"""The bulk calculator reports storage PER DAY, not per month.

Consuming it as a monthly figure understated storage 30x — $971 vs $29,127 per
30 days on one SKU, roughly $0.55/unit against a $1.36/unit unexplained profit
gap. It is an invisible error (the number looks plausible, just small), so it is
pinned here rather than left to a comment.

How it was established, so a future reader can re-derive it:
  * `storageCharges` scales linearly with `inventory` and is completely
    independent of `saleUnits` — identical at 100 / 1,000 / 10,000 / 43,007.
  * Backing the rate out of item volume gives $0.7800/cu ft/month on two
    independent SKUs to four decimal places, which is Amazon's exact
    standard-size Jan-Sep FBA MONTHLY storage rate.
"""
from __future__ import annotations

import pytest

from dashboard.live_data import _storage_30d


class _Quote:
    def __init__(self, storage):
        self.storage_charges = storage


class _Svc:
    """Records the call and returns a fixed per-day storage charge."""

    def __init__(self, storage=32.36, boom=False):
        self.storage, self.boom, self.calls = storage, boom, []

    def bulk_quote(self, sku, price, sale_units, inventory, marketing=0.0):
        if self.boom:
            raise RuntimeError("bulk calculator down")
        self.calls.append({"sku": sku, "price": price, "sale_units": sale_units,
                           "inventory": inventory})
        return _Quote(self.storage)


def test_daily_charge_is_scaled_to_the_window():
    """32.36/day over 30 days is 970.80 — not 32.36."""
    svc = _Svc(storage=32.36)
    assert _storage_30d(svc, "SKU", 26.07, 51_618, 43_007) == pytest.approx(970.80)


def test_the_real_world_case_that_exposed_the_bug():
    """$970.91/day of storage is $29,127 per 30 days, not $971."""
    svc = _Svc(storage=970.91)
    got = _storage_30d(svc, "UBMICROFIBERGUSSETPILLOWWHITEQUEEN", 26.07, 51_618, 43_007)
    assert got == pytest.approx(29_127.30)
    assert got - 970.91 == pytest.approx(28_156.39)      # what the bug was hiding


@pytest.mark.parametrize("days", [7, 14, 30, 90, 180])
def test_scales_linearly_with_the_window(days):
    svc = _Svc(storage=10.0)
    assert _storage_30d(svc, "SKU", 20.0, 1000, 5000, days=days) == pytest.approx(10.0 * days)


def test_zero_storage_stays_zero():
    assert _storage_30d(_Svc(storage=0.0), "SKU", 20.0, 1000, 5000) == 0.0


def test_a_failed_lookup_degrades_to_zero_rather_than_raising():
    """A storage lookup failure must not take down the whole analysis."""
    assert _storage_30d(_Svc(boom=True), "SKU", 20.0, 1000, 5000) == 0.0


def test_inventory_and_units_are_floored_at_one():
    """The calculator rejects zero, and a new SKU legitimately has neither."""
    svc = _Svc()
    _storage_30d(svc, "SKU", 20.0, units_30d=0, inventory=0)
    assert svc.calls[0]["sale_units"] == 1 and svc.calls[0]["inventory"] == 1