class_name SunlitShallowsEnvironment
extends Node3D

## Visual test site: flat floor, calm water, fixed daytime sun.
## The hour never changes, so the sun transform is a constant and the only
## motion is the slow ripple drift inside the two shaders.

const SURFACE_LEVEL_M := 0.0
const FLOOR_DEPTH_M := -40.0
## Air above the calm surface holds no scattering medium: a subtractive
## FogVolume cancels the global volumetric fog there so the view never shows
## an unshadowed glow above the water.
const AIR_VOLUME_HEIGHT_M := 80.0
const VOLUMETRIC_FOG_DENSITY := 0.035
const SITE_EXTENT_M := 240.0
## Sun sits ahead of the observer (world -Z) and high: shafts travel down
## toward the submarine, as in the cockpit visual target.
const SUN_ROTATION_DEGREES := Vector3(-44.0, 162.0, 0.0)
const NOISE_SEED := 7
## Calm water: ripple drift stays well under 0.05 texture units per second.
const SURFACE_DRIFT_SPEED := 0.012
## Sunlight only breaks through a pool of surface a few tens of metres ahead of
## the submarine (world -Z), so the shafts land in front of the porthole.
const SHAFT_POOL_CENTER_XZ_M := Vector2(-14.0, -31.0)
const SHAFT_POOL_RADIUS_M := 22.0
const SHAFT_POOL_EDGE_M := 12.0
## Coarser ripples give a few broken oblique shafts rather than a dense fan.
const SURFACE_RIPPLE_SCALE := 0.025
## The underside of the surface is drawn dark, lit only inside the pool.
const SURFACE_CEILING_LIT_SCALE := 0.3

const SURFACE_OCCLUDER_SHADER := preload(
	"res://game/world/sites/sunlit_shallows_surface_occluder.gdshader"
)
const CAUSTIC_FLOOR_SHADER := preload(
	"res://game/world/sites/sunlit_shallows_caustic_floor.gdshader"
)
const SURFACE_CEILING_SHADER := preload(
	"res://game/world/sites/sunlit_shallows_surface_ceiling.gdshader"
)


func _ready() -> void:
	_fix_sun()
	_add_flat_floor()
	_add_surface_occluder()
	_add_surface_ceiling()
	_add_air_fog_cut()


func _fix_sun() -> void:
	var sun := get_node_or_null("Sun") as DirectionalLight3D
	if sun == null:
		return
	sun.rotation_degrees = SUN_ROTATION_DEGREES


func _add_flat_floor() -> void:
	var plane := PlaneMesh.new()
	plane.size = Vector2(SITE_EXTENT_M, SITE_EXTENT_M)
	plane.subdivide_width = 1
	plane.subdivide_depth = 1

	var material := ShaderMaterial.new()
	material.shader = CAUSTIC_FLOOR_SHADER
	material.set_shader_parameter("caustic_noise", _make_ripple_noise(0.007))

	var body := StaticBody3D.new()
	body.name = "FlatFloor"
	body.position = Vector3(0.0, FLOOR_DEPTH_M, 0.0)
	body.set_meta("sonar_material", 1)
	body.set_meta("sonar_reflectivity", 0.6)

	var mesh_instance := MeshInstance3D.new()
	mesh_instance.name = "Mesh"
	mesh_instance.mesh = plane
	mesh_instance.material_override = material
	body.add_child(mesh_instance)

	var collision := CollisionShape3D.new()
	collision.name = "Collision"
	var shape := BoxShape3D.new()
	shape.size = Vector3(SITE_EXTENT_M, 1.0, SITE_EXTENT_M)
	collision.shape = shape
	collision.position = Vector3(0.0, -0.5, 0.0)
	body.add_child(collision)
	add_child(body)


func _add_surface_occluder() -> void:
	var plane := PlaneMesh.new()
	plane.size = Vector2(SITE_EXTENT_M, SITE_EXTENT_M)

	var material := ShaderMaterial.new()
	material.shader = SURFACE_OCCLUDER_SHADER
	material.set_shader_parameter("ripple_noise", _make_ripple_noise(0.009))
	material.set_shader_parameter("drift_speed", SURFACE_DRIFT_SPEED)
	material.set_shader_parameter("ripple_scale", SURFACE_RIPPLE_SCALE)
	material.set_shader_parameter("pool_center_xz", SHAFT_POOL_CENTER_XZ_M)
	material.set_shader_parameter("pool_radius", SHAFT_POOL_RADIUS_M)
	material.set_shader_parameter("pool_edge", SHAFT_POOL_EDGE_M)

	var occluder := MeshInstance3D.new()
	occluder.name = "CalmSurfaceOccluder"
	occluder.position = Vector3(0.0, SURFACE_LEVEL_M, 0.0)
	occluder.mesh = plane
	occluder.material_override = material
	occluder.cast_shadow = GeometryInstance3D.SHADOW_CASTING_SETTING_SHADOWS_ONLY
	add_child(occluder)


func _add_surface_ceiling() -> void:
	var plane := PlaneMesh.new()
	plane.size = Vector2(SITE_EXTENT_M * 1.5, SITE_EXTENT_M * 1.5)

	var material := ShaderMaterial.new()
	material.shader = SURFACE_CEILING_SHADER
	material.set_shader_parameter("ripple_noise", _make_ripple_noise(0.009))
	material.set_shader_parameter("drift_speed", SURFACE_DRIFT_SPEED)
	material.set_shader_parameter("pool_center_xz", SHAFT_POOL_CENTER_XZ_M)
	material.set_shader_parameter("pool_radius", SHAFT_POOL_RADIUS_M)
	material.set_shader_parameter("lit_scale", SURFACE_CEILING_LIT_SCALE)

	var ceiling := MeshInstance3D.new()
	ceiling.name = "SurfaceCeiling"
	ceiling.position = Vector3(0.0, SURFACE_LEVEL_M, 0.0)
	ceiling.mesh = plane
	ceiling.material_override = material
	ceiling.cast_shadow = GeometryInstance3D.SHADOW_CASTING_SETTING_OFF
	add_child(ceiling)


func _add_air_fog_cut() -> void:
	var air := FogVolume.new()
	air.name = "AirFogCut"
	air.shape = RenderingServer.FOG_VOLUME_SHAPE_BOX
	air.size = Vector3(SITE_EXTENT_M * 1.5, AIR_VOLUME_HEIGHT_M, SITE_EXTENT_M * 1.5)
	air.position = Vector3(0.0, SURFACE_LEVEL_M + AIR_VOLUME_HEIGHT_M * 0.5, 0.0)
	var material := FogMaterial.new()
	material.density = -VOLUMETRIC_FOG_DENSITY
	material.edge_fade = 0.0
	air.material = material
	add_child(air)


func _make_ripple_noise(frequency: float) -> NoiseTexture2D:
	var noise := FastNoiseLite.new()
	noise.seed = NOISE_SEED
	noise.noise_type = FastNoiseLite.TYPE_SIMPLEX_SMOOTH
	noise.frequency = frequency
	noise.fractal_octaves = 3
	noise.fractal_lacunarity = 2.1
	noise.fractal_gain = 0.45

	var texture := NoiseTexture2D.new()
	texture.width = 512
	texture.height = 512
	texture.seamless = true
	texture.generate_mipmaps = true
	texture.noise = noise
	return texture