upload_path.py

import os
import uuid
from base64 import urlsafe_b64encode

from django.utils.deconstruct import deconstructible

from utils.base36 import base36encode


@deconstructible
class UploadPath:
    def __init__(self, directory, sharding=False):
        self.directory = directory
        self.sharding = sharding

    def get_filename(self, instance, name, ext):
        return urlsafe_b64encode(uuid.uuid1().bytes).decode('ascii').strip('=') + ext

    def get_directory(self, instance, filename):
        return self.directory

    def __call__(self, instance, filename):
        name, ext = os.path.splitext(filename)
        directory = self.get_directory(instance, filename)
        new_filename = self.get_filename(instance, name, ext)
        return os.path.join(directory, new_filename)

    def __eq__(self, other):
        return self.directory == other.directory


@deconstructible
class ShardedUploadPath(UploadPath):
    def __init__(self, *args, **kwargs):
        self.part_size = kwargs.pop('part_size', 2)
        self.pk_field = kwargs.pop('pk_field', 'id')
        super().__init__(*args, **kwargs)

    def get_pk_value(self, instance):
        value = instance
        for attr in self.pk_field.split('.'):
            value = getattr(value, attr)
        return value

    def get_directory(self, instance, filename):
        pk = self.get_pk_value(instance)
        assert pk is not None, 'Instance must have pk for sharded upload path'
        shard = list(base36encode(pk).lower())

        parts = []
        for left in range(0, len(shard), self.part_size):
            right = left + self.part_size
            parts.append(''.join(shard[left:right]))

        return os.path.join(self.directory, *parts)