RackRewriteConfig

01_rack_rewrite_config.rb

class RackRewriteConfig
  class << self
    # Configure named rewrite rule
    def configure(name, &block)
      raise ArgumentError, "Block is required" unless block_given?
      rules[name] = block
    end

    # Apply named rule to the target
    def apply(target, name, *args)
      raise "Rule not found #{name}" unless rules.key?(name)
      target.instance_exec(*args, &rules[name])
    end

    private

    def rules
      @rules ||= {}
    end
  end
end

02_example.rb

Rails.application.configure do
  config.middleware.insert_before(Rack::Runtime, Rack::Rewrite) do
    LegacyRoutes.apply(self, :domain_redirect, host: 'bulls.com', target: 'https://www.bulls.com')
    LegacyRoutes.apply(self, :legacy_callbacks, host: 'cows.com', target: 'callbacks.bulls.com')
    LegacyRoutes.apply(self, :legacy_callbacks, host: 'www.cows.com', target: 'callbacks.bulls.com')
    LegacyRoutes.apply(self, :domain_redirect, host: 'cows.com', target: 'https://www.bulls.com')
    LegacyRoutes.apply(self, :domain_redirect, host: 'www.cows.com', target: 'https://www.bulls.com')
  end
end