"""Sum skin weights per bone group (finger vs hand vs rest) for each GLB. usage: weight_audit.py *.glb"""
import json, struct, sys
from pathlib import Path

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

def read_glb(path):
    data = Path(path).read_bytes()
    length = struct.unpack_from("<I", data, 8)[0]
    off = 12; gltf = None; binc = None
    while off < length:
        clen, ctype = struct.unpack_from("<II", data, off); off += 8
        if ctype == 0x4E4F534A: gltf = json.loads(data[off:off+clen])
        elif ctype == 0x004E4942: binc = data[off:off+clen]
        off += clen
    return gltf, binc

def acc(gltf, binc, idx):
    a = gltf["accessors"][idx]
    bv = gltf["bufferViews"][a["bufferView"]]
    ncomp = {"SCALAR":1, "VEC2":2, "VEC3":3, "VEC4":4}[a["type"]]
    fmt = {5121:"B", 5123:"H", 5125:"I", 5126:"f"}[a["componentType"]]
    stride = bv.get("byteStride")
    size = struct.calcsize(fmt)*ncomp
    off = bv.get("byteOffset",0) + a.get("byteOffset",0)
    out = []
    for i in range(a["count"]):
        o = off + i*(stride or size)
        out.append(struct.unpack_from("<%d%s" % (ncomp, fmt), binc, o))
    return out, a["componentType"]

for path in sys.argv[1:]:
    gltf, binc = read_glb(path)
    names = [nd.get("name", "") for nd in gltf["nodes"]]
    print(f"\n== {Path(path).name} ==")
    for mi, mesh in enumerate(gltf.get("meshes", [])):
        for pi, prim in enumerate(mesh.get("primitives", [])):
            att = prim["attributes"]
            if "JOINTS_0" not in att: continue
            # which skin uses this mesh
            skin_idx = next((nd.get("skin") for nd in gltf["nodes"]
                             if nd.get("mesh") == mi and "skin" in nd), None)
            if skin_idx is None: continue
            joints = gltf["skins"][skin_idx]["joints"]
            jn = [names[j] for j in joints]
            J, _ = acc(gltf, binc, att["JOINTS_0"])
            W, wt = acc(gltf, binc, att["WEIGHTS_0"])
            wsc = 1.0 if wt == 5126 else (1/255 if wt == 5121 else 1/65535)
            fing_w = hand_w = 0.0
            fing_verts = 0
            for jrow, wrow in zip(J, W):
                fv = 0
                for j, w in zip(jrow, wrow):
                    w *= wsc
                    if w <= 0: continue
                    n = jn[j].lower()
                    if any(t in n for t in FING): fing_w += w; fv = 1
                    elif n.startswith("hand"): hand_w += w
                fing_verts += fv
            print(f"  mesh[{mi}] '{mesh.get('name','')}' prim{pi}: {len(J)} verts | "
                  f"finger-weighted verts: {fing_verts} | total finger W: {fing_w:.0f} | hand W: {hand_w:.0f}")