✨ Activity-based browsing

DysonNetwork.Sphere/Activity/Activity.cs

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+using System.ComponentModel.DataAnnotations;
+
+namespace DysonNetwork.Sphere.Activity;
+
+public enum ActivityVisibility
+{
+    Public,
+    Friends,
+}
+
+public class Activity : ModelBase
+{
+    public Guid Id { get; set; } = Guid.NewGuid();
+    [MaxLength(1024)] public string Type { get; set; } = null!;
+    [MaxLength(4096)] public string ResourceIdentifier { get; set; } = null!;
+    public ActivityVisibility Visibility { get; set; } = ActivityVisibility.Public;
+    public Dictionary<string, object> Meta =  new();
+    
+    public long AccountId { get; set; }
+    public Account.Account Account { get; set; } = null!;
+}

DysonNetwork.Sphere/Activity/ActivityController.cs

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+using DysonNetwork.Sphere.Account;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+
+namespace DysonNetwork.Sphere.Activity;
+
+[ApiController]
+[Route("/activities")]
+public class ActivityController(AppDatabase db, ActivityService act, RelationshipService rels) : ControllerBase
+{
+    [HttpGet]
+    public async Task<ActionResult<List<Activity>>> ListActivities([FromQuery] int offset, [FromQuery] int take = 20)
+    {
+        HttpContext.Items.TryGetValue("CurrentUser", out var currentUserValue);
+        var currentUser = currentUserValue as Account.Account;
+        var userFriends = await rels.ListAccountFriends(currentUser!);
+
+        var totalCount = await db.Activities
+            .FilterWithVisibility(currentUser, userFriends)
+            .CountAsync();
+        var posts = await db.Activities
+            .Include(e => e.Account)
+            .FilterWithVisibility(currentUser, userFriends)
+            .OrderByDescending(e => e.CreatedAt)
+            .Skip(offset)
+            .Take(take)
+            .ToListAsync();
+
+        Response.Headers["X-Total"] = totalCount.ToString();
+
+        return Ok(posts); 
+    }
+}

DysonNetwork.Sphere/Activity/ActivityService.cs

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+using DysonNetwork.Sphere.Post;
+using NodaTime;
+
+namespace DysonNetwork.Sphere.Activity;
+
+public class ActivityService(AppDatabase db)
+{
+    public async Task<Activity> CreateActivity(
+        Account.Account user,
+        string type,
+        string identifier,
+        ActivityVisibility visibility = ActivityVisibility.Public
+    )
+    {
+        var activity = new Activity
+        {
+            Type = type,
+            ResourceIdentifier = identifier,
+            Visibility = visibility,
+            AccountId = user.Id,
+        };
+
+        db.Activities.Add(activity);
+        await db.SaveChangesAsync();
+
+        return activity;
+    }
+
+    public async Task CreateNewPostActivity(Account.Account user, Post.Post post)
+    {
+        if (post.Visibility is PostVisibility.Unlisted or PostVisibility.Private) return;
+
+        var identifier = $"posts/{post.Id}";
+        await CreateActivity(user, "posts.new", identifier,
+            post.Visibility == PostVisibility.Friends ? ActivityVisibility.Friends : ActivityVisibility.Public);
+    }
+}
+
+public static class ActivityQueryExtensions
+{
+    public static IQueryable<Activity> FilterWithVisibility(this IQueryable<Activity> source,
+        Account.Account? currentUser, List<long> userFriends)
+    {
+        var now = Instant.FromDateTimeUtc(DateTime.UtcNow);
+
+        if (currentUser is null)
+            return source.Where(e => e.Visibility == ActivityVisibility.Public);
+
+        return source
+            .Where(e => e.Visibility != ActivityVisibility.Friends ||
+                        userFriends.Contains(e.AccountId) ||
+                        e.AccountId == currentUser.Id);
+    }
+}