Template for creating a new rails app with pre-configured active admin + necessary migration and associations. It relies on a yml file to find out the model related information. Checkout the demo yml file here https://gist.github.com/4127296

maverick

# rails new maverick -m https://raw.github.com/gist/4126950/ -d mysql
# rake rails:template LOCATION=https://raw.github.com/gist/4126950/

# <------ Pre-requisits ------>
# Setting current directory (for loading the yml config file)
@current_dir = Dir.pwd.gsub("/#{app_name}", "")

def ask_wizard(question)
  ask "\033[1m\033[30m\033[46m" + "prompt".rjust(10) + "\033[1m\033[36m" + "  #{question}\033[0m"
end

def yes_wizard?(question)
  answer = ask_wizard(question + " \033[33m(y/n)\033[0m")
  case answer.downcase
    when "yes", "y", ""
      true
    when "no", "n"
      false
    # else #allowing user to hit enter and pass the check
    #   yes_wizard?(question)
  end
end

def unfullfilled_pre_requisits
  run "rm -rf #{Dir.pwd}"
  raise "aborted because of unfullfilled Pre-requisits..."
end

# <------ Pre-requisits end ------>

# ----------------------------- Configure a new application ----------------------------------------------

def configure_new_app
  say "You need to provide a yml file having models and model-attributes and model-relationships, to use 'Maverick'.", :red
  say "Download a demo yml file from https://raw.github.com/gist/4127296/", :red
  say ""

  unless yes_wizard?("Have you provided the yml file in the current directory? eg. if your app name is 'test', provide a yml namely test.yml in #{@current_dir}")
    unfullfilled_pre_requisits
  end
  unless yes_wizard?("Do you have a proper installation of ruby(or rvm) and rails")
    unfullfilled_pre_requisits
  end

  models = YAML.load_file("#{@current_dir}/#{app_name}.yml")[:models] # just to make the process end if yml file is not provided

  gem "activeadmin" # adding activeadmin gem to gemfile
  run "bundle"
  mysql_username = ask_wizard("Please enter you mysql Username...")
  mysql_password = ask_wizard("Please enter you mysql Password...")
  gsub_file "config/database.yml", /username: root/, "username: #{mysql_username}"
  gsub_file "config/database.yml", /password:/, "password: #{mysql_password rescue ''}"
  affirm = yes_wizard? "Drop any existing databases named #{app_name}?"
    if affirm
      run 'bundle exec rake db:drop'
    else
      raise "aborted at user's request"
    end
  rake "db:create"
  run "rails generate active_admin:install"

  @migrations  = []

  models = YAML.load_file("#{@current_dir}/#{app_name}.yml")[:models]
  models.each do |model, attr|
    model_name = model.titleize.gsub(" ","") + " "
    attr[:fields].each do |column|
      model_name += column.split("-").join(":") + " "
    end
    run "rails g model #{model_name}"
    attr[:associations].each do |a|
      relation, entity = a.split("~")

      if relation == "has_one"  || relation == "has_many"
        # @model_changes[entity] = "  belongs_to :#{model}"
      elsif relation == "has_and_belongs_to_many"
        item1, item2 = [entity, model].sort!{|t1,t2|t1 <=> t2}
        table_name = "#{item1.pluralize}_#{item2.pluralize}"
        # To avoid genertion of duplicate migrations while creating HABTM relation
        unless @migrations.include?(table_name)
          @migrations << table_name
          filename = ((Time.now.utc).strftime("%Y%m%d%H%M%S").to_i - 55).to_s + "_create_" + table_name
          classname = "Create" + item1.pluralize.titleize + item2.pluralize.titleize
          create_file "db/migrate/#{filename}.rb" do
            <<-CODE
              class #{classname} < ActiveRecord::Migration
                def change
                  create_table '#{table_name}', :id => false do |t|
                    t.column :#{model.singularize}_id, :integer
                    t.column :#{entity.singularize}_id, :integer
                  end
                  add_index :#{table_name}, :#{model.singularize}_id
                  add_index :#{table_name}, :#{entity.singularize}_id
                end
              end
             CODE
          end

        end
        # @model_changes[entity] = " has_and_belongs_to_many :#{model.pluralize}"
      elsif relation == "has_many_through"
        # @model_changes[entity] = " has_many :somethings, :through => otherthing"
      elsif relation == "belongs_to"
        inject_into_file "app/models/#{model}.rb", "  attr_accessible :#{entity}_id\n", :after => "class #{model.titleize} < ActiveRecord::Base\n"
        run "rails g migration add_#{entity}_reference_to_#{model} #{entity}_id:integer" 
      end

      entity = entity.to_sym
      say "  #{relation} :#{entity}\n"
      inject_into_file "app/models/#{model}.rb", "  #{relation} :#{entity}\n", :after => "class #{model.titleize} < ActiveRecord::Base\n"
    end
  end

  rake "db:migrate"
  models.each do |model, fields|
   run "rails generate active_admin:resource #{model.titleize.gsub(" ","")}"
  end
  run "rm public/index.html" # removing the index file to enable root_url to work
  route "root :to => 'admin/dashboard#index'"
end


# ----------------------------- Update Existing application ----------------------------------------------

def create_table
end

def ask_wizard(question)
  ask "\033[1m\033[30m\033[46m" + "prompt".rjust(10) + "\033[1m\033[36m" + "  #{question}\033[0m"
end
@columns = []

def table_columns
  answer  = ask_wizard("Please enter a field with datatype: (eg. name:string)")
  unless answer == "x"
    arr = answer.split(":")
    arr.delete("")
    if arr.size == 1 || @columns.include?(answer)
      say "Invalid data!!", :red
    else
      @columns << answer 
    end
    table_columns
  end 
  return @columns
end

def add_model
  say ""
  model   = ask_wizard("Please enter model name:").singularize.titleize
  say "Enter 'x' anytime, to exit & generate the model...."
  @columns = []
  @columns = table_columns
  # create_table(model, @columns)
  run "rails g model #{model} #{@columns.join(' ')}"
  run "rails generate active_admin:resource #{model}"
  # raise @columns.inspect
end

def add_association
  say "Please specify the association in one of the following formats:"
  say "modelA has_one modelB"
  say "modelA belongs_to modelB"
  say "modelA has_many modelB"
  say "modelA has_and_belongs_to_many modelB"
  say "modelA has_many_through modelB, modelC"
  association = ask_wizard("Please enter the desired association:")
  raise association.inspect
end

def destroy_model
  model   = ask_wizard("Please enter model name:").singularize.titleize
  run "rails d active_admin:resource #{model}"
  run "rails d model #{model}"
end

def display_options
  say ""
  say "Here you can select from many of the options", :green
  say ""
  say "Available options:"
  say "1) Add model"
  say "2) Remove model"
  say "3) Add fields to table"
  say "4) Remove fields to table"
  say "5) Change field's datatype for a table"
  say "6) Add Association to a model"
  say "7) Remove Association from model"
  say "8) Exit and run rake db:migration"
end

def restart_wizard
  display_options
  changes_wizzard
end

def changes_wizzard
  selected = ask_wizard("Select an option: ")
  case selected
    when "1"
      add_model
      restart_wizard    
    when "2"
      destroy_model
      restart_wizard
    when "6"
      add_association
    when "8"
      run "rake db:migrate"
    else
      changes_wizzard()
  end
end

# ----------------------------------------------------------------------------------------------------------------

say "\nSelect an option:"
say "1) Create a new application."
say "2) Make changes to my existing application."
choice = ask("You Choice:")

if choice == "1"
  configure_new_app
elsif choice == "2"
  display_options
  changes_wizzard()
else
end