from __future__ import annotations

import importlib.machinery
import importlib.util
import sys
import types
from pathlib import Path
from typing import Any

BASE_DIR = Path(__file__).resolve().parent
PYCACHE_DIR = BASE_DIR / "__pycache__"
LEGACY_PYC_DIR = BASE_DIR / "_legacy_pyc"
SUPPORTED_PYTHON = (3, 11)

_LEGACY_MODULE: Any | None = None


def _ensure_supported_runtime() -> None:
    if sys.version_info[:2] != SUPPORTED_PYTHON:
        version = ".".join(map(str, sys.version_info[:3]))
        required = ".".join(map(str, SUPPORTED_PYTHON))
        raise RuntimeError(
            f"Legacy collector bytecode requires Python {required}. Current runtime: {version}."
        )


def _ensure_package() -> None:
    package = sys.modules.get("app")
    if package is None:
        package = types.ModuleType("app")
        package.__path__ = [str(BASE_DIR)]
        sys.modules["app"] = package


def _load_sourceless_module(module_name: str, pyc_path: Path) -> Any:
    loader = importlib.machinery.SourcelessFileLoader(module_name, str(pyc_path))
    spec = importlib.util.spec_from_loader(module_name, loader)
    if spec is None:
        raise RuntimeError(f"Unable to create spec for {module_name}")
    module = importlib.util.module_from_spec(spec)
    sys.modules[module_name] = module
    loader.exec_module(module)
    return module


def load_legacy_main() -> Any:
    global _LEGACY_MODULE
    if _LEGACY_MODULE is not None:
        return _LEGACY_MODULE

    _ensure_supported_runtime()
    _ensure_package()

    for name in ("database", "fastgpt", "openai_compat"):
        full_name = f"app.{name}"
        if full_name not in sys.modules:
            pyc_dir = LEGACY_PYC_DIR if (LEGACY_PYC_DIR / f"{name}.cpython-311.pyc").exists() else PYCACHE_DIR
            _load_sourceless_module(full_name, pyc_dir / f"{name}.cpython-311.pyc")

    legacy_name = "app.main_legacy"
    if legacy_name in sys.modules:
        _LEGACY_MODULE = sys.modules[legacy_name]
        return _LEGACY_MODULE

    main_pyc_dir = LEGACY_PYC_DIR if (LEGACY_PYC_DIR / "main.cpython-311.pyc").exists() else PYCACHE_DIR
    _LEGACY_MODULE = _load_sourceless_module(legacy_name, main_pyc_dir / "main.cpython-311.pyc")
    _LEGACY_MODULE.__package__ = "app"
    return _LEGACY_MODULE