"""Small Hugging Face entry point for a grouped ActionCodec2 artifact.

Transformers copies only top-level Python files from a Hub repository into its
dynamic-module cache. This entry point locates the artifact, then loads the
versioned runtime stored in ``runtime/`` without installing another package.
"""

from __future__ import annotations

import hashlib
import importlib
import importlib.util
import sys
from pathlib import Path


class ActionCodec2:
    """Load the processor implementation bundled with a pretrained artifact."""

    @classmethod
    def register_for_auto_class(cls, auto_class="AutoProcessor"):
        """Satisfy Transformers' dynamic class hook for this thin loader."""
        return cls

    @classmethod
    def from_pretrained(cls, pretrained_model_name_or_path, **kwargs):
        source = Path(pretrained_model_name_or_path)
        subfolder = str(kwargs.pop("subfolder", ""))
        action_space = kwargs.pop("action_space", None)
        kwargs.pop("_from_auto", None)
        kwargs.pop("trust_remote_code", None)
        allowed = {
            "cache_dir",
            "force_download",
            "local_files_only",
            "token",
            "revision",
            "repo_type",
        }
        unknown = sorted(set(kwargs) - allowed)
        if unknown:
            raise TypeError(
                f"unsupported from_pretrained keyword(s): {', '.join(unknown)}"
            )
        if source.is_dir():
            root = source / subfolder
        else:
            from huggingface_hub import snapshot_download

            prefix = f"{subfolder.rstrip('/')}/" if subfolder else ""
            patterns = [
                "config.json",
                "processor_config.json",
                "router_config.yaml",
                "profiles/**",
                "runtime/**",
                "README.md",
                "requirements.txt",
                "fit_report.json",
            ]
            snapshot = snapshot_download(
                repo_id=str(pretrained_model_name_or_path),
                allow_patterns=[prefix + pattern for pattern in patterns],
                **kwargs,
            )
            root = Path(snapshot) / subfolder

        runtime = root / "runtime"
        package_file = runtime / "__init__.py"
        if not package_file.is_file():
            raise FileNotFoundError(
                f"ActionCodec2 runtime is missing from {root}; copy the whole artifact"
            )
        identity = hashlib.sha256(str(runtime.resolve()).encode()).hexdigest()[:16]
        package_name = f"_actioncodec2_artifact_{identity}"
        if package_name not in sys.modules:
            spec = importlib.util.spec_from_file_location(
                package_name, package_file, submodule_search_locations=[str(runtime)]
            )
            if spec is None or spec.loader is None:
                raise ImportError(f"cannot load ActionCodec2 runtime from {runtime}")
            package = importlib.util.module_from_spec(spec)
            sys.modules[package_name] = package
            try:
                spec.loader.exec_module(package)
            except BaseException:
                del sys.modules[package_name]
                raise
        processor = importlib.import_module(f"{package_name}.processing_actioncodec2")
        return processor.ActionCodec2.from_pretrained(root, action_space=action_space)