extends Node2D

const WORLD_SIZE := Vector2(5200.0, 3600.0)
const BACKGROUND_PATHS := [
	"res://assets/background/space/deep_space.png",
	"res://assets/background/space/teal_veil.png",
	"res://assets/background/space/crimson_rift.png",
	"res://assets/background/space/amber_expanse.png",
	"res://assets/background/space/violet_spiral.png",
	"res://assets/background/space/frozen_void.png",
]
const DUST_TEXTURE := preload("res://assets/background/space/nebula_dust.png")
const STAR_TILE := Vector2(2048.0, 1536.0)

var _far_sprite: Sprite2D

func _ready() -> void:
	# Let the engine synchronize parallax with the interpolated camera transform.
	# No camera sampling or per-frame rebuilding of draw commands is needed.
	texture_filter = CanvasItem.TEXTURE_FILTER_LINEAR_WITH_MIPMAPS
	var distant := _make_layer("DistantGalaxies", 0.04)
	_far_sprite = Sprite2D.new()
	# Only the artwork changes between systems; parallax layers stay identical.
	var background_index := posmod(GameState.system_level - 1, BACKGROUND_PATHS.size())
	_far_sprite.texture = load(BACKGROUND_PATHS[background_index]) as Texture2D
	_far_sprite.modulate = Color(0.8, 0.85, 0.95)
	distant.add_child(_far_sprite)
	_resize_background()
	get_viewport().size_changed.connect(_resize_background)

	var dust := _make_layer("NebulaDust", 0.14)
	dust.repeat_size = Vector2(DUST_TEXTURE.get_size())
	dust.repeat_times = 3
	var dust_sprite := Sprite2D.new()
	dust_sprite.texture = DUST_TEXTURE
	dust_sprite.centered = false
	dust_sprite.modulate = Color(0.65, 0.75, 0.9, 0.22)
	dust.add_child(dust_sprite)
	_make_stars("DistantStars", 0.18, 210, 0)
	_make_stars("NearStars", 0.42, 90, 1)

func _make_layer(layer_name: String, speed: float) -> Parallax2D:
	var layer := Parallax2D.new()
	layer.name = layer_name
	layer.scroll_scale = Vector2.ONE * speed
	add_child(layer)
	return layer

func _resize_background() -> void:
	var view_size := get_viewport_rect().size
	var camera := get_viewport().get_camera_2d()
	if is_instance_valid(camera):
		view_size /= camera.zoom
	# Native resolution at 720p; retain aspect ratio and cover camera travel.
	_far_sprite.position = view_size * 0.5
	var required := view_size + WORLD_SIZE * 0.04 + Vector2(32.0, 32.0)
	var ratio := required / _far_sprite.texture.get_size()
	_far_sprite.scale = Vector2.ONE * maxf(1.0, maxf(ratio.x, ratio.y))

func _make_stars(layer_name: String, speed: float, count: int, seed_offset: int) -> void:
	var rng := RandomNumberGenerator.new()
	rng.seed = GameState.system_seed + seed_offset
	var svg := '<svg xmlns="http://www.w3.org/2000/svg" width="2048" height="1536">'
	for index in count:
		var point := Vector2(rng.randf_range(4.0, STAR_TILE.x - 4.0), rng.randf_range(4.0, STAR_TILE.y - 4.0))
		svg += '<circle cx="%.3f" cy="%.3f" r="%.3f" fill="#b8d4ff" opacity="%.3f"/>' % [point.x, point.y, rng.randf_range(0.5, 1.4), rng.randf_range(0.18, 0.65)]
	svg += '</svg>'
	var image := Image.new()
	if image.load_svg_from_string(svg) != OK:
		return
	image.generate_mipmaps()
	var layer := _make_layer(layer_name, speed)
	layer.repeat_size = STAR_TILE
	layer.repeat_times = 3
	var sprite := Sprite2D.new()
	sprite.texture = ImageTexture.create_from_image(image)
	sprite.centered = false
	layer.add_child(sprite)

func _draw() -> void:
	# The map boundary remains in world space.
	draw_rect(Rect2(-WORLD_SIZE * 0.5, WORLD_SIZE), Color(0.12, 0.52, 0.68, 0.48), false, 3.0)