using System.IO;
using System.Net;

namespace PV178.Homeworks.HW05.Utils
{
    /// <summary>
    /// Utility class for downloading content from web
    /// </summary>
    public static class WebContentDownloader
    {
        private const string Route05Url = "http://is.muni.cz/www/409727/64666522/64666524/route05.gpx";

        /// <summary>
        /// Downloads file: route05.gpx from <see cref="Route05Url"/>
        /// </summary>
        /// <param name="filePath">Determines where downloaded file will be saved.</param>
        public static void DownloadContent(string filePath)
        {
            var req = (HttpWebRequest)WebRequest.Create(Route05Url);
            using (var resp = (HttpWebResponse) req.GetResponse())
            {
                using (var dataStream = resp.GetResponseStream())
                {
                    using (var fileStream = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.Write))
                    {
                        SaveResponse(fileStream, dataStream);
                    }
                }
            }
        }

        /// <summary>
        /// Saves dataStream to fileStream
        /// </summary>
        /// <param name="fileStream">File stream to save data to</param>
        /// <param name="dataStream">Stream with GPX data</param>
        private static void SaveResponse(FileStream fileStream, Stream dataStream)
        {
            var inBuf = new byte[10000];
            var bytesToRead = inBuf.Length;
            var bytesRead = 0;
            while (bytesToRead > 0)
            {
                var n = dataStream.Read(inBuf, bytesRead, bytesToRead);
                if (n == 0)
                    break;
                bytesRead += n;
                bytesToRead -= n;
                fileStream.Write(inBuf, 0, n);
            }
        }
    }
}