"""Per-finger-bone territory audit: how many verts does each finger bone actually OWN
(dominant weight) and how much total weight mass does it carry?

Why: fin_bones classifies exp05's fist tears as hand<->thumb_02 and hand<->index_02 —
the chain skips the _01 joints. If the _01 bones own no territory, every curl lands as a
hard one-edge step from the palm to phalanx 2, which must stretch. This measures that
directly instead of inferring it. usage: bone_territory.py body.glb
"""
import json
import struct
import sys
from pathlib import Path

DIGITS = ("thumb", "index", "middle", "ring", "pinky")


def read_glb(path):
    d = Path(path).read_bytes()
    ln = struct.unpack_from("<I", d, 8)[0]
    off, g, b = 12, None, None
    while off < ln:
        clen, ct = struct.unpack_from("<II", d, off)
        off += 8
        if ct == 0x4E4F534A:
            g = json.loads(d[off:off + clen])
        else:
            b = d[off:off + clen]
        off += clen
    return g, b


def acc(g, b, i):
    a = g["accessors"][i]
    bv = g["bufferViews"][a["bufferView"]]
    nc = {"SCALAR": 1, "VEC2": 2, "VEC3": 3, "VEC4": 4, "MAT4": 16}[a["type"]]
    fmt = {5121: "B", 5123: "H", 5125: "I", 5126: "f"}[a["componentType"]]
    sz = struct.calcsize(fmt) * nc
    stride = bv.get("byteStride") or sz
    off = bv.get("byteOffset", 0) + a.get("byteOffset", 0)
    out = []
    for k in range(a["count"]):
        out.append(struct.unpack_from("<" + fmt * nc, b, off + k * stride))
    return out


g, b = read_glb(sys.argv[1])
prim = g["meshes"][0]["primitives"][0]
joints = g["skins"][0]["joints"]
names = [g["nodes"][j].get("name", f"node{j}") for j in joints]
J = acc(g, b, prim["attributes"]["JOINTS_0"])
W = acc(g, b, prim["attributes"]["WEIGHTS_0"])
wt = g["accessors"][prim["attributes"]["WEIGHTS_0"]]["componentType"]
sc = 1.0 if wt == 5126 else (1 / 255 if wt == 5121 else 1 / 65535)

own = {n: 0 for n in names}     # verts whose LARGEST weight is this bone
mass = {n: 0.0 for n in names}  # total weight mass
any_w = {n: 0 for n in names}   # verts with any weight >1%
for ji, wi in zip(J, W):
    ws = [w * sc for w in wi]
    best, bw = None, 0.0
    for jj, w in zip(ji, ws):
        n = names[jj]
        mass[n] += w
        if w > 0.01:
            any_w[n] += 1
        if w > bw:
            best, bw = n, w
    if best is not None and bw > 0:
        own[best] += 1

print(f"{Path(sys.argv[1]).name}   {len(J)} verts, {len(joints)} joints")
print(f"{'bone':16s} {'owns':>7s} {'any>1%':>8s} {'mass':>9s}")
for side in ("l", "r"):
    print(f"--- hand_{side} chain ---")
    for nm in [f"hand_{side}"] + [f"{d}_{p}_{side}" for d in DIGITS
                                  for p in ("01", "02", "03")]:
        if nm not in own:
            print(f"{nm:16s}   (absent from skin)")
            continue
        flag = "   <-- STARVED" if own[nm] == 0 else ""
        print(f"{nm:16s} {own[nm]:7d} {any_w[nm]:8d} {mass[nm]:9.1f}{flag}")