import json
import boto3
import s3_backup

class Downstream:
    """Push message to downstream"""
    def __init__(self):
        self.client = boto3.client("sqs")
        self.queues = {}

    def push(self, dedup_id, group_id, body):
        try:
            name = "{}-mim.fifo".format(group_id)
            if name not in self.queues:
                # mark the queue not exist first, then try to get the queue url
                # if success, overwrite the queue url
                self.queues[name] = None
                queue = self.client.get_queue_url(QueueName=name)
                self.queues[name] = queue['QueueUrl']
            if self.queues[name]:
                self.client.send_message(
                    QueueUrl=self.queues[name], 
                    MessageGroupId=group_id, 
                    MessageBody=body, 
                    MessageDeduplicationId=dedup_id)
            else:
                print("the queue may not exist: {0}, ignoring this message...".format(group_id))
        except Exception as err:
            print("error on push record to downstream({0}): {1}".format(group_id, err))

def message_transformers():
    return [
    # disable s3 backup since we will use kafka as the stable chanel
    #    s3_backup.transformer(),
    ]

def lambda_handler(event, context):
    downstream = Downstream()
    transformers = message_transformers()
    for record in event["Records"]:
        dedup_id = record["attributes"]["MessageDeduplicationId"]
        group_id = record["attributes"]["MessageGroupId"]
        body = record["body"]
        for transformer in transformers:
            try:
                if transformer.match(group_id):
                    body = transformer.transform(group_id, body)
            except Exception as err:
                print("error on handle record({0}): {1}", json.dumps(record), err)
        downstream.push(dedup_id, group_id, body)