"""For each finger bone, report how much geometry it actually OWNS (verts where it is the
dominant influence) and where that geometry sits. On a two-finger hand rig the five-finger
bone set is present but several chains own nothing, or several chains share one fused mass.

usage: hand_bone_ownership.py body.glb [side l|r]
"""
import json, struct, sys, math
from pathlib import Path
from collections import defaultdict

FING = ("thumb", "index", "middle", "ring", "pinky")
side = sys.argv[2] if len(sys.argv) > 2 else None


def read_glb(p):
    d = Path(p).read_bytes()
    length = struct.unpack_from("<I", d, 8)[0]
    off = 12
    g = b_ = None
    while off < length:
        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"]]
    size = struct.calcsize(fmt) * nc
    stride = bv.get("byteStride") or size
    off = bv.get("byteOffset", 0) + a.get("byteOffset", 0)
    return [struct.unpack_from("<%d%s" % (nc, fmt), b, off + k * stride)
            for k in range(a["count"])], a["componentType"]


g, b = read_glb(sys.argv[1])
names = [nd.get("name", "") for nd in g["nodes"]]
prim = g["meshes"][0]["primitives"][0]
att = prim["attributes"]
skin = next(nd["skin"] for nd in g["nodes"] if nd.get("mesh") == 0 and "skin" in nd)
joints = g["skins"][skin]["joints"]
jname = [names[j] for j in joints]

P, _ = acc(g, b, att["POSITION"])
J, _ = acc(g, b, att["JOINTS_0"])
W, wt = acc(g, b, att["WEIGHTS_0"])
wsc = 1.0 if wt == 5126 else (1 / 255 if wt == 5121 else 1 / 65535)

own = defaultdict(list)
for vi, (p, jrow, wrow) in enumerate(zip(P, J, W)):
    best = (0.0, None)
    for j, w in zip(jrow, wrow):
        w *= wsc
        if w > best[0]:
            best = (w, jname[j])
    if best[1] and any(t in best[1].lower() for t in FING):
        if side and not best[1].lower().endswith("_" + side):
            continue
        own[best[1]].append(p)

print(f"{Path(sys.argv[1]).name}  dominant-owner geometry per finger bone"
      f"{' (side ' + side + ')' if side else ''}\n")
print(f"  {'bone':20s} {'verts':>7s}   {'z-centre':>9s} {'z-span':>8s}   {'x-centre':>9s}")
for fam in FING:
    rows = [(n, v) for n, v in own.items() if fam in n.lower()]
    if not rows:
        print(f"  {fam:20s} {'0':>7s}   -- owns no geometry --")
        continue
    for n in sorted(r[0] for r in rows):
        ps = own[n]
        zc = sum(p[2] for p in ps) / len(ps) * 100
        zs = (max(p[2] for p in ps) - min(p[2] for p in ps)) * 100
        xc = sum(p[0] for p in ps) / len(ps) * 100
        print(f"  {n:20s} {len(ps):7d}   {zc:8.1f}cm {zs:7.1f}cm   {xc:8.1f}cm")
    print()
tot = sum(len(v) for v in own.values())
print(f"  total finger-owned verts: {tot}")