Autodetect attachment viewers by getting all abstract viewer subclasses

boards/models/attachment/__init__.py

@@ -1,77 +1,71 b''
 import hashlib
 import os
 import time
 
 from random import random
 
 from django.db import models
 
-from boards.models.attachment.viewers import AbstractViewer, WebmViewer, \
-    AudioViewer, SvgViewer
+from boards.models.attachment.viewers import get_viewers, AbstractViewer
+
 
 FILES_DIRECTORY = 'files/'
 FILE_EXTENSION_DELIMITER = '.'
 
-VIEWERS = (
-    WebmViewer,
-    AudioViewer,
-    SvgViewer,
-)
-
 
 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 VIEWERS:
+        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()
 
 

boards/models/attachment/viewers.py

@@ -1,64 +1,68 b''
 from django.template.defaultfilters import filesizeformat
 from django.templatetags.static import static
 
 FILE_STUB_IMAGE = 'images/file.png'
 
 FILE_TYPE_WEBM = 'webm'
 FILE_TYPE_SVG = 'svg'
 FILE_TYPES_AUDIO = (
     'ogg',
     'mp3',
 )
 
 
+def get_viewers():
+    return AbstractViewer.__subclasses__()
+
+
 class AbstractViewer:
     def __init__(self, file, file_type):
         self.file = file
         self.file_type = file_type
 
     @staticmethod
     def supports(file_type):
         return True
 
     def get_view(self):
         return '<div class="image"><a href="{}">'\
                '<img src="{}" width="200" height="150"/>'\
                '</a>'\
                '<div class="image-metadata">{}, {}</div>'\
                '</div>'.format(self.file.url, static(FILE_STUB_IMAGE),
                                self.file_type, filesizeformat(self.file.size))
 
 
 class WebmViewer(AbstractViewer):
     @staticmethod
     def supports(file_type):
         return file_type == FILE_TYPE_WEBM
 
     def get_view(self):
         return '<div class="image">'\
                '<video width="200" height="150" controls src="{}"/>'\
                '</div>'.format(self.file.url)
 
 
 class AudioViewer(AbstractViewer):
     @staticmethod
     def supports(file_type):
         return file_type in FILE_TYPES_AUDIO
 
     def get_view(self):
         return '<div class="image">' \
                '<audio controls src="{}"/>' \
                '</div>'.format(self.file.url)
 
 
 class SvgViewer(AbstractViewer):
     @staticmethod
     def supports(file_type):
         return file_type == FILE_TYPE_SVG
 
     def get_view(self):
         return '<div class="image">'\
                '<a class="thumb" href="{}">'\
                '<img class="post-image-preview" width="200" height="150" src="{}"/>'\
                '</a>'\
                '</div>'.format(self.file.url, self.file.url)