extends Node3D
## Weather visuals and sound, driven by weather.gd (the model).
##
## - Rain and snow are GPU particles emitted above the camera in world space.
##   A heightfield collider that follows the camera stops them on roofs and on
##   the ground, so it doesn't rain indoors.
## - Ground wetness, settled snow and wind strength are global shader uniforms
##   (weather_wet, weather_snow, weather_wind) read by the terrain, grass,
##   foliage and rock shaders.
## - Sound is synthesised: filtered noise for rain and wind, a decaying
##   low rumble for thunder. No audio assets, nothing to license.
##
## Client-side only: in M2 the server runs weather.gd and never this.

const Campfire = preload("res://scripts/building/campfire.gd")

var weather: Node
var player: Node3D            ## for shelter muffling (survival.roofed)

var _rain: GPUParticles3D
var _snow: GPUParticles3D
var _rain_pm: ParticleProcessMaterial
var _snow_pm: ParticleProcessMaterial
var _field: GPUParticlesCollisionHeightField3D

# Audio
const MIX_RATE := 22050.0
var _audio: AudioStreamPlayer
var _playback: AudioStreamGeneratorPlayback
var _rng := RandomNumberGenerator.new()
var _rain_lp := 0.0
var _rain_hp := 0.0
var _brown := 0.0
var _brown2 := 0.0
var _gust_t := 0.0
var _thunder_env := 0.0
var _thunder_delay := -1.0
var _seen_strikes := 0
var _rain_amp := 0.0
var _wind_amp := 0.0
var _muffle := 0.0

func setup(w: Node, p: Node3D) -> void:
	weather = w
	player = p
	_seen_strikes = weather.lightning_count
	_rain_pm = ParticleProcessMaterial.new()
	_rain = _make_particles(7000, 1.5, _rain_pm, _streak_mesh())
	_rain_pm.emission_box_extents = Vector3(20, 1, 20)
	_rain_pm.initial_velocity_min = 13.0
	_rain_pm.initial_velocity_max = 16.0
	_rain_pm.gravity = Vector3(0, -6, 0)
	_rain_pm.particle_flag_align_y = true
	_rain_pm.spread = 2.0

	_snow_pm = ParticleProcessMaterial.new()
	_snow = _make_particles(5000, 9.0, _snow_pm, _flake_mesh())
	_snow_pm.emission_box_extents = Vector3(18, 1, 18)
	_snow_pm.initial_velocity_min = 0.8
	_snow_pm.initial_velocity_max = 1.4
	_snow_pm.gravity = Vector3(0, -0.6, 0)
	_snow_pm.spread = 15.0
	_snow_pm.turbulence_enabled = true
	_snow_pm.turbulence_noise_strength = 1.2
	_snow_pm.turbulence_noise_scale = 4.0
	_snow_pm.turbulence_influence_min = 0.03
	_snow_pm.turbulence_influence_max = 0.08

	_field = GPUParticlesCollisionHeightField3D.new()
	_field.size = Vector3(48, 48, 48)
	_field.resolution = GPUParticlesCollisionHeightField3D.RESOLUTION_512
	_field.update_mode = GPUParticlesCollisionHeightField3D.UPDATE_MODE_ALWAYS
	_field.follow_camera_enabled = true
	add_child(_field)

	if DisplayServer.get_name() != "headless":
		var gen := AudioStreamGenerator.new()
		gen.mix_rate = MIX_RATE
		gen.buffer_length = 0.2
		_audio = AudioStreamPlayer.new()
		_audio.stream = gen
		_audio.volume_db = -4.0
		add_child(_audio)
		_audio.play()
		_playback = _audio.get_stream_playback()

func _make_particles(amount: int, life: float, pm: ParticleProcessMaterial, mesh: Mesh) -> GPUParticles3D:
	var p := GPUParticles3D.new()
	p.amount = amount
	p.lifetime = life
	p.preprocess = life
	p.local_coords = false
	p.visibility_aabb = AABB(Vector3(-30, -40, -30), Vector3(60, 60, 60))
	p.cast_shadow = GeometryInstance3D.SHADOW_CASTING_SETTING_OFF
	p.amount_ratio = 0.0
	p.emitting = false
	pm.emission_shape = ParticleProcessMaterial.EMISSION_SHAPE_BOX
	pm.direction = Vector3.DOWN
	pm.collision_mode = ParticleProcessMaterial.COLLISION_HIDE_ON_CONTACT
	pm.collision_use_scale = false
	p.collision_base_size = 0.05
	p.process_material = pm
	p.draw_pass_1 = mesh
	add_child(p)
	return p

## Two crossed thin quads along +Y, so a streak reads from any side once the
## particle is aligned to its velocity.
static func _streak_mesh() -> ArrayMesh:
	var st := SurfaceTool.new()
	st.begin(Mesh.PRIMITIVE_TRIANGLES)
	var w := 0.012
	var h := 0.32
	for axis in [Vector3.RIGHT, Vector3.BACK]:
		var a: Vector3 = axis * w
		var quad := [-a + Vector3(0, -h, 0), a + Vector3(0, -h, 0), a + Vector3(0, h, 0), -a + Vector3(0, h, 0)]
		for i in [0, 1, 2, 0, 2, 3]:
			st.set_uv(Vector2(0.5, 1.0 if quad[i].y < 0 else 0.0))
			st.add_vertex(quad[i])
	var m := StandardMaterial3D.new()
	m.shading_mode = BaseMaterial3D.SHADING_MODE_UNSHADED
	m.transparency = BaseMaterial3D.TRANSPARENCY_ALPHA
	m.cull_mode = BaseMaterial3D.CULL_DISABLED
	m.albedo_color = Color(0.72, 0.78, 0.88, 0.22)
	m.disable_receive_shadows = true
	st.set_material(m)
	return st.commit()

static func _flake_mesh() -> QuadMesh:
	var q := QuadMesh.new()
	q.size = Vector2.ONE * 0.07
	var m := StandardMaterial3D.new()
	m.billboard_mode = BaseMaterial3D.BILLBOARD_PARTICLES
	m.transparency = BaseMaterial3D.TRANSPARENCY_ALPHA
	m.albedo_texture = Campfire._soft_dot()
	m.albedo_color = Color(1, 1, 1, 0.9)
	m.emission_enabled = true
	m.emission = Color(0.25, 0.27, 0.3)   # stays visible against a dark sky
	m.disable_receive_shadows = true
	q.material = m
	return q

func _process(delta: float) -> void:
	if weather == null:
		return
	var cam := get_viewport().get_camera_3d()
	if cam == null:
		return
	var cp := cam.global_position
	var fwd := -cam.global_basis.z
	fwd.y = 0.0
	var snow: bool = weather.snows_at(cp)
	var amount: float = weather.precip if weather.precip > 0.05 else 0.0
	var wind_v: Vector3 = Vector3(0.8, 0.0, 0.3) * float(weather.wind)
	# Emit a little ahead of the camera, so the view is full and the area
	# behind doesn't waste particles.
	_rain.global_position = cp + fwd.normalized() * 5.0 + Vector3(0, 13, 0)
	_snow.global_position = cp + fwd.normalized() * 3.0 + Vector3(0, 9, 0)
	_set_amount(_rain, 0.0 if snow else amount)
	_set_amount(_snow, amount if snow else 0.0)
	_rain_pm.direction = (Vector3.DOWN + wind_v * 0.25).normalized()
	_snow_pm.gravity = Vector3(0, -0.6, 0) + wind_v * 1.5
	_field.visible = amount > 0.0

	RenderingServer.global_shader_parameter_set("weather_wet", weather.ground_wet)
	RenderingServer.global_shader_parameter_set("weather_snow", weather.snow_cover)
	RenderingServer.global_shader_parameter_set("weather_wind", lerpf(0.7, 3.0, weather.wind))

	var roofed: bool = player != null and player.survival.roofed
	var sheltered: bool = player != null and player.survival.sheltered
	_muffle = move_toward(_muffle, 1.0 if roofed else 0.0, delta * 3.0)
	_rain_amp = weather.rain_at(cp) * 0.30 * (1.0 - 0.45 * _muffle)
	_wind_amp = weather.wind * weather.wind * 0.22 * (0.35 if sheltered else 1.0)
	if weather.lightning_count != _seen_strikes:
		_seen_strikes = weather.lightning_count
		_thunder_delay = _rng.randf_range(0.5, 2.5)
	if _thunder_delay >= 0.0:
		_thunder_delay -= delta
		if _thunder_delay < 0.0:
			_thunder_env = 1.0
	_fill_audio()

func _set_amount(p: GPUParticles3D, a: float) -> void:
	p.amount_ratio = a
	p.emitting = a > 0.0

## Synthesises as many audio frames as the generator can take.
func _fill_audio() -> void:
	if _playback == null:
		return
	var n := _playback.get_frames_available()
	if n <= 0:
		return
	var rain_cut := lerpf(0.55, 0.12, _muffle)
	var buf := PackedVector2Array()
	buf.resize(n)
	var thunder_decay := exp(-1.0 / (MIX_RATE * 0.9))
	for i in range(n):
		var white := _rng.randf() * 2.0 - 1.0
		# Rain: band-limited hiss (low-pass, minus a slower low-pass).
		_rain_lp += rain_cut * (white - _rain_lp)
		_rain_hp += 0.02 * (_rain_lp - _rain_hp)
		var rain := (_rain_lp - _rain_hp) * _rain_amp
		# Wind: brown noise, swelling in slow gusts.
		_brown = clampf(_brown * 0.998 + white * 0.03, -1.0, 1.0)
		_gust_t += 1.0 / MIX_RATE
		var gust := 0.6 + 0.4 * sin(_gust_t * 0.7) * sin(_gust_t * 0.23 + 1.0)
		var wind_s := _brown * _wind_amp * gust * 2.0
		# Thunder: a heavier brown rumble with a long decay.
		var thunder := 0.0
		if _thunder_env > 0.001:
			_brown2 = clampf(_brown2 * 0.9995 + white * 0.02, -1.0, 1.0)
			thunder = _brown2 * _thunder_env * 2.2
			_thunder_env *= thunder_decay
		var s := clampf(rain + wind_s + thunder, -1.0, 1.0)
		buf[i] = Vector2(s, s)
	_playback.push_buffer(buf)