from sqlalchemy import func, distinct, select
from sqlalchemy.orm import aliased

from orm.topic import TopicFollower, Topic
from services.db import local_session
from orm.author import AuthorFollower, Author
from orm.shout import ShoutTopic, ShoutAuthor
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.user)).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 execute_with_ministat(q):
    records = []
    with local_session() as session:
        for [entity, shouts_stat, authors_stat, followers_stat] in session.execute(q):
            entity.stat = {
                'shouts': shouts_stat,
                'authors': authors_stat,
                'followers': followers_stat,
            }
            records.append(entity)

    return records


def get_authors_with_stat(q):
    q = add_author_stat_columns(q)
    return execute_with_ministat(q)


def get_topics_with_stat(q):
    q = add_topic_stat_columns(q)
    return execute_with_ministat(q)


def author_follows_authors(author_id: int):
    aliased_author_authors = aliased(AuthorFollower, name="af")

    q = (
        select(Author)
        .join(aliased_author_authors, Author.id == aliased_author_authors.author)
        .filter(aliased_author_authors.follower == author_id)
    )

    q = add_author_stat_columns(q)
    return execute_with_ministat(q)


def author_follows_topics(author_id: int):
    q = (
        select(Topic)
        .join(TopicFollower, Topic.id == TopicFollower.topic)
        .filter(TopicFollower.follower == author_id)
    )

    q = add_topic_stat_columns(q)
    return execute_with_ministat(q)


def query_follows(author_id: int):
    try:
        topics = author_follows_topics(author_id)
        authors = author_follows_authors(author_id)
        return {
            'topics': topics,
            'authors': authors,
            'communities': [{'id': 1, 'name': 'Дискурс', 'slug': 'discours'}],
        }
    except Exception as e:
        logger.exception(f"An error occurred while executing query_follows: {e}")
        raise Exception("An error occurred while executing query_follows") from e