[backend/api] Add follow list export endpoint

Iceshrimp.Backend/Controllers/Web/SettingsController.cs

@@ -9,6 +9,7 @@ using Iceshrimp.Backend.Core.Services;
 using Iceshrimp.Shared.Schemas.Web;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.RateLimiting;
+using Microsoft.EntityFrameworkCore;
 
 namespace Iceshrimp.Backend.Controllers.Web;
 
@@ -65,6 +66,23 @@ public class SettingsController(DatabaseContext db, UserService userSvc) : Contr
 		await db.ReloadEntityAsync(settings);
 		return settings;
 	}
+	
+	[HttpPost("export/following")]
+	[ProducesResults(HttpStatusCode.Accepted)]
+	[ProducesErrors(HttpStatusCode.BadRequest)]
+	public async Task<AcceptedResult> ExportFollowing()
+	{
+		var user = HttpContext.GetUserOrFail();
+
+		var followCount = await db.Followings
+		                          .CountAsync(p => p.FollowerId == user.Id);
+		if (followCount < 1)
+			throw GracefulException.BadRequest("You do not follow any users");
+
+		await userSvc.ExportFollowingAsync(user);
+		
+		return Accepted();
+	}
 
 	[HttpPost("import/following")]
 	[ProducesResults(HttpStatusCode.Accepted)]

Iceshrimp.Backend/Core/Services/UserService.cs

@@ -1,6 +1,7 @@
 using System.Diagnostics.CodeAnalysis;
 using System.Net;
 using System.Security.Cryptography;
+using System.Text;
 using System.Text.RegularExpressions;
 using AsyncKeyedLock;
 using EntityFramework.Exceptions.Common;
@@ -946,6 +947,29 @@ public class UserService(
 		await db.UserListMembers.Where(p => p.UserList.User == user && p.User == followee).ExecuteDeleteAsync();
 	}
 
+	public async Task ExportFollowingAsync(User user)
+	{
+		var followees = await db.Followings
+		                        .Include(p => p.Followee)
+		                        .Where(p => p.FollowerId == user.Id)
+		                        .Select(p => p.Followee)
+		                        .Where(p => !p.IsDeleted && !p.IsSystemUser && p.MovedToUri == null)
+		                        .OrderBy(p => p.Host)
+		                        .ThenBy(p => p.UsernameLower)
+		                        .Select(p => p.GetFqn(instance.Value.AccountDomain))
+		                        .ToListAsync();
+
+		var stream = new MemoryStream(Encoding.UTF8.GetBytes(string.Join("\n", followees)));
+
+		await driveSvc.StoreFile(stream, user,
+		                         new DriveFileCreationRequest
+		                         {
+			                         Filename    = $"following-{DateTime.UtcNow:yyyy-MM-dd-HH-mm-ss}.csv",
+			                         IsSensitive = false,
+			                         MimeType    = "text/csv"
+		                         }, true);
+	}
+
 	public async Task ImportFollowingAsync(User user, List<string> fqns)
 	{
 		foreach (var fqn in fqns.Select(fqn => fqn.Split("@")))