from datetime import datetime, timezone

import pytest

from scripts.benchmark.generation import (
    deterministic_standard_normal,
    noisy_scada_observation,
)


AT = datetime(2026, 5, 1, tzinfo=timezone.utc)


def test_noise_is_stable_and_bound_to_observation_identity():
    value = deterministic_standard_normal(
        seed="normal-day-v1", at=AT, device_id="P1", metric="pressure",
    )
    assert value == deterministic_standard_normal(
        seed="normal-day-v1", at=AT, device_id="P1", metric="pressure",
    )
    assert value != deterministic_standard_normal(
        seed="normal-day-v1", at=AT, device_id="P2", metric="pressure",
    )


def test_pressure_keeps_metres_and_flow_converts_lps_to_m3h_before_noise():
    pressure = noisy_scada_observation(
        raw_value=20.0, device_type="pressure", at=AT, device_id="P1",
        seed="normal-day-v1", pressure_sigma_percent=0, pressure_sigma_floor_m=0,
    )
    flow = noisy_scada_observation(
        raw_value=10.0, device_type="pipe_flow", at=AT, device_id="F1",
        seed="normal-day-v1", flow_sigma_percent=0,
    )
    assert pressure == 20.0
    assert flow == 36.0


def test_noise_is_clipped_and_pressure_never_becomes_negative():
    value = noisy_scada_observation(
        raw_value=0.01, device_type="pressure", at=AT, device_id="P1",
        seed="normal-day-v1", pressure_sigma_percent=0,
        pressure_sigma_floor_m=100, clip_sigma=3,
    )
    assert value >= 0

    with pytest.raises(ValueError, match="unsupported"):
        noisy_scada_observation(
            raw_value=1, device_type="quality", at=AT, device_id="Q1",
            seed="normal-day-v1",
        )