From b343438f9eb5195fc9e3a1c8a5c1e2862bcc4b4f Mon Sep 17 00:00:00 2001
From: Mohammad Mahdi <mmm.6831.allah@gmail.com>
Date: Wed, 26 Feb 2025 13:41:43 +0330
Subject: [PATCH] Performance improvements on finding a random post for API and
 bot '/start' command

---
 Services/HandleStartMessage.cs | 16 ++++++++++------
 Web/ServerStartup.cs           | 15 +++++++++++----
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/Services/HandleStartMessage.cs b/Services/HandleStartMessage.cs
index e17a3e5..546d331 100755
--- a/Services/HandleStartMessage.cs
+++ b/Services/HandleStartMessage.cs
@@ -24,15 +24,19 @@ public class HandleStartMessage
         //     .Where(post => post.MediaAttachments.Any(media => media.Approved))
         //     .ToListAsync();
 
-        var filter = Builders<Post>.Filter.ElemMatch(post => post.MediaAttachments, Builders<MediaAttachment>.Filter.Eq(media => media.Approved, true));
-        var mediaAttachmentsToSelect = await _db.Find(filter).ToListAsync();
+        var filter = Builders<Post>.Filter.ElemMatch(post => post.MediaAttachments,
+            Builders<MediaAttachment>.Filter.Eq(media => media.Approved, true));
+        var projection = Builders<Post>.Projection
+            .Include(p => p.Url)
+            .Include(p => p.Account.DisplayName)
+            .Include(p => p.MediaAttachments);
+                
+        var selectedPost = await _db.Aggregate().Match(filter).Project<Post>(projection).Sample(1).FirstOrDefaultAsync();
         
-        // select random approved media attachment
-        var selectedMediaAttachment = mediaAttachmentsToSelect[new Random().Next(mediaAttachmentsToSelect.Count)];
         // send media attachment
         await _bot.SendPhoto(message.Chat.Id,
-            selectedMediaAttachment.MediaAttachments.FirstOrDefault(m => m.Approved == true).Url,
-            $"Here is your cat!🐈\n" + "<a href=\"" + selectedMediaAttachment.Url + "\">" +
+            selectedPost.MediaAttachments.FirstOrDefault(m => m.Approved).RemoteUrl,
+            $"Here is your cat!🐈\n" + "<a href=\"" + selectedPost.Url + "\">" +
             $"View on Mastodon " + " </a>", ParseMode.Html
             , replyMarkup: new InlineKeyboardMarkup()
                 .AddButton(InlineKeyboardButton.WithUrl("Join channel 😺", "https://t.me/catsofmastodon"))
diff --git a/Web/ServerStartup.cs b/Web/ServerStartup.cs
index 33c2558..1922e48 100755
--- a/Web/ServerStartup.cs
+++ b/Web/ServerStartup.cs
@@ -51,16 +51,23 @@ public class ServerStartup
                 var stopwatch = Stopwatch.StartNew();
 
                 // Choose all posts media attachments that are approved
-                var filter = Builders<Post>.Filter.ElemMatch(post => post.MediaAttachments, Builders<MediaAttachment>.Filter.Eq(media => media.Approved, true));
-                var mediaAttachmentsToSelect = await _db.Find(filter).ToListAsync();
+                var filter = Builders<Post>.Filter.ElemMatch(post => post.MediaAttachments,
+                    Builders<MediaAttachment>.Filter.Eq(media => media.Approved, true));
+                var projection = Builders<Post>.Projection
+                    .Include(p => p.Url)
+                    .Include(p => p.Account.DisplayName)
+                    .Include(p => p.MediaAttachments);
+                
+                var selectedPost = await _db.Aggregate().Match(filter).Project<Post>(projection).Sample(1).FirstOrDefaultAsync();
 
                 // Stop and print execution time
                 stopwatch.Stop();
                 Console.WriteLine($"Query executed in: {stopwatch.ElapsedMilliseconds} ms");
-                // Select random approved media attachment
-                var selectedPost = mediaAttachmentsToSelect[new Random().Next(mediaAttachmentsToSelect.Count)];
                 
                 // Send as JSON
+                selectedPost.MediaAttachments = selectedPost.MediaAttachments
+                    .Where(media => media.Approved)
+                    .ToList();
                 await context.Response.WriteAsJsonAsync(selectedPost);
             });
         });