extends SceneTree

## Checks the sunlit shallows visual site keeps its three promises:
## a flat floor, a calm shadow-only water surface, and a daytime sun whose
## hour never changes.

const SCENE_PATH := "res://game/world/sites/sunlit_shallows_environment.tscn"
const WORLD_SCENE_PATH := (
	"res://game/composition/vertical_slice/sunlit_shallows_world.tscn"
)

var _failures: Array[String] = []
var _checks := 0


func _init() -> void:
	_run.call_deferred()


func _run() -> void:
	var scene := load(SCENE_PATH) as PackedScene
	_expect(scene != null, "scene loads")
	if scene == null:
		_finish()
		return

	var site := scene.instantiate() as SunlitShallowsEnvironment
	_expect(site != null, "scene root is SunlitShallowsEnvironment")
	if site == null:
		_finish()
		return
	root.add_child(site)
	await process_frame

	_test_fixed_daytime_sun(site)
	_test_flat_floor(site)
	_test_calm_surface_occluder(site)
	_test_scattering_environment(site)
	_test_air_fog_cut(site)
	_test_surface_ceiling(site)

	site.queue_free()
	await process_frame
	_test_composed_world()
	_finish()


func _test_composed_world() -> void:
	var world_scene := load(WORLD_SCENE_PATH) as PackedScene
	_expect(world_scene != null, "composed world scene loads")
	if world_scene == null:
		return
	var world := world_scene.instantiate() as Node3D
	_expect(
		world.get_node_or_null("Environment") is SunlitShallowsEnvironment,
		"composed world uses the sunlit shallows environment"
	)
	var submarine := world.get_node_or_null("SubmarineActor") as Node3D
	_expect(submarine != null, "composed world has a submarine")
	if submarine != null:
		_expect(
			submarine.position.y < SunlitShallowsEnvironment.SURFACE_LEVEL_M
			and submarine.position.y > SunlitShallowsEnvironment.FLOOR_DEPTH_M,
			"submarine starts between surface and floor"
		)
		_expect(
			submarine.get_node_or_null("CockpitInterior") != null
			and submarine.get_node_or_null("CockpitCameraRig") != null,
			"submarine carries cockpit and camera rig"
		)
		for projector_name: String in ["LeftProjector", "RightProjector"]:
			var projector := submarine.get_node_or_null(projector_name) as SpotLight3D
			_expect(projector != null, "%s exists" % projector_name)
			if projector != null:
				_expect(
					projector.light_volumetric_fog_energy < 1.0,
					"%s does not wash out the sun shafts in the fog" % projector_name
				)
	world.free()


func _test_fixed_daytime_sun(site: SunlitShallowsEnvironment) -> void:
	var sun := site.get_node_or_null("Sun") as DirectionalLight3D
	_expect(sun != null, "sun is a DirectionalLight3D")
	if sun == null:
		return
	_expect(
		sun.rotation_degrees.is_equal_approx(
			SunlitShallowsEnvironment.SUN_ROTATION_DEGREES
		),
		"sun hour is the fixed constant"
	)
	var sun_direction := -sun.global_transform.basis.z
	_expect(sun_direction.y < -0.6, "sun shines downward from above the porthole (daytime)")
	_expect(
		sun_direction.z > 0.15,
		"sun shines toward the observer (rays come from ahead, world -Z)"
	)
	_expect(sun.shadow_enabled, "sun casts shadows (needed for light shafts)")
	_expect(
		sun.light_volumetric_fog_energy >= 1.0,
		"sun injects energy into the volumetric fog"
	)


func _test_flat_floor(site: SunlitShallowsEnvironment) -> void:
	var floor_mesh := site.get_node_or_null("FlatFloor/Mesh") as MeshInstance3D
	_expect(floor_mesh != null, "floor mesh exists")
	if floor_mesh == null:
		return
	var vertices := floor_mesh.mesh.get_faces()
	var flat := true
	for vertex: Vector3 in vertices:
		if not is_zero_approx(vertex.y):
			flat = false
			break
	_expect(flat, "floor mesh is flat")
	_expect(
		is_equal_approx(
			floor_mesh.global_position.y,
			SunlitShallowsEnvironment.FLOOR_DEPTH_M
		),
		"floor sits at the site depth"
	)
	_expect(
		floor_mesh.material_override is ShaderMaterial,
		"floor uses the caustic shader material"
	)
	var collision := site.get_node_or_null("FlatFloor/Collision") as CollisionShape3D
	_expect(collision != null and collision.shape is BoxShape3D, "floor has a box collider")


func _test_calm_surface_occluder(site: SunlitShallowsEnvironment) -> void:
	var occluder := site.get_node_or_null("CalmSurfaceOccluder") as MeshInstance3D
	_expect(occluder != null, "surface occluder exists")
	if occluder == null:
		return
	_expect(
		occluder.cast_shadow == GeometryInstance3D.SHADOW_CASTING_SETTING_SHADOWS_ONLY,
		"surface occluder is shadow-only"
	)
	_expect(
		is_equal_approx(
			occluder.global_position.y,
			SunlitShallowsEnvironment.SURFACE_LEVEL_M
		),
		"surface occluder sits at water level"
	)
	var material := occluder.material_override as ShaderMaterial
	_expect(material != null, "surface occluder uses a shader material")
	if material == null:
		return
	var drift: Variant = material.get_shader_parameter("drift_speed")
	_expect(
		drift is float and drift > 0.0 and drift < 0.05,
		"surface drift is slow (calm water)"
	)
	_expect(
		material.get_shader_parameter("ripple_noise") is NoiseTexture2D,
		"surface ripple noise is assigned"
	)
	var pool_center: Variant = material.get_shader_parameter("pool_center_xz")
	_expect(
		pool_center is Vector2 and pool_center.y < -20.0 and pool_center.y > -120.0,
		"light pool sits a few tens of metres ahead (world -Z)"
	)
	var pool_radius: Variant = material.get_shader_parameter("pool_radius")
	_expect(
		pool_radius is float and pool_radius > 5.0 and pool_radius < 60.0,
		"light pool radius is local, not the whole surface"
	)


func _test_scattering_environment(site: SunlitShallowsEnvironment) -> void:
	var world_environment := site.get_node_or_null("WorldEnvironment") as WorldEnvironment
	_expect(world_environment != null, "world environment exists")
	if world_environment == null:
		return
	var environment := world_environment.environment
	_expect(environment.volumetric_fog_enabled, "volumetric fog is enabled")
	_expect(environment.volumetric_fog_anisotropy > 0.5, "fog scatters forward")
	_expect(environment.fog_enabled, "depth fog is enabled")


func _test_surface_ceiling(site: SunlitShallowsEnvironment) -> void:
	var ceiling := site.get_node_or_null("SurfaceCeiling") as MeshInstance3D
	_expect(ceiling != null, "visible surface ceiling exists")
	if ceiling == null:
		return
	_expect(
		is_equal_approx(ceiling.global_position.y, SunlitShallowsEnvironment.SURFACE_LEVEL_M),
		"surface ceiling sits at water level"
	)
	_expect(
		ceiling.cast_shadow == GeometryInstance3D.SHADOW_CASTING_SETTING_OFF,
		"surface ceiling leaves shadowing to the occluder"
	)
	var ceiling_material := ceiling.material_override as ShaderMaterial
	var occluder := site.get_node_or_null("CalmSurfaceOccluder") as MeshInstance3D
	var occluder_material: ShaderMaterial = null if occluder == null else occluder.material_override
	_expect(
		ceiling_material != null
		and occluder_material != null
		and ceiling_material.get_shader_parameter("pool_center_xz")
			== occluder_material.get_shader_parameter("pool_center_xz")
		and ceiling_material.get_shader_parameter("pool_radius")
			== occluder_material.get_shader_parameter("pool_radius"),
		"surface ceiling lights the same pool the occluder opens"
	)


func _test_air_fog_cut(site: SunlitShallowsEnvironment) -> void:
	var air := site.get_node_or_null("AirFogCut") as FogVolume
	_expect(air != null, "air fog cut exists")
	if air == null:
		return
	var bottom := air.global_position.y - air.size.y * 0.5
	_expect(
		is_equal_approx(bottom, SunlitShallowsEnvironment.SURFACE_LEVEL_M),
		"air fog cut starts at the water surface"
	)
	var material := air.material as FogMaterial
	_expect(material != null and material.density < 0.0, "air fog cut subtracts fog")
	var world_environment := site.get_node("WorldEnvironment") as WorldEnvironment
	_expect(
		material != null and is_equal_approx(
			-material.density,
			world_environment.environment.volumetric_fog_density
		),
		"air fog cut cancels the global volumetric density exactly"
	)


func _expect(condition: bool, label: String) -> void:
	_checks += 1
	if not condition:
		_failures.append(label)


func _finish() -> void:
	if _failures.is_empty():
		print("Sunlit shallows environment: %d passed, 0 failed." % _checks)
		quit(0)
	else:
		for failure: String in _failures:
			push_error("sunlit shallows environment: %s" % failure)
		print("Sunlit shallows environment: %d failed." % _failures.size())
		quit(1)