Foxnouns.NET/Foxnouns.Backend/Utils/OauthUtils.cs

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('=');
}