RSS.gs

//Code here is not meant to be modified. It wraps the actual logic

//Code that is run before first call
function start() {  
  //initialize is a USER-DEFINED argument-less function, which may be a stub
  initialize ();   
}

//this function is the entry point when the script URL is pinged
//the parameter of "e" is the JSON object generated from "?key1=value1&key2=..."
function doGet(e) {
  var parameters = e.parameter;
  
  /* So as not to hit web resources too often, content is stored in cache
   for specific parameter-determined feed. Content is only refreshed when cache expires */
  //note that too many params will cause this to fail
  var id = Utilities.base64Encode(Utilities.jsonStringify(parameters));
  var cache = CacheService.getPublicCache();
  var rss   = cache.get(id);
  
  //if item not in cache...
  if ( ! rss ) {
	//get manually. processParameters is USER-DEFINED
    rss = createRSSFeed(processParameters(parameters))
    //then store in cache for USER-DEFINED amount of time (in seconds)
	cache.put(id, rss, UpdateInterval);
  }
  
  //return the RSS feed to client, whether from cache or freshly generated
  return ContentService.createTextOutput(rss)
    .setMimeType(ContentService.MimeType.RSS);
}


//Last step. Wraps a JSON object generated by processParameters into an actual feed.
/*processParameters should have the following format:
{
	title:	...
	link:	...
	date:	...
	posts:
		[ {title: ..., author: ..., id: ..., link: ..., content: ..., }, ... ]
}
*/
function createRSSFeed(object) {

	//utility method. Wraps key/value pair to HTML node
	function wrapInTag(tag, item){
		if (item === "" || tag === "")
		{
			return ""
		}
		else
		{
			return "<" + tag + ">" + item + "</" + tag + ">"
		}
	}

	rss  = '<?xml version="1.0"?><rss version="2.0">';
    rss += ' <channel>';
	rss += wrapInTag("title", object.title);
    rss += wrapInTag("link", object.link);
    rss += wrapInTag("date", object.date);
	
	for (var i = 0; i < object.posts.length; i++) {
		
		post = object.posts[i];
		
		rss += "<item>";
		rss += wrapInTag("title", post.title);
		rss += wrapInTag ("author", post.author);
		rss += wrapInTag("pubDate", post.date);
		rss += wrapInTag("guid", post.id);
		rss += wrapInTag ("link", post.link);
		rss += wrapInTag("description", "<![CDATA[<img src= " + post.content + ">]]>");
		rss += "</item>";            
		
	  }
          
	rss += "</channel></rss>";
  
	return rss;

}

//Utility function for debugging. Allows one to force wipe cache before running
function debugWrap(e, doClearCache){
  if (doClearCache){
    var id = Utilities.base64Encode(Utilities.jsonStringify(e.parameter));
    var cache = CacheService.getPublicCache();
    cache.remove(id);
  }
  doGet(e)
}