"""Compare finger-bone REST rotations between GLB skeletons.
First GLB is the reference; each other is reported as per-bone angle deviation (degrees).
usage: rest_deviation.py canonical.glb other.glb [more.glb ...]
"""
import json, struct, sys, math
from pathlib import Path

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


def read_gltf(path):
    d = Path(path).read_bytes()
    jlen = struct.unpack_from("<I", d, 12)[0]
    return json.loads(d[20:20 + jlen].decode("utf-8"))


def rests(path):
    g = read_gltf(path)
    out = {}
    for nd in g["nodes"]:
        n = nd.get("name", "")
        if any(t in n.lower() for t in FING):
            out[n] = nd.get("rotation", [0, 0, 0, 1])
    return out


def angle_between(a, b):
    """Geodesic angle (deg) between two unit quaternions, sign-insensitive."""
    d = abs(sum(x * y for x, y in zip(a, b)))
    d = max(-1.0, min(1.0, d))
    return math.degrees(2 * math.acos(d))


ref_path = sys.argv[1]
ref = rests(ref_path)
print(f"reference: {Path(ref_path).name}  ({len(ref)} finger bones)")

for p in sys.argv[2:]:
    other = rests(p)
    print(f"\n== {Path(p).name} == {len(other)} finger bones")
    missing = sorted(set(ref) - set(other))
    extra = sorted(set(other) - set(ref))
    if missing:
        print(f"  MISSING vs ref ({len(missing)}): {', '.join(missing)}")
    if extra:
        print(f"  EXTRA vs ref ({len(extra)}): {', '.join(extra)}")
    devs = []
    for n in sorted(set(ref) & set(other)):
        devs.append((angle_between(ref[n], other[n]), n))
    devs.sort(reverse=True)
    if not devs:
        continue
    over = [d for d in devs if d[0] > 1.0]
    print(f"  shared {len(devs)} | deviating >1deg: {len(over)} | max {devs[0][0]:.1f}deg ({devs[0][1]})")
    for d, n in devs[:12]:
        print(f"    {n:24s} {d:6.1f}deg")