"""Unit tests for libs/backtest/splits.py."""
from __future__ import annotations

import datetime as dt

import pytest

from libs.backtest.calendar import get_trading_days


class TestGenerateWalkForwardWindows:
    def test_basic(self):
        from libs.backtest.splits import generate_walk_forward_windows

        dates = [dt.date(2026, 1, 1) + dt.timedelta(days=i) for i in range(400)]
        windows = generate_walk_forward_windows(dates, train_days=252, test_days=63, step_days=63)
        assert len(windows) > 0
        for w in windows:
            assert w.train_start < w.train_end
            assert w.test_start <= w.test_end
            assert w.train_end < w.test_start

    def test_no_windows_when_not_enough_data(self):
        from libs.backtest.splits import generate_walk_forward_windows

        dates = [dt.date(2026, 1, 1) + dt.timedelta(days=i) for i in range(10)]
        windows = generate_walk_forward_windows(dates, train_days=252, test_days=63)
        assert windows == []

    def test_window_indices(self):
        from libs.backtest.splits import generate_walk_forward_windows

        dates = [dt.date(2026, 1, 1) + dt.timedelta(days=i) for i in range(400)]
        windows = generate_walk_forward_windows(dates, train_days=100, test_days=50, step_days=50)
        for i, w in enumerate(windows):
            assert w.window_index == i

    def test_repr(self):
        from libs.backtest.splits import WalkForwardWindow

        w = WalkForwardWindow(
            0,
            dt.date(2026, 1, 1), dt.date(2026, 6, 1),
            dt.date(2026, 6, 2), dt.date(2026, 9, 1),
        )
        assert "WalkForwardWindow" in repr(w)


class TestSplitByYear:
    def test_groups_by_year(self):
        from libs.backtest.splits import split_by_year

        dates = (
            [dt.date(2024, 12, i) for i in range(1, 10)]
            + [dt.date(2025, 1, i) for i in range(1, 10)]
        )
        by_year = split_by_year(dates)
        assert 2024 in by_year
        assert 2025 in by_year
        assert all(d.year == 2024 for d in by_year[2024])
        assert all(d.year == 2025 for d in by_year[2025])

    def test_empty(self):
        from libs.backtest.splits import split_by_year

        assert split_by_year([]) == {}


class TestSplitByRegime:
    def test_basic_grouping(self):
        from libs.backtest.splits import split_by_regime

        dates = [dt.date(2026, 1, i) for i in range(1, 11)]
        regime_map = {
            dt.date(2026, 1, 1): "bull",
            dt.date(2026, 1, 2): "bull",
            dt.date(2026, 1, 3): "bear",
        }
        grouped = split_by_regime(dates, regime_map)
        assert "bull" in grouped
        assert "bear" in grouped
        assert "unknown" in grouped  # dates without regime

    def test_custom_default(self):
        from libs.backtest.splits import split_by_regime

        dates = [dt.date(2026, 1, 5)]
        grouped = split_by_regime(dates, {}, default_regime="neutral")
        assert "neutral" in grouped