Add Steam OpenID authentication

microservices/AuthApi/Services/UserService.cs

@@ -1,5 +1,7 @@
 using AuthApi.Models;
+using MongoDB.Bson;
 using MongoDB.Driver;
+using System.Text.RegularExpressions;
 
 namespace AuthApi.Services;
 
@@ -17,6 +19,12 @@ public class UserService
 
         var keys = Builders<User>.IndexKeys.Ascending(u => u.Username);
         _col.Indexes.CreateOne(new CreateIndexModel<User>(keys, new CreateIndexOptions { Unique = true }));
+        var steamKeys = Builders<User>.IndexKeys.Ascending(u => u.SteamId);
+        _col.Indexes.CreateOne(new CreateIndexModel<User>(steamKeys, new CreateIndexOptions<User>
+        {
+            Unique = true,
+            PartialFilterExpression = new BsonDocument("SteamId", new BsonDocument("$type", "string"))
+        }));
     }
 
     public async Task<User?> GetByUsernameAsync(string username) =>
@@ -28,11 +36,36 @@ public class UserService
     public async Task<User?> GetByEmailAsync(string email) =>
         await _col.Find(u => u.Email == email).FirstOrDefaultAsync();
 
+    public async Task<List<User>> GetByLoginCandidatesAsync(string login)
+    {
+        var normalized = login.Trim();
+        var usernameMatch = await GetByUsernameAsync(normalized);
+        if (usernameMatch is not null)
+            return [usernameMatch];
+        var emailPattern = new BsonRegularExpression($"^{Regex.Escape(normalized)}$", "i");
+        return await _col.Find(Builders<User>.Filter.Regex(u => u.Email, emailPattern)).ToListAsync();
+    }
+
+    public async Task<User?> GetBySteamIdAsync(string steamId) =>
+        await _col.Find(u => u.SteamId == steamId).FirstOrDefaultAsync();
+
     public Task CreateAsync(User user) => _col.InsertOneAsync(user);
 
     public Task UpdateAsync(User user) =>
         _col.ReplaceOneAsync(u => u.Id == user.Id, user);
 
+    public async Task<bool> TryLinkSteamAsync(string userId, string steamId, string refreshToken, DateTime refreshExpiry)
+    {
+        var filter = Builders<User>.Filter.Eq(u => u.Id, userId) &
+            (Builders<User>.Filter.Eq(u => u.SteamId, null) | Builders<User>.Filter.Eq(u => u.SteamId, steamId));
+        var update = Builders<User>.Update
+            .Set(u => u.SteamId, steamId)
+            .Set(u => u.RefreshToken, refreshToken)
+            .Set(u => u.RefreshTokenExpiry, refreshExpiry);
+        var result = await _col.UpdateOneAsync(filter, update);
+        return result.MatchedCount == 1;
+    }
+
     public Task DeleteAsync(string id) => _col.DeleteOneAsync(u => u.Id == id);
 
     public Task<List<User>> GetAllAsync() =>