"""Tests for the Progress overlay endpoint."""
from __future__ import annotations

from collections.abc import AsyncIterator
from datetime import UTC, date, 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 (
    AccountSnapshot,
    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_full(session: AsyncSession) -> int:
    scen = Scenario(
        external_id="user-prog",
        kind="user",
        name="Progress test",
        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("0"),
        p50_ending_gbp=Decimal("0"),
        p90_ending_gbp=Decimal("0"),
        median_lifetime_tax_gbp=Decimal("0"),
        median_years_to_ruin=None,
        elapsed_seconds=Decimal("0"),
    )
    session.add(run)
    await session.commit()
    await session.refresh(run)

    yearly = [
        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"),
        ) for y in range(3)
    ]
    session.add_all(yearly)

    # Two snapshots a year apart
    snap_a = AccountSnapshot(
        external_id="wf:a:2024-01-01",
        snapshot_date=date(2024, 1, 1),
        account_id="a",
        account_name="Stocks",
        account_type="brokerage",
        currency="GBP",
        market_value=Decimal("1000000"),
        market_value_gbp=Decimal("1000000"),
    )
    snap_b = AccountSnapshot(
        external_id="wf:a:2025-01-01",
        snapshot_date=date(2025, 1, 1),
        account_id="a",
        account_name="Stocks",
        account_type="brokerage",
        currency="GBP",
        market_value=Decimal("1080000"),
        market_value_gbp=Decimal("1080000"),
    )
    session.add_all([snap_a, snap_b])
    await session.commit()
    return scen.id


async def test_progress_returns_actual_and_projected(
    client: AsyncClient,
    session: AsyncSession,
) -> None:
    sid = await _seed_full(session)
    resp = await client.get(f"/scenarios/{sid}/progress")
    assert resp.status_code == 200, resp.text
    body = resp.json()
    assert body["scenario_id"] == sid
    assert body["alignment_anchor"] == "2024-01-01"
    assert len(body["actual"]) == 2
    assert len(body["projected"]) == 3
    # year_idx 1 has actual £1.08M vs projected £1.05M → +30k variance.
    variance_y1 = next(v for v in body["variance"] if v["year_idx"] == 1)
    assert Decimal(variance_y1["delta_gbp"]) == Decimal("30000.00")


async def test_progress_handles_empty_snapshots(
    client: AsyncClient,
    session: AsyncSession,
) -> None:
    scen = Scenario(
        external_id="user-empty",
        kind="user",
        name="No snapshots",
        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}/progress")
    assert resp.status_code == 200
    body = resp.json()
    assert body["actual"] == []
    assert body["variance"] == []