from decimal import Decimal
from pathlib import Path

from fastapi.testclient import TestClient

from fin_hub.app import create_app
from fin_hub.routers.effectiveness import create_effectiveness_router
from fin_hub.services.effectiveness import cheaper_on_series, effectiveness_report
from fin_hub.services.ledger import import_csv, record_plan_entitlement
from fin_hub.services.session_tokens import ingest_session_token_evidence


def _write_plan(path: Path, *, period: str, amount: str) -> None:
    path.write_text(
        "provider,plan,charge_kind,amount,currency,period_month,ongoing\n"
        f"anthropic,claude-max,subscription,{amount},EUR,{period},true\n",
        encoding="utf-8",
    )


def _token_snapshot(
    *,
    record_id: str,
    period: str,
    measured: int,
    estimated: int,
    work: int,
) -> dict:
    start, end = f"{period}-01", f"{period}-28"
    totals = {
        "measured": {
            "tokens_in": measured,
            "tokens_out": 0,
            "event_count": 1 if measured else 0,
            "confidence": "1.0",
        }
    }
    if estimated:
        totals["estimated"] = {
            "tokens_in": estimated,
            "tokens_out": 0,
            "event_count": 1,
            "confidence": "0.35",
        }
    return {
        "record_id": record_id,
        "period_start": start,
        "period_end": end,
        "captured_at": "2026-08-15T12:00:00Z",
        "source_evidence": [f"state-hub:/token-events/aggregate/?month={period}"],
        "totals": totals,
        "work": {"unit": "task", "count": work, "source": "state-hub-tasks"},
    }


def test_low_coverage_month_is_unfit_and_has_no_blended_efficiency(tmp_path: Path):
    ledger = tmp_path / "ledger.db"
    high = tmp_path / "july.csv"
    low = tmp_path / "august.csv"
    _write_plan(high, period="2026-07", amount="200.00")
    _write_plan(low, period="2026-08", amount="200.00")
    import_csv(high, "ai-plan", ledger_path=ledger)
    import_csv(low, "ai-plan", ledger_path=ledger)
    record_plan_entitlement(
        provider="anthropic",
        plan="claude-max",
        period_month="2026-07",
        unit="plan",
        plan_label="Max 20x",
        source="vendor-plan",
        ledger_path=ledger,
    )
    ingest_session_token_evidence(
        _token_snapshot(
            record_id="tokens:2026-07",
            period="2026-07",
            measured=200,
            estimated=0,
            work=2,
        ),
        ledger_path=ledger,
    )
    ingest_session_token_evidence(
        _token_snapshot(
            record_id="tokens:2026-08",
            period="2026-08",
            measured=20,
            estimated=180,
            work=2,
        ),
        ledger_path=ledger,
    )

    rows = {row.period_month: row for row in effectiveness_report(ledger_path=ledger)}
    good = rows["2026-07"]
    bad = rows["2026-08"]
    assert good.trend_fit == "comparable"
    assert bad.trend_fit == "unfit"
    assert good.coverage == Decimal("1.00")
    assert bad.coverage == Decimal("0.100000")
    assert good.work_per_euro == bad.work_per_euro
    assert good.implied_basis == "inferred"
    payload = bad.as_dict()
    assert "efficiency" not in payload
    assert "blend" not in payload
    assert cheaper_on_series(bad, good, "measured_estimated") is None
    assert cheaper_on_series(bad, good, "measured") is None
    assert cheaper_on_series(bad, good, "euro") is False


def test_effectiveness_http_endpoint(tmp_path: Path):
    ledger = tmp_path / "ledger.db"
    source = tmp_path / "july.csv"
    _write_plan(source, period="2026-07", amount="200.00")
    import_csv(source, "ai-plan", ledger_path=ledger)
    ingest_session_token_evidence(
        _token_snapshot(
            record_id="tokens:2026-07",
            period="2026-07",
            measured=200,
            estimated=0,
            work=2,
        ),
        ledger_path=ledger,
    )
    app = create_app()
    app.include_router(
        create_effectiveness_router(ledger_path_resolver=lambda _: ledger),
        prefix="/test",
    )
    client = TestClient(app)
    response = client.get("/test/effectiveness?period=2026-07")
    assert response.status_code == 200
    body = response.json()
    assert body[0]["trend_fit"] == "comparable"
    assert body[0]["work_per_euro"] == "0.010000"
    assert "efficiency" not in body[0]