"""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, band, burn_rate, current_run, find_replacements, normalise,
    orderlist, 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_live_level_drives_the_countdown_not_the_stored_one():
    """The report shows the live level, so it must count down from that one.

    History lags a poll, and trends lag an hour. Displaying 20% beside a
    countdown computed from a stored 4% is how a report loses its reader.
    """
    result = analyse(series([100, 80, 60, 40]), currentlevel=20)

    assert result['currentlevel'] == 20
    assert result['burnrateperday'] == 20.0     # 60 points over 3 days
    assert result['daysleft'] == 1              # 20 / 20, not 40 / 20


def test_a_nearly_empty_cartridge_reads_as_empty_not_as_weeks_away():
    """1% draining a tenth of a point a day computes to ten days. It is out."""
    result = analyse(series([2.0, 1.7, 1.4, 1.1]), currentlevel=1)

    assert result['daysleft'] == 0


def test_empty_sorts_ahead_of_a_fast_healthy_cartridge():
    empty = analyse(series([2.0, 1.7, 1.4, 1.1]), currentlevel=1)
    healthy = analyse(series([100, 80, 60, 40]))

    assert empty['daysleft'] < healthy['daysleft']


def test_a_low_live_level_is_actionable_without_any_history():
    """A printer new to Zabbix still reports it is out of toner."""
    result = analyse([], currentlevel=1)

    assert result['daysleft'] == 0
    assert result['reason'] is None


def test_no_history_and_a_healthy_level_still_says_no_history():
    result = analyse([], currentlevel=80)

    assert result['daysleft'] is None
    assert result['reason'] == 'no history'


def test_a_live_level_above_the_stored_run_means_it_was_just_swapped():
    """Trends lag an hour; a cartridge changed in that hour must not inherit
    the rate of the one that came out."""
    result = analyse(series([40, 30, 20, 10]), currentlevel=100)

    assert result['daysleft'] is None
    assert result['reason'] == 'replaced recently'
    assert result['replacements'] == 1


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 cartridge(daysleft, partnumber='CF258X', color='black', printername='PRN',
              model='HP 428', printerid=1):
    parts = [{'partnumber': partnumber, 'marketingname': None,
              'capacitytier': 'standard'}] if partnumber else []
    return {'daysleft': daysleft, 'partnumbers': parts, 'color': color,
            'supplytype': 'toner', 'model': model, 'printerid': printerid,
            'printername': printername}


def test_bands_split_at_two_weeks_and_a_month():
    assert band(0) == 'empty'
    assert band(1) == 'soon'
    assert band(14) == 'soon'
    assert band(15) == 'month'
    assert band(30) == 'month'
    assert band(31) == 'later'


def test_no_estimate_belongs_to_no_band():
    assert band(None) is None


def test_the_same_part_in_two_printers_is_a_quantity_of_two():
    """The number purchasing needs, and the one a per-printer table makes you
    count by hand."""
    result = orderlist([cartridge(0, printername='A', printerid=1),
                        cartridge(3, printername='B', printerid=2)])

    assert len(result) == 1
    assert result[0]['quantity'] == 2
    assert [p['printername'] for p in result[0]['printers']] == ['A', 'B']


def test_the_order_list_stops_at_the_horizon():
    """Ordering only what is already empty means running empty; ordering three
    months out is a stock cupboard."""
    result = orderlist([cartridge(0), cartridge(90, partnumber='W2021A')])

    assert [item['partnumber'] for item in result] == ['CF258X']


def test_a_cartridge_with_no_part_mapped_is_still_on_the_list():
    """Dropping it would quietly shorten the order."""
    result = orderlist([cartridge(2, partnumber=None)])

    assert len(result) == 1
    assert result[0]['partnumber'] is None
    assert result[0]['quantity'] == 1


def test_unmapped_parts_sort_last():
    """They need a decision before anything can be ordered, so they do not sit
    at the top of a list meant to be read straight down."""
    result = orderlist([cartridge(1, partnumber=None), cartridge(1)])

    assert result[0]['partnumber'] == 'CF258X'
    assert result[-1]['partnumber'] is None


def test_alternate_capacity_tiers_are_offered_not_counted_separately():
    item = {**cartridge(1), 'partnumbers': [
        {'partnumber': 'CF258A', 'marketingname': None, 'capacitytier': 'standard'},
        {'partnumber': 'CF258X', 'marketingname': None, 'capacitytier': 'high'},
    ]}

    result = orderlist([item])

    assert len(result) == 1
    assert result[0]['partnumber'] == 'CF258A'
    assert result[0]['alternates'] == ['CF258X']


def test_the_same_part_for_a_different_model_is_ordered_separately():
    """Two models sharing a part number is a mapping error worth seeing, not a
    quantity to merge."""
    result = orderlist([cartridge(1, model='HP 428'),
                        cartridge(1, model='HP M454')])

    assert len(result) == 2


def test_no_estimate_never_reaches_the_order_list():
    assert orderlist([cartridge(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['cartridges'] == []
    assert body['orderlist'] == []