upgrade_rails4.rb

# encoding: utf-8

# Copyright 2013-2014, Manfred Stienstra, <manfred@fngpts.com>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to
# deal in the Software without restriction, including without limitation the
# rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
# sell copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
# DEALINGS IN THE SOFTWARE.

# USAGE
#
# 1. Update your checkouts to the latest version and make sure they're in the
#    right branch.
# 2. Run this script from anywhere with Rails installed and at least ruby 2.0.
#    ruby rails4.rb /path/to/project
# 3. $ cd /path/to/project && bundle install
# 4. Run your test suite.
# 5. Commit the changes.
# 6. Deploy.
#
# NOTE: This script changes files and might destroy your code. Deal with it!

require 'find'
require 'yaml'
require 'fileutils'

class Upgrader
  module ClassWithAttributes
    def initialize(attributes={})
      attributes.each do |key, value|
        send("#{key}=", value)
      end
    end
  end

  include ClassWithAttributes

  class Configuration
    include ClassWithAttributes

    attr_accessor :path

    def log(message)
      puts "#{rails_root}: #{message}"
    end

    def app_slug
      File.basename(path)
    end

    def tmp_path
      File.join(path, 'tmp')
    end

    def tmp_app_path
      File.join(tmp_path, app_slug)
    end

    def database_config_path
      File.join(path, 'config/database.yml')
    end

    def raw_database
      config = YAML.load_file(database_config_path)
      config.each do |env, settings|
        if env == 'development'
          return settings['adapter']
        end
      end
    end

    def database
      case raw_database
      when 'mysql2'
        'mysql'
      else
        raw_database
      end
    end

    def rails_command
      "rails new #{tmp_app_path} --force --skip-gemfile --skip-bundle --skip-git --skip-keeps --skip-sprockets --database=#{database}"
    end

    def expand_tmp_path(relative_path)
      File.join(tmp_app_path, relative_path)
    end

    def expand_app_path(relative_path)
      File.join(path, relative_path)
    end

    def bootfile_paths
      %w(
      Rakefile
      config/application.rb
      config/boot.rb
      config/environment.rb
      config/environments
      config/initializers
      )
    end

    def gemfile_path
      File.join(path, 'Gemfile')
    end
  end

  attr_accessor :path

  def configuration
    @configuration ||= Configuration.new(path: path)
  end

  def generate_tmp_app
    system(configuration.rails_command)
  end

  def copy(paths)
    paths.each do |path|
      tmp_path = configuration.expand_tmp_path(path)
      if File.directory?(tmp_path)
        Find.find(tmp_path) do |filename|
          unless File.directory?(filename)
            relative_path = filename[tmp_path.length + 1..-1]
            destination_path = configuration.expand_app_path(File.join(path, relative_path))
            FileUtils.mkdir_p(File.dirname(destination_path))
            FileUtils.cp(filename, destination_path)
          end
        end
      else
        FileUtils.cp(tmp_path, configuration.expand_app_path(path))
      end
    end
  end

  def copy_bootfiles
    copy(configuration.bootfile_paths)
  end

  def generate_gemfile
    File.open(configuration.gemfile_path, 'w') do |file|
      file.puts("source 'https://rubygems.org'\n\ngem 'rails', '~> 4.0.0'")
    end
  end

  def remove_tmp_app
    FileUtils.rm_rf(configuration.tmp_app_path)
  end

  def upgrade
    generate_tmp_app
    copy_bootfiles
    generate_gemfile
    remove_tmp_app
  end

  def self.upgrade(path)
    new(path: File.expand_path(path)).upgrade
  end
end

if __FILE__ == $0
  Upgrader.upgrade(ARGV[0])
end