from src.utils import helpers

def test_get_from_null_dict():
    # null handling
    assert helpers.get_from_dict(dict()) == dict()
    assert helpers.get_from_dict(dict(), None) == None

    # key present in nested dictionary
    # 1-level dictionary
    assert helpers.get_from_dict({'a': 1, 'b': 2}, 'a') == 1
    assert helpers.get_from_dict({'a': 1, 'b': 2}, 'c') == None

    # 2-level dictionary
    assert helpers.get_from_dict({'a': {'a_a': 1}, 'b': 2}, 'a') == {'a_a': 1}
    assert helpers.get_from_dict({'a': {'a_a': 1}, 'b': 2}, 'a', 'a_a') == 1

    # key not present in nested dictionary
    # 2-level_dictionary
    assert helpers.get_from_dict({'a': {'a_a': 1}, 'b': 2}, 'b', 'b_a') == None


def test_merge_dicts():
    # basic merge of dicts with non-overlapping keys
    assert helpers.merge_dicts(priority_dict={'a': 1}, default_dict={'b': 2}) == {'a': 1, 'b': 2}

    # use default dict items when not present in priority dict
    assert helpers.merge_dicts(priority_dict={}, default_dict={'b': 2}) == {'b': 2}

    # do not override existing key in priority_dict with default dict
    assert helpers.merge_dicts(priority_dict={'a': 1}, default_dict={'a': 2}) == {'a': 1}


def test_lru_cache():
    # Test initializing cache
    cache = helpers.LRU({'a': 1, 'b': 2}, capacity=2)
    assert cache == {'a': 1, 'b': 2}

    # Test capacity overflow
    cache['c'] = 3
    assert cache == {'b': 2, 'c': 3}

    # Test delete least recently used item from LRU cache on capacity overflow
    cache['b']      # accessing 'b' makes it the most recently used item
    cache['d'] = 4  # so 'c' is deleted from the cache instead of 'b'
    assert cache == {'b': 2, 'd': 4}