S3Property

S3Property.py

class S3Property(db.StringProperty):
    """
    On a put the value in the property is moved from the temp bucket to the
    stated permanent one.

    get_value_for_datastore is called as the model instance is placed in the 
    datastore, at this point we interrupt to process and move the asset before
    setting the assets new url in the datastore. get_value_for_datastore doesnt
    effect the model

    """

    def __init__(self, bucket, *args, **kwargs):
        super(S3Property, self).__init__(*args, **kwargs)
        self.bucket = bucket

        # This will hold the new url (the value stored in the db) for the asset
        self.new_url = None

    def __get__(self, model_instance, model_class):
        if self.new_url is not None:
            return self.new_url
        return super(S3Property, self).__get__(model_instance, model_class)

    def __set__(self, model_instance, value):
        # We clear the new url as we are setting a new one
        self.new_url = None 

        # Raise an error if its not an s3 url
        if not (
            's3-external-3.amazonaws.com/' in value
        ):
            raise db.BadValueError(
                'Property %s must be a url of a resource in a s3 bucket, not %s' 
                % (self.name, value)
            )
            
        super(S3Property, self).__set__(model_instance, value)

    def get_value_for_datastore(self, model_instance):

        # Get the current url (that would be the one that is placed in this 
        # field before saving the instance)
        url = super(S3Property, self).get_value_for_datastore(model_instance)

        # If self.bucket isnt in the url then the resource isnt in that bucket 
        # and has to be moved
        if not (
            '%s.s3-external-3.amazonaws.com/' % self.bucket in url
        ): 

            # Work out the location of the resource
            url = url.split('/')
            domain = url[2]
            bucket_name = domain.split('.')[0]
            file_name = '/'.join(url[3:])

            # # Move the asset
            self.new_url = s3.move_asset(
                bucket_name,
                urllib.unquote(file_name),
                self.bucket
            )
            
            return self.new_url
        return url