#300: Implemented basic drag and drop dependency support.

Dragging an action onto another action creates a dependency to that action.

app/controllers/todos_controller.rb

@@ -142,9 +142,13 @@ class TodosController < ApplicationController
   end
   
   def add_predecessor
-    logger.debug "add_predecessor"
     @predecessor = Todo.find(params['predecessor'])
-    @successor = Todo.find(params['successor'])
+    @todo = Todo.find(params['successor'])
+    @original_state = @todo.state
+    # Add predecessor
+    @todo.predecessors << @predecessor
+    @todo.state = 'pending'
+    @saved = @todo.save
     respond_to do |format|
       format.js
     end

app/helpers/todos_helper.rb

@@ -90,7 +90,7 @@ module TodosHelper
     if @todo.completed?
       "<span class=\"grey\">#{format_date( @todo.completed_at )}</span>"
     elsif @todo.pending?
-      "<a title='Depends on: #{@todo.predecessors.map(&:description).join(', ')}'><span class=\"orange\">Pending</span></a> "
+      "<a title='Depends on: #{@todo.uncompleted_predecessors.map(&:description).join(', ')}'><span class=\"orange\">Pending</span></a> "
     elsif @todo.deferred?
       show_date( @todo.show_from )
     else
@@ -109,7 +109,7 @@ module TodosHelper
   def grip_span
     unless @todo.completed?
       image_tag('grip.png', :width => '7', :height => '16', :border => '0', 
-        :title => 'Drag onto another action to make it depend on this action',
+        :title => 'Drag onto another action to make it depend on that action',
         :class => 'grip')
     end
   end

app/views/todos/_todo.html.erb

@@ -41,7 +41,7 @@ parameters += "&_tag_name=#{@tag_name}" if @source_view == 'tag'
   </div>
 </div>
 <%= 
-draggable_element(dom_id(todo), :revert => "'failure'", :handle =>  "'grip'", :onDrop => "''") 
+draggable_element(dom_id(todo), :revert => "'true'", :handle =>  "'grip'", :onDrop => "''") 
 %>
 <%=
 drop_receiving_element(dom_id(todo), 

app/views/todos/add_predecessor.js.rjs

@@ -0,0 +1,14 @@
+if @saved
+  # show update message
+  status_message = "Added #{@predecessor.description} as dependency."
+  unless @original_state == 'pending'
+    status_message += " #{@todo.description} set to pending"
+    page[@todo].remove
+    page['tickler-empty-nd'].hide
+    page.insert_html :bottom, item_container_id(@todo), :partial => 'todos/todo', :locals => { :todo => @todo, :parent_container_type => parent_container_type }
+  end
+  page.notify :notice, status_message, 5.0
+else
+  page.replace_html "status", content_tag("div", content_tag("h2", "Unable to add dependency"), "id" => "errorExplanation", "class" => "errorExplanation")  
+end
+