module Rails::Generators
  module MigrationHelper
    include Rails::Generators::Migration
    include Rails::Generators::BasicHelper

    module ClassMethods    
      def migration_lookup_at(dirname) #:nodoc:
        Dir.glob("#{dirname}/[0-9]*_*.rb")
      end

      def migration_exists?(dirname, file_name) #:nodoc:
        migration_lookup_at(dirname).grep(/\d+_#{file_name}.rb$/).first
      end 
      alias_method :first_migration_file, :migration_exists?              

      def latest_migration_file(dirname, file_name) #:nodoc:
        migration_lookup_at(dirname).grep(/\d+_#{file_name}.rb$/).sort.last
      end 

      def current_migration_number(dirname) #:nodoc:
        migration_lookup_at(dirname).collect do |file|
          File.basename(file).split("_").first.to_i
        end.max.to_i
      end

      def next_migration_number(dirname) #:nodoc:
        orm = Rails.configuration.generators.options[:rails][:orm]
        require "rails/generators/#{orm}"
        "#{orm.to_s.camelize}::Generators::Base".constantize.next_migration_number(dirname)
      rescue
        raise NotImplementedError
      end
    end         

    def self.included(base) #:nodoc: 
      base.extend ClassMethods      
    end

    def reverse_migration_name name
      name.gsub(/^add_/, 'remove_').gsub(/^create_/, 'drop_')
    end

    def reverse_migration! migration_path
      reverse_class_names! migration_path        
      reverse_up_down_methods! migration_path
    end

    def reverse_class_names! migration_path
      # Change class name
      gsub_file migration_path, /class Add/, 'class Remove'
      gsub_file migration_path, /class Create/, 'class Drop'
    end

    def reverse_up_down_methods! migration_path
      # swap up and down methods
      gsub_file migration_path, /up/, 'dwn'
      gsub_file migration_path, /down/, 'up'
      gsub_file migration_path, /dwn/, 'down'        
    end

    def latest_migration_file dir, name
      self.class.latest_migration_file dir, name
    end
    
    def migration(options)
      migration_template "create_users.erb", "db/migrations/#{name}"
    end
  end
end