Download Course RA's Class's Preview MP4 Videos

dlcourserapreviews.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Net;
using System.Windows.Forms;
using System.Diagnostics;
using System.Web;


namespace ConsoleTestingStuff
{
    public class DownloadPGMClass
    {
        String LecturePreviewUrl;
        String LectureUrlParse;
        Regex LectureUrlParseRegex;

        String LecturePreviewVideoUrl;
        String VideoUrlParse;
        Regex VideoUrlParseRegex;

        WebClient wc;

        public static void main(string[] args)
        {
            if (args.Length != 1) return;
            DownloadPGMClass x = new DownloadPGMClass();
            x.InitializeMyStuff(args[0]);
            x.StartDownload();
        }

        private void InitializeMyStuff(string ClassAbreviation)
        {
            LecturePreviewUrl = string.Format("https://class.coursera.org/{0}/lecture/preview", ClassAbreviation);

            LectureUrlParse = string.Format(@"https://class\.coursera\.org/{0}/lecture/preview_view\?lecture_id=(\d+)", ClassAbreviation); ;
            //"https://class\\.coursera\\.org/pgm/lecture/preview_view\\?lecture_id=(\\d+)";
            LectureUrlParseRegex = new Regex(LectureUrlParse, RegexOptions.Compiled | RegexOptions.IgnoreCase | RegexOptions.Multiline);

            LecturePreviewVideoUrl = string.Format("https://class.coursera.org/{0}/lecture/preview_view?lecture_id=", ClassAbreviation);

            VideoUrlParse = "<source type=\"video/mp4\" src=\"(.*?)\"";
            VideoUrlParseRegex = new Regex(VideoUrlParse, RegexOptions.Compiled | RegexOptions.IgnoreCase | RegexOptions.Multiline);

            wc = new WebClient();
        }

        private void StartDownload()
        {
            String DefaultPath;
            using (FolderBrowserDialog dlg = new FolderBrowserDialog())
            {
                dlg.Description = "Select a folder";
                if (dlg.ShowDialog() != DialogResult.OK) { MessageBox.Show("Download Canceled : No Folder Selected"); return; }
                DefaultPath = dlg.SelectedPath;
            }

            //Why not just use a Dictionary? Because
            List<KeyValuePair<string, string>> VideoList = new List<KeyValuePair<string, string>>();
            String LectureLinks = wc.DownloadString(LecturePreviewUrl);
            var myMatches = LectureUrlParseRegex.Matches(LectureLinks);
            Debug.Assert(myMatches.Count >= 1);
            foreach (Match m in myMatches)
            {
                String LectureID = m.Groups[1].Value;
                String LectureHtml = wc.DownloadString(LecturePreviewVideoUrl + LectureID);
                var LectureVideoMatch = VideoUrlParseRegex.Match(LectureHtml);
                Debug.Assert(LectureVideoMatch.Success);
                if (!LectureVideoMatch.Success)
                    continue;
                String LectureVideoUrl = HttpUtility.UrlDecode(LectureVideoMatch.Groups[1].Value);
                String FileName = LectureVideoUrl.Substring(LectureVideoUrl.LastIndexOf('/') + 1);
                VideoList.Add(new KeyValuePair<string, string>(LectureVideoUrl, DefaultPath + "\\" + FileName));
            }
            foreach (KeyValuePair<string, string> VideoPathPair in VideoList)
            {
                wc.DownloadFile(VideoPathPair.Key, VideoPathPair.Value);
            }
        }
    }
}