"""
This module defines Celery_ tasks to manage PostgreSQL users and databases.

"""
from celery import shared_task
from celery.utils.log import get_task_logger
from psycopg2 import connect
from psycopg2.extensions import ISQLQuote

from pgsqltasks import settings

_LOGGER = get_task_logger(__name__)


class Ident(object):
    """
    Wrap a PostgreSQL identifier.

    Inspired by
    http://osdir.com/ml/python-db-psycopg-devel/2009-03/msg00019.html.

    Note that this adapter needs to make an SQL SELECT to correctly quote the
    identifier (that is then cached) so it can be a good idea to pre-allocate
    identifiers by calling getquoted() on the, before entering critical
    sections of code.
    """

    def __init__(self, ident):
        self.ident = ident
        self.ident_quoted = None

    def prepare(self, conn):
        self._conn = conn

    def getquoted(self):
        if not self.ident_quoted:
            with self._conn.cursor() as curs:
                curs.execute("SELECT quote_ident(%s)", (self.ident,))
                self.ident_quoted = curs.fetchone()[0]
        return self.ident_quoted

    def __str__(self):
        return str(self.ident_quoted)

    def __conform__(self, proto):
        if proto == ISQLQuote:
            return self


def _get_connection():
    return connect(
        host=settings.GVAPGSQL_DBADMIN_HOST,
        port=settings.GVAPGSQL_DBADMIN_PORT,
        user=settings.GVAPGSQL_DBADMIN_USER,
        password=settings.GVAPGSQL_DBADMIN_PASSWORD,
        database="postgres",
    )


@shared_task
def create_pgsql_user(username, password):
    """
    This task creates a new PostgreSQL user.

    :param str username: the user name
    :param str password: the password
    :return: the created user's name
    :rtype: str

    """
    with _get_connection() as conn:
        with conn.cursor() as curs:
            curs.execute(
                """
                CREATE USER %(username)s WITH PASSWORD %(password)s
                """,
                {"username": Ident(username), "password": password},
            )


@shared_task
def set_pgsql_userpassword(username, password):
    """
    Set a new password for an existing PostgreSQL user.

    :param str username: the user name
    :param str password: the password
    :return: True if the password could be set, False otherwise
    :rtype: boolean

    """
    with _get_connection() as conn:
        with conn.cursor() as curs:
            curs.execute(
                """
                ALTER ROLE %(username)s WITH PASSWORD %(password)s
                """,
                {"username": Ident(username), "password": password},
            )


@shared_task
def delete_pgsql_user(username):
    """
    This task deletes an existing PostgreSQL user.

    :param str username: the user name
    :return: True if the user has been deleted, False otherwise
    :rtype: boolean

    """
    with _get_connection() as conn:
        with conn.cursor() as curs:
            curs.execute(
                """
                DROP ROLE %(username)s
                """,
                {"username": Ident(username)},
            )


@shared_task
def create_pgsql_database(dbname, username):
    """
    This task creates a new PostgreSQL database for the given PostgreSQL user.

    :param str dbname: database name
    :param str username: the user name of an existing PostgreSQL user
    :return: the database name
    :rtype: str

    """
    with _get_connection() as conn:
        conn.autocommit = True
        curs = conn.cursor()
        curs.execute(
            """
            CREATE DATABASE %(dbname)s OWNER %(username)s
            TEMPLATE template0 ENCODING 'UTF8'
            """,
            {"dbname": Ident(dbname), "username": Ident(username)},
        )


@shared_task
def delete_pgsql_database(dbname):
    """
    This task deletes an existing PostgreSQL database.

    :param str dbname: database name
    :return: True if the database has been deleted, False otherwise
    :rtype: boolean

    """
    with _get_connection() as conn:
        conn.autocommit = True
        curs = conn.cursor()
        curs.execute(
            """
            DROP DATABASE %(dbname)s
            """,
            {"dbname": Ident(dbname)},
        )