"""S3 common functions."""

import boto3
import botocore

from src import config

client = boto3.client('s3')
resource = boto3.resource('s3')


def object_exists(bucket, key):
    """Check if S3 object exists.

    Args:
        bucket (str): target S3 bucket.
        key (str): target S3 key.
    """
    try:
        client.head_object(
            Bucket=bucket,
            Key=key,
            ExpectedBucketOwner=config.EXPECTED_BUCKET_OWNER
        )
    except botocore.exceptions.ClientError as e:
        if e.response['Error']['Code'] == '404':
            return False
        else:
            raise
    else:
        return True


def head_object(bucket, key):
    """Retrieve object metadata without object downloading.

    Args:
        bucket (str): target S3 bucket.
        key (str): target object key.

    Returns:
        dict: Response from S3.

    """
    return client.head_object(
        Bucket=bucket,
        Key=key,
        ExpectedBucketOwner=config.EXPECTED_BUCKET_OWNER)


def create_presigned_url(
        bucket, key, client_method='get_object', expires_in=86400):
    """Generate a presigned url.

    Args:
        bucket (str): Bucket name.
        key (str): Existing S3 object key.
        client_method (str): Client method for operation by result URL.
        expires_in (int):  The number of seconds the presigned url is valid
            for. By default it expires in 24 hours (86400 seconds).

    Returns:
        str: Presigned url.

    """
    return client.generate_presigned_url(
        ClientMethod=client_method,
        ExpiresIn=expires_in,
        Params={
            'Bucket': bucket,
            'Key': key
        }
    )