#!/usr/bin/env python3
"""Intake for the Quaternius modular character parts.

The upstream modular pack is distributed as a Google Drive folder, so it cannot be
fetched reproducibly by CI. The owner downloads it once into the gitignored
`tmp/quaternius-intake/`; everything after that is scripted here:

    # 1. what is in the download?
    python3 tools/quaternius_parts.py inventory --dir tmp/quaternius-intake

    # 2. keep one mesh as a part (a single skinned mesh on the 62-joint rig)
    python3 tools/quaternius_parts.py extract \
      --file tmp/quaternius-intake/Male_Modular.glb \
      --mesh "Male_Hair_1" --part hair_1

    # 3. record the provenance of what was kept
    python3 tools/quaternius_parts.py verify \
      --dir assets/models/blender_src/quaternius/parts

`inventory` and `verify` run outside Blender (they parse the GLB container);
`extract` needs Blender, because it re-parents the mesh and rewrites the skin.

Part contract: one mesh, the standard 62-joint vertex-group names, materials named
after a contract slot (`skin`, `cloth`, `pants`, `hair`, `accessory`) or a
fixed-colour detail. `blender_assets.py` refuses a part that breaks it.
"""

import argparse
import hashlib
import json
import struct
import sys
from pathlib import Path

ROOT = Path(__file__).resolve().parent.parent
PARTS = ROOT / "assets" / "models" / "blender_src" / "quaternius" / "parts"
INTAKE = ROOT / "tmp" / "quaternius-intake"

# The runtime rig. A part that does not carry these groups cannot be skinned by
# `NpcAvatar`, so it is not a part for this project.
REQUIRED_GROUPS = ("Hips", "Chest", "Head", "UpperArm.L", "UpperArm.R",
                   "UpperLeg.L", "UpperLeg.R")


def _glb_json(path: Path):
    """Return (gltf_json, binary_length) from a GLB container."""
    data = path.read_bytes()
    magic, version, _length = struct.unpack("<III", data[:12])
    if magic != 0x46546C67:
        raise ValueError(f"{path}: not a GLB")
    offset = 12
    gltf = None
    binary = 0
    while offset < len(data):
        chunk_length, chunk_type = struct.unpack("<II", data[offset:offset + 8])
        chunk = data[offset + 8:offset + 8 + chunk_length]
        if chunk_type == 0x4E4F534A:  # JSON
            gltf = json.loads(chunk)
        elif chunk_type == 0x004E4942:  # BIN
            binary = chunk_length
        offset += 8 + chunk_length + (-chunk_length % 4)
    if gltf is None:
        raise ValueError(f"{path}: no JSON chunk")
    return gltf, binary


def _node_names(gltf):
    return [n.get("name", "") for n in gltf.get("nodes", [])]


def _skin_bones(gltf):
    nodes = _node_names(gltf)
    return [nodes[j] for s in gltf.get("skins", []) for j in s.get("joints", [])]


def _mesh_node_names(gltf):
    """Node names that reference a mesh: the names a Blender import exposes."""
    names = []
    for node in gltf.get("nodes", []):
        if "mesh" in node:
            names.append(node.get("name", f"mesh{node['mesh']}"))
    return names


def inventory_file(path: Path):
    gltf, binary = _glb_json(path)
    bones = _skin_bones(gltf)
    materials = [m.get("name", "") for m in gltf.get("materials", [])]
    node_names = _mesh_node_names(gltf)
    meshes = []
    for index, mesh in enumerate(gltf.get("meshes", [])):
        tris = 0
        verts = 0
        skinned = True
        for prim in mesh.get("primitives", []):
            attributes = prim.get("attributes", {})
            if "indices" in prim:
                tris += gltf["accessors"][prim["indices"]]["count"] // 3
            if "POSITION" in attributes:
                verts += gltf["accessors"][attributes["POSITION"]]["count"]
            if "JOINTS_0" not in attributes:
                skinned = False
        # Prefer the node name (what Blender shows and what `extract --mesh` takes).
        name = node_names[index] if index < len(node_names) else mesh.get("name", "")
        meshes.append({"name": name, "triangles": tris,
                       "vertices": verts, "skinned": skinned})
    parts_ready = all(group in bones for group in REQUIRED_GROUPS)
    return {
        "file": str(path),
        "bytes": path.stat().st_size,
        "sha256": hashlib.sha256(path.read_bytes()).hexdigest(),
        "meshes": meshes,
        "bones": len(bones),
        "rig_ready": parts_ready,
        "materials": materials,
        "binary_bytes": binary,
    }


def inventory(root: Path):
    files = sorted(p for p in root.rglob("*.glb"))
    if not files:
        print(f"no .glb under {root}\n"
              f"  download the pack into {INTAKE.relative_to(ROOT)}/ first "
              f"(see TODO.md, 'Outfit part library')")
        return 1
    rows = []
    for path in files:
        try:
            rows.append(inventory_file(path))
        except (ValueError, KeyError) as error:
            print(f"skip {path.name}: {error}")
    print(f"{'file':44s} {'meshes':>6s} {'tris':>7s} {'bones':>5s} rig   meshes")
    for row in rows:
        tris = sum(m["triangles"] for m in row["meshes"])
        names = ", ".join(m["name"] for m in row["meshes"][:4])
        print(f"{Path(row['file']).name[:44]:44s} {len(row['meshes']):6d} {tris:7d} "
              f"{row['bones']:5d} {'yes' if row['rig_ready'] else 'NO ':5s} {names}")
    ready = [r for r in rows if r["rig_ready"]]
    print(f"\n{len(ready)}/{len(rows)} files carry the 62-joint rig and can be cut into parts.")
    print("Next: `extract --file <glb> --mesh <name> --part <name>` for each part to keep.")
    return 0


def verify(root: Path):
    files = sorted(p for p in root.glob("*.glb"))
    if not files:
        print(f"no part files in {root.relative_to(ROOT)}")
        return 1
    print(f"{'part':32s} {'sha256':64s} {'tris':>6s} bones")
    problems = 0
    for path in files:
        gltf, _binary = _glb_json(path)
        bones = _skin_bones(gltf)
        missing = [group for group in REQUIRED_GROUPS if group not in bones]
        tris = sum(gltf["accessors"][p["indices"]]["count"] // 3
                   for mesh in gltf.get("meshes", [])
                   for p in mesh.get("primitives", {}) if "indices" in p)
        digest = hashlib.sha256(path.read_bytes()).hexdigest()
        status = "ok" if not missing else "MISSING " + ",".join(missing)
        print(f"{path.stem[:32]:32s} {digest} {tris:6d} {len(bones):5d} {status}")
        problems += 1 if missing else 0
    print(f"\n{len(files)} parts, {problems} unusable. Record the hashes in CREDITS.md.")
    return 1 if problems else 0


def extract(source: Path, mesh_name: str, part: str, out_dir: Path):
    try:
        import bpy  # type: ignore
        from mathutils import Matrix  # type: ignore
    except ImportError:
        print("extract must run inside Blender:\n"
              f"  flatpak run org.blender.Blender --background --python {Path(__file__).name} "
              f"-- extract --file {source} --mesh {mesh_name} --part {part}",
              file=sys.stderr)
        return 2
    bpy.ops.wm.read_factory_settings(use_empty=True)
    bpy.ops.import_scene.gltf(filepath=str(source))
    target = None
    for obj in bpy.context.scene.objects:
        if obj.type == "MESH" and obj.name.split(".")[0] == mesh_name.split(".")[0]:
            target = obj
            break
    if target is None:
        names = [o.name for o in bpy.context.scene.objects if o.type == "MESH"]
        print(f"mesh '{mesh_name}' not found; the file has: {', '.join(names)}")
        return 1
    # Keep the armature: a glTF mesh only carries JOINTS_0/WEIGHTS_0 when a skin
    # references a skeleton, so a parts file without one validates as bone-less and
    # cannot be skinned. The builder drops the part's armature when it joins the mesh
    # onto the base body, which already owns the skeleton.
    armour = next((o for o in bpy.context.scene.objects
                   if o.type == "ARMATURE" and o is not target), None)
    for obj in list(bpy.context.scene.objects):
        if obj is not target and obj is not armour:
            bpy.data.objects.remove(obj, do_unlink=True)
    for group in list(target.vertex_groups):
        if group.name not in REQUIRED_GROUPS + (
                "LowerArm.L", "LowerArm.R", "LowerLeg.L", "LowerLeg.R", "Wrist.L",
                "Wrist.R", "Foot.L", "Foot.R", "Neck", "Shoulder.L", "Shoulder.R",
                "Abdomen", "Torso", "Body", "Root", "PT.L", "PT.R"):
            target.vertex_groups.remove(group)
    out_dir.mkdir(parents=True, exist_ok=True)
    path = out_dir / f"{part}.glb"
    target.name = part
    target.data.name = part
    for obj in bpy.context.scene.objects:
        obj.select_set(obj is target or obj is armour)
    bpy.context.view_layer.objects.active = target
    bpy.ops.export_scene.gltf(filepath=str(path), export_format="GLB",
                              use_selection=True, export_apply=False,
                              export_animations=False, export_skins=True,
                              export_yup=True, export_materials="EXPORT")
    print(f"wrote {path.relative_to(ROOT)} ({len(target.data.vertices)} verts)")
    return 0


def main(argv=None):
    parser = argparse.ArgumentParser(description="Quaternius modular part intake")
    sub = parser.add_subparsers(dest="cmd", required=True)
    inv = sub.add_parser("inventory", help="list the GLBs in a download")
    inv.add_argument("--dir", default=str(INTAKE))
    ver = sub.add_parser("verify", help="hash and validate the kept parts")
    ver.add_argument("--dir", default=str(PARTS))
    ext = sub.add_parser("extract", help="write one mesh as a part (needs Blender)")
    ext.add_argument("--file", required=True)
    ext.add_argument("--mesh", required=True)
    ext.add_argument("--part", required=True)
    ext.add_argument("--out", default=str(PARTS))
    argv = list(argv if argv is not None else sys.argv[1:])
    if "--" in argv:  # Blender hands the script path over before its own `--`
        argv = argv[argv.index("--") + 1:]
    args = parser.parse_args(argv)
    if args.cmd == "inventory":
        return inventory(Path(args.dir))
    if args.cmd == "verify":
        return verify(Path(args.dir))
    return extract(Path(args.file), args.mesh, args.part, Path(args.out))


if __name__ == "__main__":
    sys.exit(main())