using GB5Shared.Connection;

namespace FrameworkBLL.Encryption
{
    public class EncryptionBLL : IEncryptionBLL
    {
        private const string DefaultKey = "GB5";

        private readonly IApplicationConnection _ApplicationConnection;

        public EncryptionBLL(IApplicationConnection ApplicationConnection)
        {
            _ApplicationConnection = ApplicationConnection;
        }

        public string Encrypt(string data) => Encrypt(data, DefaultKey);

        public string Encrypt(string data, string publicKey)
        {
            if (string.IsNullOrEmpty(data))
                throw new ArgumentException("data is required.");
            if (string.IsNullOrEmpty(publicKey))
                throw new ArgumentException("PublicKey is required.");

            string ciphertext = _ApplicationConnection.Encrypt(data, publicKey);
            return ToUrlSafeBase64(ciphertext);
        }

        public string Decrypt(string token) => Decrypt(token, DefaultKey);

        public string Decrypt(string token, string publicKey)
        {
            if (string.IsNullOrEmpty(token))
                throw new ArgumentException("data is required.");
            if (string.IsNullOrEmpty(publicKey))
                throw new ArgumentException("PublicKey is required.");

            string ciphertext = FromUrlSafeBase64(token);
            return _ApplicationConnection.Decrypt(ciphertext, publicKey);
        }

        // The token travels in query strings/headers, where standard Base64's '+', '/' and '='
        // are prone to being mangled by clients/proxies that don't URL-encode them. Re-encoding
        // to URL-safe Base64 (RFC 4648 §5 — same scheme JWTs use) avoids that class of bug entirely.
        private static string ToUrlSafeBase64(string standardBase64)
        {
            return standardBase64.Replace('+', '-').Replace('/', '_').TrimEnd('=');
        }

        private static string FromUrlSafeBase64(string urlSafeBase64)
        {
            string base64 = urlSafeBase64.Replace('-', '+').Replace('_', '/');
            int padding = (4 - base64.Length % 4) % 4;
            return base64 + new string('=', padding);
        }
    }
}