import logging

from sqlalchemy import create_engine

from platypush.message.response import Response

from .. import Plugin

class DbPlugin(Plugin):
    """ Database plugin. It allows you to programmatically select, insert,
        update and delete records on a database backend through requests,
        procedures and event hooks """

    engine = None

    def __init__(self, engine=None, *args, **kwargs):
        """
        Params:
            engine -- Default SQLAlchemy connection engine string
            (e.g. sqlite:///:memory: or mysql://user:pass@localhost/test)
            that will be used. You can override this value in your statement actions

            args, kwargs -- Extra arguments for sqlalchemy.create_engine
        """

        self.engine = self._get_engine(engine, *args, **kwargs)


    def _get_engine(self, engine=None, *args, **kwargs):
        if engine:
            return create_engine(engine, *args, **kwargs)
        else:
            return self.engine

    def execute(self, statement, engine=None, *args, **kwargs):
        """ Executes a generic SQL statement """

        engine = self._get_engine(engine, *args, **kwargs)

        with engine.connect() as connection:
            result = connection.execute(statement)

        return Response()


    def select(self, query, engine=None, *args, **kwargs):
        """ Returns rows (as a list of dicts) given a query """

        engine = self._get_engine(engine, *args, **kwargs)

        with engine.connect() as connection:
            result = connection.execute(query)
            columns = result.keys()
            rows = [
                { columns[i]: row[i] for i in range(0, len(columns)) }
                for row in result.fetchall()
            ]

        return Response(output=rows)


    def insert(self, table, records, engine=None, *args, **kwargs):
        """ Inserts records (as a list of dicts) into a table """

        engine = self._get_engine(engine, *args, **kwargs)

        for record in records:
            statement = 'INSERT INTO {}({}) VALUES({})'.format \
                (table, ','.join(record.keys()),
                 ','.join([ ':' + key for key in record.keys() ]))

            with engine.connect() as connection:
                connection.execute(statement, **record)

        return Response()


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