: improve enemy-manager

scenes/managers/enemy_manager.gd

@@ -4,6 +4,7 @@ extends Node2D
 @export var max_enemies: int
 @export var spawn_rate: float
 @export var target: CollisionObject2D
+@export var camera: Camera2D
 
 @onready var timer: Timer = $Timer
 
@@ -22,11 +23,61 @@ func _on_timer_timeout() -> void:
 	GlobalConst.sig_debug_stats_set.emit("enemy_count", "%s" % len(enemies))
 	if len(enemies) < max_enemies:
 		var new_enemy = ENEMY_RAT.instantiate()
-		new_enemy.position = target.position + Vector2(50, 50)
+		new_enemy.position = _get_spawn_pos()
 		new_enemy.target = target
 		add_child(new_enemy)
 
 
+func _get_spawn_pos() -> Vector2:
+	var rect = _get_camera_rect()
+	var side = randi() % 4
+	var margin = 50
+	var pos: Vector2
+
+	match side:
+		0:  # Top
+			pos = Vector2(
+				randf_range(rect.position.x, rect.position.x + rect.size.x),
+				rect.position.y - margin
+			)
+		1:  # Bottom
+			pos = Vector2(
+				randf_range(rect.position.x, rect.position.x + rect.size.x),
+				rect.position.y + rect.size.y + margin
+			)
+		2:  # Left
+			pos = Vector2(
+				rect.position.x - margin,
+				randf_range(rect.position.y, rect.position.y + rect.size.y)
+			)
+		3:  # Right
+			pos = Vector2(
+				rect.position.x + rect.size.x + margin,
+				randf_range(rect.position.y, rect.position.y + rect.size.y)
+			)
+	if !_is_pos_valid(pos):
+		pos = _get_spawn_pos()
+	return pos
+
+
+func _is_pos_valid(pos: Vector2) -> bool:
+	var space = get_world_2d().direct_space_state
+	var parameters = PhysicsPointQueryParameters2D.new()
+	parameters.collide_with_areas = false
+	parameters.collide_with_bodies = true
+	parameters.collision_mask = 1
+	parameters.position = pos
+	var result = space.intersect_point(parameters, 1)
+	return result.size() == 0
+
+
+func _get_camera_rect() -> Rect2:
+	var viewport_size = camera.get_viewport_rect().size
+	var half_size = viewport_size * 0.5
+	var top_left = camera.global_position - half_size
+	return Rect2(top_left, viewport_size)
+
+
 func _on_stop_spawning(val: bool):
 	if val:
 		timer.stop()