[backend/api] Add bite back endpoint

Iceshrimp.Backend/Controllers/Web/MiscController.cs

@@ -6,6 +6,7 @@ using Iceshrimp.Backend.Controllers.Web.Renderers;
 using Iceshrimp.Backend.Core.Database;
 using Iceshrimp.Backend.Core.Extensions;
 using Iceshrimp.Backend.Core.Middleware;
+using Iceshrimp.Backend.Core.Services;
 using Iceshrimp.Shared.Schemas.Web;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.RateLimiting;
@@ -19,8 +20,28 @@ namespace Iceshrimp.Backend.Controllers.Web;
 [EnableRateLimiting("sliding")]
 [Route("/api/iceshrimp/misc")]
 [Produces(MediaTypeNames.Application.Json)]
-public class MiscController(DatabaseContext db, NoteRenderer noteRenderer) : ControllerBase
+public class MiscController(DatabaseContext db, NoteRenderer noteRenderer, BiteService biteSvc) : ControllerBase
 {
+	[HttpPost("bite_back/{id}")]
+	[Authenticate]
+	[Authorize]
+	[ProducesResults(HttpStatusCode.OK)]
+	[ProducesErrors(HttpStatusCode.BadRequest, HttpStatusCode.NotFound)]
+	public async Task BiteBack(string id)
+	{
+		var user = HttpContext.GetUserOrFail();
+		var target = await db.Bites
+		                     .IncludeCommonProperties()
+		                     .Where(p => p.Id == id)
+		                     .FirstOrDefaultAsync()
+		             ?? throw GracefulException.NotFound("Bite not found");
+
+		if (user.Id != (target.TargetUserId ?? target.TargetNote?.UserId ?? target.TargetBite?.UserId))
+			throw GracefulException.BadRequest("You can only bite back at a user who bit you");
+		
+		await biteSvc.BiteAsync(user, target);
+	}
+	
 	[HttpGet("muted_threads")]
 	[LinkPagination(20, 40)]
 	[ProducesResults(HttpStatusCode.OK)]

Iceshrimp.Backend/Core/Extensions/QueryableExtensions.cs

@@ -717,6 +717,13 @@ public static class QueryableExtensions
 		return query.Include(p => p.UserProfile);
 	}
 	
+	public static IQueryable<Bite> IncludeCommonProperties(this IQueryable<Bite> query)
+	{
+		return query.Include(p => p.TargetNote)
+		            .Include(p => p.TargetBite)
+		            .Include(p => p.User);
+	}
+
 	public static IQueryable<FollowRequest> IncludeCommonProperties(this IQueryable<FollowRequest> query)
 	{
 		return query.Include(p => p.Follower.UserProfile)

Iceshrimp.Backend/Core/Services/BiteService.cs

@@ -8,6 +8,29 @@ namespace Iceshrimp.Backend.Core.Services;
 
 public partial class BiteService(DatabaseContext db, ActivityPub.ActivityRenderer activityRenderer, ActivityPub.ActivityDeliverService deliverSvc, NotificationService notificationSvc, IOptions<Config.InstanceSection> config)
 {
+    public async Task BiteAsync(User user, Bite target)
+    {
+        var bite = new Bite
+        {
+            Id         = IdHelpers.GenerateSlowflakeId(),
+            CreatedAt  = DateTime.UtcNow,
+            User       = user,
+            TargetBite = target
+        };
+        bite.Uri = bite.GetPublicUri(config.Value);
+
+        await db.Bites.AddAsync(bite);
+        await db.SaveChangesAsync();
+
+        if (target.UserHost != null)
+        {
+            var activity = activityRenderer.RenderBite(bite, target.Uri ?? target.GetPublicUri(config.Value), target.User);
+            await deliverSvc.DeliverToAsync(activity, user, target.User);
+        }
+
+        await notificationSvc.GenerateBiteNotification(bite);
+    }
+    
     public async Task BiteAsync(User user, Note target)
     {
         var bite = new Bite