import pytest

from llm_connect.fx import DEFAULT_EUR_PER_USD, FxRate, resolve_fx_rate


def test_resolve_fx_prefers_explicit_rate():
    rate = resolve_fx_rate(0.85)

    assert rate is not None
    assert rate.eur_per_usd == pytest.approx(0.85)
    assert rate.source == "explicit"
    assert rate.usd_to_eur(10.0) == pytest.approx(8.5)


def test_resolve_fx_reads_env(monkeypatch):
    monkeypatch.setenv("LLM_CONNECT_EUR_PER_USD", "0.9")

    rate = resolve_fx_rate()

    assert rate is not None
    assert rate.eur_per_usd == pytest.approx(0.9)
    assert rate.source == "env:LLM_CONNECT_EUR_PER_USD"


def test_resolve_fx_falls_back_to_snapshot():
    rate = resolve_fx_rate(env={})

    assert rate is not None
    assert rate.eur_per_usd == pytest.approx(DEFAULT_EUR_PER_USD)
    assert rate.source.startswith("snapshot:")


def test_invalid_env_rate_raises():
    with pytest.raises(ValueError, match="LLM_CONNECT_EUR_PER_USD"):
        resolve_fx_rate(env={"LLM_CONNECT_EUR_PER_USD": "0"})


def test_fx_rate_rejects_non_positive():
    with pytest.raises(ValueError, match="eur_per_usd"):
        FxRate(eur_per_usd=-1, source="x")