require "thread"

module Vagrant
  module Action
    module Builtin
      # This built-in middleware handles the `box_url` setting, downloading
      # the box if necessary. You should place this early in your middleware
      # sequence for a provider after configuration validation but before
      # you attempt to use any box.
      class HandleBoxUrl
        @@big_lock = Mutex.new
        @@handle_box_url_locks = Hash.new { |h,k| h[k] = Mutex.new }

        def initialize(app, env)
          @app = app
        end

        def call(env)
          if !env[:machine].box
            # Get a "big lock" to make sure that our more fine grained
            # lock access is thread safe.
            lock = nil
            @@big_lock.synchronize do
              lock = @@handle_box_url_locks[env[:machine].config.vm.box]
            end

            # We can assume a box URL is set because the Vagrantfile
            # validation should do this for us. If not, though, we do
            # raise a terrible runtime error.
            box_name = env[:machine].config.vm.box
            box_url  = env[:machine].config.vm.box_url

            lock.synchronize do
              # First see if we actually have the box now.
              has_box = false

              formats = env[:machine].provider_options[:box_format] ||
                env[:machine].provider_name
              [formats].flatten.each do |format|
                if env[:box_collection].find(box_name, format)
                  has_box = true
                  break
                end
              end

              if !has_box
                # Add the box then reload the box collection so that it becomes
                # aware of it.
                env[:ui].info I18n.t(
                  "vagrant.actions.vm.check_box.not_found",
                  :name => box_name,
                  :provider => env[:machine].provider_name)

                begin
                  env[:action_runner].run(Vagrant::Action.action_box_add, {
                    :box_name     => box_name,
                    :box_provider => env[:machine].provider_name,
                    :box_url      => box_url
                  })
                rescue Errors::BoxAlreadyExists
                  # Just ignore this, since it means the next part will succeed!
                  # This can happen in a multi-threaded environment.
                end
              end
            end

            # Reload the environment and set the VM to be the new loaded VM.
            env[:machine] = env[:machine].env.machine(
              env[:machine].name, env[:machine].provider_name, true)
          end

          @app.call(env)
        end
      end
    end
  end
end