"""IMP-43 (#72) u1 + u5 — focused tests for the ``--reuse-from`` CLI surface.

u1 scope (per the Stage 2 Exit Report):

- argparse flag ``--reuse-from PREV_RUN_ID`` parses without error.
- Fail-closed precondition guard runs AFTER the ``user_overrides.json``
  merge and BEFORE dispatch. With ``--reuse-from`` set, the guard
  must:
    * accept frame-only overrides (or no overrides at all);
    * reject layout / zone-geometry / zone-section / image overrides
      with ``sys.exit(2)`` whose stderr names every rejected axis.

u5 scope (added 2026-05-24):

- ``reuse_from`` is keyword-only on ``run_phase_z2_mvp1`` and defaults
  to ``None`` so the absent-flag path preserves pre-u5 behaviour.
- The CLI dispatch forwards ``args.reuse_from`` verbatim — both
  ``None`` (flag absent) and ``"PREV_RUN_ID"`` (flag present) reach
  the kwarg unchanged.
- The fake ``run_phase_z2_mvp1`` stub below mirrors the production
  signature so the forwarding lock would fail loudly on any
  forwarding regression.

The harness mirrors ``tests/test_phase_z2_cli_overrides.py`` — the
``if __name__ == "__main__"`` block of ``src.phase_z2_pipeline`` is
exec'd inside the module's namespace after monkeypatching
``run_phase_z2_mvp1`` with a recording stub. The persistence fallback
is silenced by redirecting ``src.user_overrides_io.DEFAULT_OVERRIDES_ROOT``
to a clean tmp directory so persisted state from prior runs cannot bleed
into the parser-only assertions here.
"""
from __future__ import annotations

import ast
import sys
from pathlib import Path
from typing import Any

import pytest

import src.phase_z2_pipeline as _pz2
import src.user_overrides_io as _io


# -- harness ---------------------------------------------------------------


def _exec_main_block(
    captured: dict[str, Any], argv: list[str], monkeypatch
) -> None:
    """Run the ``__main__`` body of phase_z2_pipeline.py with a fake
    ``run_phase_z2_mvp1`` so its kwargs are observable. Captures the
    presence of the call (``called=True``) so guard-driven early exits
    can be distinguished from a successful parse + dispatch."""

    def _fake_run(
        mdx_path,
        run_id,
        *,
        override_layout=None,
        override_frames=None,
        override_zone_geometries=None,
        override_section_assignments=None,
        override_image_overrides=None,
        override_slide_css=None,
        reuse_from=None,
    ):
        captured["called"] = True
        captured["mdx_path"] = mdx_path
        captured["run_id"] = run_id
        captured["override_layout"] = override_layout
        captured["override_frames"] = override_frames
        captured["override_zone_geometries"] = override_zone_geometries
        captured["override_section_assignments"] = override_section_assignments
        captured["override_image_overrides"] = override_image_overrides
        captured["override_slide_css"] = override_slide_css
        captured["reuse_from"] = reuse_from

    monkeypatch.setattr(_pz2, "run_phase_z2_mvp1", _fake_run)
    monkeypatch.setattr(sys, "argv", argv)

    src_path = Path(_pz2.__file__)
    source = src_path.read_text(encoding="utf-8")
    tree = ast.parse(source)
    for node in tree.body:
        if (
            isinstance(node, ast.If)
            and isinstance(node.test, ast.Compare)
            and isinstance(node.test.left, ast.Name)
            and node.test.left.id == "__name__"
        ):
            block = ast.Module(body=node.body, type_ignores=[])
            exec(compile(block, str(src_path), "exec"), _pz2.__dict__)
            return
    raise AssertionError("no `if __name__ == '__main__'` block found")


def _redirect_overrides_root(tmp_path: Path, monkeypatch) -> None:
    """Isolate the persistence fallback so file state never leaks in."""
    monkeypatch.setattr(_io, "DEFAULT_OVERRIDES_ROOT", tmp_path)


# -- success paths --------------------------------------------------------


def test_reuse_from_alone_parses_and_dispatches(tmp_path, monkeypatch):
    """``--reuse-from`` with no other overrides must parse cleanly and
    fall through to dispatch (frame-only / empty override is allowed).
    u5 (2026-05-24): also asserts the CLI threads ``args.reuse_from``
    verbatim into the ``reuse_from`` kwarg."""
    _redirect_overrides_root(tmp_path, monkeypatch)
    captured: dict[str, Any] = {}
    _exec_main_block(
        captured,
        [
            "src.phase_z2_pipeline",
            "03.mdx",
            "--reuse-from",
            "03__DX_20260508025134",
        ],
        monkeypatch,
    )

    assert captured.get("called") is True
    # u5 — verbatim threading.
    assert captured["reuse_from"] == "03__DX_20260508025134"


def test_reuse_from_with_frame_override_dispatches(tmp_path, monkeypatch):
    """Frame overrides ARE preserved across Step 0/1/2/5/6 reuse, so
    ``--reuse-from`` + ``--override-frame`` must reach dispatch.
    u5: forwards both ``reuse_from`` and ``override_frames`` in the
    same call."""
    _redirect_overrides_root(tmp_path, monkeypatch)
    captured: dict[str, Any] = {}
    _exec_main_block(
        captured,
        [
            "src.phase_z2_pipeline",
            "03.mdx",
            "--reuse-from",
            "03__DX_20260508025134",
            "--override-frame",
            "03-1=frame_foo",
        ],
        monkeypatch,
    )

    assert captured.get("called") is True
    assert captured["override_frames"] == {"03-1": "frame_foo"}
    # u5 — frame override + reuse_from reach the kwarg simultaneously.
    assert captured["reuse_from"] == "03__DX_20260508025134"


# -- u5 — flag-absent default + signature surface ------------------------


def test_no_reuse_from_threads_none_kwarg(tmp_path, monkeypatch):
    """u5 — when ``--reuse-from`` is absent, the kwarg must reach
    ``run_phase_z2_mvp1`` as ``None`` (not omitted, not ``""``). This
    locks the "default None preserves current behavior" requirement
    from the Stage 2 plan §u5."""
    _redirect_overrides_root(tmp_path, monkeypatch)
    captured: dict[str, Any] = {}
    _exec_main_block(
        captured,
        ["src.phase_z2_pipeline", "03.mdx"],
        monkeypatch,
    )

    assert captured.get("called") is True
    assert captured["reuse_from"] is None


def test_run_phase_z2_mvp1_signature_includes_reuse_from():
    """Production signature lock — ``reuse_from`` must be a keyword-only
    parameter with default ``None``. Mirror of the entry-tests
    invariant; kept here so the CLI-surface test file fails loudly if
    the production signature drifts away from the dispatch contract."""
    import inspect

    sig = inspect.signature(_pz2.run_phase_z2_mvp1)
    assert "reuse_from" in sig.parameters, list(sig.parameters)
    param = sig.parameters["reuse_from"]
    assert param.kind is inspect.Parameter.KEYWORD_ONLY, param.kind
    assert param.default is None, param.default


# -- fail-closed (single-axis rejection) ----------------------------------


def test_reuse_from_with_layout_override_exits(tmp_path, monkeypatch, capsys):
    _redirect_overrides_root(tmp_path, monkeypatch)
    captured: dict[str, Any] = {}
    with pytest.raises(SystemExit) as excinfo:
        _exec_main_block(
            captured,
            [
                "src.phase_z2_pipeline",
                "03.mdx",
                "--reuse-from",
                "03__DX_20260508025134",
                "--override-layout",
                "horizontal-2",
            ],
            monkeypatch,
        )

    assert excinfo.value.code == 2
    err = capsys.readouterr().err
    assert "--reuse-from incompatible with override axes" in err
    assert "layout" in err
    assert captured.get("called") is not True


def test_reuse_from_with_zone_geometry_override_exits(
    tmp_path, monkeypatch, capsys
):
    _redirect_overrides_root(tmp_path, monkeypatch)
    captured: dict[str, Any] = {}
    with pytest.raises(SystemExit) as excinfo:
        _exec_main_block(
            captured,
            [
                "src.phase_z2_pipeline",
                "03.mdx",
                "--reuse-from",
                "03__DX_20260508025134",
                "--override-zone-geometry",
                "top=0,0,1,0.3",
            ],
            monkeypatch,
        )

    assert excinfo.value.code == 2
    err = capsys.readouterr().err
    assert "--reuse-from incompatible with override axes" in err
    assert "zone_geometry" in err
    assert captured.get("called") is not True


def test_reuse_from_with_zone_section_override_exits(
    tmp_path, monkeypatch, capsys
):
    _redirect_overrides_root(tmp_path, monkeypatch)
    captured: dict[str, Any] = {}
    with pytest.raises(SystemExit) as excinfo:
        _exec_main_block(
            captured,
            [
                "src.phase_z2_pipeline",
                "03.mdx",
                "--reuse-from",
                "03__DX_20260508025134",
                "--override-section-assignment",
                "top=03-1",
            ],
            monkeypatch,
        )

    assert excinfo.value.code == 2
    err = capsys.readouterr().err
    assert "--reuse-from incompatible with override axes" in err
    assert "zone_section" in err
    assert captured.get("called") is not True


def test_reuse_from_with_image_override_exits(tmp_path, monkeypatch, capsys):
    _redirect_overrides_root(tmp_path, monkeypatch)
    captured: dict[str, Any] = {}
    with pytest.raises(SystemExit) as excinfo:
        _exec_main_block(
            captured,
            [
                "src.phase_z2_pipeline",
                "03.mdx",
                "--reuse-from",
                "03__DX_20260508025134",
                "--override-image",
                "img-abc=10,15,30,25",
            ],
            monkeypatch,
        )

    assert excinfo.value.code == 2
    err = capsys.readouterr().err
    assert "--reuse-from incompatible with override axes" in err
    assert "image" in err
    assert captured.get("called") is not True


# -- fail-closed (multi-axis aggregation) ---------------------------------


def test_reuse_from_with_multiple_rejected_axes_lists_all(
    tmp_path, monkeypatch, capsys
):
    """Stderr must enumerate every rejected axis (not stop at first)."""
    _redirect_overrides_root(tmp_path, monkeypatch)
    captured: dict[str, Any] = {}
    with pytest.raises(SystemExit) as excinfo:
        _exec_main_block(
            captured,
            [
                "src.phase_z2_pipeline",
                "03.mdx",
                "--reuse-from",
                "03__DX_20260508025134",
                "--override-layout",
                "horizontal-2",
                "--override-zone-geometry",
                "top=0,0,1,0.3",
                "--override-image",
                "img-abc=10,15,30,25",
            ],
            monkeypatch,
        )

    assert excinfo.value.code == 2
    err = capsys.readouterr().err
    assert "layout" in err
    assert "zone_geometry" in err
    assert "image" in err
    assert captured.get("called") is not True


# -- guard inactive when --reuse-from absent ------------------------------


def test_no_reuse_from_layout_override_still_dispatches(
    tmp_path, monkeypatch
):
    """Without ``--reuse-from``, the guard must be silent — existing
    override behaviour is preserved end-to-end."""
    _redirect_overrides_root(tmp_path, monkeypatch)
    captured: dict[str, Any] = {}
    _exec_main_block(
        captured,
        [
            "src.phase_z2_pipeline",
            "03.mdx",
            "--override-layout",
            "horizontal-2",
        ],
        monkeypatch,
    )

    assert captured.get("called") is True
    assert captured["override_layout"] == "horizontal-2"


# -- fail-closed honours persisted overrides ------------------------------


def test_reuse_from_with_persisted_layout_override_exits(
    tmp_path, monkeypatch, capsys
):
    """The guard runs AFTER the user_overrides.json merge, so a layout
    persisted on disk (not on the CLI) must still reject when
    ``--reuse-from`` is set. This locks the Stage 2 placement rule."""
    _redirect_overrides_root(tmp_path, monkeypatch)
    # Persist a layout override keyed by the MDX stem ``03``.
    overrides_dir = tmp_path
    overrides_dir.mkdir(parents=True, exist_ok=True)
    (overrides_dir / "03.json").write_text(
        '{"layout": "vertical-2"}', encoding="utf-8"
    )
    captured: dict[str, Any] = {}
    with pytest.raises(SystemExit) as excinfo:
        _exec_main_block(
            captured,
            [
                "src.phase_z2_pipeline",
                "03.mdx",
                "--reuse-from",
                "03__DX_20260508025134",
            ],
            monkeypatch,
        )

    assert excinfo.value.code == 2
    err = capsys.readouterr().err
    assert "--reuse-from incompatible with override axes" in err
    assert "layout" in err
    assert captured.get("called") is not True