"""The SQS helpers."""
import boto3

from feed_sender.conf import config


def get_messages(queue_name, max_messages=None, msg_timeout=None):
    """Retrieve messages up to max number of messages from SQS queue.

    Args:
        queue_name (str): Name of SQS queue.
        max_messages (int): Maximum number of messages to be received by queue.

    Returns:
        list: list of messages received from queue
    """
    sqs = boto3.resource('sqs', config.AWS_REGION)
    queue = sqs.get_queue_by_name(QueueName=queue_name)
    if msg_timeout:
        queue.set_attributes(
            Attributes={'VisibilityTimeout': msg_timeout})

    messages = []
    request_count = 10
    queue_count = (int)(queue.attributes.get('ApproximateNumberOfMessages'))
    if not max_messages or max_messages > queue_count:
        max_messages = queue_count
    fetch_messages = max_messages > 0

    while fetch_messages:
        if max_messages - len(messages) < request_count:
            request_count = max_messages - len(messages)

        new_messages = queue.receive_messages(
            MaxNumberOfMessages=request_count,
            WaitTimeSeconds=20)
        if len(new_messages) == 0:
            queue.reload()
            queue_count = (int)(
                queue.attributes.get('ApproximateNumberOfMessages'))
            if queue_count == 0:
                fetch_messages = False
        else:
            messages.extend(new_messages)
            # hit maximum message count
            if len(messages) >= max_messages:
                fetch_messages = False

    return messages


def delete_messages(messages):
    """Delete provided messages from queue.

    Args:
        messages (list): List of messages to be deleted

    Returns: None
    """
    for message in messages:
        message.delete()
    return