boards/models/attachment/__init__.py

import hashlib
import os
import time

from random import random

from django.db import models

from boards.models.attachment.viewers import get_viewers, AbstractViewer


FILES_DIRECTORY = 'files/'
FILE_EXTENSION_DELIMITER = '.'


class AttachmentManager(models.Manager):
    def create_with_hash(self, file):
        file_hash = self.get_hash(file)
        existing = self.filter(hash=file_hash)
        if len(existing) > 0:
            attachment = existing[0]
        else:
            file_type = file.name.split(FILE_EXTENSION_DELIMITER)[-1].lower()
            attachment = Attachment.objects.create(file=file,
                    mimetype=file_type, hash=file_hash)

        return attachment

    def get_hash(self, file):
        """
        Gets hash of an file.
        """
        md5 = hashlib.md5()
        for chunk in file.chunks():
            md5.update(chunk)
        return md5.hexdigest()


class Attachment(models.Model):
    objects = AttachmentManager()

    # TODO Dedup the method
    def _update_filename(self, filename):
        """
        Gets unique filename
        """

        # TODO Use something other than random number in file name
        new_name = '{}{}.{}'.format(
            str(int(time.mktime(time.gmtime()))),
            str(int(random() * 1000)),
            filename.split(FILE_EXTENSION_DELIMITER)[-1:][0])

        return os.path.join(FILES_DIRECTORY, new_name)

    file = models.FileField(upload_to=_update_filename)
    mimetype = models.CharField(max_length=50)
    hash = models.CharField(max_length=36)

    def get_view(self):
        file_viewer = None
        for viewer in get_viewers():
            if viewer.supports(self.mimetype):
                file_viewer = viewer(self.file, self.mimetype)
                break
        if file_viewer is None:
            file_viewer = AbstractViewer(self.file, self.mimetype)

        return file_viewer.get_view()