import re

valid_re = re.compile('^[\w-]+$')


def validate_feed_id(feed_id):
    '''
    Validates the input is in the format of user:1

    :param feed_id: a feed such as user:1

    Raises ValueError if the format doesnt match
    '''
    feed_id = str(feed_id)
    if len(feed_id.split(':')) != 2:
        msg = 'Invalid feed_id spec %s, please specify the feed_id as feed_slug:feed_id'
        raise ValueError(msg % feed_id)
    
    feed_slug, user_id = feed_id.split(':')
    feed_slug = validate_feed_slug(feed_slug)
    user_id = validate_user_id(user_id)
    return feed_id
    

def validate_feed_slug(feed_slug):
    '''
    Validates the feed slug falls into \w
    '''
    feed_slug = str(feed_slug)
    if not valid_re.match(feed_slug):
        msg = 'Invalid feed slug %s, please only use letters, numbers and _'
        raise ValueError(msg % feed_slug)
    return feed_slug


def validate_user_id(user_id):
    '''
    Validates the user id falls into \w
    '''
    user_id = str(user_id)
    if not valid_re.match(user_id):
        msg = 'Invalid user id %s, please only use letters, numbers and _'
        raise ValueError(msg % user_id)
    return user_id
    

def validate_foreign_id_time(foreign_id_time):
    if not isinstance(foreign_id_time, (list, tuple)):
        raise ValueError('foreign_id_time should be a list of tuples')

    for v in foreign_id_time:
        if not isinstance(v, (list, tuple)):
            raise ValueError('foreign_id_time elements should be lists or tuples')

        if len(v) != 2:
            raise ValueError('foreign_id_time elements should have two elements')