zen-http.js

/**
 * Zen for triadic handler. Plus proper http error handling and responder
 */

// environment
var env = process.env.NODE_ENV || 'development';

/**
* Log error using console.error.
*/
function logerror(err){
	if (env !== 'test') console.error("Error:",err.stack || err.toString());
}

/**
 * Default error handler
 */
var errorHandler = function error(req, resp, err) {
	if (err) {
		if (resp.writeHead) resp.writeHead(500, {
			"Content-Type": "text/plain"
		});
		if (resp.end) resp.end(err.stack + "\n");
		logerror(err);
		return;
	}
	if (resp.writeHead) resp.writeHead(404, {
		"Content-Type": "text/plain"
	});
	if (resp.end) resp.end("Not Found\n");
};
/**
 * Default result handler
 */
var resultHandler = function result(req, resp, result) {
	if (resp.writeHead) resp.writeHead(200, {
		"Content-Type": "octet/stream"
	});
	if (resp.end) resp.end(result);
};
/**
 * Zen uses a 'setup' pattern, returning a callable engine function
 */
module.exports= function (/*handlers*/) {
	/**
	 * Default handler delegates to the error handler
	 */
	var defaultHandler = function(a,b) {
		try {
			return engine.errorHandler(a,b,undefined); //explicit undef error passing
		} catch (ex) {
			return errorHandler(a,b,ex);
		}
	};
	var handlers=Array.prototype.slice.call(arguments);
	handlers.push(defaultHandler); //last handler

	var _engineRequests=[];
	var _enginePaused=false;
	var _engineStopped=false;
	var firstM=handlers[0];
	// The real Zen Engine
	var engine= function (a,b) {
		if (_enginePaused || _engineStopped) {		
			if (_enginePaused) {_engineRequests.push([a,b]);return;}
			return defaultHandler(a,b);
		}
	
		var i=1;
		try {
			function next(err,res) {
				if (res||err){
					if (res)
						return engine.resultHandler(a,b,res)
					return engine.errorHandler(a,b,err);	
				}
				return handlers[i++](a,b,next); //next handler
			}
			return firstM(a,b,next);
		} catch (err) {
			try {
				return engine.errorHandler(a,b, err);
			} catch (ex) {
				return errorHandler(a,b,ex);
			}
		}
	}
	if (handlers.length==1)
		engine=defaultHandler; //default
	engine.errorHandler = errorHandler;
	engine.resultHandler = resultHandler;
	
	/*EXTRA FEATURE*/
	engine.pause=function (){_enginePaused=true;};	
	engine.stop =function (){_engineStopped=true;};	
	engine.resume=function(){
		_enginePaused=_engineStopped=false;
		var requests= Array.prototype.slice.call(_engineRequests);
		_engineRequests=[];
		var request=requests.shift();
		while(typeof request !=='undefined'){
			engine(request[0],request[1]);
			request=requests.shift();
		}		
	};
	
	return engine;
};