import pytest
from datetime import datetime, timedelta
from data_analysis import core


@pytest.fixture
def sample_run_data():
    base_time = datetime(2024, 1, 1, 12, 0, 0)
    return [
        {
            'run_id': 'r1',
            'timestamp': base_time,
            'delta_t': 0.5,
            'expiring_at': base_time + timedelta(hours=1)
        },
        {
            'run_id': 'r2',
            'timestamp': base_time + timedelta(seconds=5),
            'delta_t': -0.2,
            'expiring_at': base_time + timedelta(hours=2)
        },
        {
            'run_id': 'r3',
            'timestamp': base_time + timedelta(seconds=10),
            'delta_t': 0.0,
            'expiring_at': base_time + timedelta(hours=3)
        }
    ]


def test_analyze_runs_structure(sample_run_data):
    result = core.analyze_runs(sample_run_data)
    assert isinstance(result, dict), 'Result must be a dict'
    expected_keys = {'total_runs', 'negative_dt_count', 'negative_dt_ratio'}
    for key in expected_keys:
        assert key in result, f'Missing key: {key}'


def test_analyze_runs_negative_count(sample_run_data):
    result = core.analyze_runs(sample_run_data)
    assert result['negative_dt_count'] == 1
    assert result['total_runs'] == 3
    assert result['negative_dt_ratio'] == pytest.approx(1/3, rel=1e-3)


def test_analyze_runs_empty_list():
    result = core.analyze_runs([])
    assert result['total_runs'] == 0
    assert result['negative_dt_count'] == 0
    assert result['negative_dt_ratio'] == 0.0


def test_analyze_runs_type_validation():
    with pytest.raises((TypeError, AssertionError)):
        core.analyze_runs('invalid_input')