Simple script to allowing to migrate hardcoded URLs in model fields to other hosts

replace_models_assets_url.rake

#!/usr/bin/env ruby
#
# This script allows for parsing every models of your app, looking for string
# and text fields, then replacing every previous hardcoded URL with a new
# URL reflecting your new assets location
#
# Example usage :
#
#   # Replace all URLs targeting an S3 bucket to a locale system URL
#   rake replace_models_assets_url MATCHER="http://s3.amazonaws.com/mybucket/" REPLACEMENT="/system/"
#
class ModelsAssetsURLReplacer
  def initialize
    eager_load_models!
  end

  def run
    ask_user_confirmation!

    models.each do |model|
      next unless model.table_name.present?

      ModelReplacer.new(model).replace!
    end
  end

  private

  def eager_load_models!
    # Eager load all models
    $LOAD_PATH.each do |path|
      next unless path.to_s.match(/\/models/)

      Dir[File.join(path, '**', '*.rb')].each do |file|
        load(file)
      end
    end
  end

  def models
    @models ||= ActiveRecord::Base.descendants
  end

  def ask_user_confirmation!
    answer = ask "Every string found in your models starting with \"#{ ENV['MATCHER'] }\" " +
                 "will be replaced with a starting \"#{ ENV['REPLACEMENT'] }\". " +
                 "Are you sure ? (y/n) "

    if answer.match(/^y/i)
      puts "\n" # Jump a line
    else
      puts "Aborted !"
      Process.exit
    end
  end

  def ask(question)
    print question
    STDIN.gets
  end
end

class ModelReplacer
  attr_reader :model, :changes_count

  def initialize(model)
    @model = model
    @changes_count = 0
  end

  def replace!
    print "Replace URLs for model : #{ model.name } ... "

    model.find_each do |resource|
      attributes = text_columns.each_with_object({}) do |column, hash|
        if (value = resource.send(column)) && String === value
          hash[column] = value.gsub(ENV['MATCHER'], ENV['REPLACEMENT'])
        end
      end

      resource.assign_attributes(attributes)
      @changes_count += 1 if resource.changed?

      resource.save(validate: false)
    end

    puts "Done ! #{ changes_count } rows changed."
  end

  private

  def text_columns
    @text_columns ||= model.columns.select { |c|
      c.type.in?([:string, :text])
    }.map(&:name)
  end
end

task replace_models_assets_url: :environment do |t, args|
  # Run the script
  ModelsAssetsURLReplacer.new.run
end