"""What a node's code reaches — the narrow answer a cache key is keyed on."""

import sys
import textwrap

from fluksio.sdk.imports import digest_of, reached


def _write(root, name, body):
    path = root / f"{name}.py"
    path.write_text(textwrap.dedent(body).lstrip())
    return path


def _study(tmp_path):
    """A package whose node function delegates to a helper beside it."""
    root = tmp_path / "study"
    root.mkdir()
    (root / "__init__.py").write_text("VERSION = 1\n")
    _write(
        root,
        "train",
        """
        import json

        from study.helpers import curve


        def fit(lr):
            return json.dumps(curve(lr))
        """,
    )
    _write(root, "helpers", "def curve(lr):\n    return [lr]\n")
    _write(root, "unused", "def nothing():\n    return 0\n")
    return root


def test_the_walk_follows_a_helper_and_stops_at_installed_code(tmp_path, monkeypatch):
    """The shim says nothing about this, and the repository says too much."""
    _study(tmp_path)
    monkeypatch.syspath_prepend(str(tmp_path))
    for name in [n for n in sys.modules if n == "study" or n.startswith("study.")]:
        del sys.modules[name]

    from study.train import fit

    files = reached(fit)

    # The module, the helper it calls into, and the package whose `__init__`
    # runs on the way in. Not the sibling nobody imports, and not `json`.
    assert set(files) == {"study", "study.train", "study.helpers"}
    assert all(path.endswith(".py") for path in files.values())


def test_the_digest_moves_with_the_helper_and_not_with_the_neighbour(
    tmp_path, monkeypatch
):
    """The whole point: it is neither necessary nor sufficient otherwise."""
    root = _study(tmp_path)
    monkeypatch.syspath_prepend(str(tmp_path))
    for name in [n for n in sys.modules if n == "study" or n.startswith("study.")]:
        del sys.modules[name]

    from study.train import fit

    files = reached(fit)
    before = digest_of(files)

    _write(root, "unused", "def nothing():\n    return 1\n")
    assert digest_of(files) == before

    _write(root, "helpers", "def curve(lr):\n    return [lr, lr]\n")
    assert digest_of(files) != before

    # A file this engine cannot see is not half an answer.
    assert digest_of({**files, "study.gone": str(root / "gone.py")}) == ""


def test_the_tool_itself_is_not_the_projects_code(tmp_path, monkeypatch):
    """Every node imports the authoring API, and from a checkout that is source."""
    root = tmp_path / "arm"
    root.mkdir()
    (root / "__init__.py").write_text("")
    _write(
        root,
        "work",
        """
        from fluksio import node


        def fit(lr):
            return lr
        """,
    )
    monkeypatch.syspath_prepend(str(tmp_path))
    for name in [n for n in sys.modules if n == "arm" or n.startswith("arm.")]:
        del sys.modules[name]

    from arm.work import fit

    assert set(reached(fit)) == {"arm", "arm.work"}