From f8a94eeb04bec54e92c753aeff11dbed51ae7e6d Mon Sep 17 00:00:00 2001
From: Tom Hacohen <tom@stosb.com>
Date: Thu, 12 Mar 2020 15:52:36 +0200
Subject: [PATCH] Revision: add a proper uid for revisions (which we also use
 for sync tag).

---
 .../0024_collectionitemrevision_uid.py        | 19 +++++++++++++++++++
 .../migrations/0025_auto_20200312_1350.py     | 19 +++++++++++++++++++
 django_etesync/models.py                      |  4 +++-
 django_etesync/serializers.py                 | 15 ++++++++++-----
 4 files changed, 51 insertions(+), 6 deletions(-)
 create mode 100644 django_etesync/migrations/0024_collectionitemrevision_uid.py
 create mode 100644 django_etesync/migrations/0025_auto_20200312_1350.py

diff --git a/django_etesync/migrations/0024_collectionitemrevision_uid.py b/django_etesync/migrations/0024_collectionitemrevision_uid.py
new file mode 100644
index 0000000..6134c89
--- /dev/null
+++ b/django_etesync/migrations/0024_collectionitemrevision_uid.py
@@ -0,0 +1,19 @@
+# Generated by Django 3.0.3 on 2020-03-12 13:41
+
+import django.core.validators
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('django_etesync', '0023_auto_20200310_1556'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='collectionitemrevision',
+            name='uid',
+            field=models.CharField(db_index=True, max_length=44, validators=[django.core.validators.RegexValidator(message='Not a valid UID', regex='[a-zA-Z0-9]')]),
+        ),
+    ]
diff --git a/django_etesync/migrations/0025_auto_20200312_1350.py b/django_etesync/migrations/0025_auto_20200312_1350.py
new file mode 100644
index 0000000..b54aeff
--- /dev/null
+++ b/django_etesync/migrations/0025_auto_20200312_1350.py
@@ -0,0 +1,19 @@
+# Generated by Django 3.0.3 on 2020-03-12 13:50
+
+import django.core.validators
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('django_etesync', '0024_collectionitemrevision_uid'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='collectionitemrevision',
+            name='uid',
+            field=models.CharField(db_index=True, max_length=44, unique=True, validators=[django.core.validators.RegexValidator(message='Not a valid UID', regex='[a-zA-Z0-9]')]),
+        ),
+    ]
diff --git a/django_etesync/models.py b/django_etesync/models.py
index df25867..8079c28 100644
--- a/django_etesync/models.py
+++ b/django_etesync/models.py
@@ -78,6 +78,8 @@ class CollectionItemChunk(models.Model):
 
 
 class CollectionItemRevision(models.Model):
+    uid = models.CharField(db_index=True, unique=True, blank=False, null=False,
+                           max_length=44, validators=[UidValidator])
     item = models.ForeignKey(CollectionItem, related_name='revisions', on_delete=models.CASCADE)
     chunks = models.ManyToManyField(CollectionItemChunk, related_name='items')
     hmac = models.CharField(max_length=50, blank=False, null=False)
@@ -88,7 +90,7 @@ class CollectionItemRevision(models.Model):
         unique_together = ('item', 'current')
 
     def __str__(self):
-        return '{} {} current={}'.format(self.item.uid, self.id, self.current)
+        return '{} {} current={}'.format(self.uid, self.item.uid, self.current)
 
 
 class CollectionMember(models.Model):
diff --git a/django_etesync/serializers.py b/django_etesync/serializers.py
index c24239b..c6d3a86 100644
--- a/django_etesync/serializers.py
+++ b/django_etesync/serializers.py
@@ -16,12 +16,17 @@ import base64
 
 from django.contrib.auth import get_user_model
 from django.db import transaction
+from django.utils.crypto import get_random_string
 from rest_framework import serializers
 from . import models
 
 User = get_user_model()
 
 
+def generate_rev_uid(length=32):
+    return get_random_string(length)
+
+
 class BinaryBase64Field(serializers.Field):
     def to_representation(self, value):
         return base64.b64encode(value).decode('ascii')
@@ -54,14 +59,12 @@ class CollectionSerializer(serializers.ModelSerializer):
         return None
 
     def get_ctag(self, obj):
-        # FIXME: we need to have something that's more privacy friendly. Can probably just generate a uid per revision
-        # on revision creation (on the server) and just use that.
         last_revision = models.CollectionItemRevision.objects.filter(item__collection=obj).last()
         if last_revision is None:
             # FIXME: what is the etag for None? Though if we use the revision for collection it should be shared anyway.
             return None
 
-        return str(last_revision.id)
+        return last_revision.uid
 
     def create(self, validated_data):
         """Function that's called when this serializer creates an item"""
@@ -148,7 +151,8 @@ class CollectionItemSerializer(serializers.ModelSerializer):
             instance.save()
 
             chunks = revision_data.pop('chunks')
-            revision = models.CollectionItemRevision.objects.create(**revision_data, item=instance)
+            revision = models.CollectionItemRevision.objects.create(**revision_data, uid=generate_rev_uid(),
+                                                                    item=instance)
             revision.chunks.set(chunks)
 
         return instance
@@ -165,7 +169,8 @@ class CollectionItemSerializer(serializers.ModelSerializer):
             current_revision.save()
 
             chunks = revision_data.pop('chunks')
-            revision = models.CollectionItemRevision.objects.create(**revision_data, item=instance)
+            revision = models.CollectionItemRevision.objects.create(**revision_data, uid=generate_rev_uid(),
+                                                                    item=instance)
             revision.chunks.set(chunks)
 
         return instance