def test_one_rule_or():
test_input = '''0: 1 | 2
1: "x"
2: "y"'''
expected = '^(x|y)$'
assert expected == grammar_to_regexp(test_input)
def test_two_rules_are_correctly_expanded():
test_input = '''0: 1 2
1: "a"
2: "f"'''
expected = "^af$"
assert expected == grammar_to_regexp(test_input)
def test_a_single_rule_is_just_followed():
test_input = '''0: 1
1: "c"'''
expected = "^c$"
assert expected == grammar_to_regexp(test_input)
def test_start_from_different_root():
test_input = '''0: 1 | 2
1: "a"
2: 3 | 4
3: "b"
4: "c"'''
expected = '^(b|c)$'
assert expected == grammar_to_regexp(test_input, root=2)
def test_nested_or():
test_input = '''0: 1 | 2
1: "a"
2: 3 | 4
3: "b"
4: "c"'''
expected = '^(a|(b|c))$'
assert expected == grammar_to_regexp(test_input)
def test_two_rule_or():
test_input = '''0: 1 2 | 3 4
1: "a"
2: "b"
3: "x"
4: "y"'''
expected = '^(ab|xy)$'
assert expected == grammar_to_regexp(test_input)
def test_down_the_rabbithole():
test_input = '''0: 1 2
1: 3
2: 4
3: "c"
4: "u"'''
expected = "^cu$"
assert expected == grammar_to_regexp(test_input)
def main():
input_str = get_data(day=19)
grammar, messages = read_data(input_str)
regexp = grammar_to_regexp(grammar)
pattern = re.compile(regexp)
num_match = sum(check_message(pattern, message) for message in messages)
print(f"There's {num_match} messages matching the rule.")
res = part2(grammar, messages)
print(f"There's now {res} matching messages with the new rules.")
def test_single_character_becomes_single_character(c):
test_input = f'0: "{c}"'
expected = f"^{c}$"
assert expected == grammar_to_regexp(test_input)
