#!/usr/bin/env python3
"""Create an inference-only MMEngine checkpoint from a trusted training checkpoint.

The source checkpoints used for this release contain MMEngine runtime objects,
the full training configuration, optimizer/runtime state, and local filesystem
paths. This script loads those trusted files with an explicit safe-global
allowlist and writes only:

* ``state_dict`` tensors on CPU
* minimal, non-sensitive dataset metadata
* the source epoch and a format version

Never use this script on an untrusted checkpoint.
"""

from __future__ import annotations

import argparse
import builtins
import hashlib
import zipfile
from collections import OrderedDict
from pathlib import Path

import numpy as np
import torch
from mmengine.logging.history_buffer import HistoryBuffer


_DTYPES = (
    np.float16,
    np.float32,
    np.float64,
    np.int8,
    np.int16,
    np.int32,
    np.int64,
    np.uint8,
    np.uint16,
    np.uint32,
    np.uint64,
    np.bool_,
)

_SAFE_GLOBALS = [
    HistoryBuffer,
    (np._core.multiarray._reconstruct, "numpy.core.multiarray._reconstruct"),
    (np._core.multiarray.scalar, "numpy.core.multiarray.scalar"),
    np.ndarray,
    np.dtype,
    *{type(np.dtype(dtype)) for dtype in _DTYPES},
    builtins.getattr,
]

_FORBIDDEN_MARKERS = (
    b"/data",
    b"HistoryBuffer",
    b"message_hub",
    b"optimizer",
    b"experiment_name",
)


def _sha256(path: Path) -> str:
    digest = hashlib.sha256()
    with path.open("rb") as handle:
        for chunk in iter(lambda: handle.read(1024 * 1024), b""):
            digest.update(chunk)
    return digest.hexdigest()


def _pickle_payload(path: Path) -> bytes:
    with zipfile.ZipFile(path) as archive:
        pickle_names = [name for name in archive.namelist() if name.endswith("/data.pkl")]
        if len(pickle_names) != 1:
            raise RuntimeError(f"Expected one data.pkl member, found {pickle_names}")
        return archive.read(pickle_names[0])


def sanitize(source: Path, destination: Path) -> None:
    torch.serialization.add_safe_globals(_SAFE_GLOBALS)
    checkpoint = torch.load(source, map_location="cpu", weights_only=True)

    if not isinstance(checkpoint, dict) or "state_dict" not in checkpoint:
        raise TypeError("Source is not an MMEngine checkpoint with a state_dict")

    source_state = checkpoint["state_dict"]
    if not isinstance(source_state, dict):
        raise TypeError("state_dict must be a mapping")
    if not source_state or not all(torch.is_tensor(value) for value in source_state.values()):
        raise TypeError("state_dict must contain tensors only")

    state_dict = OrderedDict(
        (name, tensor.detach().cpu().contiguous())
        for name, tensor in source_state.items()
    )
    source_meta = checkpoint.get("meta") or {}
    source_epoch = int(source_meta.get("epoch", 0))

    clean_checkpoint = {
        "state_dict": state_dict,
        "meta": {
            "dataset_meta": {
                "classes": ("nodule",),
                "palette": [(220, 20, 60)],
            },
            "source_epoch": source_epoch,
            "format_version": 1,
        },
    }

    destination.parent.mkdir(parents=True, exist_ok=True)
    torch.save(clean_checkpoint, destination)

    verified = torch.load(destination, map_location="cpu", weights_only=True)
    verified_state = verified.get("state_dict", {})
    if list(verified_state) != list(state_dict):
        raise RuntimeError("State-dict keys changed during serialization")
    for name, tensor in state_dict.items():
        if not torch.equal(tensor, verified_state[name]):
            raise RuntimeError(f"Tensor changed during serialization: {name}")

    payload = _pickle_payload(destination)
    leaked = [marker.decode("ascii") for marker in _FORBIDDEN_MARKERS if marker in payload]
    if leaked:
        raise RuntimeError(f"Sanitized checkpoint still contains forbidden markers: {leaked}")

    print(f"source_sha256={_sha256(source)}")
    print(f"output_sha256={_sha256(destination)}")
    print(f"source_epoch={source_epoch}")
    print(f"tensor_count={len(state_dict)}")
    print(f"parameter_numel={sum(tensor.numel() for tensor in state_dict.values())}")


def main() -> None:
    parser = argparse.ArgumentParser()
    parser.add_argument("source", type=Path)
    parser.add_argument("destination", type=Path)
    args = parser.parse_args()
    sanitize(args.source, args.destination)


if __name__ == "__main__":
    main()