Javascript module implementation.

require.js

(function() {
	
	function Module(id) {
		this.id = id;
		this.exports = {};

		this.filename = null;
		this.loaded = false;
		this.exited = false;
	}

	//instance methods
	
	Module.prototype.load = function(filename, success, failure) {
		if(this.loaded){
			failure("module already loaded");
			return;
		}
		
		var $this = this;
		
		this.filename = filename;
		
		this.fetchSource(function(src){
			$this._compile(src);
		
			$this.loaded = true;
		
			success($this.exports);
		}, failure);
	};
	
	Module.prototype._fetchSource = function(success, failure) {
		
		var req = new XMLHttpRequest();
		
		req.open('GET', this.filename, true);
		req.onreadystatechange = function (aEvt) {
  			if (req.readyState == 4) {
     			if(req.status == 200){
      				success(req.responseText);
      			} else {
      				
      				
      				
      				var txt = "Failed GET request to '"+this.filename+"'";
      				if (req.statusText) txt += ": "+req.statusText;
      				if (req.status) txt += " ("+req.status+")";
      				failure(txt);      				
      			}
  			}
		};
		
      	req.overrideMimeType("text/plain");		
		req.send(null);
	};
	
	// Returns exception if any
	Module.prototype._compile = function(src) {
		// remove shebang
		src = src.replace(/^\#\!.*/, '');

		// create wrapper function
		var fn = new Function("exports", "require", "module", "__filename", src);

		var args = [this.exports, Module.require, this, this.filename];
		return f.apply(this.exports, args);
	};
	
	//class methods
	
	Module._cache = {};
	Module._pathCache = {};

	Module._resolveFilename = function(id) {
		if (/\/|\\|\.js$/.test(id)) 
			return id;
			
        if (Module._pathCache[id]) 
        	return Module._pathCache[id];

        var parts = id.split('.'), used = [], ns;
        while (parts.length) {
            if (Module._pathCache[ns = parts.join('.')]) 
            	return Module._pathCache[ns] + used.reverse().join('/') + '.js';
            used.push(parts.pop());
        }

        return used.reverse().join('/') + '.js';
	};
	
	Module.require = function(id, success, failure) {
		var resolved = Module._resolveFilename(id);
		var id = resolved[0];
		var filename = resolved[1];

		var cachedModule = Module._cache[filename];
		if (cachedModule) {
			success(cachedModule.exports);
			return;
		}

		var module = new Module(id);

		Module._cache[filename] = module;

		module.load(filename, success, function(error){
			delete Module._cache[filename];
			failure(error)
		});
	};	

	Module.require.resolve = function(id) {
		return Module._resolveFilename(id)[1];
	}
	
	Module.require.cache = Module._cache;
	
	this.require = Module.require;
})();