"""Tests for the per-year stats endpoint."""
from __future__ import annotations

from collections.abc import AsyncIterator
from datetime import UTC, datetime
from decimal import Decimal

import pytest_asyncio
from httpx import ASGITransport, AsyncClient
from sqlalchemy.ext.asyncio import AsyncEngine, AsyncSession, async_sessionmaker

from fire_planner.api.dependencies import get_session
from fire_planner.app import app
from fire_planner.db import McRun, ProjectionYearly, Scenario


@pytest_asyncio.fixture
async def client(engine: AsyncEngine,
                 session: AsyncSession) -> AsyncIterator[AsyncClient]:
    factory = async_sessionmaker(engine, expire_on_commit=False)

    async def _override() -> AsyncIterator[AsyncSession]:
        async with factory() as s:
            yield s

    app.dependency_overrides[get_session] = _override
    transport = ASGITransport(app=app)
    async with AsyncClient(transport=transport, base_url="http://test") as ac:
        yield ac
    app.dependency_overrides.clear()


async def _seed_scenario_with_run(session: AsyncSession) -> int:
    scen = Scenario(
        external_id="user-yr-stats",
        kind="user",
        name="Yr Stats",
        jurisdiction="uk",
        strategy="trinity",
        leave_uk_year=0,
        glide_path="static",
        spending_gbp=Decimal("60000"),
        horizon_years=5,
        nw_seed_gbp=Decimal("1000000"),
        savings_per_year_gbp=Decimal("0"),
        config_json={},
    )
    session.add(scen)
    await session.commit()
    await session.refresh(scen)

    run = McRun(
        scenario_id=scen.id,
        run_at=datetime.now(UTC),
        n_paths=100,
        seed=1,
        success_rate=Decimal("1"),
        p10_ending_gbp=Decimal("900000"),
        p50_ending_gbp=Decimal("1100000"),
        p90_ending_gbp=Decimal("1300000"),
        median_lifetime_tax_gbp=Decimal("50000"),
        median_years_to_ruin=None,
        elapsed_seconds=Decimal("1.234"),
    )
    session.add(run)
    await session.commit()
    await session.refresh(run)

    rows = [
        ProjectionYearly(
            mc_run_id=run.id,
            year_idx=y,
            p10_portfolio_gbp=Decimal("900000"),
            p25_portfolio_gbp=Decimal("950000"),
            p50_portfolio_gbp=Decimal(str(1_000_000 + y * 50_000)),
            p75_portfolio_gbp=Decimal("1100000"),
            p90_portfolio_gbp=Decimal("1200000"),
            p50_withdrawal_gbp=Decimal("60000"),
            p50_tax_gbp=Decimal("8000"),
            survival_rate=Decimal("1.0"),
        ) for y in range(5)
    ]
    session.add_all(rows)
    await session.commit()
    return scen.id


async def test_year_stats_returns_per_year_metrics(
    client: AsyncClient,
    session: AsyncSession,
) -> None:
    sid = await _seed_scenario_with_run(session)
    resp = await client.get(f"/scenarios/{sid}/year-stats?year=2")
    assert resp.status_code == 200, resp.text
    body = resp.json()
    assert body["year_idx"] == 2
    # year 2 NW = 1_100_000; year 1 NW = 1_050_000 → change 50_000.
    assert body["net_worth_p50"] == "1100000.00"
    assert body["change_in_nw"] == "50000.00"
    assert body["spending"] == "60000.00"
    assert body["taxes"] == "8000.00"


async def test_year_stats_404_when_no_run(client: AsyncClient,
                                          session: AsyncSession) -> None:
    scen = Scenario(
        external_id="user-no-run",
        kind="user",
        name="No run",
        jurisdiction="uk",
        strategy="trinity",
        leave_uk_year=0,
        glide_path="static",
        spending_gbp=Decimal("60000"),
        horizon_years=5,
        nw_seed_gbp=Decimal("1000000"),
        savings_per_year_gbp=Decimal("0"),
        config_json={},
    )
    session.add(scen)
    await session.commit()
    await session.refresh(scen)
    resp = await client.get(f"/scenarios/{scen.id}/year-stats?year=0")
    assert resp.status_code == 404