"""
A/R aging bands.

The bands measure days **past due**, not days since the transaction. An Amazon receivable is
not due when the order posts — it is due when its settlement disburses, roughly 14 days after
the settlement's last activity plus the clearing lag.

This distinction is the whole report. Banding by transaction date instead pushes a perfectly
normal biweekly settlement into 1-30 (on the Jan-2026 close that misfiled 9,556,111.11 of USA's
11,110,308 as overdue) and the aging stops meaning anything. Banding by due date keeps a healthy
month at ~100% Current — matching the Finance workbook — while a settlement Amazon is actually
holding still ages out of Current, which is the point.
"""
from __future__ import annotations

import datetime as dt

import pytest

# The test database is redirected in conftest.py, which runs before any test module is
# imported. (An earlier version set "AR_DB_URL" here — a name app/config.py does not read —
# so these tests wrote into the production database instead.)
from fastapi.testclient import TestClient        # noqa: E402
from sqlalchemy.orm import Session as OrmSession  # noqa: E402

from app.api.main import app                     # noqa: E402
from app.db import models                        # noqa: E402
from app.db.database import SessionLocal, init_db  # noqa: E402

MONTH_END = dt.date(2026, 1, 31)


def _session_with_settlement(last_date: dt.date, amount: float = 100_000.0) -> int:
    """A processed closing holding one receivable settlement with the given last activity."""
    init_db()
    db: OrmSession = SessionLocal()
    try:
        s = models.Session(name="aging", reporting_month="2026-01", month_end_date=MONTH_END,
                           clearing_lag_days=2, status="processed")
        db.add(s)
        db.commit()
        db.add(models.Settlement(
            session_id=s.id, marketplace="USA", account_type="Standard Orders",
            settlement_id="900", order_total=amount, transfer_total=0.0, row_count=1,
            first_date=last_date, last_date=last_date, status="receivable"))
        db.add(models.ReceivableResultRow(
            session_id=s.id, marketplace="USA", account_type="TOTAL",
            additional_sales=amount, reserve=0.0, receivable_local=amount,
            fx_rate=1.0, receivable_usd=amount, currency="USD"))
        db.commit()
        return s.id
    finally:
        db.close()


@pytest.mark.parametrize("last_date,expected_band", [
    # due = last activity + 14 (settlement cycle) + 2 (clearing lag); overdue vs 31 Jan 2026
    (dt.date(2026, 1, 29), "Current"),    # due 14 Feb — 14 days before it is even due
    (dt.date(2026, 1, 15), "Current"),    # due 31 Jan — due exactly today, not yet late
    (dt.date(2026, 1, 14), "1-30"),       # due 30 Jan —  1 day  overdue
    (dt.date(2025, 12, 20), "1-30"),      # due  5 Jan — 26 days overdue
    (dt.date(2025, 11, 20), "31-60"),     # due  6 Dec — 56 days overdue
    (dt.date(2025, 11, 1), "61-90"),      # due 17 Nov — 75 days overdue
    (dt.date(2025, 10, 15), "91-Over"),   # due 31 Oct — 92 days overdue
])
def test_settlements_band_by_days_past_due(last_date, expected_band):
    sid = _session_with_settlement(last_date)
    with TestClient(app) as c:
        row = c.get(f"/api/sessions/{sid}/aging").json()["rows"][0]
    banded = {b: v for b, v in row.items() if b in
              ("Current", "1-30", "31-60", "61-90", "91-Over")}
    hit = max(banded, key=lambda b: abs(banded[b]))
    assert hit == expected_band, f"last activity {last_date} landed in {hit}, expected {expected_band}"


def test_normal_biweekly_settlement_stays_current():
    """The regression that matters: a healthy settlement must not read as overdue."""
    sid = _session_with_settlement(dt.date(2026, 1, 29), amount=9_556_111.11)
    with TestClient(app) as c:
        row = c.get(f"/api/sessions/{sid}/aging").json()["rows"][0]
    assert row["Current"] == pytest.approx(9_556_111.11, abs=0.01)
    assert row["1-30"] == 0.0


def test_bands_always_tie_to_the_headline_receivable():
    """Reserve and rounding land in Current so the row still sums to the published figure."""
    sid = _session_with_settlement(dt.date(2025, 11, 20), amount=100_000.0)
    with TestClient(app) as c:
        data = c.get(f"/api/sessions/{sid}/aging").json()
    row = data["rows"][0]
    assert sum(row[b] for b in data["bands"]) == pytest.approx(row["Total"], abs=0.01)
    assert row["Total"] == pytest.approx(100_000.0, abs=0.01)