"""Lambda expiring_contracts function module."""

import boto3

from common_config import logger

import config

from constants import general

import mysql

import sql_queries

import sqlalchemy

from warmer_util import catch_warmer_event


@catch_warmer_event()
def handler(event, context):
    """Lambda entry point."""
    expiring_contracts = get_expiring_contracts()
    if not expiring_contracts:
        return logger.error('There are no expiring Contract(s)')

    formatted_msg = format_sns_message(expiring_contracts)
    send_sns(formatted_msg)


@mysql.wrap_db_errors
def get_expiring_contracts():
    """Get set of expiring_contracts details from AR.

    Returns:
       list: expiring_contracts details as dict
    """
    with mysql.ar_db_session() as session:
        # execute query
        query = session.execute(
            sqlalchemy.text(sql_queries.OBTAIN_EXPIRING_CONTRACTS))
        contracts = query.all()
    return [contract for contract in contracts]


def format_sns_message(message):
    """Format message for SNS.

    Args:
        message (list): expiring_contracts details as dict
    Returns:
        string: expiring_contracts sns details as string
    """
    response_list = []
    for vendor in message:
        response_list.append(
            general.SNS_MAIL_STR.format(
                company=vendor.company,
                vendor_id=vendor.vendor_id))

    response_str = '\n\n'.join(response_list)

    formatted_msg = '{header}\n\n{result}'.format(
        header=general.SNS_MAIL_HEADER,
        result=response_str)

    return formatted_msg


def send_sns(message):
    """Publish message using AWS SNS.

    Args:
        message (string): expiring_contracts sns details as string
    """
    sns = boto3.client(service_name='sns', region_name=config.AWS_REGION)

    return sns.publish(
        TopicArn=config.SNS_ARN,
        Message=message,
        Subject=general.SNS_ARN_SUBJECT)