"""Unit tests for kernel loading and version semantics."""

from __future__ import annotations

from pathlib import Path

import pytest

from fable_selfplay.kernel import load_kernel

REPO_ROOT = Path(__file__).resolve().parents[2]
KERNEL_V01 = REPO_ROOT / "kernel" / "kernel-v0.1.yaml"
KERNEL_V02 = REPO_ROOT / "kernel" / "kernel-v0.2.yaml"


def test_load_kernel_v01():
    kernel = load_kernel(KERNEL_V01)
    assert kernel.version.startswith("0.1")


def test_load_kernel_v02():
    kernel = load_kernel(KERNEL_V02)
    assert kernel.version.startswith("0.2")


def test_versions_are_distinct():
    assert load_kernel(KERNEL_V01).version != load_kernel(KERNEL_V02).version


def test_kernel_exposes_governance_parameters():
    """The legality gate must read thresholds from the kernel, not from code.

    Both kernel versions must therefore expose a non-empty parameter mapping;
    a kernel with no parameters would mean the rules live in Python, which
    breaks the entire replay-under-different-text mechanism.
    """
    for path in (KERNEL_V01, KERNEL_V02):
        kernel = load_kernel(path)
        assert isinstance(kernel.params, dict)
        assert kernel.params, f"{path.name} exposes no governance parameters"


def test_v02_params_differ_from_v01():
    """v0.2 was driven by failing regression tests; if its effective
    parameters are identical to v0.1's, the amendments are cosmetic and the
    six closed exploits would still reproduce."""
    p1 = load_kernel(KERNEL_V01).params
    p2 = load_kernel(KERNEL_V02).params
    assert p1 != p2


def test_missing_kernel_file_raises():
    with pytest.raises((FileNotFoundError, OSError)):
        load_kernel(REPO_ROOT / "kernel" / "kernel-v9.9.yaml")