✨ Ranked posts

DysonNetwork.Sphere/Activity/ActivityService.cs

@@ -1,19 +1,43 @@
+
 using DysonNetwork.Sphere.Account;
+using DysonNetwork.Sphere.Discovery;
 using DysonNetwork.Sphere.Post;
 using DysonNetwork.Sphere.Publisher;
 using Microsoft.EntityFrameworkCore;
 using NodaTime;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
 
 namespace DysonNetwork.Sphere.Activity;
 
-public class ActivityService(AppDatabase db, PublisherService pub, RelationshipService rels, PostService ps)
+public class ActivityService(AppDatabase db, PublisherService pub, RelationshipService rels, PostService ps, DiscoveryService ds)
 {
+    private double CalculateHotRank(Post.Post post, Instant now)
+    {
+        var score = post.Upvotes - post.Downvotes;
+        var postTime = post.PublishedAt ?? post.CreatedAt;
+        var hours = (now - postTime).TotalHours;
+        // Add 1 to score to prevent negative results for posts with more downvotes than upvotes
+        return (score + 1) / Math.Pow(hours + 2, 1.8);
+    }
+
     public async Task<List<Activity>> GetActivitiesForAnyone(int take, Instant? cursor)
     {
         var activities = new List<Activity>();
 
-        // Crunching up data
-        var posts = await db.Posts
+        if (cursor == null)
+        {
+            var realms = await ds.GetPublicRealmsAsync(null, null);
+            if (realms.Count > 0)
+            {
+                activities.Add(new DiscoveryActivity("Explore Realms", realms.Cast<object>().ToList()).ToActivity());
+            }
+        }
+
+        // Fetch a larger batch of recent posts to rank
+        var postsQuery = db.Posts
             .Include(e => e.RepliedPost)
             .Include(e => e.ForwardedPost)
             .Include(e => e.Categories)
@@ -22,8 +46,9 @@ public class ActivityService(AppDatabase db, PublisherService pub, RelationshipS
             .Where(p => cursor == null || p.PublishedAt < cursor)
             .OrderByDescending(p => p.PublishedAt)
             .FilterWithVisibility(null, [], [], isListing: true)
-            .Take(take)
-            .ToListAsync();
+            .Take(take * 5); // Fetch more posts to have a good pool for ranking
+
+        var posts = await postsQuery.ToListAsync();
         posts = await ps.LoadPostInfo(posts, null, true);
 
         var postsId = posts.Select(e => e.Id).ToList();
@@ -32,8 +57,17 @@ public class ActivityService(AppDatabase db, PublisherService pub, RelationshipS
             post.ReactionsCount =
                 reactionMaps.TryGetValue(post.Id, out var count) ? count : new Dictionary<string, int>();
 
+        // Rank and sort
+        var now = SystemClock.Instance.GetCurrentInstant();
+        var rankedPosts = posts
+            .Select(p => new { Post = p, Rank = CalculateHotRank(p, now) })
+            .OrderByDescending(x => x.Rank)
+            .Select(x => x.Post)
+            .Take(take)
+            .ToList();
+
         // Formatting data
-        foreach (var post in posts)
+        foreach (var post in rankedPosts)
             activities.Add(post.ToActivity());
 
         if (activities.Count == 0)
@@ -53,6 +87,15 @@ public class ActivityService(AppDatabase db, PublisherService pub, RelationshipS
         var userFriends = await rels.ListAccountFriends(currentUser);
         var userPublishers = await pub.GetUserPublishers(currentUser.Id);
 
+        if (cursor == null)
+        {
+            var realms = await ds.GetPublicRealmsAsync(null, null);
+            if (realms.Count > 0)
+            {
+                activities.Add(new DiscoveryActivity("Explore Realms", realms.Cast<object>().ToList()).ToActivity());
+            }
+        }
+
         // Get publishers based on filter
         var filteredPublishers = filter switch
         {
@@ -81,7 +124,7 @@ public class ActivityService(AppDatabase db, PublisherService pub, RelationshipS
         // Complete the query with visibility filtering and execute
         var posts = await postsQuery
             .FilterWithVisibility(currentUser, userFriends, filter is null ? userPublishers : [], isListing: true)
-            .Take(take)
+            .Take(take * 5) // Fetch more posts to have a good pool for ranking
             .ToListAsync();
 
         posts = await ps.LoadPostInfo(posts, currentUser, true);
@@ -97,8 +140,17 @@ public class ActivityService(AppDatabase db, PublisherService pub, RelationshipS
             await ps.IncreaseViewCount(post.Id, currentUser.Id.ToString());
         }
 
+        // Rank and sort
+        var now = SystemClock.Instance.GetCurrentInstant();
+        var rankedPosts = posts
+            .Select(p => new { Post = p, Rank = CalculateHotRank(p, now) })
+            .OrderByDescending(x => x.Rank)
+            .Select(x => x.Post)
+            .Take(take)
+            .ToList();
+
         // Formatting data
-        foreach (var post in posts)
+        foreach (var post in rankedPosts)
             activities.Add(post.ToActivity());
 
         if (activities.Count == 0)

DysonNetwork.Sphere/Activity/DiscoveryActivity.cs

@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using NodaTime;
+
+namespace DysonNetwork.Sphere.Activity
+{
+    public class DiscoveryActivity : IActivity
+    {
+        public string Title { get; set; }
+        public List<object> Items { get; set; }
+
+        public DiscoveryActivity(string title, List<object> items)
+        {
+            Title = title;
+            Items = items;
+        }
+
+        public Activity ToActivity()
+        {
+            var now = SystemClock.Instance.GetCurrentInstant();
+            return new Activity
+            {
+                Id = Guid.NewGuid(),
+                Type = "discovery",
+                ResourceIdentifier = "discovery",
+                Data = this,
+                CreatedAt = now,
+                UpdatedAt = now,
+            };
+        }
+    }
+}