#!/usr/bin/env python3
"""Headless Blender script for GLB → VRM conversion.

Invoked via:
    blender --background --python scripts/vrm_export.py -- \\
        --input rigged_model.glb \\
        --output avatar.vrm \\
        --name "Avatar Name" \\
        --author "DaviesTechLabs Pipeline"

Requires:
    - Blender 4.x
    - VRM Add-on for Blender (https://vrm-addon-for-blender.info/en/)
"""

import argparse
import sys

# Blender's bpy is only available when running inside Blender
try:
    import bpy  # type: ignore[import-untyped]
except ImportError:
    print("ERROR: This script must be run inside Blender.")
    print("Usage: blender --background --python scripts/vrm_export.py -- --input model.glb --output model.vrm")
    sys.exit(1)


def parse_args() -> argparse.Namespace:
    """Parse arguments after the '--' separator in Blender CLI."""
    argv = sys.argv[sys.argv.index("--") + 1 :] if "--" in sys.argv else []
    parser = argparse.ArgumentParser(description="Convert rigged GLB to VRM")
    parser.add_argument("--input", required=True, help="Path to rigged GLB file")
    parser.add_argument("--output", required=True, help="Output VRM file path")
    parser.add_argument("--name", default="Generated Avatar", help="Avatar display name")
    parser.add_argument("--author", default="DaviesTechLabs Pipeline", help="Author name")
    return parser.parse_args(argv)


def clear_scene() -> None:
    """Remove all objects from the scene."""
    bpy.ops.wm.read_factory_settings(use_empty=True)


def import_glb(path: str) -> None:
    """Import a GLB file into the current scene."""
    bpy.ops.import_scene.gltf(filepath=path)
    print(f"Imported: {path}")
    print(f"  Objects: {[obj.name for obj in bpy.data.objects]}")


def find_armature() -> "bpy.types.Object":
    """Find the armature object in the scene."""
    armatures = [obj for obj in bpy.data.objects if obj.type == "ARMATURE"]
    if not armatures:
        print("ERROR: No armature found in imported model.")
        print("  Available objects:", [obj.name for obj in bpy.data.objects])
        sys.exit(1)
    if len(armatures) > 1:
        print(f"WARNING: Multiple armatures found, using first: {armatures[0].name}")
    return armatures[0]


def configure_vrm_metadata(armature: "bpy.types.Object", name: str, author: str) -> None:
    """Set VRM 1.0 metadata on the armature."""
    # The VRM Add-on stores metadata as a custom property
    armature["vrm_addon_extension"] = {
        "spec_version": "1.0",
        "vrm0": {
            "meta": {
                "title": name,
                "author": author,
                "allowedUserName": "Everyone",
                "violentUsageName": "Disallow",
                "sexualUsageName": "Disallow",
                "commercialUsageName": "Allow",
                "licenseName": "MIT",
            }
        },
    }
    print(f"  VRM metadata: name={name}, author={author}")


def export_vrm(path: str) -> None:
    """Export the scene as VRM."""
    bpy.ops.export_scene.vrm(filepath=path)
    print(f"Exported VRM: {path}")


def main() -> None:
    args = parse_args()

    print(f"Converting GLB to VRM:")
    print(f"  Input:  {args.input}")
    print(f"  Output: {args.output}")
    print(f"  Name:   {args.name}")

    clear_scene()
    import_glb(args.input)

    armature = find_armature()
    bpy.context.view_layer.objects.active = armature
    armature.select_set(True)

    configure_vrm_metadata(armature, args.name, args.author)
    export_vrm(args.output)

    print("Done.")


if __name__ == "__main__":
    main()