"""Unit tests for ``runner.helpers.egress_observer`` (NFT-SEC-02 + NFT-SEC-05 / AZ-437)."""

from __future__ import annotations

import csv
from pathlib import Path

import pytest

from runner.helpers import egress_observer as eo


def _snap(other: int = 0, internal: int = 0, udp53: int = 0) -> eo.EgressCounterSnapshot:
    return eo.EgressCounterSnapshot(
        egress_packets_to_internal_net=internal,
        egress_packets_to_other_destinations=other,
        udp53_egress_packets=udp53,
    )


def test_egress_counter_rejects_negative_values() -> None:
    with pytest.raises(ValueError, match="cannot be negative"):
        eo.EgressCounterSnapshot(
            egress_packets_to_internal_net=-1,
            egress_packets_to_other_destinations=0,
            udp53_egress_packets=0,
        )


def test_no_egress_zero_delta_passes() -> None:
    before = _snap(other=10, internal=5)
    after = _snap(other=10, internal=42)  # internal traffic grew; that's fine

    report = eo.evaluate_no_egress(before, after, window_label="5min")

    assert report.delta_other_destinations == 0
    assert report.passes


def test_no_egress_nonzero_delta_fails() -> None:
    before = _snap(other=10)
    after = _snap(other=11)

    report = eo.evaluate_no_egress(before, after, window_label="5min")

    assert report.delta_other_destinations == 1
    assert not report.passes


def test_no_egress_records_internal_delta_for_evidence() -> None:
    before = _snap(internal=100)
    after = _snap(internal=200)

    report = eo.evaluate_no_egress(before, after, window_label="5min-derkachi")

    assert report.delta_internal == 100  # informational; does not affect verdict
    assert report.passes


def test_dns_blackhole_passes_on_full_silence_and_failed_lookup() -> None:
    before = _snap(udp53=7)
    after = _snap(udp53=7)

    report = eo.evaluate_dns_blackhole(
        before,
        after,
        lookup_outcome=eo.DnsLookupOutcome.NXDOMAIN,
        sidecar_healthy=True,
    )

    assert report.passes


def test_dns_blackhole_fails_on_successful_lookup() -> None:
    before = _snap(udp53=7)
    after = _snap(udp53=7)

    report = eo.evaluate_dns_blackhole(
        before,
        after,
        lookup_outcome=eo.DnsLookupOutcome.SUCCESS,
        sidecar_healthy=True,
    )

    assert not report.passes_lookup
    assert not report.passes


def test_dns_blackhole_fails_when_udp53_packets_escaped() -> None:
    before = _snap(udp53=7)
    after = _snap(udp53=8)

    report = eo.evaluate_dns_blackhole(
        before,
        after,
        lookup_outcome=eo.DnsLookupOutcome.NXDOMAIN,
        sidecar_healthy=True,
    )

    assert not report.passes_udp_silence
    assert not report.passes


def test_dns_blackhole_fails_when_sidecar_unhealthy() -> None:
    before = _snap()
    after = _snap()

    report = eo.evaluate_dns_blackhole(
        before,
        after,
        lookup_outcome=eo.DnsLookupOutcome.NXDOMAIN,
        sidecar_healthy=False,
    )

    assert not report.passes


@pytest.mark.parametrize(
    "outcome",
    [
        eo.DnsLookupOutcome.NXDOMAIN,
        eo.DnsLookupOutcome.TIMEOUT,
        eo.DnsLookupOutcome.NO_SERVERS,
        eo.DnsLookupOutcome.OTHER_FAILURE,
    ],
)
def test_all_failure_outcomes_pass_lookup_check(outcome: eo.DnsLookupOutcome) -> None:
    report = eo.evaluate_dns_blackhole(
        _snap(),
        _snap(),
        lookup_outcome=outcome,
        sidecar_healthy=True,
    )

    assert report.passes_lookup


def test_no_egress_csv_evidence_round_trip(tmp_path: Path) -> None:
    before = _snap(other=0, internal=5)
    after = _snap(other=0, internal=42)
    report = eo.evaluate_no_egress(before, after, window_label="5min")

    out = tmp_path / "out.csv"
    eo.write_no_egress_csv_evidence(out, report)

    with out.open() as fh:
        rows = list(csv.reader(fh))
    assert rows[0][0] == "window_label"
    assert rows[1][0] == "5min"
    assert rows[1][-1] == "true"


def test_dns_blackhole_csv_evidence_round_trip(tmp_path: Path) -> None:
    report = eo.evaluate_dns_blackhole(
        _snap(udp53=7),
        _snap(udp53=7),
        lookup_outcome=eo.DnsLookupOutcome.NXDOMAIN,
        sidecar_healthy=True,
    )

    out = tmp_path / "out.csv"
    eo.write_dns_blackhole_csv_evidence(out, report)

    with out.open() as fh:
        rows = list(csv.reader(fh))
    assert rows[0][0] == "sidecar_healthy"
    assert rows[1][1] == "nxdomain"
    assert rows[1][-1] == "true"