Introduce autosave feature

Fix #8.

lib/notational-velocity.coffee

@@ -1,4 +1,6 @@
-{CompositeDisposable} = require 'atom'
+path = require 'path'
+fs = require 'fs-plus'
+{CompositeDisposable, Disposable} = require 'atom'
 
 module.exports =
   config:
@@ -11,6 +13,8 @@ module.exports =
   notationalVelocityView: null
 
   activate: (state) ->
+    @rootDirectory = fs.realpathSync(atom.config.get('notational-velocity.directory'))
+
     # Events subscribed to in atom's system can be easily cleaned up with a
     # CompositeDisposable
     @subscriptions = new CompositeDisposable
@@ -19,6 +23,20 @@ module.exports =
     @subscriptions.add atom.commands.add 'atom-workspace',
       'notational-velocity:toggle': => @createView(state).toggle()
 
+    handleBeforeUnload = @autosaveAll.bind(this)
+    window.addEventListener('beforeunload', handleBeforeUnload, true)
+    @subscriptions.add new Disposable -> window.removeEventListener('beforeunload', handleBeforeUnload, true)
+
+    handleBlur = (event) =>
+      if event.target is window
+        @autosaveAll()
+      else if event.target.matches('atom-text-editor:not([mini])') and not event.target.contains(event.relatedTarget)
+        @autosave(event.target.getModel())
+    window.addEventListener('blur', handleBlur, true)
+    @subscriptions.add new Disposable -> window.removeEventListener('blur', handleBlur, true)
+
+    @subscriptions.add atom.workspace.onWillDestroyPaneItem ({item}) => @autosave(item)
+
   deactivate: ->
     @subscriptions.dispose()
     @notationalVelocityView.destroy()
@@ -31,3 +49,14 @@ module.exports =
       NotationalVelocityView = require './notational-velocity-view'
       @notationalVelocityView = new NotationalVelocityView(state.notationalVelocityViewState)
     @notationalVelocityView
+
+  autosave: (paneItem) ->
+    return unless paneItem?.getURI?()?
+    return unless paneItem?.isModified?()
+    uri = paneItem.getURI()
+    return unless uri.indexOf(@rootDirectory) == 0
+    return unless fs.isMarkdownExtension(path.extname(uri))
+    paneItem?.save?()
+
+  autosaveAll: ->
+    @autosave(paneItem) for paneItem in atom.workspace.getPaneItems()