extends SceneTree

# Headless test: run with
#   godot --headless -s res://tests/test_surface_background_shared.gd
# The landed surface and the setup editor drew DIFFERENT backgrounds for the
# same planet. Each scene carried its own hand-written ShaderMaterial (the
# game's baked-and-tiled lunar shader, the editor's per-pixel procedural one)
# and only the game's side ever swapped in a profile's own shader - so a gas
# giant authored in the editor showed recoloured craters while the game showed
# cloud bands. An editor that lies about what the player will see is worse
# than no preview.
#
# Both scenes now instance ONE SurfaceBackground.tscn and configure it through
# ONE method. This test guards that, since nothing about the code stops
# someone re-adding a local material to one scene and pulling them apart
# again.
#
# Covers:
#   A. both scenes get their backdrop from the same PackedScene file
#   B. neither overrides the shared material - the two start out identical
#   C. every surface profile names its own background_shader; a null one
#      would mean "whatever this scene already had", which is the ambiguity
#      that caused the drift
#   D. applying each profile through the shared entry point produces the same
#      shader AND the same colours on both scenes, for every profile

const BACKGROUND_SCENE_PATH := "res://surface/SurfaceBackground.tscn"
const HOST_SCENES := {
	"PlanetSurface.tscn": "res://surface/PlanetSurface.tscn",
	"PlanetSetupEditor.tscn": "res://surface/PlanetSetupEditor.tscn",
}
const COLOR_PARAMETERS := ["base_color", "crater_color", "highlight_color"]

var backgrounds: Dictionary = {}
var hosts: Array = []


func _initialize() -> void:
	var surface_profiles: Script = load("res://surface/PlanetSurfaceProfiles.gd")

	# --- A/B: same source scene, same untouched material ---------------------
	for scene_name in HOST_SCENES:
		var host: Node = load(HOST_SCENES[scene_name]).instantiate()
		hosts.append(host)
		var layer: Node = host.get_node_or_null("BackgroundLayer")
		if layer == null:
			_fail("%s has no BackgroundLayer" % scene_name)
			return
		if layer.scene_file_path != BACKGROUND_SCENE_PATH:
			_fail("%s builds its own background (%s) instead of instancing %s" \
				% [scene_name, layer.scene_file_path, BACKGROUND_SCENE_PATH])
			return
		var background: Node = layer.get_node_or_null("Background")
		if background == null:
			_fail("%s's background layer has no Background node" % scene_name)
			return
		if not background.has_method("apply_profile"):
			_fail("%s's background has no apply_profile() - the shared entry point is gone" % scene_name)
			return
		backgrounds[scene_name] = background
	print("both scenes instance %s and expose apply_profile()" % BACKGROUND_SCENE_PATH)

	var names: Array = backgrounds.keys()
	var reference: ShaderMaterial = backgrounds[names[0]].material
	for i in range(1, names.size()):
		var other: ShaderMaterial = backgrounds[names[i]].material
		# Same configuration, SEPARATE objects. Sub-resources in a PackedScene
		# are shared between instances by default, which would make the whole
		# comparison below vacuous - it would be reading one material twice -
		# and would mean two live surfaces repainting each other, baked
		# texture included. SurfaceBackground.tscn marks the material
		# resource_local_to_scene for exactly this reason.
		if other == reference:
			_fail("%s and %s share one ShaderMaterial object, so applying a profile to either repaints both" \
				% [names[0], names[i]])
			return
		if other.shader != reference.shader:
			_fail("%s and %s start on different shaders (%s vs %s), so one of them overrides the shared material" \
				% [names[0], names[i], reference.shader.resource_path, other.shader.resource_path])
			return
	print("both start on the same shader: %s" % reference.shader.resource_path)

	# --- C: no profile leaves its shader unstated ----------------------------
	for profile_id in surface_profiles.PROFILES:
		var profile: Resource = surface_profiles.get_profile(profile_id)
		if profile.background_shader == null:
			_fail("the '%s' profile does not name a background_shader, so what it draws depends on which scene happens to be hosting it" % profile_id)
			return
	print("all %d profiles name their own background shader" % surface_profiles.PROFILES.size())

	# --- D: applying a profile lands identically on both ---------------------
	for profile_id in surface_profiles.PROFILES:
		var profile: Resource = surface_profiles.get_profile(profile_id)
		for scene_name in backgrounds:
			backgrounds[scene_name].apply_profile(profile)

		var first: ShaderMaterial = backgrounds[names[0]].material
		if first.shader != profile.background_shader:
			_fail("applying '%s' did not put its own shader on the background" % profile_id)
			return
		for i in range(1, names.size()):
			var other: ShaderMaterial = backgrounds[names[i]].material
			if other.shader != first.shader:
				_fail("'%s' resolved to %s in %s but %s in %s" \
					% [profile_id, first.shader.resource_path, names[0],
						other.shader.resource_path, names[i]])
				return
			for parameter in COLOR_PARAMETERS:
				var a: Color = first.get_shader_parameter(parameter)
				var b: Color = other.get_shader_parameter(parameter)
				if not a.is_equal_approx(b):
					_fail("'%s' set %s to %s in %s but %s in %s" \
						% [profile_id, parameter, a, names[0], b, names[i]])
					return
		# Identical to each other is only half of it - both have to match the
		# profile, or the shared path could be uniformly ignoring it.
		for parameter in COLOR_PARAMETERS:
			var applied: Color = first.get_shader_parameter(parameter)
			var declared: Color = profile.get(parameter)
			if not applied.is_equal_approx(declared):
				_fail("'%s' declares %s %s but the background ended up with %s" \
					% [profile_id, parameter, declared, applied])
				return
		print("  '%s' -> %s, identical on both" % [profile_id, first.shader.resource_path.get_file()])

	for host in hosts:
		host.free()
	print("TEST_SURFACE_BACKGROUND_SHARED: PASS")
	quit(0)


func _fail(message: String) -> void:
	print("TEST_SURFACE_BACKGROUND_SHARED: FAIL (%s)" % message)
	quit(1)