extends Node3D
## Queensland Raceway's National Circuit -- "the Paperclip" -- built in code.
## The centreline is digitised from the official track map (pixel coords) and
## scaled so the lap is exactly 3126 m, the real National Circuit length.
## Three tilted parallel straights, two outer hairpins, the inner loop and the
## T6 fishhook. Corners get kerbs, sand traps and tyre stacks automatically
## from curvature; straights get billboard hoardings.
##
## Race mode picks up the RacePath (same curve) and grids the field on it.

const TEX := "res://assets/textures/%s.jpg"

const LAP_M := 3126.0
const ROAD_W := 13.0
const STEP := 4.0             # road-mesh sampling, metres
## National Circuit red line off the track map, in image pixels (x, y-down).
## Drive order: SF heading west -> T1 -> west straight -> T2 hairpin -> top
## straight east -> east 180 -> middle straight west -> inner loop left ->
## third straight east -> T6 fishhook -> front straight -> SF.
const CENTRE_PX := [
	[680, 795], [300, 800], [150, 782], [85, 720], [70, 620], [68, 400],
	[85, 290], [130, 235], [220, 215], [700, 262], [1290, 335],
	[1345, 372], [1352, 420], [1300, 452], [900, 470], [460, 485],
	[400, 505], [375, 545], [385, 590], [430, 622], [520, 640],
	[800, 680], [1080, 718], [1150, 720], [1200, 748], [1195, 782],
	[1140, 795],
]

var curve: Curve3D

func _ready() -> void:
	var rng := RandomNumberGenerator.new()
	rng.seed = 3126
	curve = _build_curve()
	var samples := _samples()

	# grass world sized off the track's bounding box
	var lo := Vector3(INF, 0, INF)
	var hi := Vector3(-INF, 0, -INF)
	for s in samples:
		lo.x = minf(lo.x, s["pos"].x); lo.z = minf(lo.z, s["pos"].z)
		hi.x = maxf(hi.x, s["pos"].x); hi.z = maxf(hi.z, s["pos"].z)
	var mid := (lo + hi) * 0.5
	var span := hi - lo
	_slab(Vector3(mid.x, -0.5, mid.z), Vector3(span.x + 260, 1, span.z + 260), _mat("grass", 18.0))

	_road(samples)
	var corners := _corners(samples)
	_kerbs(samples)
	for c in corners:
		_corner_dressing(c, samples)
	_hoardings(samples, corners)
	_start_finish(samples)
	_pits(samples)

	# the pond, as seen from every aerial photo of the place
	var pond := Vector3(lo.x + span.x * 0.25, 0.03, lo.z + span.z * 0.37)
	_slab(pond, Vector3(55, 0.03, 38), _flat(Color(0.13, 0.25, 0.30), 0.15), false)

	_gums(rng, samples, lo, hi)

	var path := Path3D.new()
	path.name = "RacePath"
	path.curve = curve
	add_child(path)

	var spawn := Marker3D.new()
	spawn.name = "Spawn"
	var t0: Dictionary = samples[3]
	spawn.transform = Transform3D(Basis.looking_at(t0["tan"], Vector3.UP),
		t0["pos"] + Vector3.UP * 0.5)
	add_child(spawn)

func _build_curve() -> Curve3D:
	# raw pixel loop -> catmull tangents -> measure -> scale to LAP_M exactly
	var raw: Array[Vector3] = []
	for p in CENTRE_PX:
		raw.append(Vector3(p[0], 0, p[1]))
	var c := Curve3D.new()
	var n := raw.size()
	for i in n + 1:
		var p := raw[i % n]
		var t: Vector3 = (raw[(i + 1) % n] - raw[(i - 1 + n) % n]) * 0.2
		c.add_point(p, -t, t)
	var scale := LAP_M / c.get_baked_length()
	var sc := Curve3D.new()
	for i in c.point_count:
		sc.add_point(c.get_point_position(i) * scale,
			c.get_point_in(i) * scale, c.get_point_out(i) * scale)
	return sc

func _samples() -> Array:
	## [{pos, tan, side, dist}] every STEP metres. side points to the LEFT of
	## the drive direction.
	var out: Array = []
	var L := curve.get_baked_length()
	var d := 0.0
	while d < L:
		var p := curve.sample_baked(d)
		var q := curve.sample_baked(fmod(d + 2.0, L))
		var tn := (q - p)
		tn.y = 0.0
		tn = tn.normalized() if tn.length_squared() > 0.0001 else Vector3.FORWARD
		out.append({"pos": p, "tan": tn, "side": Vector3.UP.cross(tn).normalized(), "dist": d})
		d += STEP
	return out

func _road(samples: Array) -> void:
	## One long quad strip with real collision -- cars live on this surface.
	var st := SurfaceTool.new()
	st.begin(Mesh.PRIMITIVE_TRIANGLES)
	var h := Vector3.UP * 0.05
	var n := samples.size()
	for i in n:
		var a: Dictionary = samples[i]
		var b: Dictionary = samples[(i + 1) % n]
		var al: Vector3 = a["pos"] + a["side"] * ROAD_W * 0.5 + h
		var ar: Vector3 = a["pos"] - a["side"] * ROAD_W * 0.5 + h
		var bl: Vector3 = b["pos"] + b["side"] * ROAD_W * 0.5 + h
		var br: Vector3 = b["pos"] - b["side"] * ROAD_W * 0.5 + h
		var va: float = a["dist"] * 0.14
		var vb: float = (a["dist"] + STEP) * 0.14
		# Godot front faces wind CLOCKWISE seen from the normal side: the first
		# cut of this strip wound CCW and the entire road was culled from above
		for v in [[al, Vector2(0, va)], [br, Vector2(1.8, vb)], [ar, Vector2(1.8, va)],
				[al, Vector2(0, va)], [bl, Vector2(0, vb)], [br, Vector2(1.8, vb)]]:
			st.set_normal(Vector3.UP)
			st.set_uv(v[1])
			st.add_vertex(v[0])
	var mesh := st.commit()
	var m := StandardMaterial3D.new()
	m.albedo_texture = load(TEX % "asphalt")
	m.roughness = 0.92
	mesh.surface_set_material(0, m)
	var body := StaticBody3D.new()
	var mi := MeshInstance3D.new()
	mi.mesh = mesh
	body.add_child(mi)
	var cs := CollisionShape3D.new()
	cs.shape = mesh.create_trimesh_shape()
	body.add_child(cs)
	add_child(body)

func _curvature(samples: Array, i: int) -> float:
	## signed heading change per metre; positive = turning left
	var n := samples.size()
	var a: Vector3 = samples[i]["tan"]
	var b: Vector3 = samples[(i + 1) % n]["tan"]
	return a.signed_angle_to(b, Vector3.UP) / STEP

func _corners(samples: Array) -> Array:
	## contiguous runs of |curvature| > threshold, min 6 samples (24 m)
	## -> [{from, to, sign}] as sample indices
	var out: Array = []
	var n := samples.size()
	var run_start := -1
	var run_sign := 0.0
	for i in n:
		var k := _curvature(samples, i)
		if absf(k) > 0.010:
			if run_start < 0:
				run_start = i
				run_sign = signf(k)
		else:
			if run_start >= 0 and i - run_start >= 6:
				out.append({"from": run_start, "to": i - 1, "sign": run_sign})
			run_start = -1
	if run_start >= 0 and n - run_start >= 6:
		out.append({"from": run_start, "to": n - 1, "sign": run_sign})
	return out

func _kerbs(samples: Array) -> void:
	## red/white kerb blocks along both edges wherever the road actually turns
	var red := _flat(Color(0.78, 0.12, 0.10), 0.7)
	var white := _flat(Color(0.90, 0.90, 0.86), 0.7)
	var n := samples.size()
	for i in n:
		if absf(_curvature(samples, i)) < 0.008 or i % 2 != 0:
			continue
		var s: Dictionary = samples[i]
		for e in [-1.0, 1.0]:
			var at: Vector3 = s["pos"] + s["side"] * e * (ROAD_W * 0.5 + 0.7) + Vector3.UP * 0.045
			var mi := MeshInstance3D.new()
			var bm := BoxMesh.new()
			bm.size = Vector3(1.4, 0.07, STEP * 2.0)
			bm.material = red if (i / 2) % 2 == 0 else white
			mi.mesh = bm
			mi.position = at
			mi.basis = Basis.looking_at(s["tan"], Vector3.UP)
			add_child(mi)

func _corner_dressing(c: Dictionary, samples: Array) -> void:
	## outside of every real corner: a sand trap; inside: a tyre stack
	var midi := int((int(c["from"]) + int(c["to"])) / 2.0)
	var s: Dictionary = samples[midi]
	# turning left (+sign) means the outside is the RIGHT edge (-side)
	var out_dir: Vector3 = s["side"] * (-1.0 if float(c["sign"]) > 0.0 else 1.0)
	var span := (int(c["to"]) - int(c["from"])) * STEP
	if span > 40.0:   # only proper corners earn a gravel trap
		var at: Vector3 = s["pos"] + out_dir * (ROAD_W * 0.5 + 13.0)
		var mi := MeshInstance3D.new()
		var bm := BoxMesh.new()
		bm.size = Vector3(minf(span * 0.9, 60.0), 0.04, 26.0)
		bm.material = _mat("sand", 5.0)
		mi.mesh = bm
		mi.position = Vector3(at.x, 0.035, at.z)
		mi.basis = Basis.looking_at(s["tan"], Vector3.UP)
		add_child(mi)
	var rubber := _flat(Color(0.07, 0.07, 0.08), 0.85)
	var inn: Vector3 = s["pos"] - out_dir * (ROAD_W * 0.5 + 3.5)
	for j in 5:
		var mi := MeshInstance3D.new()
		var cm := CylinderMesh.new()
		cm.top_radius = 0.58
		cm.bottom_radius = 0.58
		cm.height = 1.05
		cm.radial_segments = 9
		cm.material = rubber
		mi.mesh = cm
		mi.position = inn + s["tan"] * (j - 2.0) * 1.3 + Vector3.UP * 0.53
		add_child(mi)

func _hoardings(samples: Array, corners: Array) -> void:
	## sponsor boards down the straights, FLUX gibberish and all
	var ads := ["billboard_ad", "billboard_ad2", "billboard_ad3"]
	var n := samples.size()
	var since := 0.0
	var adi := 0
	for i in n:
		since += STEP
		if since < 130.0 or absf(_curvature(samples, i)) > 0.004:
			continue
		since = 0.0
		var s: Dictionary = samples[i]
		var at: Vector3 = s["pos"] + s["side"] * (ROAD_W * 0.5 + 9.0)
		var post := _flat(Color(0.3, 0.31, 0.33), 0.5)
		for j in [-3.2, 3.2]:
			_boxat(at + s["tan"] * j + Vector3.UP * 0.9, Vector3(0.18, 1.8, 0.18), post, s["tan"])
		_boxat(at + Vector3.UP * 1.9, Vector3(8.0, 1.9, 0.12), _mat(ads[adi % 3], 0.24, 0.4), s["tan"])
		adi += 1

func _start_finish(samples: Array) -> void:
	var s: Dictionary = samples[0]
	for row in 2:
		for i in 9:
			var c := Color(0.05, 0.05, 0.06) if (i + row) % 2 == 0 else Color(0.92, 0.92, 0.9)
			var at: Vector3 = s["pos"] + s["side"] * (-6.0 + i * 1.5) + s["tan"] * float(row) * 1.5
			_boxat(Vector3(at.x, 0.06, at.z), Vector3(1.5, 0.02, 1.5), _flat(c, 0.7), s["tan"])
	var steel := _flat(Color(0.25, 0.26, 0.28), 0.5)
	for e in [-1.0, 1.0]:
		_boxat(s["pos"] + s["side"] * e * (ROAD_W * 0.5 + 1.2) + Vector3.UP * 3.5,
			Vector3(0.35, 7.0, 0.35), steel, s["tan"])
	_boxat(s["pos"] + Vector3.UP * 6.6, Vector3(ROAD_W + 4.5, 1.6, 0.3),
		_mat("billboard_ad2", 0.22, 0.4), s["tan"])

func _pits(samples: Array) -> void:
	## the red pit complex on the outside of the front straight: garage row,
	## pit wall, paddock awnings, a couple of transporters
	var s: Dictionary = samples[mini(20, samples.size() - 1)]   # ~80 m up-track of SF
	var out_dir: Vector3 = -s["side"]   # outside of the circuit on the front straight
	var red := _flat(Color(0.72, 0.10, 0.08), 0.55)
	var base: Vector3 = s["pos"] + out_dir * (ROAD_W * 0.5 + 22.0)
	_boxat(base + Vector3.UP * 4.0, Vector3(14, 8.0, 95), red, s["tan"], true)
	_boxat(base + Vector3.UP * 8.2, Vector3(15, 0.4, 98), _flat(Color(0.16, 0.17, 0.19), 0.6), s["tan"])
	_boxat(base - out_dir * 7.1 + Vector3.UP * 5.9, Vector3(0.2, 2.2, 88),
		_mat("facade_glass", 0.2, 0.25), s["tan"])
	_boxat(base - out_dir * 7.1 + Vector3.UP * 2.0, Vector3(0.25, 3.4, 88),
		_mat("shopfront", 0.2, 0.4), s["tan"])
	# pit wall between track and pit lane
	_boxat(s["pos"] + out_dir * (ROAD_W * 0.5 + 2.5) + Vector3.UP * 0.45,
		Vector3(0.4, 0.9, 130), _mat("concrete_ground", 3.0), s["tan"], true)
	# paddock: white awnings + transporters behind the garages
	var wt := _mat("panel_white", 0.5, 0.5)
	for j in 4:
		_boxat(base + out_dir * 16.0 + s["tan"] * (-33.0 + j * 22.0) + Vector3.UP * 2.9,
			Vector3(9, 0.2, 7), wt, s["tan"])
	for j in 2:
		_boxat(base + out_dir * 27.0 + s["tan"] * (-12.0 + j * 26.0) + Vector3.UP * 1.9,
			Vector3(2.5, 3.8, 13.5), _flat(Color(0.82, 0.83, 0.86), 0.4), s["tan"], true)

func _gums(rng: RandomNumberGenerator, samples: Array, lo: Vector3, hi: Vector3) -> void:
	## eucalypt scatter anywhere that's 25 m clear of the racing line
	var pts: Array[Vector3] = []
	for i in range(0, samples.size(), 3):
		pts.append(samples[i]["pos"])
	var placed := 0
	var tries := 0
	while placed < 40 and tries < 400:
		tries += 1
		var at := Vector3(rng.randf_range(lo.x - 90, hi.x + 90), 0, rng.randf_range(lo.z - 90, hi.z + 90))
		var ok := true
		for p in pts:
			if Vector2(at.x - p.x, at.z - p.z).length_squared() < 625.0:
				ok = false
				break
		if not ok:
			continue
		placed += 1
		var trunk := MeshInstance3D.new()
		var cm := CylinderMesh.new()
		cm.top_radius = 0.14
		cm.bottom_radius = 0.24
		cm.height = rng.randf_range(5.0, 8.5)
		cm.radial_segments = 7
		cm.material = _mat("bark", 1.4)
		trunk.mesh = cm
		trunk.position = at + Vector3(0, cm.height * 0.5, 0)
		add_child(trunk)
		var crown := MeshInstance3D.new()
		var sm := SphereMesh.new()
		sm.radius = rng.randf_range(2.4, 3.6)
		sm.height = sm.radius * 1.6
		sm.radial_segments = 10
		sm.rings = 6
		sm.material = _mat("foliage", 0.55)
		crown.mesh = sm
		crown.position = at + Vector3(0, cm.height + sm.radius * 0.4, 0)
		add_child(crown)

func _boxat(pos: Vector3, size: Vector3, mat: Material, along: Vector3, collide := false) -> void:
	var mi := MeshInstance3D.new()
	var bm := BoxMesh.new()
	bm.size = size
	bm.material = mat
	mi.mesh = bm
	if collide:
		var body := StaticBody3D.new()
		var cs := CollisionShape3D.new()
		var bs := BoxShape3D.new()
		bs.size = size
		cs.shape = bs
		body.add_child(cs)
		body.add_child(mi)
		body.position = pos
		body.basis = Basis.looking_at(along, Vector3.UP)
		add_child(body)
	else:
		mi.position = pos
		mi.basis = Basis.looking_at(along, Vector3.UP)
		add_child(mi)

func _mat(tex: String, scale: float, rough := 0.9) -> StandardMaterial3D:
	var m := StandardMaterial3D.new()
	m.albedo_texture = load(TEX % tex)
	m.uv1_scale = Vector3(scale, scale, scale)
	m.uv1_triplanar = true
	m.roughness = rough
	m.metallic = 0.0
	return m

func _flat(color: Color, rough := 0.85) -> StandardMaterial3D:
	var m := StandardMaterial3D.new()
	m.albedo_color = color
	m.roughness = rough
	m.metallic = 0.0
	return m

func _slab(pos: Vector3, size: Vector3, mat: Material, collide := true) -> void:
	var body := StaticBody3D.new()
	var mi := MeshInstance3D.new()
	var bm := BoxMesh.new()
	bm.size = size
	bm.material = mat
	mi.mesh = bm
	body.add_child(mi)
	if collide:
		var shape := CollisionShape3D.new()
		var bs := BoxShape3D.new()
		bs.size = size
		shape.shape = bs
		body.add_child(shape)
	body.position = pos
	add_child(body)