"""T4.3 Monte Carlo 模拟 + 组合再平衡测试。

测试边际回报率计算、组合再平衡和 Monte Carlo 模拟。
"""

import pytest

from app.services.monte_carlo import simulate_portfolio
from app.services.portfolio_rebalancer import (
    calculate_marginal_return,
    rebalance_portfolio,
    run_monte_carlo,
)


class TestCalculateMarginalReturn:
    """边际回报率测试。"""

    def test_positive_investment(self):
        """正常投入计算边际回报。"""
        result = calculate_marginal_return(1000, 500, 0.2)
        assert result > 0

    def test_zero_additional(self):
        """追加投入为 0 时返回 0。"""
        result = calculate_marginal_return(1000, 0, 0.2)
        assert result == 0.0

    def test_negative_additional(self):
        """追加投入为负时返回 0。"""
        result = calculate_marginal_return(1000, -100, 0.2)
        assert result == 0.0


class TestRebalancePortfolio:
    """组合再平衡测试。"""

    def test_returns_dict(self):
        """返回再平衡结果。"""
        companies = [
            {"company_id": "c1", "marginal_return": 0.15},
            {"company_id": "c2", "marginal_return": 0.08},
            {"company_id": "c3", "marginal_return": 0.20},
            {"company_id": "c4", "marginal_return": 0.05},
        ]
        result = rebalance_portfolio(companies)
        assert "marginal_returns" in result
        assert "reallocation_plan" in result
        assert "irr_impact" in result
        assert "dpi_impact" in result

    def test_top_quartile_increased(self):
        """高回报企业应被增加投入。"""
        companies = [
            {"company_id": "c1", "marginal_return": 0.05},
            {"company_id": "c2", "marginal_return": 0.20},
            {"company_id": "c3", "marginal_return": 0.15},
            {"company_id": "c4", "marginal_return": 0.01},
        ]
        result = rebalance_portfolio(companies)
        increase = result["reallocation_plan"]["increase"]
        assert "c2" in increase


class TestRunMonteCarlo:
    """Monte Carlo 模拟测试。"""

    def test_with_floats(self):
        """浮点数回报率列表。"""
        result = run_monte_carlo([0.1, 0.2, 0.15, 0.05], iterations=100)
        assert "irr_distribution" in result
        assert "percentile_p5" in result
        assert "percentile_p50" in result
        assert "percentile_p95" in result

    def test_with_dicts(self):
        """字典格式回报率列表。"""
        result = run_monte_carlo(
            [{"irr": 0.1}, {"irr": 0.2}, {"irr": 0.15}],
            iterations=100,
        )
        assert "irr_distribution" in result

    def test_empty_returns(self):
        """空列表返回默认结果。"""
        result = run_monte_carlo([], iterations=100)
        assert result["percentile_p5"] == 0
        assert result["percentile_p50"] == 0


class TestSimulatePortfolio:
    """Monte Carlo 异步接口测试。"""

    async def test_simulate(self):
        """异步模拟接口。"""
        result = await simulate_portfolio([0.1, 0.2, 0.15], iterations=100)
        assert "irr_distribution" in result