import re


class InvalidMenuMessageError(Exception):
    """
    Custom exception raised when a menu can  not be parsed correctly.
    Usually happens when trying to parse a random message like "Estamos de vuelta!!!")
    """

    def __init__(self, message):
        self.message = f"Invalid message while parsing into a menu, message: '{message}'"
        super().__init__(self.message)


def parse_menu_message(message: str) -> list[list]:
    """
    Using `menu=parse_menu_message(my_message)`, `menu[0]` are the options for the first course (`menu[0]=["Pasta a la boloñesa", "Ensaladilla rusa"]` for example). `menu[1]` is the same but for the second course

    :param message: Will receive a message's content as sent in the telegram channel.

    :returns: A list of lists with the options for each course.
    """

    message = re.sub(r'\n\s*\n+', '\n\n', message)
    lines = message.splitlines()

    if lines == []:
        raise InvalidMenuMessageError(message)

    first_line = lines[0].lower()
    first_line_is_header = "menu" in first_line or "menú" in first_line
    if first_line_is_header:
        lines.pop(0)
        # Remove the newline after the header if it exists
        if not lines[0].strip():
            lines.pop(0)

    # Initialize this to none in case we don't get it
    course_separator_index = None

    # Check if course separator is a blank line
    for i, line in enumerate(lines):
        if not line.strip():
            course_separator_index = i
            break

    if course_separator_index is None:
        # Old menus use - for first course and > for second course, or otherwise
        second_course_char = '-' if lines[0][0] == '>' else '>' if lines[0][0] == '-' else None
        if not second_course_char is None:
            for i, line in enumerate(lines):
                if line[0] == second_course_char:
                    course_separator_index = i
                    break

    if course_separator_index is None:
        raise InvalidMenuMessageError(message)

    # Some messages have "TAMBIEN PARA LLEVAR" at the end of them
    last_line = lines[-1].lower()
    if "llevar" in last_line or "preguntar" in last_line:
        lines.pop()

    def fix_line(line):
        # Remove first character if it is not a letter (- and > are common in 2023). Leading whitespace might appear, will be deleted later
        line = re.sub(r'^[^\w]+', '', line)

        # Strips the line (leading and trailing whitespaces on menu items are common)
        line = line.strip()

        # Replace occurrences of "c/" with "con " (if extra space was added it will be removed after)
        line = line.replace("c/", "con ")

        # Remove extra whitespaces in the middle of the string
        line = ' '.join(line.split())

        # Remove trailing dot
        if line[-1] == '.':
            line = line[:-1]

        # Capitalize
        line = line.capitalize()

        return line

    lines = [fix_line(line) for line in lines if line.strip()]

    # First two lines are first course, and second two ones are second course
    first_course = lines[:course_separator_index]
    second_course = lines[course_separator_index:]

    if len(first_course) <= 1 or len(second_course) <= 1:
        raise InvalidMenuMessageError(message)

    courses = [first_course, second_course]

    return courses