extends SceneTree

## Dev tool: is the skirt STRETCHING around the thigh, or tearing open?
##
##   godot --headless --path . -s res://debug/cloth_stretch_check.gd -- [skin_glb]
##
## The collision and drape solve each cloth bone on its own. Neighbouring skirt
## panels therefore get different answers, and the mesh between them has to
## absorb the difference — which linear-blend skinning does by pulling the shared
## edge apart. On screen that reads as the skirt "breaking" open around the thigh
## instead of deforming over it, and no capsule or spring number shows it,
## because every individual bone is behaving.
##
## So measure the MESH: skin every cloth triangle over a movement sweep and
## compare each edge against its own rest length. An edge whose two ends are
## driven by different panels is a SEAM — that is where a tear appears — so those
## are reported separately from edges inside one panel.
##
## Reports, worst over the sweep:
##   stretch   posed edge length / rest length
##   gap       how many millimetres that edge grew

const SWEEP := [["ground", 9.0], ["ground", 3.0], ["air", 6.0],
	["air", -8.0], ["slide", 10.0], ["dash", 14.0]]
const FRAMES_PER_STATE := 30
## An edge has to grow by more than this to count as a tear rather than noise.
const REPORT_MM := 8.0

var _frames := 0
var _model: SkinnedPlayerModel = null
var _cloth := {}          # bone index -> panel family name
var _edges: Array = []    # [mesh, surface, ia, ib, rest_len, family_a, family_b]
var _skins: Array = []    # [mesh, skin, bone_of, verts, bones, weights, per]
var _worst := {}          # "famA|famB" -> [stretch, grow_m, bones, rest_m, state]
## The single worst edge seen, kept so _report can dump what actually drives it.
var _peak := 0.0
var _peak_edge: Array = []
var _state := ""
var _ready := false


func _initialize() -> void:
	var args := OS.get_cmdline_user_args()
	var path: String = args[0] if args.size() > 0 \
		else "res://assets/characters/skins/taila.glb"
	var scene := Node3D.new()
	root.add_child(scene)
	current_scene = scene
	_model = SkinnedPlayerModel.new()
	_model.model_path = path
	scene.add_child(_model)


## Panel a bone belongs to: the chain root's name, with the segments built by
## tools/retarget.py::subdivide_cloth_panels stripped off. Two segments of the
## same panel are meant to bend apart; two different panels are not.
static func _family(bone_name: String) -> String:
	var n := bone_name
	var cut := n.find(".seg")
	return n.substr(0, cut) if cut >= 0 else n


func _build(skel: Skeleton3D) -> void:
	var side: String = _model.model_path.get_basename() + ".rig.json"
	var info = JSON.parse_string(FileAccess.get_file_as_string(side))
	if typeof(info) != TYPE_DICTIONARY:
		print("no sidecar")
		return
	for c in info.get("chains", []):
		if String(c.get("class", "")) == "hair":
			continue
		for n in c.get("bones", []):
			var i := skel.find_bone(String(n))
			if i >= 0:
				_cloth[i] = _family(String(n))

	for mi in _model.find_children("*", "MeshInstance3D", true, false):
		if mi.mesh == null or mi.skin == null:
			continue
		var skin: Skin = mi.skin
		var bone_of := {}
		for b in skin.get_bind_count():
			var bi := skin.get_bind_bone(b)
			if bi < 0:
				bi = skel.find_bone(skin.get_bind_name(b))
			bone_of[b] = bi
		for s in range(mi.mesh.get_surface_count()):
			var arrays: Array = mi.mesh.surface_get_arrays(s)
			var verts: PackedVector3Array = arrays[Mesh.ARRAY_VERTEX]
			var bones: PackedInt32Array = arrays[Mesh.ARRAY_BONES]
			var weights: PackedFloat32Array = arrays[Mesh.ARRAY_WEIGHTS]
			var idx: PackedInt32Array = arrays[Mesh.ARRAY_INDEX]
			if bones.is_empty() or verts.is_empty() or idx.is_empty():
				continue
			var per: int = bones.size() / verts.size()
			var sk := [mi, skin, bone_of, verts, bones, weights, per]
			# Which panel drives each vertex, and its rest position.
			var fam := []
			var drv := []
			var rest := PackedVector3Array()
			var any := false
			fam.resize(verts.size())
			drv.resize(verts.size())
			rest.resize(verts.size())
			for v in verts.size():
				var bw := 0.0
				var cw := 0.0
				var f := ""
				var dn := ""
				var q := Vector3.ZERO
				for k in per:
					var w: float = weights[v * per + k]
					var bind: int = bones[v * per + k]
					var bi: int = bone_of[bind]
					if bi < 0 or w <= 0.0:
						continue
					q += (skel.get_bone_global_rest(bi) * skin.get_bind_pose(bind)
						* verts[v]) * w
					if _cloth.has(bi):
						cw += w
						if w > bw:
							bw = w
							f = _cloth[bi]
							dn = skel.get_bone_name(bi)
				# The cloth chains must actually OWN this vertex. Body surfaces
				# carry stray cloth influence — one arm vertex measured 0.54
				# forearm, 0.35 skirt — and counting those made the skirt look
				# like it was tearing by half a metre when the arm was simply
				# moving during a dash.
				if cw < 0.75:
					f = ""
					dn = ""
				fam[v] = f
				drv[v] = dn
				rest[v] = q
				if f != "":
					any = true
			if not any:
				continue
			_skins.append(sk)
			var seen := {}
			for t in range(0, idx.size(), 3):
				for pair in [[idx[t], idx[t + 1]], [idx[t + 1], idx[t + 2]],
						[idx[t + 2], idx[t]]]:
					var a: int = mini(pair[0], pair[1])
					var b: int = maxi(pair[0], pair[1])
					if String(fam[a]) == "" or String(fam[b]) == "":
						continue
					var key := "%d_%d_%d" % [_skins.size(), a, b]
					if seen.has(key):
						continue
					seen[key] = true
					var L := rest[a].distance_to(rest[b])
					if L < 0.0005:
						continue
					_edges.append([_skins.size() - 1, a, b, L,
						String(fam[a]), String(fam[b]),
						"%s -> %s" % [drv[a], drv[b]]])
	var seams := 0
	for e in _edges:
		if e[4] != e[5]:
			seams += 1
	print("tracking %d cloth edges, %d of them across a panel seam" % [
		_edges.size(), seams])


func _process(_delta: float) -> bool:
	_frames += 1
	if _frames < 8 or not _model.loaded:
		return false
	var skel: Skeleton3D = _model.skeleton
	if skel == null:
		return true
	if not _ready:
		_build(skel)
		_ready = true
		if _edges.is_empty():
			return true
		return false
	var phase: int = clampi((_frames - 9) / FRAMES_PER_STATE, 0, SWEEP.size() - 1)
	_model.update_state(SWEEP[phase][0], SWEEP[phase][1], false)
	_model.set_locomotion(0.0, 1.0, 0.0)
	_state = "%s %.0f" % [SWEEP[phase][0], SWEEP[phase][1]]
	_measure(skel)
	if _frames > 9 + FRAMES_PER_STATE * SWEEP.size():
		_report()
		return true
	return false


func _measure(skel: Skeleton3D) -> void:
	# Skin every cloth vertex once, then walk the edges.
	var posed: Array = []
	for sk in _skins:
		var skin: Skin = sk[1]
		var bone_of: Dictionary = sk[2]
		var verts: PackedVector3Array = sk[3]
		var bones: PackedInt32Array = sk[4]
		var weights: PackedFloat32Array = sk[5]
		var per: int = sk[6]
		var out := PackedVector3Array()
		out.resize(verts.size())
		for v in verts.size():
			var q := Vector3.ZERO
			for k in per:
				var w: float = weights[v * per + k]
				var bind: int = bones[v * per + k]
				var bi: int = bone_of[bind]
				if bi < 0 or w <= 0.0:
					continue
				q += (skel.get_bone_global_pose(bi) * skin.get_bind_pose(bind)
					* verts[v]) * w
			out[v] = q
		posed.append(out)

	for e in _edges:
		var p: PackedVector3Array = posed[e[0]]
		var L: float = p[e[1]].distance_to(p[e[2]])
		var grow: float = L - float(e[3])
		if grow <= 0.0:
			continue
		var key: String = "%s | %s" % [e[4], e[5]] if e[4] != e[5] else "%s (inside)" % e[4]
		var cur: Array = _worst.get(key, [0.0, 0.0])
		if grow > cur[1]:
			_worst[key] = [L / float(e[3]), grow, e[6], float(e[3]), _state]
		if grow > _peak:
			_peak = grow
			_peak_edge = [e[0], e[1], e[2], float(e[3]), _state]


func _report() -> void:
	print("\n=== worst cloth EDGE STRETCH over the sweep ===")
	print("   a growing seam is the skirt tearing open between two panels;")
	print("   growth inside one panel is the panel itself being stretched.\n")
	var keys := _worst.keys()
	keys.sort_custom(func(a, b): return _worst[a][1] > _worst[b][1])
	var shown := 0
	for k in keys:
		var w: Array = _worst[k]
		if w[1] * 1000.0 < REPORT_MM:
			break
		print("   %-30s x%6.2f  +%6.1f mm  rest %5.1f mm  %-42s %s" % [
			k, w[0], w[1] * 1000.0, w[3] * 1000.0, w[2], w[4]])
		shown += 1
		if shown >= 24:
			break
	if shown == 0:
		print("   nothing grew by more than %.0f mm" % REPORT_MM)
	_dissect()
	print("")


## Everything that drives the two ends of the single worst edge. A rigid bone
## cannot change the distance between two points, so an edge that grew while
## both ends report the same DOMINANT bone is being pulled by something else in
## their influence lists — which is the only way to find out what.
func _dissect() -> void:
	if _peak_edge.is_empty():
		return
	var skel: Skeleton3D = _model.skeleton
	var sk: Array = _skins[_peak_edge[0]]
	var skin: Skin = sk[1]
	var bone_of: Dictionary = sk[2]
	var bones: PackedInt32Array = sk[4]
	var weights: PackedFloat32Array = sk[5]
	var per: int = sk[6]
	print("
   worst single edge: rest %.1f mm, grew %.1f mm, during %s" % [
		_peak_edge[3] * 1000.0, _peak * 1000.0, _peak_edge[4]])
	for which in [1, 2]:
		var v: int = _peak_edge[which]
		var line := "     vertex %d:" % v
		for k in per:
			var w: float = weights[v * per + k]
			if w <= 0.0001:
				continue
			var bi: int = bone_of[bones[v * per + k]]
			line += "  %s %.2f" % [
				skel.get_bone_name(bi) if bi >= 0 else "?", w]
		print(line)