#!/usr/bin/env python3
import hashlib
import json
import pathlib
import sys
import tempfile
import os
import bpy

def report():
    data = bpy.data.grease_pencils.get("GreasePencilData")
    if data is None: raise RuntimeError("GreasePencilData is missing")
    layers = []
    for layer in data.layers:
        frames = sorted(int(frame.frame_number) for frame in layer.frames)
        layers.append({"name": layer.name, "frames": frames})
    return {"name": data.name, "layers": layers}

def main():
    args = sys.argv[sys.argv.index("--") + 1:]
    if len(args) != 2: raise SystemExit("usage: blender -b --python check-grease-pencil-desktop.py -- FIXTURE REPORT")
    fixture, output = (pathlib.Path(value).resolve() for value in args)
    bpy.ops.wm.open_mainfile(filepath=str(fixture), load_ui=False); before = report(); descriptor, temporary = tempfile.mkstemp(prefix="m16-gp-reopen-", suffix=".blend"); os.close(descriptor)
    try: bpy.ops.wm.save_as_mainfile(filepath=temporary, check_existing=False, compress=True); bpy.ops.wm.open_mainfile(filepath=temporary, load_ui=False); after = report()
    finally: pathlib.Path(temporary).unlink(missing_ok=True)
    if before != after: raise RuntimeError(f"Grease Pencil save/reopen drift: {before} != {after}")
    value = {"schemaVersion": 1, "task": "M16-GAP-00009", "operation": "GREASE_PENCIL_DATABLOCK_DESKTOP", "fixture": str(fixture), "fixtureSha256": hashlib.sha256(fixture.read_bytes()).hexdigest(), "greasePencil": after, "saveReopen": "EXACT", "blenderVersion": bpy.app.version_string}; output.parent.mkdir(parents=True, exist_ok=True); output.write_text(json.dumps(value, indent=2, sort_keys=True) + "\n", encoding="utf-8"); print(f"grease-pencil-desktop-ok layers={len(after['layers'])} saveReopen=exact")
if __name__ == "__main__": main()