Add a delay to comment back-and-forths

tildes/scss/modules/_btn.scss

@@ -101,6 +101,7 @@
   // Status message (errors) should be on their own line as well
   > .text-status-message {
     min-width: 100%;
+    margin: 0.4rem;
   }
 }
 

tildes/tildes/views/api/web/comment.py

@@ -3,6 +3,8 @@
 
 """Web API endpoints related to comments."""
 
+from typing import Optional
+
 from marshmallow.fields import Boolean
 from pyramid.httpexceptions import HTTPUnprocessableEntity
 from pyramid.request import Request
@@ -20,6 +22,7 @@ from tildes.models.comment import (
     CommentVote,
 )
 from tildes.models.log import LogComment
+from tildes.models.user import User
 from tildes.schemas.comment import CommentLabelSchema, CommentSchema
 from tildes.views import IC_NOOP
 from tildes.views.decorators import ic_view_config, rate_limit_view
@@ -88,6 +91,13 @@ def post_toplevel_comment(request: Request, markdown: str) -> dict:
 def post_comment_reply(request: Request, markdown: str) -> dict:
     """Post a reply to a comment with Intercooler."""
     parent_comment = request.context
+
+    wait_mins = _reply_wait_minutes(request, request.user, parent_comment.user)
+    if wait_mins:
+        raise HTTPUnprocessableEntity(
+            f"You can't reply to this user yet. Please wait {wait_mins} minutes."
+        )
+
     new_comment = Comment(
         topic=parent_comment.topic,
         author=request.user,
@@ -138,6 +148,12 @@ def get_comment_contents(request: Request) -> dict:
 )
 def get_comment_reply(request: Request) -> dict:
     """Get the reply form for a comment with Intercooler."""
+    wait_mins = _reply_wait_minutes(request, request.user, request.context.user)
+    if wait_mins:
+        raise HTTPUnprocessableEntity(
+            f"You can't reply to this user yet. Please wait {wait_mins} minutes."
+        )
+
     return {"parent_comment": request.context}
 
 
@@ -451,3 +467,45 @@ def delete_comment_bookmark(request: Request) -> dict:
 def get_comment_markdown_source(request: Request) -> dict:
     """Get the Markdown source for a comment with Intercooler."""
     return {"post": request.context}
+
+
+def _reply_wait_minutes(
+    request: Request, replying_user: User, replying_to_user: User
+) -> Optional[int]:
+    """Return how many mins replying_user needs to wait to respond to replying_to_user.
+
+    `replying_user` is the one that wants to be able to post a new reply. They can't do
+    so if there exists a back-and-forth between them and `replying_to_user` where the
+    most recent comment is within the time threshold.
+
+    That is, call the user trying to reply "A", and the user they're replying to "B".
+    If a sequence of comments exists that are written by users (B, A, B) and the last
+    comment is "too recent", this will return how many minutes they need to wait. If
+    there isn't any recent sequence like that, it will return None.
+    """
+    threshold_minutes = 30
+
+    # if a "too recent" exchange exists, this will return a single value for how many
+    # minutes ago the final comment in the back-and-forth was posted
+    result = request.db_session.execute(
+        """
+        select ceil(extract(epoch from now() - main.created_time) / 60)
+        from comments as main
+        inner join comments as parent on parent.comment_id = main.parent_comment_id
+        inner join comments as grandparent
+            on grandparent.comment_id = parent.parent_comment_id
+        where main.user_id = :replying_to_user_id
+            and parent.user_id = :replying_user_id
+            and grandparent.user_id = :replying_to_user_id
+            and main.created_time > now() - interval ':threshold_minutes minutes'""",
+        {
+            "replying_to_user_id": replying_to_user.user_id,
+            "replying_user_id": replying_user.user_id,
+            "threshold_minutes": threshold_minutes,
+        },
+    ).fetchone()
+
+    if not result:
+        return None
+
+    return threshold_minutes - int(result[0])