Plugin support

- Homebridge is now designed to be `npm install`d globally and
executed via "homebridge" script
  - Remove all specific accessories/platforms except for an example
  - New internal structure and "cli"

lib/plugin.js

@@ -0,0 +1,176 @@
+var path = require('path');
+var fs = require('fs');
+var semver = require('semver');
+var User = require('./user').User;
+var version = require('./version');
+
+'use strict';
+
+module.exports = {
+  Plugin: Plugin
+}
+
+/**
+ * Homebridge Plugin.
+ * 
+ * Allows for discovering and loading installed Homebridge plugins.
+ */
+
+function Plugin(pluginPath) {
+  this.pluginPath = pluginPath; // like "/usr/local/lib/node_modules/plugin-lockitron"
+  
+  // these are exports pulled from the loaded plugin module
+  this.accessory = null; // single exposed accessory
+  this.platform = null; // single exposed platform
+  this.accessories = []; // array of exposed accessories
+  this.platforms = []; // array of exposed platforms
+}
+
+Plugin.prototype.name = function() {
+  return path.basename(this.pluginPath);
+}
+
+Plugin.prototype.load = function(options) {
+  options = options || {};
+  
+  // does this plugin exist at all?
+  if (!fs.existsSync(this.pluginPath)) {
+    throw new Error("Plugin " + this.pluginPath + " was not found. Make sure the module '" + this.pluginPath + "' is installed.");
+  }
+  
+  // attempt to load package.json
+  var pjson = Plugin.loadPackageJSON(this.pluginPath);
+    
+  // pluck out the HomeBridge version requirement
+  if (!pjson.peerDepdendencies || !pjson.peerDepdendencies.homebridge) {
+    throw new Error("Plugin " + this.pluginPath + " does not contain the 'homebridge' package in 'peerDepdendencies'.");
+  }
+  
+  var versionRequired = pjson.peerDepdendencies.homebridge;
+
+  // make sure the version is satisfied by the currently running version of HomeBridge
+  if (!semver.satisfies(version, versionRequired)) {
+    throw new Error("Plugin " + this.pluginPath + " requires a HomeBridge version of " + versionRequired + " which does not satisfy the current HomeBridge version of " + version + ". You may need to upgrade your installation of HomeBridge.");
+  }
+  
+  // figure out the main module - index.js unless otherwise specified
+  var main = pjson.main || "./index.js";
+
+  var mainPath = path.join(this.pluginPath, main);
+  
+  // try to require() it
+  var pluginModule = require(mainPath);
+  
+  // extract all exposed accessories and platforms
+  this.accessories = pluginModule.accessories || {};
+  this.platforms = pluginModule.platforms || {};
+}
+
+Plugin.loadPackageJSON = function(pluginPath) {
+  // check for a package.json
+  var pjsonPath = path.join(pluginPath, "package.json");
+  var pjson = null;
+  
+  if (!fs.existsSync(pjsonPath)) {
+    throw new Error("Plugin " + pluginPath + " does not contain a package.json.");
+  }
+  
+  try {
+    // attempt to parse package.json
+    pjson = JSON.parse(fs.readFileSync(pjsonPath));
+  }
+  catch (err) {
+    throw new Error("Plugin " + pluginPath + " contains an invalid package.json. Error: " + err);
+  }
+  
+  // verify that it's tagged with the correct keyword
+  if (!pjson.keywords || pjson.keywords.indexOf("homebridge-plugin") == -1) {
+    throw new Error("Plugin " + pluginPath + " package.json does not contain the keyword 'homebridge-plugin'.");
+  }
+  
+  return pjson;
+}
+
+Plugin.getDefaultPaths = function() {
+  var win32 = process.platform === 'win32';
+  var paths = [];
+
+  // add the paths used by require()
+  paths = paths.concat(require.main.paths);
+
+  // THIS SECTION FROM: https://github.com/yeoman/environment/blob/master/lib/resolver.js
+
+  // Adding global npm directories
+  // We tried using npm to get the global modules path, but it haven't work out
+  // because of bugs in the parseable implementation of `ls` command and mostly
+  // performance issues. So, we go with our best bet for now.
+  if (process.env.NODE_PATH) {
+    paths = process.env.NODE_PATH.split(path.delimiter)
+      .filter(function(p) { return !!p; }) // trim out empty values
+      .concat(paths);
+  } else {
+    // Default paths for each system
+    if (win32) {
+      paths.push(path.join(process.env.APPDATA, 'npm/node_modules'));
+    } else {
+      paths.push('/usr/local/lib/node_modules');
+      paths.push('/usr/lib/node_modules');
+    }
+  }
+
+  return paths;
+}
+
+// All search paths we will use to discover installed plugins
+Plugin.paths = Plugin.getDefaultPaths();
+
+Plugin.addPluginPath = function(pluginPath) {
+  Plugin.paths.unshift(path.resolve(process.cwd(), pluginPath));
+}
+
+// Gets all plugins installed on the local system
+Plugin.installed = function() {
+
+  var plugins = [];
+  var pluginsByName = {}; // don't add duplicate plugins
+  
+  // search for plugins among all known paths, in order
+  for (var index in Plugin.paths) {
+    var requirePath = Plugin.paths[index];
+    
+    // just because this path is in require.main.paths doesn't mean it necessarily exists!
+    if (!fs.existsSync(requirePath))
+      continue;
+    
+    var names = fs.readdirSync(requirePath);
+    
+    // read through each directory in this node_modules folder
+    for (var index2 in names) {
+      var name = names[index2];
+    
+      // reconstruct full path
+      var pluginPath = path.join(requirePath, name);
+    
+      // we only care about directories
+      if (!fs.statSync(pluginPath).isDirectory()) continue;
+      
+      // does this module contain a package.json?
+      try {
+        // throws an Error if this isn't a homebridge plugin
+        Plugin.loadPackageJSON(pluginPath);
+      }
+      catch (err) {
+        // swallow error and skip this module
+        continue;
+      }
+      
+      // add it to the return list
+      if (!pluginsByName[name]) {
+        pluginsByName[name] = true;
+        plugins.push(new Plugin(pluginPath));
+      }
+    }
+  }
+  
+  return plugins;
+}