require 'masterview'
require File.join( File.dirname(__FILE__), 'actionview_helper' )

class ScaffoldingSandbox
  include ActionView::Helpers::ActiveRecordHelper

  attr_accessor :singular_name, :controller_file_name, :controller_view_dir_name, :suffix, :model_instance

  def sandbox_binding
    binding
  end
  
  def default_input_block
    Proc.new { |record, column| 
      "  <div class=\"record\">\n    <div class=\"label\"><label for=\"#{record}_#{column.name}\">#{column.human_name}:</label></div>\n    <div class=\"field\">#{input(record, column.name)}</div>\n  </div>\n" }
  end
end

class ListHeadScaffoldingSandbox < ScaffoldingSandbox
  def default_input_block
    Proc.new { |record, column| "<th class=\"th_#{column.name}\">#{column.human_name}</th>" }
  end
end

class ListLineScaffoldingSandbox < ScaffoldingSandbox
  def default_input_block
    Proc.new { |record, column| "<td class=\"td_#{column.name}\" mv:content=\"h #{record}.send(:#{column.name})\">#{record} #{column.human_name}</td>" }
  end
end

class ShowScaffoldingSandbox < ScaffoldingSandbox
  def default_input_block
    Proc.new { |record, column| 
     "  <div class=\"record\">\n    <div class=\"label\"><label>#{column.human_name}:</label></div>\n    <div class=\"field\" mv:content=\"h @#{record}.send(:#{column.name})\">#{record} #{column.human_name}</div>\n  </div>\n" }
  end
end


class ActionView::Helpers::InstanceTag
  include ::MasterView::Generator::ActionViewHelper
  def to_input_field_tag(field_type, options={})
    field_meth = "#{field_type}_field"
    case field_meth
    when 'text_field'
      text_field options
    when 'hidden_field'
      hidden_field options
    when 'password_field'
      password_field options
    end
  end

  def to_text_area_tag(options = {})
    text_area options
  end

  def to_date_select_tag(options = {})
    date_select options
  end
  
  def to_datetime_select_tag(options = {})
    datetime_select options
  end
end

module Rails
  module Generator
    module Commands
      class Create < Base
        def string_to_file(content, relative_destination, file_options = {}, &block)
          template_mio = MasterView::IOMgr.template.path(relative_destination)

          # If source and destination are identical then we're done.
          if template_mio.identical?(content)
            return logger.identical(relative_destination) 
          end

          # Check for and resolve file collisions.
          if template_mio.exist?

            # Make a choice whether to overwrite the file.  :force and
            # :skip already have their mind made up, but give :ask a shot.
            choice = case (file_options[:collision] || options[:collision]).to_sym #|| :ask
              when :ask   then force_file_collision?(relative_destination)
              when :force then :force
              when :skip  then :skip
              else raise "Invalid collision option: #{options[:collision].inspect}"
            end

            # Take action based on our choice.  Bail out if we chose to
            # skip the file; otherwise, log our transgression and continue.
            case choice
              when :force then logger.force(relative_destination)
              when :skip  then return(logger.skip(relative_destination))
              else raise "Invalid collision choice: #{choice}.inspect"
            end

          # File doesn't exist so log its unbesmirched creation.
          else
            logger.create relative_destination
          end

          # If we're pretending, back off now.
          return if options[:pretend]

          template_mio.write(content, :disable_logging => true) # it is already being logged

          # Optionally change permissions.
          #if file_options[:chmod]
          #  FileUtils.chmod(file_options[:chmod], destination)
          #end
          
          # Optionally add file to subversion
          #system("svn add #{destination}") if options[:svn]
        end

        def multi_include_template(relative_source, relative_destination, template_options = {}, multi_assign_options = {})
          options = template_options.dup
          options[:assigns] ||= {}
          multi_assign_options.each do |k,v|
            options[:assigns][k] = render_template_part(v)
          end
          # Render the source file with the temporary binding.
          src_io = File.new( source_path(relative_source) )
          vars = options[:assigns] || {}
          b = binding
          vars.each { |k,v| eval "#{k} = vars[:#{k}] || vars['#{k}']", b }
          combined_contents = ERB.new(src_io.read, nil, '-').result(b)
          string_to_file(combined_contents, relative_destination, template_options)
        end

        def multi_file_multi_include_template(relative_source, relative_destination_map, template_options = {}, multi_assign_options = {})
          options = template_options.dup
          options[:assigns] ||= {}
          multi_assign_options.each do |k,v|
            options[:assigns][k] = render_template_part(v)
          end
          vars = options[:assigns] || {}
          b = binding
          vars.each { |k,v| eval "#{k} = vars[:#{k}] || vars['#{k}']", b }

          # Render the source file with the temporary binding.
          src_io = File.new( source_path(relative_source) )
          combined_contents = ERB.new(src_io.read, nil, '-').result(b)
          content_hash = {}
          MasterView::TemplateSpec.scan_template(combined_contents, 'MasterViewTemporaryCombinedSource', content_hash)
          relative_destination_map.each do |page_type, relative_destination|
            template_spec = MasterView::TemplateSpec.new(relative_destination)
            yield(page_type, template_spec) #allow the template_spec to be modified
            content = template_spec.rebuild_template(content_hash)
            string_to_file(content, relative_destination, template_options)
          end
        end
      end

      class Destroy < RewindBase
        def multi_include_template(relative_source, relative_destination, template_options = {}, multi_assign_options = {})
        end

        def multi_file_multi_include_template(relative_source, relative_destination_map, template_options = {}, multi_assign_options = {})
        end
      end

      class List < Base
        def multi_include_template(relative_source, relative_destination, template_options = {}, multi_assign_options = {})
          str = ""
          multi_assign_options.each do |k,v|
            str << v[:insert] << ' '
          end
          logger.template "#{str} inside #{relative_destination.inspect}"
        end

        def multi_file_multi_include_template(relative_source, relative_destination_map, template_options = {}, multi_assign_options = {})
          str = ""
          multi_assign_options.each do |k,v|
            str << v[:insert] << ' '
          end
          logger.template "#{str} inside #{relative_destination_map.inspect}"
        end
      end

      class Update < Create
        def multi_include_template(relative_source, relative_destination, template_options = {}, multi_assign_options = {})          
          return if relative_source.is_a?(StringIO) && relative_destination.is_a?(StringIO)
           begin
             dest_file = destination_path(relative_destination)
             source_to_update = MasterView::IOMgr.template.path(dest_file).read
           rescue Errno::ENOENT
             logger.missing relative_destination
             return
           end
           multi_assign_options.each do |k,v|
             template_options = v
             logger.refreshing "#{template_options[:insert].gsub(/\.rhtml/,'')} inside #{relative_destination}"
             begin_mark = Regexp.quote(template_part_mark(template_options[:begin_mark], template_options[:mark_id]))
             end_mark = Regexp.quote(template_part_mark(template_options[:end_mark], template_options[:mark_id]))
             # Refreshing inner part of the template with freshly rendered part.
             rendered_part = render_template_part(template_options)
             source_to_update.gsub!(/#{begin_mark}.*?#{end_mark}/m, rendered_part)
           end
           MasterView::IOMgr.template.path(dest_file).write(source_to_update, :disable_logging => true ) # already logging
        end

        def multi_file_multi_include_template(relative_source, relative_destination_map, template_options = {}, multi_assign_options = {})
        end
      end
    end
  end
end

class MasterviewGenerator < Rails::Generator::NamedBase
  attr_reader   :controller_name,
                :controller_class_path,
                :controller_file_path,
                :controller_class_nesting,
                :controller_class_nesting_depth,
                :controller_class_name,
                :controller_singular_name,
                :controller_plural_name
  alias_method  :controller_file_name,  :controller_singular_name
  alias_method  :controller_view_dir_name, :controller_singular_name
  alias_method  :controller_masterview_name, :controller_singular_name
  alias_method  :controller_table_name, :controller_plural_name

  def initialize(runtime_args, runtime_options = {})
    super
    @controller_name = args.shift || @name
    base_name, @controller_class_path, @controller_file_path, @controller_class_nesting, @controller_class_nesting_depth = extract_modules(@controller_name)
    @controller_class_name_without_nesting, @controller_singular_name, @controller_plural_name = inflect_names(base_name)
    if @controller_class_nesting.empty?
      @controller_class_name = @controller_class_name_without_nesting
    else
      @controller_class_name = "#{@controller_class_nesting}::#{@controller_class_name_without_nesting}"
    end
    default_options[:showSection] = :new
  end

  def design_time_stylesheets
    dts = ''
    if full_options[:single_file]
      com = <<-END
      <!--
           These stylesheets below are for design time use to allow working with only one visible section at a time, especially 
           when trying to use absolute positioning. You may comment/uncomment which ever section you wish to work with.
	   You may comment all of them out to work with all at design time. These stylesheets will not be used at runtime
      -->
      END

      dts << com

      dts << html_comment( '<link rel="stylesheet" type="text/css" href="../../masterview/extra/show_only_new.css" mv:preview="remove" mv:replace=""/>', 
                           full_options[:showSection] != :new )
      dts << html_comment( '<link rel="stylesheet" type="text/css" href="../../masterview/extra/show_only_edit.css" mv:preview="remove" mv:replace=""/>', true)
      dts << html_comment( '<link rel="stylesheet" type="text/css" href="../../masterview/extra/show_only_show.css" mv:preview="remove" mv:replace=""/>', true)
      dts << html_comment( '<link rel="stylesheet" type="text/css" href="../../masterview/extra/show_only_list.css" mv:preview="remove" mv:replace=""/>', 
                           full_options[:showSection] != :list )
      dts << html_comment( '<link rel="stylesheet" type="text/css" href="../../masterview/extra/show_only_destroy.css" mv:preview="remove" mv:replace=""/>', true)
    end
  end

  def html_comment(orig, comment_out)
    t = '      '
    t << '<!-- ' if comment_out
    t << orig
    t << ' -->' if comment_out
    t << "\n"
  end

  def design_time_javascript
    dtj = ''
    # todo make this relative to whereever IOMgr.template is
    if full_options[:single_file]      
      dtj << %Q[    <script type="text/javascript" mv:replace="" src="../../masterview/extra/mvpreview.js"></script>\n]
      dtj << %Q[    <script type="text/javascript" mv:replace="">\n]
      dtj << %Q[      mvpreview.preparePage( '#{controller_file_name}', {showOneSection: '#{controller_file_name}_list', single_file: true } );\n]
      dtj << %Q[    </script>\n]
    else
      dtj << %Q[    <script type="text/javascript" mv:replace="" src="../../masterview/extra/mvpreview.js"></script>\n]
      dtj << %Q[    <script type="text/javascript" mv:replace="">\n]
      dtj << %Q[      mvpreview.preparePage( '#{controller_file_name}', {} );\n]
      dtj << %Q[    </script>\n]
    end
  end

  def stylesheets
    ss = ''
    # todo make this relative to whereever IOMgr.template is
    if full_options[:stylesheets]
      full_options[:stylesheets].each do |stylesheet|
        ss << %Q(      <link rel="stylesheet" type="text/css" href="../../../public/stylesheets/#{stylesheet}.css" mv:stylesheet_link="#{stylesheet}"/>\n)
      end
    else # unless --style option was present we output the default stylesheets
      ss << %Q{      <link rel="stylesheet" type="text/css" href="../../../public/stylesheets/masterview/style.css" mv:stylesheet_link="masterview/style"/>\n}
      ss << %Q{      <link rel="stylesheet" type="text/css" href="../../../public/stylesheets/masterview/sidebox.css" mv:stylesheet_link="masterview/sidebox"/>\n}
      ss << %Q{      <link rel="stylesheet" type="text/css" href="../../../public/stylesheets/masterview/color-scheme.css" mv:stylesheet_link="masterview/color-scheme"/>\n}
    end
    ss
  end

  def messages
    if full_options[:single_file]
      unless full_options[:stylesheets]
        mess = <<-END
        messages here - Note: Other page sections in this MasterView file are hidden at design time, disable the stylesheet &apos;extra/show_only_new.css&apos; or uncomment different extra/*.css to work with other page sections (other stylesheets are show_only_edit.css, show_only_show.css, show_only_list.css, show_only_destroy.css and they are commented out in this masterview file&apos;s head section)
        END
      else
        mess = 'messages here'
      end
    else # multi-file
      mess = <<-END
        messages here - Note: Modify list.html template to edit layout, and message partials. Modify new.html if you want to edit the _form partial. Other templates import these partials to allow for design time editing in a full page context. View the MasterView Admin page, run the rake mv:list_all command, or view the source to learn which parts this particular template controls.
      END
    end
    mess
  end


  def manifest
    record do |m|
      # Depend on model generator but skip if the model exists.
      m.dependency 'model', [singular_name], :collision => :skip, :skip_migration => true

      # Check for class naming collisions.
      m.class_collisions controller_class_path, "#{controller_class_name}Controller", "#{controller_class_name}ControllerTest", "#{controller_class_name}Helper"

      # Controller, helper, views, and test directories.
      m.directory File.join('app/controllers', controller_class_path)
      m.directory File.join('app/helpers', controller_class_path)
      m.directory File.join('app/views', controller_class_path, controller_view_dir_name)
      m.directory 'public/stylesheets/masterview'
      m.directory 'app/masterview'
      m.directory 'app/masterview/extra'
      m.directory File.join('test/functional', controller_class_path)

      # Controller class, functional test, helper, and views.
      m.template 'controller.rb',
                  File.join('app/controllers',
                            controller_class_path,
                            "#{controller_file_name}_controller.rb")

      m.template 'functional_test.rb',
                  File.join('test/functional',
                            controller_class_path,
                            "#{controller_file_name}_controller_test.rb")

      m.template 'helper.rb',
                  File.join('app/helpers',
                            controller_class_path,
                            "#{controller_file_name}_helper.rb")

      # MasterView
      if full_options[:single_file]
        m.multi_include_template "masterview.rhtml","#{controller_masterview_name}/masterview.html", {}, 
         { 
          'form_inclusion' =>
            { :insert => 'form_scaffold.rhtml',
            :sandbox => lambda { create_multi_sandbox('ScaffoldingSandbox') },
            :begin_mark => 'form',
            :end_mark => 'eoform',
            :mark_id => singular_name
          },
          'list_head_inclusion' => 
            { :insert => 'list_head_scaffold.rhtml',
            :sandbox => lambda { create_multi_sandbox('ListHeadScaffoldingSandbox') },
            :begin_mark => 'listhead',
            :end_mark => 'eolisthead',
            :mark_id => singular_name
          },
          'list_line_inclusion' => 
            { :insert => 'list_line_scaffold.rhtml',
            :sandbox => lambda { create_multi_sandbox('ListLineScaffoldingSandbox') },
            :begin_mark => 'listline',
            :end_mark => 'eolistline',
            :mark_id => singular_name
          },
          'show_inclusion' =>
            { :insert => 'show_scaffold.rhtml',
            :sandbox => lambda { create_multi_sandbox('ShowScaffoldingSandbox') },
            :begin_mark => 'show',
            :end_mark => 'eoshow',
            :mark_id => singular_name
          }
         }
      else #multi file
        m.multi_file_multi_include_template "masterview.rhtml",
          { 
            :list => "#{controller_masterview_name}/list.html",
            :new => "#{controller_masterview_name}/new.html",
            :edit => "#{controller_masterview_name}/edit.html",
            :show => "#{controller_masterview_name}/show.html",
            :destroy => "#{controller_masterview_name}/destroy.html",
          },
          {}, 
          { 
          'form_inclusion' =>
            { :insert => 'form_scaffold.rhtml',
            :sandbox => lambda { create_multi_sandbox('ScaffoldingSandbox') },
            :begin_mark => 'form',
            :end_mark => 'eoform',
            :mark_id => singular_name
            },
          'list_head_inclusion' => 
            { :insert => 'list_head_scaffold.rhtml',
            :sandbox => lambda { create_multi_sandbox('ListHeadScaffoldingSandbox') },
            :begin_mark => 'listhead',
            :end_mark => 'eolisthead',
            :mark_id => singular_name
            },
          'list_line_inclusion' => 
            { :insert => 'list_line_scaffold.rhtml',
            :sandbox => lambda { create_multi_sandbox('ListLineScaffoldingSandbox') },
            :begin_mark => 'listline',
            :end_mark => 'eolistline',
            :mark_id => singular_name
            },
          'show_inclusion' =>
            { :insert => 'show_scaffold.rhtml',
            :sandbox => lambda { create_multi_sandbox('ShowScaffoldingSandbox') },
            :begin_mark => 'show',
            :end_mark => 'eoshow',
            :mark_id => singular_name
            }
        } do |page_type, template_spec|
          case page_type
            when :list
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("layouts/#{controller_file_name}.rhtml", 0, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/list.rhtml", 0, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/_messages.rhtml", -1, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/list.rhtml", 1, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/_#{singular_name}.rhtml", -1, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/list.rhtml", -1, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("layouts/#{controller_file_name}.rhtml", -1, false)
            when :new
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("layouts/#{controller_file_name}.rhtml", 0, true)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/new.rhtml", 0, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/_messages.rhtml", -1, true)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/new.rhtml", 1, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/_form.rhtml", -1, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/new.rhtml", -1, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("layouts/#{controller_file_name}.rhtml", -1, true)
            when :edit
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("layouts/#{controller_file_name}.rhtml", 0, true)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/edit.rhtml", 0, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/_messages.rhtml", -1, true)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/edit.rhtml", 1, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/_form.rhtml", -1, true)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/edit.rhtml", -1, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("layouts/#{controller_file_name}.rhtml", -1, true)
            when :show
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("layouts/#{controller_file_name}.rhtml", 0, true)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/show.rhtml", 0, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/_messages.rhtml", -1, true)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/show.rhtml", 1, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/_show.rhtml", -1, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/show.rhtml", -1, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("layouts/#{controller_file_name}.rhtml", -1, true)
            when :destroy
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("layouts/#{controller_file_name}.rhtml", 0, true)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/destroy.rhtml", 0, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/_messages.rhtml", -1, true)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/destroy.rhtml", 1, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/_show.rhtml", -1, true)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("#{controller_view_dir_name}/destroy.rhtml", -1, false)
              template_spec.build_list << MasterView::Analyzer::ListEntry.new("layouts/#{controller_file_name}.rhtml", -1, true)
          end
        end
      end


      m.file 'style.css', 'public/stylesheets/masterview/style.css'
      m.file 'sidebox.css', 'public/stylesheets/masterview/sidebox.css'
      m.file 'color-scheme.css', 'public/stylesheets/masterview/color-scheme.css'

      # design time files
      m.file 'mvpreview.js',      'app/masterview/extra/mvpreview.js'
      m.file 'show_only_new.css', 'app/masterview/extra/show_only_new.css'
      m.file 'show_only_edit.css', 'app/masterview/extra/show_only_edit.css'
      m.file 'show_only_show.css', 'app/masterview/extra/show_only_show.css'
      m.file 'show_only_list.css', 'app/masterview/extra/show_only_list.css'
      m.file 'show_only_destroy.css', 'app/masterview/extra/show_only_destroy.css'


    end
  end

  protected
    # Override with your own usage banner.
    def banner
      "Usage: #{$0} masterview ModelName [ControllerName] [--style [cssStylesheet]] [--single-file] [--show-all | --show-only list]"
    end

    def add_options!(opt)
      opt.on('-C', '--single-file', 'Generate masterview template as a single combined file'){ options[:single_file] = true }
      opt.on('-A', '--show-all', 'Generate with ALL sections visible at design time (no css hiding)',
                   '(valid only in conjunction with --single-file') { options[:showSection] = :all }
      opt.on("-O", "--show-only SECTION_NAME",
              "Generate with only sectionName section visible at design time (rest hidden with css)",
              "  (Valid options are: new, list) (Only valid if used with --single-file)",
              "  (example: --showOnly list  - would generate to show only 'list' section at design time)" ) do |section|
        options[:showSection] = section.to_sym
      end

      opt.on("-S", "--style [CSS_STYLESHEET]",
              "Add this stylesheet instead of defaults",
              "  (You may add this option multiple times for each stylesheet to add)",
              "  (If you omit the cssStylesheet then no default stylesheets will be added)" ) do |stylesheet|
        options[:stylesheets] ||= []
        options[:stylesheets] << File.basename(stylesheet, File.extname(stylesheet)) if stylesheet #get only the base part, so if /home/foo.css get foo
      end
    end

    def scaffold_views
      %w(list show new edit destroy)
    end

    def scaffold_actions
      scaffold_views + %w(index)
    end

    def unscaffolded_actions
      args - scaffold_actions
    end

    def suffix
      "_#{singular_name}" if options[:suffix]
    end
    
    def model_name 
      class_name.demodulize
    end

    def create_sandbox
      sandbox = ScaffoldingSandbox.new
      sandbox.singular_name = singular_name
      begin
        sandbox.model_instance = model_instance
        sandbox.instance_variable_set("@#{singular_name}", sandbox.model_instance)
      rescue ActiveRecord::StatementInvalid => e
        logger.error "Before updating scaffolding from new DB schema, try creating a table for your model (#{class_name})"
        raise SystemExit
      end
      sandbox.suffix = suffix
      sandbox
    end

    def create_multi_sandbox( sandbox_class_name )
      sandbox = eval("#{sandbox_class_name}.new")
      sandbox.singular_name = singular_name
      sandbox.controller_file_name = controller_file_name
      sandbox.controller_view_dir_name = controller_view_dir_name
      begin
        sandbox.model_instance = model_instance
        sandbox.instance_variable_set("@#{singular_name}", sandbox.model_instance)
      rescue ActiveRecord::StatementInvalid => e
        logger.error "Before updating scaffolding from new DB schema, try creating a table for your model (#{class_name})"
        raise SystemExit
      end
      sandbox.suffix = suffix
      sandbox
    end

    def model_instance
      base = class_nesting.split('::').inject(Object) do |base, nested|
        break base.const_get(nested) if base.const_defined?(nested)
        base.const_set(nested, Module.new)
      end
      unless base.const_defined?(@class_name_without_nesting)
        base.const_set(@class_name_without_nesting, Class.new(ActiveRecord::Base))
      end
      class_name.constantize.new
    end
end