"""Load data from the database."""

import MySQLdb

from accounting import config


class DatabaseAdapter():
    """DatabaseAdapter."""

    def __init__(self):
        """Create the adapter."""
        self._init = False

    def __del__(self):
        """Teardown connection."""
        try:
            self._cursor.close()
        except AttributeError:
            pass

        try:
            self._connection.close()
        except AttributeError:
            pass

    def yield_rows(self, sql, args=()):
        """Yield 10000 rows at a time. For larger result sets."""
        if not self._init:
            self._connect()
            self._init = True

        self._cursor.execute(sql, args)
        while True:
            results = self._cursor.fetchmany(10000)
            if not results:
                break
            for result in results:
                yield result

    def fetch_rows(self, sql, args=()):
        """Execute a query against the db and return the results.

        Args:
            sql (str): Valid MySQL select statement.

        Returns:
            Tuple[]: List of ordered tuples with the selected values in order.

        """
        if not self._init:
            self._connect()
            self._init = True

        self._cursor.execute(sql, args)

        return self._cursor.fetchall()

    def execute(self, sql):
        """Execute SQL."""
        if not self._init:
            self._connect()
            self._init = True
        self._cursor.execute(sql)

    def _connect(self):
        """Connect to db."""
        self._connection = self._get_connection()
        self._connection.autocommit(True)
        self._cursor = self._connection.cursor()

    def _get_connection(self, db_config={}):
        """Mockable getter."""
        if not db_config:
            db_config = {
                'user': config.DB_USER,
                'password': config.DB_PASS,
                'host': config.DB_HOST,
                'database': config.DB_NAME,
            }

        if config.DB_POOL_SIZE:
            db_config['pool_size'] = config.DB_POOL_SIZE

        return MySQLdb.connect(**db_config)