from sqlalchemy import func, distinct, select, join, and_, case, true
from sqlalchemy.orm import aliased

from orm.reaction import Reaction, ReactionKind
from orm.topic import TopicFollower, Topic
from services.db import local_session
from orm.author import AuthorFollower, Author, AuthorRating
from orm.shout import ShoutTopic, ShoutAuthor, Shout
from services.logger import root_logger as logger


def add_topic_stat_columns(q):
    aliased_shout_author = aliased(ShoutAuthor)
    aliased_topic_follower = aliased(TopicFollower)
    aliased_shout_topic = aliased(ShoutTopic)

    q = (
        q.outerjoin(aliased_shout_topic, aliased_shout_topic.topic == Topic.id)
        .add_columns(
            func.count(distinct(aliased_shout_topic.shout)).label('shouts_stat')
        )
        .outerjoin(
            aliased_shout_author,
            aliased_shout_topic.shout == aliased_shout_author.shout,
        )
        .add_columns(
            func.count(distinct(aliased_shout_author.author)).label('authors_stat')
        )
        .outerjoin(aliased_topic_follower)
        .add_columns(
            func.count(distinct(aliased_topic_follower.follower)).label(
                'followers_stat'
            )
        )
    )

    q = q.group_by(Topic.id)

    return q


def add_author_stat_columns(q):
    aliased_shout_author = aliased(ShoutAuthor)
    aliased_author_authors = aliased(AuthorFollower)
    aliased_author_followers = aliased(AuthorFollower)

    q = (
        q.outerjoin(aliased_shout_author, aliased_shout_author.author == Author.id)
        .add_columns(
            func.count(distinct(aliased_shout_author.shout)).label('shouts_stat')
        )
        .outerjoin(aliased_author_authors, aliased_author_authors.follower == Author.id)
        .add_columns(
            func.count(distinct(aliased_shout_author.author)).label('authors_stat')
        )
        .outerjoin(
            aliased_author_followers, aliased_author_followers.author == Author.id
        )
        .add_columns(
            func.count(distinct(aliased_author_followers.follower)).label(
                'followers_stat'
            )
        )
    )

    q = q.group_by(Author.id)

    return q


def add_author_ratings(q):
    aliased_author = aliased(Author)
    ratings_subquery = (
        select([
            aliased_author.id.label('author_id'),
            func.count().filter(and_(
                Reaction.created_by == aliased_author.id,
                Reaction.kind == ReactionKind.COMMENT.value,
                Reaction.deleted_at.is_(None),
                )).label('comments_count'),
            func.sum(case((AuthorRating.plus == true(), 1), else_=0)).label('likes_count'),
            func.sum(case((AuthorRating.plus != true(), 1), else_=0)).label('dislikes_count'),
            func.sum(case((and_(Reaction.kind == ReactionKind.LIKE.value, Shout.authors.any(id=aliased_author.id)), 1), else_=0)).label('shouts_likes'),
            func.sum(case((and_(Reaction.kind == ReactionKind.DISLIKE.value, Shout.authors.any(id=aliased_author.id)), 1), else_=0)).label('shouts_dislikes')
        ])
        .select_from(aliased_author)
        .join(AuthorRating, AuthorRating.author == aliased_author.id)
        .outerjoin(Shout, Shout.authors.any(id=aliased_author.id))
        .filter(
            Reaction.deleted_at.is_(None)
        )
        .group_by(aliased_author.id)
        .alias('ratings_subquery')
    )

    q = q.join(ratings_subquery, Author.id == ratings_subquery.c.author_id)

    return q



def get_with_stat(q):
    is_author = f'{q}'.lower().startswith('select author')
    is_topic = f'{q}'.lower().startswith('select topic')
    if is_author:
        q = add_author_stat_columns(q)
        q = add_author_ratings(q)
    elif is_topic:
        q = add_topic_stat_columns(q)
    records = []
    logger.debug(f'{q}'.replace('\n', ' '))
    with local_session() as session:
        for cols in session.execute(q):
            entity = cols[0]
            entity.stat = {'shouts': cols[1], 'authors': cols[2], 'followers': cols[3]}
            if is_author:
                entity.stat['comments'] = cols[4]
                entity.stat['rating'] = cols[5] - cols[6]
                entity.stat['rating_shouts'] = cols[7] - cols[8]
            records.append(entity)

    return records


def author_follows_authors(author_id: int):
    af = aliased(AuthorFollower, name='af')
    q = (
        select(Author)
        .select_from(join(Author, af, Author.id == af.author))
        .where(af.follower == author_id)
    )
    return get_with_stat(q)


def author_follows_topics(author_id: int):
    q = (
        select(Topic)
        .select_from(join(Topic, TopicFollower, Topic.id == TopicFollower.topic))
        .where(TopicFollower.follower == author_id)
    )
    return get_with_stat(q)