import pytest
from markovian_rsa_mlx.guards import (
    estimate_kv_bytes, estimate_total_bytes, check_memory_budget,
    check_context_budget,
)
from markovian_rsa_mlx.config import RSAConfig


def test_estimate_kv_bytes_for_known_zaya():
    bytes_per_token = estimate_kv_bytes(zaya_per_token_bytes=40_000, tokens=16384, parallel=4)
    assert bytes_per_token == 40_000 * 16384 * 4


def test_total_bytes_includes_weights():
    total = estimate_total_bytes(weights_bytes=4_700_000_000, kv_bytes=2_600_000_000, workspace_bytes=500_000_000)
    assert total == 4_700_000_000 + 2_600_000_000 + 500_000_000


def test_memory_check_returns_ok_when_under_limit():
    cfg = RSAConfig(parallel=4, chunk_tokens=16384, memory_fraction=0.80)
    decision = check_memory_budget(
        cfg=cfg,
        weights_bytes=4_700_000_000,
        per_token_kv_bytes=40_000,
        workspace_bytes=500_000_000,
        metal_limit_bytes=24_000_000_000,
    )
    assert decision.ok is True
    assert decision.fallback_to_serial is False


def test_memory_check_recommends_serial_when_over():
    cfg = RSAConfig(parallel=8, chunk_tokens=16384, memory_fraction=0.80, auto_serial=True)
    decision = check_memory_budget(
        cfg=cfg,
        weights_bytes=4_700_000_000,
        per_token_kv_bytes=40_000,
        workspace_bytes=4_000_000_000,
        metal_limit_bytes=16_000_000_000,
    )
    assert decision.ok is False
    assert decision.fallback_to_serial is True


def test_memory_check_raises_when_auto_serial_disabled():
    cfg = RSAConfig(parallel=8, chunk_tokens=16384, memory_fraction=0.80, auto_serial=False)
    with pytest.raises(MemoryError):
        check_memory_budget(
            cfg=cfg,
            weights_bytes=4_700_000_000,
            per_token_kv_bytes=40_000,
            workspace_bytes=4_000_000_000,
            metal_limit_bytes=16_000_000_000,
        )


def test_context_check_passes_within_limit():
    cfg = RSAConfig(chunk_tokens=8000, tail_tokens=2000, aggregation_subsample=4)
    check_context_budget(cfg=cfg, prompt_tokens=1000, max_context_tokens=131072)


def test_context_check_raises_when_over():
    cfg = RSAConfig(chunk_tokens=80000, tail_tokens=20000, aggregation_subsample=4)
    with pytest.raises(ValueError, match="exceed"):
        check_context_budget(cfg=cfg, prompt_tokens=1000, max_context_tokens=131072)