add a bunch of stuff copied from Foxchat.NET

Foxnouns.Backend/Utils/OauthUtils.cs

@@ -0,0 +1,67 @@
+using System.Security.Cryptography;
+
+namespace Foxnouns.Backend.Utils;
+
+public static class OauthUtils
+{
+    public const string ClientCredentials = "client_credentials";
+    public const string AuthorizationCode = "authorization_code";
+    private static readonly string[] ForbiddenSchemes = ["javascript", "file", "data", "mailto", "tel"];
+
+    public static readonly string[] UserScopes =
+        ["user.read_hidden", "user.read_privileged", "user.update"];
+
+    public static readonly string[] MemberScopes = ["member.read", "member.update", "member.create"];
+
+    /// <summary>
+    /// All scopes endpoints can be secured by. This does *not* include the catch-all token scopes.
+    /// </summary>
+    public static readonly string[] Scopes = ["identify", ..UserScopes, ..MemberScopes];
+
+    /// <summary>
+    /// All scopes that can be granted to applications and tokens. Includes the catch-all token scopes,
+    /// except for "*" which is only granted to the frontend.
+    /// </summary>
+    public static readonly string[] ApplicationScopes = [..Scopes, "user", "member"];
+
+    public static string[] ExpandScopes(this string[] scopes)
+    {
+        if (scopes.Contains("*")) return Scopes;
+        List<string> expandedScopes = ["identify"];
+        if (scopes.Contains("user")) expandedScopes.AddRange(UserScopes);
+        if (scopes.Contains("member")) expandedScopes.AddRange(MemberScopes);
+
+        return expandedScopes.ToArray();
+    }
+
+    public static bool ValidateRedirectUri(string uri)
+    {
+        try
+        {
+            var scheme = new Uri(uri).Scheme;
+            return !ForbiddenSchemes.Contains(scheme);
+        }
+        catch
+        {
+            return false;
+        }
+    }
+
+
+    public static bool TryFromBase64String(string b64, out byte[] bytes)
+    {
+        try
+        {
+            bytes = Convert.FromBase64String(b64);
+            return true;
+        }
+        catch
+        {
+            bytes = [];
+            return false;
+        }
+    }
+
+    public static string RandomToken(int bytes = 48) =>
+        Convert.ToBase64String(RandomNumberGenerator.GetBytes(bytes)).Trim('=');
+}