Add Plugin architecture

README.md

@@ -76,6 +76,11 @@ CrispyFi provides a command line-like interface to its internal playlist handlin
 * `list rename <old name> <new name>` - Renames the specified list.
 * `list <name>` - Selects the specified list and starts playback.
 
+## Plugins
+If CrispyFi doesn't do what you need, you can extend it. The plugin architecture is pretty minimal at this point, but at least there's a standardized interface. If none of the default trigger words matched, each plugin's `handle` method will be called until one is found that returns `true`. If a plugin returns `true`, the plugin chain is halted and the plugin's `status` attribute is checked for content. If it's not empty, its content will be replied to the Slack channel CrispyFi listens to. If it's empty, nothing further will happen (the plugin chain will *not* be traversed further, though).
+
+Plugins live in `/plugins` and need a `name` attribute. A minimal example implementation is provided in `examples/my_first_plugin.coffee`.
+
 ## Getting your groove on(line)
 Since your Pi will probably be behind a firewall/some sort of NAT or have a dynamic IP, you'll have difficulties tying Slack's webhooks to its IP address. We're currently using [ngrok](http://ngrok.com) to get around that, mainly because it's awesome and makes developing web services much easier. Also, using ngrok you avoid the hassle of updating some other service's configuration whenever your IP changes, instead you have to run a small binary all the time. YMMV, so use whatever you're comfortable with (but give ngrok a try).
 

examples/my_first_plugin.coffee

@@ -0,0 +1,15 @@
+class MyFirstPlugin
+  constructor: () ->
+    @name = 'My First Plugin'
+    @response = null
+
+  handle: (auth, spotify, volume) ->
+    if auth.command == 'plugin'
+      # This will be replied to the channel. If nothing is set, no reply will be sent.
+      @response = "This is a reply from #{@name}."
+      return true
+    else
+      return false
+
+module.exports = () ->
+  return new MyFirstPlugin()

lib/plugin_handler.coffee

@@ -0,0 +1,29 @@
+class PluginHandler
+  constructor: () ->
+    # Plugin cache
+    @plugins = []
+
+  # Adds all plugins to the cache
+  load_plugins: () ->
+    # Reset the plugin cache
+    @plugins = []
+    console.log "Loading Plugins..."
+    root_dir = require('path').dirname require.main.filename
+    require("fs").readdirSync("#{root_dir}/plugins").forEach (file) =>
+      plugin = require("#{root_dir}/plugins/" + file)()
+      @plugins.push plugin
+      console.log " -- #{plugin.name}"
+    console.log "...done."
+    return
+
+  handle: (auth, spotify, volume) ->
+    state = false
+    for plugin in @plugins
+      if plugin.handle(auth, spotify, volume)
+        return plugin.response
+
+module.exports = () ->
+  if !@handler?
+    @handler = new PluginHandler()
+    @handler.load_plugins()
+  return @handler

lib/slack_interface/request_handler.coffee

@@ -3,6 +3,7 @@ class SlackInterfaceRequestHandler
     @auth = auth
     @spotify = spotify
     @volume = volume
+    @plugin_handler = require("../../lib/plugin_handler")()
 
     @endpoints =
       handle:
@@ -58,6 +59,11 @@ class SlackInterfaceRequestHandler
               when 'help'
                 reply_data['text'] = "You seem lost. Maybe trying one of these commands will help you out:\n*play* [Spotify-URI] - Starts or resumes playback. If you provide a Spotify-URI it will be played immediately.\n*stop* - Stops playback.\n*pause* - Pauses playback (can be resumed using *play*).\n*skip*: Skips to the next track.\n*list* [listname] - Switches to the specified Spotify-Playlist. If no list name is provided, all available lists will be shown. Playlists need to be configured beforehand, please check the project's readme for details.\n*vol* [up|down|0-10] - Sets the output volume. Either goes up or down one notch or directly to a level ranging from 0 to 10 (inclusive). 0 is mute."
 
+              else
+                # Fallback to external plugins.
+                status = @plugin_handler.handle(@auth, @spotify, @volume)
+                if status?
+                  reply_data['text'] = status
 
             response.serveJSON reply_data
             return