Neil/lost updates (#341)

* Created version number field; check version number field on each update request

* Handled delete case + refactor

meow/frontend/src/actions/post.js

@@ -29,7 +29,7 @@ export const savePost = (postId, postData) => dispatch => {
     },
     err => {
       if (err.response.status === 403) {
-        console.log("Logging off because of 403 from saving posts");
+        // console.log("Logging off because of 403 from saving posts");
         dispatch({
           type: "LOGOUT"
         });
@@ -41,6 +41,10 @@ export const savePost = (postId, postData) => dispatch => {
       if (data["story_url"] !== undefined) {
         description = "Invalid URL";
       }
+      if (data["error"] !== undefined) {
+        description = data["error"];
+      }
+      console.log(data);
       alertError("Saving failed :(", description)(dispatch);
       dispatch({
         type: "NETWORK_ERROR",

meow/frontend/src/components/AddPost/index.js

@@ -26,6 +26,7 @@ const AddPost = () => {
     pub_ready_copy: false,
     pub_ready_online: false,
     section: null,
+    version_number: 0,
     pub_date: new Intl.DateTimeFormat("en-GB", dateOpts)
       .format(date)
       .split("/")

meow/frontend/src/components/EditPost/index.js

@@ -116,6 +116,7 @@ class EditPost extends React.Component {
       post_instagram: this.state.post_instagram,
       pub_ready_copy: this.state.pub_ready_copy,
       pub_ready_online: this.state.pub_ready_online,
+      version_number: this.state.version_number,
       tags: this.state.tags
         ? this.state.tags.map(x => {
             return x.text;
@@ -138,12 +139,14 @@ class EditPost extends React.Component {
   deletePost = () => {
     const { postId } = this.props.match.params;
 
-    this.props.savePost(postId, { is_active: false }).then(data => {
-      if (data) {
-        this.props.history.push("/");
-      } else {
-      }
-    });
+    this.props
+      .savePost(postId, { is_active: false, version_number: this.state.version_number })
+      .then(data => {
+        if (data) {
+          this.props.history.push("/");
+        } else {
+        }
+      });
   };
 
   sendNow = () => {

meow/scheduler/migrations/0018_smpost_version_number.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.2.6 on 2020-10-15 22:49
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('scheduler', '0017_smpost_post_instagram'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='smpost',
+            name='version_number',
+            field=models.IntegerField(default=0),
+        ),
+    ]

meow/scheduler/models.py

@@ -70,6 +70,7 @@ class SMPost(models.Model):
         default=True, help_text="If false, consider mock-deleted.")
 
     tags = models.ManyToManyField(SMPostTag)
+    version_number = models.IntegerField(default=0)
 
     def __str__(self):
         return "" if self.slug is None else self.slug

meow/scheduler/views.py

@@ -38,6 +38,8 @@
 # Oauth stuff
 from requests_oauthlib import OAuth2Session
 from requests_oauthlib.compliance_fixes import facebook_compliance_fix
+from django.db.models import F
+from django.db import transaction
 
 
 
@@ -110,6 +112,12 @@ def get_object(self, post_id):
         except SMPost.DoesNotExist:
             raise Http404
 
+    def get_object_with_lock(self, post_id):
+        try:
+            return SMPost.objects.select_for_update().get(id=post_id)
+        except SMPost.DoesNotExist:
+            raise Http404
+
     def get(self, request, post_id, format=None):
         if not request.user.is_authenticated:
             return Response("Must be logged in", status=403)
@@ -118,60 +126,86 @@ def get(self, request, post_id, format=None):
         serializer = SMPostSerializer(post)
         return Response(serializer.data)
 
-    def put(self, request, post_id, format=None):
-        if not request.user.is_authenticated:
-            return Response("Must be logged in", status=403)
-
-        post = self.get_object(post_id)
-
-        serializer = SMPostSerializer(post, data=request.data)
-        if serializer.is_valid():
-            b_should_update_copy_user = False
-            update_copy_user_to = None
-            b_should_update_online_user = False
-            update_online_user_to = None
-
-            #print(type(request.data["pub_ready_copy"]));
-
-            if "pub_ready_copy" in request.data and post.pub_ready_copy != request.data["pub_ready_copy"]:
-                # it means that the sender of this request tried to change it
-                # we have to check if they have copy permissions
-                #if request.user.group
-                if request.user.groups.filter(name="Copy").count() <= 0: # user is not part of copy group
-                    #  TODO: what data should the response send back
-                    return Response({"error":"Permission denied"}, status=status.HTTP_400_BAD_REQUEST)
+    def user_action_history_update(self, request, post):
+        """
+        Returns a tuple
+        success, object
+
+        it will be unsuccessful only if the user does nott have permission
+        """
+        b_should_update_copy_user = False
+        update_copy_user_to = None
+        b_should_update_online_user = False
+        update_online_user_to = None
+
+
+        if "pub_ready_copy" in request.data and post.pub_ready_copy != request.data["pub_ready_copy"]:
+            # it means that the sender of this request tried to change it
+            # we have to check if they have copy permissions
+            if request.user.groups.filter(name="Copy").count() <= 0: # user is not part of copy group
+                #  TODO: what data should the response send back
+                return False, None
+            else:
+                b_should_update_copy_user = True
+                if request.data["pub_ready_copy"]:
+                    update_copy_user_to = request.user
                 else:
-                    b_should_update_copy_user = True
-                    if request.data["pub_ready_copy"]:
-                        update_copy_user_to = request.user
-                    else:
-                        update_copy_user_to = None # means that the user marked it as not copy edited so clear the copy edited user
-            if "pub_ready_online" in request.data and post.pub_ready_online != request.data["pub_ready_online"]:
-
-                if request.user.groups.filter(name="Online").count() <= 0: # user is not part of group
-                    return Response({"error":"Permission denied"}, status=status.HTTP_400_BAD_REQUEST)
+                    update_copy_user_to = None # means that the user marked it as not copy edited so clear the copy edited user
+        if "pub_ready_online" in request.data and post.pub_ready_online != request.data["pub_ready_online"]:
+
+            if request.user.groups.filter(name="Online").count() <= 0: # user is not part of group
+                return False, None
+            else:
+                b_should_update_online_user = True
+                if request.data["pub_ready_online"]:
+                    update_online_user_to = request.user
                 else:
-                    b_should_update_online_user = True
-                    if request.data["pub_ready_online"]:
-                        update_online_user_to = request.user
-                    else:
-                        update_online_user_to = None
-
-            # will be passed into serializer.save()
-            serializer_keyword_args = {
-                "last_edit_user": request.user
-            }
+                    update_online_user_to = None
+
+        # will be passed into serializer.save()
+        serializer_keyword_args = {
+            "last_edit_user": request.user
+        }
 
-            # if the user updated the copy edited or online approved status,
-            # record them as the copy_user or online_user
-            if b_should_update_copy_user:
-                serializer_keyword_args["pub_ready_copy_user"] = update_copy_user_to
+        # if the user updated the copy edited or online approved status,
+        # record them as the copy_user or online_user
+        if b_should_update_copy_user:
+            serializer_keyword_args["pub_ready_copy_user"] = update_copy_user_to
 
-            if b_should_update_online_user:
-                serializer_keyword_args["pub_ready_online_user"] = update_online_user_to
+        if b_should_update_online_user:
+            serializer_keyword_args["pub_ready_online_user"] = update_online_user_to
 
-            post = serializer.save(**serializer_keyword_args)
+        return True, serializer_keyword_args
+
+
+    def put(self, request, post_id, format=None):
+        if not request.user.is_authenticated:
+            return Response("Must be logged in", status=403)
 
+
+        with transaction.atomic():
+            # lock the row. This lock will be released at the end of this transaction
+            # https://docs.djangoproject.com/en/3.1/ref/models/querysets/#select-for-update
+            post = self.get_object_with_lock(post_id)
+
+            serializer = SMPostSerializer(post, data=request.data)
+            if serializer.is_valid():
+                success, serializer_keyword_args = self.user_action_history_update(request, post)
+                if not success:
+                    return Response({"error": "Permission denied"})
+                # version number is incremented each time someone updates
+                # a post. If someone saves while another person is editing,
+                # the editing person will not see their changes. When 
+                # the editing person saves, the first person's updates will be lost
+                # to prevent this and other confusion, we have this check
+                if request.data["version_number"] < post.version_number:
+                    return Response({"error":"Someone updated this meow before you saved! Please open this meow in a new tab and reapply your changes."}, status=status.HTTP_400_BAD_REQUEST)
+
+                post = serializer.save(**serializer_keyword_args)
+                # increment version number
+                post.version_number += 1
+                post.save()
+            # at the end of the transaction, the lock will automatically be released
             return Response(serializer.data)
         return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)