# Author: Roland Peto <petoroland1234@gmail.com>
# Created: 2018-12-09
# Last modified: 2018-12-09
# Version 0.1
# Short description: Delete old EC2 snapshots in the Ireland region.

import boto3
import re
from datetime import datetime, timedelta
import json
import os


ec2 = boto3.client('ec2', region_name='eu-west-1')
sns = boto3.client('sns', region_name='eu-west-1')
iam = boto3.client('iam')


def lambda_handler(event, context):

    # Get account ID
    account_ids = list()
    try:
        iam.get_user()
    except Exception as e:
        # use the exception message to get the account ID the function executes under
        account_ids.append(re.search(r'(arn:aws:sts::)([0-9]+)', str(e)).groups()[1])

    # Get snapshots
    snapshot_response = ec2.describe_snapshots(OwnerIds=account_ids)
    delete_response_codes = []
    for snapshot in snapshot_response['Snapshots']:
        # if the snapshot is older than 8 days
        if ((datetime.now() - snapshot['StartTime'].replace(tzinfo=None)) > timedelta(days=int(os.environ['retentionDays']))):
            # delete snapshot, save response code and log the result
            delete_response = ec2.delete_snapshot(SnapshotId=snapshot['SnapshotId'])
            delete_response_codes.append(delete_response['ResponseMetadata']['HTTPStatusCode'])
            if(delete_response['ResponseMetadata']['HTTPStatusCode'] == 200):
                print 'Old snapshot ('+snapshot['SnapshotId']+') has been deleted successfully.'
            else:
                print 'Something went wrong with the deletion of '+snapshot['SnapshotId']+'. Response: ' + delete_response

    # check if something went wrong with the deletions
    error = False
    for code in delete_response_codes:
        if (code != 200):
            error = True

    # get the snapshot list again
    snapshot_response = ec2.describe_snapshots(OwnerIds=account_ids)

    # send SNS notifications to Admins
    if (not error):
        message = 'EBS snapshot mgmt scipt has just finished successfully. Current available snapshots: ' + str(snapshot_response['Snapshots'])
    else:
        message = 'EBS snapshot mgmt scipt has just finished, but there were some errors. Check logs for details.'

    sns.publish(
        TargetArn='arn:aws:sns:eu-west-1:127095825479:AdminMessages',
        Subject='EBS snapshot management',
        Message=message
    )