using System.Diagnostics;
using System.Globalization;
using System.Threading.Tasks;
using MediaBrowser.Common.Extensions;
using MediaBrowser.Controller.Configuration;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Extensions;
using Microsoft.Extensions.Logging;

namespace Jellyfin.Server.Middleware
{
    /// <summary>
    /// Response time middleware.
    /// </summary>
    public class ResponseTimeMiddleware
    {
        private const string ResponseHeaderResponseTime = "X-Response-Time-ms";

        private readonly RequestDelegate _next;
        private readonly ILogger<ResponseTimeMiddleware> _logger;

        /// <summary>
        /// Initializes a new instance of the <see cref="ResponseTimeMiddleware"/> class.
        /// </summary>
        /// <param name="next">Next request delegate.</param>
        /// <param name="logger">Instance of the <see cref="ILogger{ExceptionMiddleware}"/> interface.</param>
        public ResponseTimeMiddleware(
            RequestDelegate next,
            ILogger<ResponseTimeMiddleware> logger)
        {
            _next = next;
            _logger = logger;
        }

        /// <summary>
        /// Invoke request.
        /// </summary>
        /// <param name="context">Request context.</param>
        /// <param name="serverConfigurationManager">Instance of the <see cref="IServerConfigurationManager"/> interface.</param>
        /// <returns>Task.</returns>
        public async Task Invoke(HttpContext context, IServerConfigurationManager serverConfigurationManager)
        {
            var startTimestamp = Stopwatch.GetTimestamp();

            var enableWarning = serverConfigurationManager.Configuration.EnableSlowResponseWarning;
            var warningThreshold = serverConfigurationManager.Configuration.SlowResponseThresholdMs;
            context.Response.OnStarting(() =>
            {
                var responseTime = Stopwatch.GetElapsedTime(startTimestamp);
                var responseTimeMs = responseTime.TotalMilliseconds;
                if (enableWarning && responseTimeMs > warningThreshold && _logger.IsEnabled(LogLevel.Debug))
                {
                    _logger.LogDebug(
                        "Slow HTTP Response from {Url} to {RemoteIp} in {Elapsed:g} with Status Code {StatusCode}",
                        context.Request.GetDisplayUrl(),
                        context.GetNormalizedRemoteIp(),
                        responseTime,
                        context.Response.StatusCode);
                }

                context.Response.Headers[ResponseHeaderResponseTime] = responseTimeMs.ToString(CultureInfo.InvariantCulture);
                return Task.CompletedTask;
            });

            // Call the next delegate/middleware in the pipeline
            await this._next(context).ConfigureAwait(false);
        }
    }
}
