Bug #300: First shot at dependency entry in edit form

Limitations:
* No javascript update of dependency changes.
* No resolution for duplicate descriptions.

Conflicts:

	app/views/todos/_edit_form.rhtml

app/models/todo.rb

@@ -154,6 +154,39 @@ class Todo < ActiveRecord::Base
     return self.recurring_todo_id != nil
   end
   
+  def add_predecessor(predecessor)
+    logger.debug "add_predecessor #{predecessor.description}"
+  end
+  
+  # TODO: DELIMITER
+  # TODO: Todo::Error
+  # TODO: Handle todos with the same description
+  def add_predecessor_list(predecessor_list)
+    logger.debug "add_predecessor_list #{predecessor_list}"
+    raise "Can't handle other types than string for now" unless predecessor_list.kind_of? String
+    list = predecessor_list.split(',').map do |description| 
+      description.strip.squeeze(" ")            
+    end
+    current = self.predecessors.map(&:description)
+    remove_list = current - list
+    # This is probably a bit naive code...
+    remove_list.each do |description|
+      t = Todo.find_by_description(description)
+      logger.debug "Removing #{t.description} from #{self.description} as predecessor"
+      self.predecessors.delete(t)
+    end
+    add_list = list - current
+    # ... as is this?
+    add_list.each do |description|
+      t = Todo.find_by_description(description)
+      #raise Todo::Error, "predecessor could not be found: #{description}" if t.nil?
+      # Create dependency record
+      self.predecessors << t unless self.predecessors.include?(t)
+    end
+#    debugger
+    
+  end
+  
   # Rich Todo API
   
   def self.from_rich_message(user, default_context_id, description, notes)