Revamp DI module

di.js

@@ -1,17 +1,154 @@
 /**
- * Dependency Injection
+ * Dependency injection
  * 
  * @author Mohammad Fares <faressoft.com@gmail.com>
  */
 
-/**
- * Set/Add a dependency
- * 
- * @param {String} key
- * @param {Object} value
- */
-module.exports.set = function(key, value) {
+var path = require('path'),
+    _ = require('lodash');
 
-  module.exports[key] = value;
+/**
+ * Dependency injection
+ */
+function DI() {
+
+  /**
+   * Injected dependecies
+   * @type {Object}
+   */
+  this._dependencies = {};
+
+  /**
+   * A wrapper proxy object to set traps
+   * @type {Proxy}
+   */
+  this._proxy = new Proxy(this, {
+    get: this.getHandler,
+    set: this.setHandler
+  });
+
+  return this._proxy;
+
+}
+
+/**
+ * Trap for getting a property value
+ * 
+ * @param  {Object} target
+ * @param  {String} key
+ * @return {*}
+ */
+DI.prototype.getHandler = function(target, key) {
+
+  if (key in target) {
+    return target[key];
+  }
+
+  if (key in target._dependencies) {
+    return target._dependencies[key];
+  }
 
 };
+
+/**
+ * Trap for setting a property value
+ * 
+ * @param  {Object} target
+ * @param  {String} key
+ * @param  {*}      value
+ * @return {*}
+ */
+DI.prototype.setHandler = function(target, key, value) {
+
+  if (key in target) {
+    throw new Error(`It is not allowed to set '${key}'`);
+  }
+
+  target._dependencies[key] = value;
+
+  return true;
+
+};
+
+/**
+ * Require and set a package
+ *
+ * - Require the module
+ * - Add the module as depndency
+ * - Format the key as
+ *   - Convert the moduleName to camelCase
+ *   - Remove the extension
+ * - Resolve third party packages as the native `require`.
+ * - Resolve our own scripts with paths relative to
+ *   the app's root path `require`.
+ * 
+ * @param {String} moduleName
+ * @param {String} key        (Optional) (Default: the moduleName camel cased)
+ */
+DI.prototype.require = function(moduleName, key) {
+
+  var parsedModuleName = path.parse(moduleName);
+
+  // Default value for key
+  if (typeof key == 'undefined') {
+    key = _.camelCase(parsedModuleName.name);
+  }
+
+  // Is not a third party package
+  if (parsedModuleName.dir != '') {
+
+    // Resolve the path to an absolute path
+    moduleName = path.resolve(this._getAppRootPath(), moduleName);
+
+  }
+
+  this._dependencies[key] = require(moduleName);
+
+};
+
+/**
+ * Inject a dependency
+ * 
+ * @param {String} key
+ * @param {*}      value
+ */
+DI.prototype.set = function(key, value) {
+
+  this[key] = value;
+  
+};
+
+/**
+ * Get an injected dependency
+ * 
+ * @param  {String} key
+ * @return {*}
+ */
+DI.prototype.get = function(key) {
+
+  return this[key];
+  
+};
+
+/**
+ * Get the root path of the app
+ *
+ * - Follow the module.parent.parent... etc until null
+ * 
+ * @return {String}
+ */
+DI.prototype._getAppRootPath = function() {
+
+  var parent = module.parent;
+
+  while (parent.parent) {
+
+    parent = parent.parent;
+    
+  }
+
+  return path.dirname(parent.filename);
+
+};
+
+module.exports = DI;