"""
Update Status Lambda
====================
The lambda is listening to s3 events (all create events), find the file,
parse the s3 key and update the particular dynamodb item with the parsed
information. Important: this is python 2.7, since Lambda does not support
python 3.
"""

from __future__ import print_function

import collections

import boto3


dynamodb = boto3.client('dynamodb')
TABLE_NAME = 'prod_accounting_statement_export'
KEY_FORMAT = '{period_ids}__{trans_types}__AVRO__en_US'
Key = collections.namedtuple(
    'Key', ['user_id_type', 'user_params', 'period_ids'])


def _get_bucket_key(event):
    """Get bucket and key from the S3 put event.

    Args:
        event (dict): event dictionary.

    Returns:
        tuple(str, str): bucket and key tuple.
    """

    # Get the object from the event and show its content type
    bucket = event['Records'][0]['s3']['bucket']['name']
    key = event['Records'][0]['s3']['object']['key'].replace(
        '%3D', '=').replace('%2C', ',')
    return bucket, key


def _parse_s3_object_key(key):
    """Parse key and structure it in a namedtuple.

    Args:
        key (str): object key path's parts. Example:
            "schematized_files/199_label_all_all_month/
            user_id_type=18805L/file.avro".

    Returns:
        namedtuple: namedtuple with properties: period_ids, user_id_type and
            user_params.
    """

    key_parts = key.split('/')
    vfolder_parts = key_parts[1].split('_')
    user_id_type = key_parts[2].replace('user_id_type=', '')
    user_params = KEY_FORMAT.format(
        period_ids=vfolder_parts[0], trans_types=vfolder_parts[3])
    period_ids = vfolder_parts[0]
    return Key(
        user_id_type=user_id_type, user_params=user_params,
        period_ids=period_ids)


def lambda_handler(event, context):
    """Lambda handler for updating status

    Args:
        event (dict): S3 put event information.
        context (dict): statistic information.
    """

    bucket, key = _get_bucket_key(event)
    file_metadata = _parse_s3_object_key(key)
    s3_path = 's3://{}/{}'.format(bucket, key)
    dynamodb = boto3.client('dynamodb')
    try:
        # Update dynamodb items
        dynamodb.put_item(
            TableName=TABLE_NAME,
            Item={
                'user_id_type': {
                    'S': file_metadata.user_id_type
                },
                'user_params': {
                    'S': file_metadata.user_params
                },
                'file_type': {
                    'S': 'AVRO'
                },
                'period_ids': {
                    'S': file_metadata.period_ids
                },
                's3_path': {
                    'S': s3_path
                },
                'status': {
                    'S': 'GENERATED'
                }
            }
        )
    except Exception as e:
        print(
            'Error saving status for key: {} bucket: {}.'.format(key, bucket))
        raise e