Google App Script of reader2plus A script record user's Google reader starred items as activities.

gplus.gs

//
// 1. Depoly as web app (https://developers.google.com/apps-script/execution_web_apps#deploying)
// 2. register as web app through the APIs Console (https://code.google.com/apis/console#access)
// 3. add 'client_id', 'client_secret' to project properties.
// 4. If published to anyone else, make sure they access to the code. (https://developers.google.com/apps-script/execution_time_triggers)
//

var script_url = ScriptApp.getService().getUrl();
var client_id = ScriptProperties.getProperty('client_id');
var client_secret = ScriptProperties.getProperty('client_secret');
var scope = "https://www.googleapis.com/auth/plus.login http://www.google.com/reader/api";
var activity_types = ["http://schemas.google.com/AddActivity", "http://schemas.google.com/BuyActivity", "http://schemas.google.com/CheckInActivity",
                      "http://schemas.google.com/CommentActivity", "http://schemas.google.com/CreateActivity", "http://schemas.google.com/DiscoverActivity",
                      "http://schemas.google.com/ListenActivity", "http://schemas.google.com/ReserveActivity", "http://schemas.google.com/ReviewActivity" ];
var request_visible_actions = "http://schemas.google.com/DiscoverActivity http://schemas.google.com/AddActivity";
  
function doGet(request) {
  if (request && request.parameter && request.parameter.logout) {
    logout();
    return HtmlService.createHtmlOutput('done <a href="'+script_url+'">continue</a>');
  }
  
  if (request && request.parameter && request.parameter.state == 'gplus' && request.parameter.code) {
    var result = get_token(request.parameter.code);
    welcome_moment();
    do_update();
    reset_tigger();
    return result;
  }
  
  if (UserProperties.getProperty('gplus_access_token')) {
    return status();
  }
  
  return HtmlService.createTemplateFromFile('index').evaluate();
}

function get_auth_url() {
  return "https://accounts.google.com/o/oauth2/auth?"
         +"scope="+encodeURIComponent(scope)
         +"&state="+encodeURIComponent("gplus")
         +"&redirect_uri="+encodeURIComponent(script_url)
         +"&response_type=code&access_type=offline"
         +"&client_id="+encodeURIComponent(client_id)
         +'&request_visible_actions='+encodeURIComponent(request_visible_actions)
}

function get_token(code) {
  var payload = {
    "code" : code,
    "client_id" : client_id,
    "client_secret" : client_secret,
    "redirect_uri" : script_url,
    "grant_type" : "authorization_code"
  };
  var options = {
    "method" : "post",
    "payload" : payload
  };

  var response = UrlFetchApp.fetch('https://accounts.google.com/o/oauth2/token', options);
  var token = Utilities.jsonParse(response.getContentText());
  for (var key in token) {
    UserProperties.setProperty('gplus_'+key, token[key]);
  }
  UserProperties.setProperty('gplus_token_expire', ((new Date()).getTime()+token.expires_in*1000).toString());
  
  return HtmlService.createHtmlOutput('done <a href="'+script_url+'">continue</a>');
}

function gplus_request(url, data) {
  if (!UserProperties.getProperty('gplus_access_token')) {
    return false;
  }
  if (UserProperties.getProperty('gplus_token_expire') <= (new Date()).getTime() && !refresh_token()) {
    return false;
  }
  
  var options = {
    "method": data ? "POST" : "GET",
    "payload": data ? Utilities.jsonStringify(data) : "",
    "contentType": "application/json",
    "headers" : {
      "Authorization" : "Bearer " + UserProperties.getProperty('gplus_access_token')
    },
    "muteHttpExceptions": true,
  };
  
  var response = UrlFetchApp.fetch(url, options);
  response = Utilities.jsonParse(response.getContentText());
  return response;
}

function refresh_token() {
  if (!UserProperties.getProperty('gplus_refresh_token')) {
    logout();
    return false;
  }
  
  var payload = {
    "refresh_token" : UserProperties.getProperty('gplus_refresh_token'),
    "client_id" : client_id,
    "client_secret" : client_secret,
    "grant_type" : "refresh_token"
  };
  var options = {
    "method" : "post",
    "payload" : payload
  };

  try {
    var response = UrlFetchApp.fetch('https://accounts.google.com/o/oauth2/token', options);
    Logger.log(response.getContentText());
    var token = Utilities.jsonParse(response.getContentText());
    for (var key in token) {
      UserProperties.setProperty('gplus_'+key, token[key]);
    }
    UserProperties.setProperty('gplus_token_expire', ((new Date()).getTime()+token.expires_in*1000).toString());
    return true;
  } catch (e) {
    Logger.log(e.message);
    logout();
    return false;
  }
}

function verify_token() {
  var options = {
    "muteHttpExceptions": true,
  };
  
  var response = UrlFetchApp.fetch('https://www.googleapis.com/oauth2/v1/tokeninfo?access_token='+UserProperties.getProperty('gplus_access_token'), options);
  response = Utilities.jsonParse(response.getContentText());
  if (response.error) {
    return false;
  } else {
    UserProperties.setProperty('gplus_token_expire', ((new Date()).getTime()+response.expires_in*1000).toString());
    return true;
  }
}

function logout() {
  var triggers = ScriptApp.getScriptTriggers();
  for (var i = 0; i < triggers.length; i++) {
    ScriptApp.deleteTrigger(triggers[i]);
  }
  
  var options = {
    "muteHttpExceptions": true,
  };
  UrlFetchApp.fetch("https://accounts.google.com/o/oauth2/revoke?token="+UserProperties.getProperty('gplus_access_token'), options);
  
  UserProperties.deleteAllProperties();
}

index.html

<html>
<body>
  <a href="<?= get_auth_url() ?>"><img src="https://developers.google.com/+/images/branding/sign-in-buttons/Red-signin_Medium_base_44dp.png" /></a>
</body>
</html>

reader.gs

function reset_tigger() {
  var triggers = ScriptApp.getScriptTriggers();
  for (var i = 0; i < triggers.length; i++) {
    ScriptApp.deleteTrigger(triggers[i]);
  }
  
  ScriptApp.newTrigger("do_update")
  .timeBased()
  .everyMinutes(5)
  .create();
}

function welcome_moment() {
    var moment = {
      "type": "http://schemas.google.com/AddActivity",
      "target": {
        "id": "welcome-moment",
        "type":"http://schemas.google.com/AddActivity",
        "name": "reader2plus is now working",
        "description": "A script record user's Google reader starred items as activities.",
      },
    };
    var response = gplus_request("https://www.googleapis.com/plus/v1/people/me/moments/vault", moment);
}

function status() {
  return HtmlService.createTemplateFromFile('status').evaluate();
}

function do_update() {
  var reader;
  if (UserProperties.getProperty('last_update')) {
    reader = gplus_request("https://www.google.com/reader/api/0/stream/contents/user/-/state/com.google/starred?n=100&ot="+UserProperties.getProperty('last_update'));
  } else {
    reader = gplus_request("https://www.google.com/reader/api/0/stream/contents/user/-/state/com.google/starred?n=1");
  }
  UserProperties.setProperty("last_update", parseInt((new Date()).getTime() / 1000).toString());
  
  var sheet = get_sheet();
  var scriptdb = ScriptDb.getMyDb();
  reader.items.forEach(function(e) {
    if (e.alternate.length <= 0 || !e.alternate[0].href) return ;
    if (scriptdb.query({"id": e.id}).getSize() > 0) return;
    
    var moment = {
      "type": "http://schemas.google.com/DiscoverActivity",
      "target": {
        "url": e.alternate[0].href,
      },
    };
    var response = gplus_request("https://www.googleapis.com/plus/v1/people/me/moments/vault", moment);
    if (response.id) {
      scriptdb.save({'id': e.id});
    }
    sheet.appendRow([e.origin.title, e.id, e.alternate[0].href, e.title, response.id]);
  });
}

function get_sheet() {
  var sheet = SpreadsheetApp.getActiveSpreadsheet();
  if (sheet) {
    return sheet;
  } else if (UserProperties.getProperty('sheet')) {
    sheet = SpreadsheetApp.openById(UserProperties.getProperty('sheet'));
  } else {
    sheet = SpreadsheetApp.create('reader2plus');
    UserProperties.setProperty('sheet', sheet.getId());
  }
  
  return sheet;
}

status.html

<html>
  <body>
  <? 
  var reader_user = gplus_request('https://www.google.com/reader/api/0/user-info');
  var me = gplus_request("https://www.googleapis.com/plus/v1/people/me");
  ?>
  <?= reader_user.userEmail ?> => <a href="<?= me.url ?>" target=_blank>+<?= me.displayName ?></a> <a href="<?= script_url ?>?logout=1">logout</a>
  <hr />
  last updatetime: <?= UserProperties.getProperty('last_update') ?> (<?= (new Date()).getTime() / 1000 - UserProperties.getProperty('last_update') ?>s ago)
  <a href="#" onclick="google.script.run.do_update();return false;">update now</a>
  <br />
  <a href="<?= get_sheet().getUrl() ?>" target="_blank">log sheet</a><br />
  <a href="#" onclick="document.getElementById('debug_area').setAttribute('style', '')">show debug</a>
  
  <div id="debug_area" style="display: none;">
    <p>
      trigger:
      <a href="#" onclick="google.script.run.reset_tigger();return false;">reset tigger</a> <br />
      <? for (var t = ScriptApp.getScriptTriggers(), i = 0; i < t.length; ++i) { ?>
        <?= t[i].getHandlerFunction() ?> <?= t[i].getEventType() ?> <?= t[i].getUniqueId() ?><br />
      <? } ?>
    </p>
    <p>
      UserProperties:<br />
      <a href="#" onclick="google.script.run.refresh_token();return false;">refresh_token</a> <br />
      <? var p = UserProperties.getProperties(); for (var key in p) { ?>
      <?= key ?> = <?= p[key] ?> <br />
      <? } ?>
    </p>
  </div>
  </body>
</html>