"""Balance-sheet invariants of the Model C ledger under random sequences of operations (Hypothesis)."""
import numpy as np
from hypothesis import given, settings, strategies as st

from age.banking.ledger import Ledger


def make(n=6, margin=0.5, rf=0.01, fee=0.001):
    return Ledger(n, np.full(n, 1.0), np.full(n, 1.0), 2.0, margin, fee, price0=5.0, rf=rf, bank_capital_ratio=0.05)


@settings(max_examples=100, deadline=None)
@given(ops=st.lists(st.tuples(st.sampled_from(['div', 'int', 'borrow', 'repay', 'trade', 'mtm']),
                              st.integers(0, 5), st.integers(0, 5), st.floats(0.0, 2.0), st.floats(0.5, 8.0)),
                    min_size=1, max_size=40))
def test_invariants_hold_under_random_operations(ops):
    led = make()
    for op, i, j, q, px in ops:
        if op == 'div':
            led.pay_dividend(q * 0.05)
        elif op == 'int':
            led.accrue_interest()
        elif op == 'borrow':
            led.borrow(i, q)
        elif op == 'repay':
            led.repay(i, q)
        elif op == 'trade':
            led.settle_trade(i, j, q * 0.3, px)
        else:
            led.mark_to_market(px, liquidation_impact=0.5)
        led.check()                       # raises on any violated identity
    # margin rule holds after mark-to-market
    led.mark_to_market(led.price)
    assert np.all(led.loan <= (1 - led.margin) * led.price * led.holdings + 1e-6)


def test_every_flow_has_a_counterparty():
    led = make()
    before = led.cash.sum() + led.F + led.bank_equity - led.loan.sum()
    assert led.settle_trade(0, 1, 0.1, 5.0)
    after = led.cash.sum() + led.F + led.bank_equity - led.loan.sum()
    assert np.isclose(before, after)       # trades and fees are transfers, reserves unchanged
    led.pay_dividend(0.1)
    assert np.isclose(led.reserves - led._reserves0, led.injections)


def test_default_and_bail_in_are_explicit():
    led = Ledger(3, np.array([0.0, 5.0, 5.0]), np.array([3.0, 0.0, 0.0]), 0.2, 0.5, 0.0, price0=2.0, rf=0.0)
    granted = led.borrow(0, 3.0)           # capacity (1-m) p h = 3.0
    assert np.isclose(granted, 3.0)
    led.cash[0] = 0.0                      # borrower spends the loan outside the system? no: keep in system
    led.settle_trade(1, 0, 0.0, 2.0)
    # price collapses -> margin breach, forced sale, default, bank equity 0.2 cannot absorb -> bail-in
    led.cash[0] = 0.0; led.reserves -= 3.0; led.injections -= 3.0   # simulate consumption of the loan (explicit outflow)
    led.check()
    res = led.mark_to_market(0.4, liquidation_impact=0.0)
    assert res['defaults'] == 1
    assert led.bank_equity >= -1e-9
    assert led.deposit_haircuts > 0 or led.loan_losses > 0