blender-studio/common/storage.py

"""Custom file storage classes."""
import logging

from django.conf import settings
from django.db import models
from django.db.models.fields.files import FieldFile

from botocore.client import Config
import boto3
import botocore.exceptions

import nginx_secure_links.storages

from storages.backends.s3boto3 import S3Boto3Storage

logger = logging.getLogger(__name__)
_s3_client = None


class S3PublicStorage(S3Boto3Storage):
    """Disable signing for URLs generated by this storage.

    Useful for files that are publicly readable and don't need signed URLs, such as thumbnails.
    """

    querystring_auth = False


class S3Boto3CustomStorage(S3Boto3Storage):
    """Override some upload parameters, such as ContentDisposition header."""

    def _get_write_parameters(self, name, content):
        """Set ContentDisposition header using original file name.

        While docstring recommends overriding `get_object_parameters` for this purpose,
        `get_object_parameters` only gets a `name` which is not the original file name,
        but the result of `upload_to`.
        """
        params = super()._get_write_parameters(name, content)
        original_name = getattr(content, 'name', None)
        if original_name and name != original_name:
            content_disposition = f'attachment; filename="{original_name}"'
            params['ContentDisposition'] = content_disposition
        return params


def _get_s3_client():
    return boto3.client(
        's3',
        config=Config(signature_version='s3v4'),
        aws_access_key_id=settings.AWS_ACCESS_KEY_ID,
        aws_secret_access_key=settings.AWS_SECRET_ACCESS_KEY,
        region_name=settings.AWS_S3_REGION_NAME,
    )


def get_s3_url(path, expires_in_seconds=settings.FILE_LINK_EXPIRE_SECONDS):
    """Generate a pre-signed S3 URL to a given path."""
    global _s3_client
    if not _s3_client:
        _s3_client = _get_s3_client()

    return _s3_client.generate_presigned_url(
        'get_object',
        Params={'Bucket': settings.AWS_STORAGE_BUCKET_NAME, 'Key': path},
        HttpMethod='GET',
        ExpiresIn=expires_in_seconds,
    )


def file_exists(path, bucket=settings.AWS_STORAGE_BUCKET_NAME):
    """Check if given file exists in S3."""
    global _s3_client
    if not _s3_client:
        _s3_client = _get_s3_client()

    try:
        _s3_client.head_object(Bucket=bucket, Key=path)
    except botocore.exceptions.ClientError as e:
        return int(e.response['Error']['Code']) != 404
    return True


def file_head(path, bucket=settings.AWS_STORAGE_BUCKET_NAME) -> object:
    """Return headers of the given file it if exists in S3."""
    global _s3_client
    if not _s3_client:
        _s3_client = _get_s3_client()

    try:
        return _s3_client.head_object(Bucket=bucket, Key=path)
    except botocore.exceptions.ClientError:
        logger.exception(f'Unable to get header for {path}')
        return {}


def get_s3_post_url_and_fields(
    path,
    bucket=settings.AWS_STORAGE_BUCKET_NAME,
    fields=None,
    conditions=None,
    expires_in_seconds=settings.FILE_LINK_EXPIRE_SECONDS,
):
    """Generate a presigned URL S3 POST request to upload a file to a given bucket and path.

    :param path: string
    :param bucket: string
    :param fields: Dictionary of prefilled form fields
    :param conditions: List of conditions to include in the policy
    :param expires_in_seconds: Time in seconds for the presigned URL to remain valid
    :return: Dictionary with the following keys:
        url: URL to post to
        fields: Dictionary of form fields and values to submit with the POST
    :return: None if error.
    """
    global _s3_client
    if not _s3_client:
        _s3_client = _get_s3_client()

    _s3_client = boto3.client('s3')
    try:
        response = _s3_client.generate_presigned_post(
            bucket, str(path), Fields=fields, Conditions=conditions, ExpiresIn=expires_in_seconds,
        )
    except botocore.exceptions.ClientError as e:
        logger.error(e)
        return None

    # The response contains the presigned URL and required fields
    return response


class DynamicStorageFieldFile(FieldFile):
    """Defines which storage the file is located at."""

    def __init__(self, instance, *args, **kwargs):
        """Choose between S3 and file system storage depending on `source_storage`."""
        super().__init__(instance, *args, **kwargs)
        if instance.source_storage is None:  # S3 is default
            self.storage = S3Boto3CustomStorage()
        elif instance.source_storage == 'fs':
            self.storage = nginx_secure_links.storages.FileStorage()
        else:
            raise


class CustomFileField(models.FileField):
    """Defines which storage the file field is located at."""

    attr_class = DynamicStorageFieldFile

    def pre_save(self, model_instance, add):
        """Choose between S3 and file system storage depending on `source_storage`."""
        if model_instance.source_storage is None:
            storage = S3Boto3CustomStorage()
        elif model_instance.source_storage == 'fs':
            storage = nginx_secure_links.storages.FileStorage()
        else:
            raise
        self.storage = storage
        model_instance.source.storage = storage
        # TODO: do the same for thumbnail?
        return super().pre_save(model_instance, add)