"""Schema/code agreement must be observable (STATE-WP-0083-T07).

Central served two revisions behind the code with no signal at all. The API
started fine and would only have failed when a request touched a missing table.
"""

from __future__ import annotations

import pytest

from api.services import schema_state as ss


class _Session:
    def __init__(self, revision=None, raises=False):
        self._revision = revision
        self._raises = raises

    async def execute(self, *_a, **_k):
        if self._raises:
            raise RuntimeError("no connection")
        rev = self._revision

        class R:
            def scalar(self_inner):
                return rev

        return R()


def test_code_head_is_readable_from_the_shipped_migrations():
    """Must not require a database: it is what the code expects, not what ran."""
    assert ss.code_head_revision()


@pytest.mark.asyncio
async def test_matching_revision_reports_ok(monkeypatch):
    monkeypatch.setattr(ss, "code_head_revision", lambda: "abc123")
    assert (await ss.schema_state(_Session("abc123")))["status"] == "ok"


@pytest.mark.asyncio
async def test_behind_revision_is_reported_with_both_values(monkeypatch):
    monkeypatch.setattr(ss, "code_head_revision", lambda: "newrev")
    state = await ss.schema_state(_Session("oldrev"))
    assert state["status"] == "behind"
    assert state["applied"] == "oldrev" and state["expected"] == "newrev"


@pytest.mark.asyncio
async def test_unknown_is_not_reported_as_ok(monkeypatch):
    """An instance that cannot establish agreement must not claim it."""
    monkeypatch.setattr(ss, "code_head_revision", lambda: "newrev")
    assert (await ss.schema_state(_Session(raises=True)))["status"] == "unknown"
    monkeypatch.setattr(ss, "code_head_revision", lambda: None)
    assert (await ss.schema_state(_Session("oldrev")))["status"] == "unknown"