django-assetkit/example_site/main/medialibrary/fields.py

# -*- coding: utf-8 -*-
from __future__ import unicode_literals
# Erik Stein <code@classlibrary.net>, 2016

from django import forms
from django.contrib.admin.widgets import AdminFileWidget
from django.db import models
from django.db.models.fields.files import FileDescriptor
from django.utils.functional import curry

from assetkit.files.storage import ProtectedMediaAssetStorage
from .utils import get_upload_path


# TODO Define the central storage somewhere more central
MEDIA_ASSET_STORAGE = ProtectedMediaAssetStorage()
DEFAULT_UPLOAD_TO = get_upload_path


class MediaAssetFileWidget(AdminFileWidget):
    """
    Widget which understands ProtectedMediaAssetStorage
    (knows that the url property is not relevant), also
    does not provide a link to the original file.
    # TODO Only admin access to the original file, if permissions apply
    # TODO Add permission "allowed to view original file"
    """

    # template_with_initial = (
    #     '%(initial_text)s: %(initial)s '
    #     '%(clear_template)s<br />%(input_text)s: %(input)s'
    # )

    def is_initial(self, value):
        # Checks for 'name' instead of 'url' property
        return bool(value and hasattr(value, 'name'))

    # def get_template_substitution_values(self, value):
    #     # Does not use value.url
    #     return {
    #         'initial': conditional_escape(value),
    #     }


class MediaAssetFileDescriptor(FileDescriptor):
    # TODO Assign metadata fields like width/height

    def __set__(self, instance, value):
        previous_file = instance.__dict__.get(self.field.name)
        super(MediaAssetFileDescriptor, self).__set__(instance, value)

        # TODO Check if previous_file is actually None in our case; remove comment
        # To prevent recalculating image dimensions when we are instantiating
        # an object from the database (bug #11084), only update dimensions if
        # the field had a value before this assignment.  Since the default
        # value for FileField subclasses is an instance of field.attr_class,
        # previous_file will only be None when we are called from
        # Model.__init__().  The ImageField.update_dimension_fields method
        # hooked up to the post_init signal handles the Model.__init__() cases.
        # Assignment happening outside of Model.__init__() will trigger the
        # update right here.
        if previous_file is not None:
            pass  # self.field.update_dimension_fields(instance, force=True)


# TODO MediaAssetFormField unused
class MediaAssetFormField(forms.FileField):
    widget = MediaAssetFileWidget


class MediaAssetField(models.FileField):
    # The descriptor to use for accessing the attribute off of the class.
    description_class = MediaAssetFileDescriptor

    def __init__(self, verbose_name=None, name=None, upload_to='', storage=None, *args, **kwargs):
        storage = kwargs.get('storage', MEDIA_ASSET_STORAGE)
        kwargs['storage'] = storage

        upload_func = kwargs.get('upload_to', DEFAULT_UPLOAD_TO)
        if callable(upload_func):
            kwargs['upload_to'] = curry(upload_func, storage=storage)
        else:
            kwargs['upload_to'] = upload_func

        # Field max length is the length of the file name plus the
        # string ORIGINAL_FILE_PREFIX, two slashes and the uuid. The filename
        # is shortened in the get_upload_path function.
        field_max_length = storage.FILENAME_MAX_LENGTH + 2 \
            + len(storage.ORIGINAL_FILE_PREFIX) \
            + 32  # uuid_hex
        kwargs['max_length'] = kwargs.get('max_length', field_max_length)

        super(MediaAssetField, self).__init__(verbose_name, name, **kwargs)

    def formfield(self, **kwargs):
        defaults = {
            # 'form_class': MediaAssetFormField,
            'widget': MediaAssetFileWidget,
            'max_length': self.storage.FILENAME_MAX_LENGTH,
        }
        kwargs.update(defaults)  # Force our values
        return super(MediaAssetField, self).formfield(**kwargs)