extends Node3D

@export var radius  : float = 1024.0
@export var segments: int   = 128
@export var seed_val: int   = 42
@export var erosion : float = 0.18

func _ready() -> void:
	_build()

func _build() -> void:
	var noise := FastNoiseLite.new()
	noise.seed = seed_val
	noise.noise_type = FastNoiseLite.TYPE_SIMPLEX_SMOOTH
	noise.frequency  = 0.008

	var st  := SurfaceTool.new()
	st.begin(Mesh.PRIMITIVE_TRIANGLES)
	var verts: PackedVector3Array = []
	var colrs: PackedColorArray   = []
	var seg := segments

	for i in range(seg + 1):
		for j in range(seg + 1):
			var u     := float(i) / seg
			var v     := float(j) / seg
			var angle := u * TAU
			var r     := v * radius
			var en    := 1.0 + noise.get_noise_2d(
							cos(angle) * 80.0,
							sin(angle) * 80.0) * erosion
			var x  := cos(angle) * r * en
			var z  := sin(angle) * r * en
			var dn := r / radius
			# Komplett flach — nur Rand fällt ab
			var y  := -6.0 * pow(dn, 6.0)
			verts.append(Vector3(x, y, z))
			colrs.append(_col(dn))

	for i in range(seg):
		for j in range(seg):
			var idx := i * (seg + 1) + j
			var a := idx;         var b := idx + 1
			var c := idx+(seg+1); var d := idx+(seg+1)+1
			var n := (verts[b]-verts[a]).cross(verts[c]-verts[a]).normalized()
			for vtx in [a, b, c]:
				st.set_normal(n); st.set_color(colrs[vtx])
				st.add_vertex(verts[vtx])
			for vtx in [b, d, c]:
				st.set_normal(n); st.set_color(colrs[vtx])
				st.add_vertex(verts[vtx])

	var mesh := st.commit()
	var mat  := StandardMaterial3D.new()
	mat.vertex_color_use_as_albedo = true
	mat.shading_mode = BaseMaterial3D.SHADING_MODE_UNSHADED
	mesh.surface_set_material(0, mat)
	var mi  := MeshInstance3D.new()
	mi.mesh = mesh
	add_child(mi)

	_build_underside()

func _col(dn: float) -> Color:
	if dn > 0.93: return Color(0.45, 0.38, 0.28)  # Erdrand
	if dn > 0.85: return Color(0.38, 0.55, 0.25)  # Gras außen
	return Color(0.42, 0.65, 0.30)                 # Gras

func _build_underside() -> void:
	var st  := SurfaceTool.new()
	st.begin(Mesh.PRIMITIVE_TRIANGLES)
	var seg := 80
	var bot := Vector3(0, -18.0, 0)
	var noise := FastNoiseLite.new()
	noise.seed = seed_val + 1
	for i in range(seg):
		var a0 := float(i)   / seg * TAU
		var a1 := float(i+1) / seg * TAU
		var r  := radius * 0.9
		var e0 := 1.0 + noise.get_noise_2d(cos(a0)*80, sin(a0)*80) * erosion
		var e1 := 1.0 + noise.get_noise_2d(cos(a1)*80, sin(a1)*80) * erosion
		var p0 := Vector3(cos(a0)*r*e0, -2.0, sin(a0)*r*e0)
		var p1 := Vector3(cos(a1)*r*e1, -2.0, sin(a1)*r*e1)
		var col := Color(0.30, 0.25, 0.18)
		st.set_color(col); st.set_normal(Vector3(0,-1,0))
		st.add_vertex(bot); st.add_vertex(p1); st.add_vertex(p0)
		# Seite
		var t0 := Vector3(p0.x, 0.0, p0.z)
		var t1 := Vector3(p1.x, 0.0, p1.z)
		st.add_vertex(p0); st.add_vertex(t0); st.add_vertex(p1)
		st.add_vertex(t0); st.add_vertex(t1); st.add_vertex(p1)
	var mesh := st.commit()
	var mat  := StandardMaterial3D.new()
	mat.vertex_color_use_as_albedo = true
	mat.shading_mode = BaseMaterial3D.SHADING_MODE_UNSHADED
	mat.cull_mode    = BaseMaterial3D.CULL_DISABLED
	mesh.surface_set_material(0, mat)
	var mi  := MeshInstance3D.new()
	mi.mesh = mesh
	add_child(mi)