Add support for serving users' avatars through the Libravatar API

users/migrations/0013_auto_20180323_1200.py

@@ -0,0 +1,24 @@
+# Generated by Django 2.0.3 on 2018-03-23 01:00
+
+import computed_property.fields
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('users', '0012_auto_20180129_1614'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='user',
+            name='email_md5',
+            field=computed_property.fields.ComputedCharField(compute_from='calc_email_md5', default='', editable=False, max_length=32, unique=True),
+        ),
+        migrations.AddField(
+            model_name='user',
+            name='email_sha256',
+            field=computed_property.fields.ComputedCharField(compute_from='calc_email_sha256', default='', editable=False, max_length=64, unique=True),
+        ),
+    ]

users/models.py

@@ -1,7 +1,9 @@
+from computed_property import ComputedCharField
 from django.db import models
 from django.contrib.auth.models import AbstractUser, UserManager as DjangoUserManager
 from django.contrib.sites.models import Site as DjangoSite
 from django.utils.functional import cached_property
+from hashlib import md5, sha256
 from meta.models import ModelMeta
 from urllib.parse import urljoin
 from lemoncurry import utils
@@ -46,6 +48,21 @@ class User(ModelMeta, AbstractUser):
     # This is gonna need to change if I ever decide to add multiple-user support ;)
     url = '/'
 
+    email_md5 = ComputedCharField(
+        compute_from='calc_email_md5', max_length=32, unique=True
+    )
+    email_sha256 = ComputedCharField(
+        compute_from='calc_email_sha256', max_length=64, unique=True
+    )
+
+    @property
+    def calc_email_md5(self):
+        return md5(self.email.lower().encode('utf-8')).hexdigest()
+
+    @property
+    def calc_email_sha256(self):
+        return sha256(self.email.lower().encode('utf-8')).hexdigest()
+
     @property
     def name(self):
         return '{0} {1}'.format(self.first_name, self.last_name)

users/urls.py

@@ -0,0 +1,8 @@
+from django.conf.urls import url
+
+from .views import libravatar
+
+app_name = 'users'
+urlpatterns = (
+    url('^avatar/(?P<hash>[a-z0-9]+)$', libravatar, name='libravatar'),
+)

users/views.py

@@ -0,0 +1,49 @@
+from django.http import HttpResponse, HttpResponseRedirect
+from PIL import Image
+
+from lemoncurry import utils
+from .models import User
+
+
+def try_libravatar_org(hash, get):
+    url = 'https://seccdn.libravatar.org/avatar/' + hash
+    if get:
+        url += '?' + get.urlencode()
+    return HttpResponseRedirect(url)
+
+
+def libravatar(request, hash):
+    g = request.GET
+    size = g.get('s', g.get('size', 80))
+    try:
+        size = int(size)
+    except ValueError:
+        return utils.bad_req('size parameter must be an integer')
+    if not 1 <= size <= 128:
+        return utils.bad_req('size parameter must be between 1 and 128')
+
+    if len(hash) == 32:
+        where = {'email_md5': hash}
+    elif len(hash) == 64:
+        where = {'email_sha256': hash}
+    else:
+        return utils.bad_req('hash must be either md5 or sha256')
+
+    # If the user doesn't exist or lacks an avatar, see if libravatar.org has
+    # one for them - libravatar.org falls back to Gravatar when possible (only
+    # for MD5 hashes, since Gravatar doesn't support SHA-256), so this ensures
+    # all the most likely places are checked.
+    try:
+        user = User.objects.get(**where)
+    except User.DoesNotExist:
+        return try_libravatar_org(hash, g)
+
+    if not user.avatar:
+        return try_libravatar_org(hash, g)
+
+    im = Image.open(user.avatar)
+    im_resized = im.resize((size, size))
+
+    response = HttpResponse(content_type='image/'+im.format.lower())
+    im_resized.save(response, im.format)
+    return response