import os
from sqlalchemy import create_engine

DEFAULT_CONN_STR = 'postgresql://{0}:{1}@{2}:5432/{3}?client_encoding=utf8'

DB_USER = os.environ.get('DB_USER')
DB_PASS = os.environ.get('DB_PASS')
DB_HOST = os.environ.get('DB_HOST')
DB_DB_NAME = os.environ.get('DB_DB_NAME')


def get_connection_string(conn_name):
    available_connections = {'db': DEFAULT_CONN_STR.format(DB_USER, DB_PASS,
                                                           DB_HOST, DB_DB_NAME)
                             }

    try:
        return available_connections[conn_name]
    except KeyError:
        print("Cannot find connection for that string.")


def create_db_connection(db_name):
    conn = get_connection_string(db_name)
    return create_engine(conn)