guild.mod: refactor guild prune list in pure sql

close #54

litecord/blueprints/guild/mod.py

@@ -133,36 +133,29 @@ async def get_prune(guild_id: int, days: int) -> list:
     - did not login in ``days`` days.
     - don't have any roles.
     """
-    # a good solution would be in pure sql.
+
+    # @everyone role is always counted as a role in the db
+    # (its not implicit to every member as one would think)
+    # (that is probably the best solution in the future)
+    # (but we live with what we got)
     member_ids = await app.db.fetch(
         f"""
     SELECT id
     FROM users
     JOIN members
     ON members.guild_id = $1 AND members.user_id = users.id
-    WHERE users.last_session < (now() - (interval '{days} days'))
-    """,
-        guild_id,
-    )
-
-    member_ids = [r["id"] for r in member_ids]
-    members = []
-
-    for member_id in member_ids:
-        role_count = await app.db.fetchval(
-            """
-        SELECT COUNT(*)
+    WHERE
+        users.last_session < (now() - (interval '{days} days'))
+        AND (
+            SELECT COUNT(member_roles.role_id)
             FROM member_roles
-        WHERE guild_id = $1 AND user_id = $2
+            WHERE member_roles.user_id = members.user_id
+            ) <= 1
     """,
         guild_id,
-            member_id,
     )
 
-        if role_count == 1:  # only the @everyone role
-            members.append(member_id)
-
-    return members
+    return [r["id"] for r in member_ids]
 
 
 @bp.route("/<int:guild_id>/prune", methods=["GET"])