Add migration script to remove 'project_hidden'

db/migrate/20160131233303_remove_project_hidden_state_from_todos.rb

@@ -0,0 +1,42 @@
+class RemoveProjectHiddenStateFromTodos < ActiveRecord::Migration
+  class Todo < ActiveRecord::Base
+    has_many :successor_dependencies, :foreign_key => 'successor_id', :class_name => 'Dependency'
+    belongs_to :project
+  end
+
+  class Project < ActiveRecord::Base
+  end
+
+  class Dependency < ActiveRecord::Base
+    belongs_to :predecessor, :foreign_key => 'predecessor_id', :class_name => 'Todo'
+  end
+
+  def self.up
+    Todo.where(state: 'project_hidden').find_each do |todo|
+      if todo.show_from.present?
+        todo.state = 'deferred'
+      elsif has_uncompleted_predecessor(todo)
+        todo.state = 'pending'
+      else
+        todo.state = 'active'
+      end
+      todo.save
+    end
+  end
+
+  def self.down
+    Project.where(state: 'hidden').find_each do |project|
+      Todo.where(project_id:  project.id).where.not(state: 'completed').find_each do |todo|
+        todo.state = 'project_hidden'
+        todo.save
+      end
+    end
+  end
+
+  def has_uncompleted_predecessor(todo)
+    todo.successor_dependencies.each do |dependency|
+      return true unless dependency.predecessor.state == 'completed'
+    end
+    false
+  end
+end