"""Tests for toner burn-rate and replacement counting.

The analysis is pure arithmetic over a list of readings, so it is tested that
way - no Zabbix, no fixtures. What matters is that it refuses to guess: the
cases where an estimate would be dishonest are the ones most likely to reach a
purchasing decision.
"""

from datetime import datetime, timedelta, timezone

from plugins.printers.services.supply_history import (
    analyse, burn_rate, current_run, find_replacements, normalise, soonest,
)

START = datetime(2026, 6, 1, tzinfo=timezone.utc)


def series(levels, hours=24):
    """[(clock, value)] one reading per `hours`, as Zabbix returns them."""
    return [(str(int((START + timedelta(hours=i * hours)).timestamp())), str(v))
            for i, v in enumerate(levels)]


def test_counts_one_replacement_per_upward_step():
    points = normalise(series([80, 60, 40, 20, 100, 80, 60, 95, 70]))

    assert len(find_replacements(points)) == 2


def test_ignores_a_wobble_that_is_not_a_replacement():
    """SNMP rounding and a gauge settling both nudge a reading upward."""
    points = normalise(series([60, 58, 61, 57, 55]))

    assert find_replacements(points) == []


def test_estimate_uses_only_the_current_cartridge():
    """Fitting across a swap averages a spent cartridge with a fresh one."""
    points = normalise(series([90, 60, 30, 100, 90, 80, 70]))

    run = current_run(points)

    assert [level for _, level in run] == [100, 90, 80, 70]


def test_days_left_from_a_steady_drain():
    # 10 points a day apart, 5% a day, ending at 55%
    result = analyse(series([100, 95, 90, 85, 80, 75, 70, 65, 60, 55]))

    assert result['burnrateperday'] == 5.0
    assert result['daysleft'] == 11          # 55 / 5
    assert result['reason'] is None
    assert result['basisdays'] == 9.0


def test_no_estimate_from_two_readings():
    """Two points through a coarse gauge can prove any rate at all."""
    result = analyse(series([100, 90]))

    assert result['daysleft'] is None
    assert result['reason'] == 'not enough history yet'


def test_no_estimate_while_the_gauge_has_not_moved():
    """A printer reporting in 10% steps sits on a plateau for a fortnight."""
    result = analyse(series([70, 70, 70, 70, 70, 70]))

    assert result['daysleft'] is None
    assert result['reason'] == 'level has not moved enough to estimate'


def test_a_recent_replacement_says_so_rather_than_guessing():
    result = analyse(series([40, 30, 20, 10, 100, 98]))

    assert result['daysleft'] is None
    assert result['reason'] == 'replaced recently'
    assert result['replacements'] == 1
    assert result['lastreplaced'] is not None


def test_empty_history_is_reported_not_crashed():
    result = analyse([])

    assert result['reason'] == 'no history'
    assert result['currentlevel'] is None
    assert result['replacements'] == 0


def test_junk_rows_are_dropped_not_fatal():
    points = normalise([('notaclock', '50'), ('1780000000', 'n/a'),
                        ('1780000000', '50')])

    assert len(points) == 1


def test_days_left_never_goes_negative():
    result = analyse(series([20, 15, 10, 5, 0]))

    assert result['daysleft'] == 0


def test_printer_sorts_by_its_soonest_supply():
    """A colour MFP is as urgent as its most pressing cartridge."""
    supplies = [{'daysleft': 40}, {'daysleft': 6}, {'daysleft': None}]

    assert soonest(supplies) == 6


def test_soonest_is_none_when_nothing_can_be_estimated():
    assert soonest([{'daysleft': None}, {'daysleft': None}]) is None


def test_burn_rate_needs_elapsed_time():
    """Several readings in the same second is not a rate."""
    clock = str(int(START.timestamp()))
    points = normalise([(clock, '90'), (clock, '80'), (clock, '70'), (clock, '60')])

    assert burn_rate(points) is None


def test_forecast_endpoint_says_so_when_zabbix_is_absent(client, db):
    """A dashboard must be told the data is missing, not shown an empty list
    that reads as 'nothing runs out soon'."""
    response = client.get('/api/printers/supplies/forecast')

    assert response.status_code == 200
    body = response.get_json()['data']
    assert body['available'] is False
    assert 'not configured' in body['reason']
    assert body['printers'] == []