/**
 * @OnlyCurrentDoc
 */

function getXmlData(url, user, pass) {
  var pass = (typeof pass !== 'undefined')? pass : "";

  try {
  var resp = UrlFetchApp.fetch(url,
                              (typeof user !== 'undefined')
                              // if 'user' is set, pass 'headers' with auth stuff
                              ?{'headers':
                                {'Authorization': "Basic " + Utilities.base64Encode(user+':'+pass)},
                                'muteHttpExceptions': true
                               }
                              // else, don't pass any parameters
                              :{}
                             );
  } catch (e) {
    return [["#ERROR!", "could not open connection"],
            e.toString(),
            "response is: " + ((typeof resp === 'undefined')?'undefined':resp.toString())];
  }

  var connectionError = [];
  var headers = resp.getAllHeaders();

  var code; // report anything but success codes (HTTP 2XX):
  if ((code = resp.getResponseCode()) < 200 || code >= 300) {
    connectionError = [["#ERROR!"], ["server responded with code: ", code], "headers: "].concat(__formatHeaders(headers));
  }

  if (code == 401) { // specific additional info for 401 Unauthorized
    var headersHasBasicAuth = 0;
    if (typeof headers['WWW-Authenticate'] === 'string') {
      headersHasBasicAuth = headers['WWW-Authenticate'].match(/^Basic/) !== undefined;
    } else {
      Object.keys(headers['WWW-Authenticate']).reduce(function(a, val){
        return val.match(/^Basic/) !== undefined;
      }, 0);
    }
    if (headersHasBasicAuth) {
      connectionError[0].push("Server does not advertise Basic auth!");
    }
  }

  if (connectionError.length > 0) {
    return connectionError;
  }

  //Otherwise, the request was successful. Begin actually parsing XML:

  var xml = resp.getContentText();

  var document = XmlService.parse(xml);
  var root = document.getRootElement();
  var atom = XmlService.getNamespace('http://www.w3.org/2005/Atom');
  var metadata = XmlService.getNamespace('http://schemas.microsoft.com/ado/2007/08/dataservices/metadata')

  var entries = root.getChildren('entry', atom);
  var ret = []; // 2d array which we'll fill width-first; every dimension is a row

  for (var i = 0; i < entries.length; i++) {
    var content = entries[i].getChild('content', atom);
    var contentProperties = content.getChild('properties', metadata).getChildren();

    row = []
    for (var j = 0; j < contentProperties.length; j++) {
      /* wasteful way to populate an 'index' row, thus naming the columns.
         it requires you to change 'ret = []' to 'ret = [[]]' higher up.
         it'd be better (though maybe less readable) to do this in an
         earlier loop, but it's just here for debugging anyway. */
      // ret[0][j] = contentProperties[j].getName(); // wasteful, but easy to read
      row.push(contentProperties[j].getText());
    }
    ret.push(row);
  }

  return ret;
}

function __formatHeaders(rawHeaders) {
  /** Accepts a headers Object (from HTTPResponse.getAllHeaders()) and returns the
      headers, formatted as a 2d array that fits nicely in a spreadsheet. **/
  var names = Object.keys(rawHeaders);
  var headers2d = [];

  for (var i = 0; i < names.length; i++) {
    var row = [];
    row.push(names[i]);
    var header = rawHeaders[names[i]];

    if(typeof header === 'string') {
      row.push(header);
    } else {
      // header is an Object, not an Array, so we can't Array.prototype.concat()
      for (var j = 0; j < header.length; j++) {
       row.push(header[j]);
      }
    }

    headers2d.push(row);
  }

  // Transpose the array because it's sideways

  // Every row has to be the same length, so we'll pad them with null:
  var maxlen = headers2d.reduce(function(a, row) { if (row.length > a) return row.length; return a; }, 0);
  for (var i = 0; i < headers2d.length; i++) {
    while (headers2d[i].length < maxlen) {
      headers2d[i].push(null);
    }
  }

  // The actual transposition:
  headers2d = headers2d[0].map(function(col, i) { return headers2d.map(function(row) { return row[i]; } ); } );

  return headers2d;
}