feat: initial fediverse registration/login

Foxnouns.Backend/Controllers/Authentication/FediverseAuthController.cs

@@ -1,11 +1,26 @@
+using Foxnouns.Backend.Database;
+using Foxnouns.Backend.Database.Models;
 using Foxnouns.Backend.Services;
+using Foxnouns.Backend.Services.Auth;
+using Foxnouns.Backend.Utils;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+using NodaTime;
+using FediverseAuthService = Foxnouns.Backend.Services.Auth.FediverseAuthService;
 
 namespace Foxnouns.Backend.Controllers.Authentication;
 
 [Route("/api/internal/auth/fediverse")]
-public class FediverseAuthController(FediverseAuthService fediverseAuthService) : ApiControllerBase
+public class FediverseAuthController(
+    ILogger logger,
+    DatabaseContext db,
+    FediverseAuthService fediverseAuthService,
+    AuthService authService,
+    KeyCacheService keyCacheService
+) : ApiControllerBase
 {
+    private readonly ILogger _logger = logger.ForContext<FediverseAuthController>();
+
     [HttpGet]
     [ProducesResponseType<FediverseUrlResponse>(statusCode: StatusCodes.Status200OK)]
     public async Task<IActionResult> GetFediverseUrlAsync([FromQuery] string instance)
@@ -14,12 +29,88 @@ public class FediverseAuthController(FediverseAuthService fediverseAuthService)
         return Ok(new FediverseUrlResponse(url));
     }
 
+    [HttpPost("callback")]
+    [ProducesResponseType<CallbackResponse>(statusCode: StatusCodes.Status200OK)]
     public async Task<IActionResult> FediverseCallbackAsync([FromBody] CallbackRequest req)
     {
-        throw new NotImplementedException();
+        var app = await fediverseAuthService.GetApplicationAsync(req.Instance);
+        var remoteUser = await fediverseAuthService.GetRemoteFediverseUserAsync(app, req.Code);
+
+        var user = await authService.AuthenticateUserAsync(
+            AuthType.Fediverse,
+            remoteUser.Id,
+            instance: app
+        );
+        if (user != null)
+            return Ok(await authService.GenerateUserTokenAsync(user));
+
+        var ticket = AuthUtils.RandomToken();
+        await keyCacheService.SetKeyAsync(
+            $"fediverse:{ticket}",
+            new FediverseTicketData(app.Id, remoteUser),
+            Duration.FromMinutes(20)
+        );
+
+        return Ok(
+            new CallbackResponse(
+                HasAccount: false,
+                Ticket: ticket,
+                RemoteUsername: $"@{remoteUser.Username}@{app.Domain}",
+                User: null,
+                Token: null,
+                ExpiresAt: null
+            )
+        );
+    }
+
+    [HttpPost("register")]
+    [ProducesResponseType<AuthController.AuthResponse>(statusCode: StatusCodes.Status200OK)]
+    public async Task<IActionResult> RegisterAsync(
+        [FromBody] AuthController.OauthRegisterRequest req
+    )
+    {
+        var ticketData = await keyCacheService.GetKeyAsync<FediverseTicketData>(
+            $"fediverse:{req.Ticket}"
+        );
+        if (ticketData == null)
+            throw new ApiError.BadRequest("Invalid ticket", "ticket", req.Ticket);
+
+        var app = await db.FediverseApplications.FindAsync(ticketData.ApplicationId);
+        if (
+            await db.AuthMethods.AnyAsync(a =>
+                a.AuthType == AuthType.Fediverse
+                && a.RemoteId == ticketData.User.Id
+                && a.FediverseApplicationId == app.Id
+            )
+        )
+        {
+            _logger.Error(
+                "Fediverse user {Id}/{ApplicationId} ({Username} on {Domain}) has valid ticket but is already linked to an existing account",
+                ticketData.User.Id,
+                ticketData.ApplicationId,
+                ticketData.User.Username,
+                app.Domain
+            );
+            throw new ApiError.BadRequest("Invalid ticket", "ticket", req.Ticket);
+        }
+
+        var user = await authService.CreateUserWithRemoteAuthAsync(
+            req.Username,
+            AuthType.Fediverse,
+            ticketData.User.Id,
+            ticketData.User.Username,
+            instance: app
+        );
+
+        return Ok(await authService.GenerateUserTokenAsync(user));
     }
 
     public record CallbackRequest(string Instance, string Code);
 
     private record FediverseUrlResponse(string Url);
+
+    private record FediverseTicketData(
+        Snowflake ApplicationId,
+        FediverseAuthService.FediverseUser User
+    );
 }