"""Interface for fetching assets from s3."""

import os

import boto3
from botocore.exceptions import ResponseStreamingError
from src.common.exceptions import exceptions

s3_client = boto3.client('s3')

ENV_CONFIG = {
    'dev': {
        'bucket': 'dev-orcd-raw-assets',
        'prefix': 'fingerprinting/acrcloud/'
    },
    'qa': {
        'bucket': 'qa-orcd-mezzanine-assets',
        'prefix': ''
    },
    'prod': {
        'bucket': 'prod-orcd-mezzanine-assets',
        'prefix': ''
    }
}

# 2 GiB
MAX_FILESIZE_BYTES = 1.074e+9 * 2


class FileTooLarge(Exception):
    """File too large to load into memory."""


def download_asset(filename, extension):
    """Fetch raw bytes of asset from s3.

    Args:
        filename (str): file identifier
        extension (str): file suffix

    Returns:
        bytes
    """
    (bucket, prefix) = _config()
    obj_key = f'{prefix}{filename}.{extension}'

    try:
        # verify file is not too large to be fingerprinted
        head_s3_response = s3_client.head_object(
            Bucket=bucket,
            Key=obj_key
        )
        size_bytes = head_s3_response['ContentLength']
        if size_bytes > MAX_FILESIZE_BYTES:
            raise FileTooLarge()

        # fetch actual bytes of the file
        s3_response = s3_client.get_object(
            Bucket=bucket,
            Key=obj_key
        )
        return s3_response['Body'].read()
    except ResponseStreamingError as e:
        raise exceptions.RetryableException(f'Error retrieving file: {e}')


def _config():
    """Get config based on value of Environment var."""
    env = os.environ['ENVIRONMENT']
    config = ENV_CONFIG[env]
    return (
        config['bucket'],
        config['prefix']
    )