from os import environ
from collections import namedtuple
import pg8000

from flask import g

def db():
    if not hasattr(g, 'db_connection'):
        g.db_connection = pg8000.connect(
            host=environ['DB_HOST'],
            database=environ['DB_NAME'],
            user=environ['DB_USER'],
            password=environ['DB_PASSWORD'],
        )

    return g.db_connection

def query(querystring, **params):
    try:
        cursor = db().cursor()
        cursor.paramstyle = "named"
        cursor.execute(querystring, params)
        db().commit()
        return cursor
    except:
        db().rollback()
        raise

def select(querystring, **params):
    cursor = query(querystring, **params)
    columns = [x[0] for x in cursor.description]
    return [dict(zip(columns, row)) for row in cursor.fetchall()]