Downloading Documents with the Google Docs API

Lately I’ve been working on an app that uses the Google Docs GData API. I’ve found that Google Apps shares a lot of the properties that make SharePoint development particularly interesting:

Searching for error messages doesn’t help much because the platform and its bugs are quite new
The tools have pieces missing and don’t quite work as they should
Documentation is inadequate at best

One of the most obviously missing functions in the API is the ability to download a document. I found a workaround on google groups easily enough, creating the http request manually and setting the Authorization header, but unfortunately that doesn’t seem to work for hosted accounts.

With a few wrong turns trying to get a new auth token manually, it took me a full day of trial and error to find something that worked - setting a cookie and adding the hosted domain name to the start of the auth token.

To save anyone else from going through the same process, here’s the code:

        public static string DownloadDocumentFromAltUri(string altUri, string token)
        {
            var service = GetService(token);
            string docurl;
            string domain = null;

            var docId = altUri.ToDocumentId();


            if (altUri.Contains("docs.google.com/a/"))
            {
                // google apps

                var s1 = altUri.Substring(altUri.IndexOf("docs.google.com/a/") + 18);
                domain = s1.Substring(0, s1.IndexOf("/"));

                docurl = string.Format("http://docs.google.com/a/{0}/RawDocContents?revision=_latest&docID={1}&justBody=true&browserok=true", domain, docId);
            }
            else
            {
                // google docs
                docurl = string.Format("http://docs.google.com/RawDocContents?revision=_latest&docID={0}&justBody=true&browserok=true", docId);
            }

            Debug.WriteLine(string.Format("Downloading. DocId={0}, AltUri={1}, DocUri={2}", docId, altUri, docurl));

            HttpWebRequest wreq = (HttpWebRequest)HttpWebRequest.Create(docurl);
            if (UseAuthSub)
            {
                wreq.Headers.Add("Authorization", string.Format("AuthSub token={0}", token));
            }
            else
            {
                var authToken = ((GDataGAuthRequestFactory)service.RequestFactory).QueryAuthToken(service.Credentials);

                if (string.IsNullOrEmpty(domain))
                {
                    // unhosted accounts should accept this header
                    wreq.Headers.Add("Authorization", string.Format("GoogleLogin auth={0}", authToken));
                }
                else
                {
                    wreq.Headers.Add("Cookie",
                           string.Format("WRITELYH={0}={1}",
                                    domain,
                                    authToken
                                    )

                        );

                }

            }

            wreq.KeepAlive = true;
            var wresp = wreq.GetResponse();
            var stream1 = wresp.GetResponseStream();
            var cl = wresp.ContentLength;
            StreamReader sr = new StreamReader(stream1);
            var resp = sr.ReadToEnd();
            return resp;
        }