# Blender headless: convert with-skin Mixamo FBX clips to anim-only FBX
# (deletes meshes, keeps armature+action). MIRPAMO's retarget mapper needs
# anim-only sources.
#
# Usage: Blender -b --python pipeline/strip_skin.py -- --clips "a.fbx,b.fbx" --out dir
import argparse
import sys
from pathlib import Path

import bpy


def parse_args():
    argv = sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else []
    ap = argparse.ArgumentParser()
    ap.add_argument("--clips", required=True)
    ap.add_argument("--out", required=True)
    return ap.parse_args(argv)


args = parse_args()
out = Path(args.out).expanduser()
out.mkdir(parents=True, exist_ok=True)
for clip in args.clips.split(","):
    clip = Path(clip).expanduser()
    # GLB out: Blender 5's FBX exporter flattens slotted actions to identity;
    # the glTF exporter is slot-native and MIRPAMO imports glb clips fine.
    dest = (out / clip.name).with_suffix(".glb")
    if dest.exists():
        print("SKIP", clip.name)
        continue
    bpy.ops.wm.read_factory_settings(use_empty=True)
    bpy.ops.import_scene.fbx(filepath=str(clip), use_anim=True)
    for o in list(bpy.data.objects):
        if o.type == "MESH":
            bpy.data.objects.remove(o, do_unlink=True)
    # normalise numbered Mixamo namespaces (mixamorig7: -> mixamorig:) so
    # downstream mappers (MIRPAMO retarget) match by exact name.
    # NOTE: bone rename does NOT fix up slotted-action fcurve paths in
    # Blender 5 — rewrite them explicitly or the action drives nothing.
    import re

    def all_fcurves(act):
        if hasattr(act, "fcurves") and len(getattr(act, "fcurves", [])):
            return list(act.fcurves)
        out = []
        for layer in act.layers:
            for strip in layer.strips:
                for cb in strip.channelbags:
                    out.extend(cb.fcurves)
        return out

    for o in bpy.data.objects:
        if o.type == "ARMATURE":
            for b in o.data.bones:
                b.name = re.sub(r"^mixamorig\d+:", "mixamorig:", b.name)
    for act in bpy.data.actions:
        for fc in all_fcurves(act):
            if '"' in fc.data_path:
                bone = fc.data_path.split('"')[1]
                fixed = re.sub(r"^mixamorig\d+:", "mixamorig:", bone)
                if fixed != bone:
                    fc.data_path = fc.data_path.replace('"%s"' % bone, '"%s"' % fixed)
    bpy.ops.export_scene.gltf(filepath=str(dest), export_format="GLB",
                              export_animations=True)
    print("STRIPPED", clip.name)
print("DONE")