"""Tests para el calculo de costes del orquestador.

Replica la formula de coste de OrchestratorEngine._run_pipeline():
    cost_usd = (input_tokens / 1_000_000) * cost_per_1m_input
             + (output_tokens / 1_000_000) * cost_per_1m_output

Defaults: cost_per_1m_input=2.50, cost_per_1m_output=15.00
"""

import pytest


def calculate_cost(
    input_tokens: int,
    output_tokens: int,
    cost_per_1m_input: float = 2.50,
    cost_per_1m_output: float = 15.00,
) -> float:
    """Replica exacta de la formula de coste en engine.py."""
    return (
        (input_tokens / 1_000_000) * cost_per_1m_input
        + (output_tokens / 1_000_000) * cost_per_1m_output
    )


class TestCostCalculation:
    def test_1m_input_tokens(self):
        cost = calculate_cost(1_000_000, 0)
        assert cost == pytest.approx(2.50)

    def test_1m_output_tokens(self):
        cost = calculate_cost(0, 1_000_000)
        assert cost == pytest.approx(15.00)

    def test_500k_input_100k_output(self):
        cost = calculate_cost(500_000, 100_000)
        # (500_000 / 1_000_000) * 2.50 + (100_000 / 1_000_000) * 15.00
        # = 1.25 + 1.50 = 2.75
        assert cost == pytest.approx(2.75)

    def test_zero_tokens(self):
        cost = calculate_cost(0, 0)
        assert cost == 0.0

    def test_custom_pricing(self):
        cost = calculate_cost(
            1_000_000, 1_000_000,
            cost_per_1m_input=3.00,
            cost_per_1m_output=10.00,
        )
        assert cost == pytest.approx(13.00)

    def test_small_token_count(self):
        """Pocos tokens = coste muy bajo pero no cero."""
        cost = calculate_cost(100, 50)
        assert cost > 0
        assert cost < 0.01

    def test_round_to_6_decimals(self):
        """El engine hace round(cost_usd, 6)."""
        cost = calculate_cost(1, 1)
        rounded = round(cost, 6)
        # (1/1M)*2.50 + (1/1M)*15.00 = 1.75e-05
        # round(1.75e-05, 6) = 1.7e-05 (banker's rounding: 5 rounds to even)
        assert rounded == pytest.approx(0.000017, abs=1e-7)

    def test_output_more_expensive_than_input(self):
        """Con defaults, output es 6x mas caro que input."""
        input_cost = calculate_cost(1_000_000, 0)
        output_cost = calculate_cost(0, 1_000_000)
        assert output_cost == pytest.approx(input_cost * 6.0)