using System;
using System.Net;

namespace Laservall.Solidworks.Server
{
    /// <summary>
    /// Per-session auth token. Passed to browser via URL fragment (#token=xxx),
    /// returned via Authorization: Bearer header or ?token= query param.
    /// </summary>
    internal sealed class AuthTokenMiddleware
    {
        private readonly string _token;

        public AuthTokenMiddleware()
        {
            _token = Guid.NewGuid().ToString("N");
        }

        public string Token => _token;

        public bool IsAuthorized(HttpListenerRequest request)
        {
            if (request.Url.AbsolutePath == "/")
            {
                return true;
            }

            string authHeader = request.Headers["Authorization"];
            if (!string.IsNullOrEmpty(authHeader))
            {
                const string bearerPrefix = "Bearer ";
                if (authHeader.StartsWith(bearerPrefix, StringComparison.OrdinalIgnoreCase))
                {
                    string headerToken = authHeader.Substring(bearerPrefix.Length).Trim();
                    if (string.Equals(headerToken, _token, StringComparison.Ordinal))
                    {
                        return true;
                    }
                }
            }

            // ?token= fallback for SSE/download (can't set custom headers)
            string queryToken = request.QueryString["token"];
            if (!string.IsNullOrEmpty(queryToken))
            {
                return string.Equals(queryToken, _token, StringComparison.Ordinal);
            }

            return false;
        }

        public static void RejectUnauthorized(HttpListenerResponse response)
        {
            response.StatusCode = 401;
            response.ContentType = "application/json; charset=utf-8";
            byte[] body = System.Text.Encoding.UTF8.GetBytes("{\"error\":\"Unauthorized\"}");
            response.ContentLength64 = body.Length;
            response.OutputStream.Write(body, 0, body.Length);
            response.Close();
        }
    }
}