"""Tests for gateway code-skew detection (stale-checkout guard).

Companion to ``tests/test_stale_utils_module_import.py``: that test proves the
crash; these prove the guard that turns it into a clear "restart the gateway"
message before a model switch can hit it.
"""

import pytest

from gateway import code_skew


@pytest.fixture(autouse=True)
def _reset_boot_fingerprint(monkeypatch):
    """Each test starts with no recorded boot fingerprint."""
    monkeypatch.setattr(code_skew, "_boot_fingerprint", None)


class TestDetectCodeSkew:
    def test_no_boot_fingerprint_means_no_skew(self, monkeypatch):
        # Nothing recorded (e.g. non-git install) -> never a false positive.
        monkeypatch.setattr(code_skew, "_fingerprint", lambda: "git:refs/heads/main:def456")
        assert code_skew.detect_code_skew() is None

    def test_unchanged_checkout_is_not_skew(self, monkeypatch):
        monkeypatch.setattr(code_skew, "_fingerprint", lambda: "git:refs/heads/main:abc1234567890")
        code_skew.record_boot_fingerprint()
        assert code_skew.detect_code_skew() is None

    def test_drift_is_detected_with_short_revs(self, monkeypatch):
        monkeypatch.setattr(code_skew, "_fingerprint", lambda: "git:refs/heads/main:abc1234567890")
        code_skew.record_boot_fingerprint()

        monkeypatch.setattr(code_skew, "_fingerprint", lambda: "git:refs/heads/main:def4567890123")
        skew = code_skew.detect_code_skew()
        assert skew == ("abc1234567", "def4567890")

    def test_unreadable_current_rev_does_not_false_positive(self, monkeypatch):
        monkeypatch.setattr(code_skew, "_fingerprint", lambda: "git:refs/heads/main:abc1234567890")
        code_skew.record_boot_fingerprint()

        monkeypatch.setattr(code_skew, "_fingerprint", lambda: None)
        assert code_skew.detect_code_skew() is None

    def test_record_is_idempotent(self, monkeypatch):
        monkeypatch.setattr(code_skew, "_fingerprint", lambda: "git:refs/heads/main:first")
        code_skew.record_boot_fingerprint()
        monkeypatch.setattr(code_skew, "_fingerprint", lambda: "git:refs/heads/main:second")
        code_skew.record_boot_fingerprint()  # must not overwrite the boot snapshot
        assert code_skew._boot_fingerprint == "git:refs/heads/main:first"


class TestShort:
    def test_shortens_long_sha(self):
        assert code_skew._short("git:refs/heads/main:abcdef0123456789") == "abcdef0123"

    def test_keeps_unresolved_marker(self):
        assert code_skew._short("git:refs/heads/main:unresolved") == "unresolved"

    def test_passes_short_sha_through_untruncated(self):
        assert code_skew._short("git:HEAD:abc1234") == "abc1234"


class TestModelSwitchSkewGuard:
    def test_guard_returns_none_without_skew(self, monkeypatch):
        from gateway import slash_commands

        monkeypatch.setattr(code_skew, "detect_code_skew", lambda: None)
        assert slash_commands._model_switch_skew_guard() is None

    def test_guard_message_names_revs_and_restart(self, monkeypatch):
        from gateway import slash_commands

        monkeypatch.setattr(code_skew, "detect_code_skew", lambda: ("abc1234567", "def4567890"))
        msg = slash_commands._model_switch_skew_guard()
        assert msg is not None
        assert "abc1234567" in msg
        assert "def4567890" in msg
        assert "hermes gateway restart" in msg
