import boto3
import base64

DDB = boto3.resource('dynamodb').Table('events')

def lambda_handler(event, context):

    print("Received %s records" % len(event['Records']))  # logging is free!

    totals = {}
    for record in event['Records']:
        payload = base64.b64decode(record['kinesis']['data'])  # base64 decode
        if not payload in totals:
            totals[payload] = 0  # init to 0
        totals[payload] += 1  # simply inc

    # 1 DDB write for each event name in the given batch (counter update)
    for name, total in totals.iteritems():
        print("Recording %s %s events" % (total, name))  # logging is free!
        DDB.update_item(
            Key={'Name': name},
            UpdateExpression='ADD EventCount :val',
            ExpressionAttributeValues={':val': total},
        )

    return 'Successfully processed {} records.'.format(len(event['Records']))