follows.py

from typing import List

from data.connection import db_cursor
from data.users import User

from psycopg2.errors import UniqueViolation


def follow(follower: User, followee: User):
    with db_cursor() as cur:
        try:
            cur.execute(
                "INSERT INTO follows (follower, followee) VALUES (%(follower_id)s, %(followee_id)s)",
                dict(
                    follower_id=follower.id,
                    followee_id=followee.id,
                ),
            )
        except UniqueViolation:
            # Already following - treat as idempotent request.
            pass
        
# do the opposite for unfollow
def unfollow(follower: User, followee: User):
    with db_cursor() as cur:
        cur.execute(
            "DELETE FROM follows WHERE follower = %(follower_id)s AND followee = %(followee_id)s",
            dict(follower_id=follower.id, followee_id=followee.id)
        )


def get_followed_usernames(follower: User) -> List[str]:
    """get_followed_usernames returns a list of usernames followee follows."""
    with db_cursor() as cur:
        cur.execute(
            "SELECT users.username FROM follows INNER JOIN users ON follows.followee = users.id WHERE follower = %s",
            (follower.id,),
        )
        rows = cur.fetchall()
        return [row[0] for row in rows]


def get_inverse_followed_usernames(followee: User) -> List[str]:
    """get_followed_usernames returns a list of usernames followed by follower."""
    with db_cursor() as cur:
        cur.execute(
            "SELECT users.username FROM follows INNER JOIN users ON follows.follower = users.id WHERE followee = %s",
            (followee.id,),
        )
        rows = cur.fetchall()
        return [row[0] for row in rows]