"""``get_dhcp_leases()``: an empty answer is only ever a real one (#27).

The getter tries Kea, then ISC DHCP, then falls back to the ARP table (rows
with ``state: "arp"``). A caller stores the answer as the server's lease set,
so ``[]`` must mean "a lease source answered and has no leases". When no lease
source answered and the ARP fallback gives nothing either, the getter raises:
an empty list there would wipe the leases the caller knows.
"""

from __future__ import annotations

from unittest.mock import MagicMock

import pytest

from napalm_opnsense.opnsense import OPNsenseDriver

KEA = "/api/kea/leases4/search"
ISC = "/api/dhcpv4/leases/searchlease"
ARP = "/api/diagnostics/interface/get_arp"

KEA_ROW = {"hwaddr": "AA:BB:CC:DD:EE:01", "address": "10.0.0.11", "hostname": "nas", "state": "0"}
ISC_ROW = {"mac": "aa:bb:cc:dd:ee:02", "address": "10.0.0.12", "ends": "1700000000"}
ARP_ROW = {"intf": "igb0", "mac": "AA:BB:CC:DD:EE:03", "ip": "10.0.0.13", "expires": "1200"}


def _driver(kea=None, isc=None, arp=None) -> OPNsenseDriver:
    """Each source answers its value, or raises it when it is an exception."""

    def answer(value):
        if isinstance(value, Exception):
            raise value
        return value

    driver = OPNsenseDriver("gw-01", "user", "secret")
    driver._get = MagicMock(side_effect=lambda path: answer({KEA: kea, ARP: arp}[path]))
    driver._post = MagicMock(side_effect=lambda path, data=None: answer({ISC: isc}[path]))
    return driver


def _macs(leases: list[dict]) -> list[str]:
    return [lease["mac"] for lease in leases]


class TestALeaseSourceAnswers:
    def test_kea_leases_come_first(self):
        driver = _driver(kea={"rows": [KEA_ROW]}, isc=RuntimeError("404"), arp=RuntimeError("x"))
        assert _macs(driver.get_dhcp_leases()) == ["aa:bb:cc:dd:ee:01"]

    def test_isc_leases_when_kea_has_none(self):
        driver = _driver(kea={"rows": []}, isc={"rows": [ISC_ROW]}, arp=RuntimeError("x"))
        assert _macs(driver.get_dhcp_leases()) == ["aa:bb:cc:dd:ee:02"]

    def test_isc_leases_when_kea_fails(self):
        driver = _driver(kea=RuntimeError("404"), isc={"rows": [ISC_ROW]}, arp=RuntimeError("x"))
        assert _macs(driver.get_dhcp_leases()) == ["aa:bb:cc:dd:ee:02"]


class TestTheArpFallback:
    """No source has leases: the ARP table stands in, marked ``state: "arp"`` (#1168)."""

    def test_when_both_lease_sources_fail(self):
        driver = _driver(kea=RuntimeError("404"), isc=RuntimeError("404"), arp=[ARP_ROW])
        leases = driver.get_dhcp_leases()
        assert leases == [
            {
                "mac": "aa:bb:cc:dd:ee:03",
                "ip": "10.0.0.13",
                "hostname": "",
                "lease_end": 0,
                "state": "arp",
            }
        ]

    def test_when_a_lease_source_answers_empty(self):
        driver = _driver(kea={"rows": []}, isc=RuntimeError("404"), arp=[ARP_ROW])
        assert [lease["state"] for lease in driver.get_dhcp_leases()] == ["arp"]


class TestAnEmptyAnswer:
    """[] only when Kea or ISC answered and has no leases."""

    def test_kea_empty_and_no_arp_fallback(self):
        driver = _driver(kea={"rows": []}, isc=RuntimeError("404"), arp=RuntimeError("timeout"))
        assert driver.get_dhcp_leases() == []

    def test_isc_empty_and_an_empty_arp_table(self):
        driver = _driver(kea=RuntimeError("404"), isc={"rows": []}, arp=[])
        assert driver.get_dhcp_leases() == []


class TestNothingAnswered:
    """No lease source answered and the fallback gave no rows: that is no answer."""

    def test_all_three_fail(self):
        driver = _driver(
            kea=RuntimeError("kea down"), isc=RuntimeError("isc down"), arp=RuntimeError("arp down")
        )
        with pytest.raises(RuntimeError) as excinfo:
            driver.get_dhcp_leases()
        message = str(excinfo.value)
        assert "kea down" in message
        assert "isc down" in message
        assert "arp down" in message

    def test_lease_sources_fail_and_the_arp_table_is_empty(self):
        driver = _driver(kea=RuntimeError("kea down"), isc=RuntimeError("isc down"), arp=[])
        with pytest.raises(RuntimeError, match="kea down"):
            driver.get_dhcp_leases()