"""Tests for Part VII, VIII, IX (shadow banking, CCP, CBDC)."""

import pytest
from fqbm.sheets.shadow_banking import (
    leverage_ratio,
    margin_spiral_risk,
    repo_multiplier,
    margin_spiral_simulation,
)
from fqbm.sheets.ccp import (
    ccp_identity,
    default_waterfall_triggered,
    variation_margin_flow,
    ccp_clearing_simulation,
)
from fqbm.sheets.cbdc import deposit_to_cbdc_shift, funding_gap


def test_leverage_ratio():
    assert leverage_ratio(1000, 100) == 10.0
    assert leverage_ratio(500, 0) == 0.0


def test_margin_spiral_risk():
    r = margin_spiral_risk(100, 80, 0.1)
    assert "margin_call_triggered" in r
    assert "shortfall" in r
    assert r["shortfall"] >= 0


def test_ccp_identity():
    assert ccp_identity(100, 100) is True
    assert ccp_identity(100, 99) is False


def test_default_waterfall_triggered():
    assert default_waterfall_triggered(150, 100) is True
    assert default_waterfall_triggered(50, 100) is False


def test_deposit_to_cbdc_shift():
    d = deposit_to_cbdc_shift(50)
    assert d["d_deposits"] == -50
    assert d["d_reserves"] == -50
    assert d["d_cbdc_liability"] == 50


def test_funding_gap():
    assert funding_gap(100, 60) == 40
    assert funding_gap(50, 80) == -30


def test_repo_multiplier():
    r = repo_multiplier(100.0, haircut=0.02, rounds=3)
    assert r["total_effective_collateral"] > 100
    assert r["multiplier_implied"] > 1
    assert r["rounds_used"] == 3
    r0 = repo_multiplier(0, rounds=2)
    assert r0["total_effective_collateral"] == 0


def test_margin_spiral_simulation():
    r = margin_spiral_simulation(
        initial_collateral=100,
        margin_requirement=90,
        haircut=0.1,
        liquidity_buffer=5,
        fire_sale_impact=0.2,
        max_rounds=10,
    )
    assert "path_collateral" in r
    assert "path_margin_calls" in r
    assert "cumulative_forced_sales" in r
    assert "waterfall_triggered" in r
    assert len(r["path_collateral"]) >= 1


def test_variation_margin_flow():
    vm = variation_margin_flow(-10.0, member_pays_when_positive=True)
    assert vm == pytest.approx(10.0)
    vm2 = variation_margin_flow(5.0, member_pays_when_positive=True)
    assert vm2 == pytest.approx(-5.0)


def test_ccp_clearing_simulation():
    results = ccp_clearing_simulation(
        vm_calls_per_period=[5, 10, 15],
        liquidity_buffer_start=20,
    )
    assert len(results) == 3
    assert results[0]["buffer_end"] == 15
    assert results[1]["buffer_end"] == 5
    assert results[2]["waterfall_triggered"] is True