"""Tests for circular imports in all local packages and modules.

This ensures all internal packages can be imported right away without
any need to import some other module before doing so.

This module is based on the idea that pytest uses for self-testing:
* https://github.com/sanitizers/octomachinery/blob/be18b54/tests/circular_imports_test.py  # noqa: E501
* https://github.com/pytest-dev/pytest/blob/d18c75b/testing/test_meta.py
* https://twitter.com/codewithanthony/status/1229445110510735361
"""

from __future__ import annotations

import os
import pkgutil
import subprocess
import sys
from itertools import chain
from pathlib import Path
from types import ModuleType
from typing import Generator

import pytest

import multidict


def _find_all_importables(pkg: ModuleType) -> list[str]:
    """Find all importables in the project.

    Return them in order.
    """
    return sorted(
        set(
            chain.from_iterable(
                _discover_path_importables(Path(p), pkg.__name__) for p in pkg.__path__
            ),
        ),
    )


def _discover_path_importables(
    pkg_pth: Path,
    pkg_name: str,
) -> Generator[str, None, None]:
    """Yield all importables under a given path and package."""
    yield pkg_name
    for dir_path, _d, file_names in os.walk(pkg_pth):
        pkg_dir_path = Path(dir_path)

        if pkg_dir_path.parts[-1] == "__pycache__":
            continue

        if all(Path(_).suffix != ".py" for _ in file_names):
            continue

        rel_pt = pkg_dir_path.relative_to(pkg_pth)
        pkg_pref = ".".join((pkg_name,) + rel_pt.parts)
        yield from (
            pkg_path
            for _, pkg_path, _ in pkgutil.walk_packages(
                (str(pkg_dir_path),),
                prefix=f"{pkg_pref}.",
            )
        )


@pytest.fixture(params=_find_all_importables(multidict))
def import_path(request: pytest.FixtureRequest) -> str:
    """Return an importable from the multidict package."""
    importable_module: str = request.param
    if importable_module == "multidict._multidict":
        request.applymarker(pytest.mark.c_extension)

    return importable_module


def test_no_warnings(import_path: str) -> None:
    """Verify that importing modules and packages doesn't explode.

    This is seeking for any import errors including ones caused
    by circular imports.
    """
    imp_cmd = (
        # fmt: off
        sys.executable,
        "-I",
        "-W", "error",
        "-c", f"import {import_path!s}",
        # fmt: on
    )

    subprocess.check_call(imp_cmd)


@pytest.mark.c_extension
def test_c_extension_preferred_by_default(monkeypatch: pytest.MonkeyPatch) -> None:
    """Verify that the C-extension is exposed by default."""
    monkeypatch.delenv("MULTIDICT_NO_EXTENSIONS", raising=False)

    imp_cmd = (
        # fmt: off
        sys.executable,
        "-I",
        "-W", "error",
        "-c", "import multidict; raise SystemExit(int("
        "multidict.istr.__module__ != 'multidict._multidict' "
        "or multidict.USE_EXTENSIONS is not True))",
        # fmt: on
    )

    subprocess.check_call(imp_cmd)