class Post(Entity):
    """
    A user-created post.
    """
    using_options(tablename='user_post')
    user = ManyToOne('User', primary_key=True, ondelete='cascade')
    post_id = Field(Integer, primary_key=True)
    actual_ts = Field(DateTime, default=datetime.utcnow, nullable=False)
    actual_tzoffset = Field(Integer)
    apparent_ts = Field(DateTime, default=datetime.utcnow, nullable=False)
    apparent_tzoffset = Field(Integer)
    mood = ManyToOne('Mood', ondelete='restrict')
    mood_name_db = Field(Unicode(30))
    location = Field(Unicode(200))
    music = Field(Unicode(200))
    title = Field(Unicode(300))
    userpic_keyword = Field(Unicode(40))
    post_tags = OneToMany('UserPostTag', order_by='name')
    has_many('tags', through='post_tags', via='user_tag')

    def set_mood_name(self, text):
        mood_name_db = text
    def get_mood_name(self):
        if (mood_name_db is None) and mood:
            mood_name_db = mood.name
        return mood_name_db
    mood_name = property(fget=get_mood_name, fset=set_mood_name)


class UserPostTag(Entity):
    """
    A tag applied to a post.
    """
    using_options(tablename='user_post_tag')

    post = ManyToOne('Post', colname=['user_id', 'post_id'],
                     primary_key=True, ondelete='cascade')
    name = Field(Unicode(40), primary_key=True)
    has_property('user_tag',
                 lambda c: sa_relation(
        UserTag, primaryjoin=((c.user_id == UserTag.c.user_id) and \
                              (c.name == UserTag.c.name)),
        foreign_keys=[UserTag.c.user_id, UserTag.c.name],
        uselist=False
        )
                 )


class UserTag(Entity):
    """
    Tags a user has used on various posts.
    """
    using_options(tablename='user_tag')

    user = ManyToOne('User', colname='user_id',
                     primary_key=True, ondelete='cascade')
    name = Field(Unicode(40), primary_key=True)
    has_property('post_tags',
                 lambda c: sa_relation(
        UserPostTag, primaryjoin=((c.user_id == UserPostTag.c.user_id) and \
                                  (c.name == UserPostTag.c.name)),
        foreign_keys=[UserPostTag.c.user_id, UserPostTag.c.name],
        order_by=['user_post_tag.post_id']
        )
                 )
    has_many('posts', through='post_tags', via='post')