# Asset Host module
class Middleman::Extensions::AssetHost < ::Middleman::Extension
  option :host, nil, 'The asset host to use, or false for no asset host, or a Proc to determine asset host'

  def initialize(app, options_hash={}, &block)
    super

    # Backwards compatible API
    app.config.define_setting :asset_host, nil, 'The asset host to use, or false for no asset host, or a Proc to determine asset host'

    app.compass_config do |config|
      if asset_host = extensions[:asset_host].host
        if asset_host.is_a?(Proc)
          config.asset_host(&asset_host)
        else
          config.asset_host do |asset|
            asset_host
          end
        end
      end
    end if app.respond_to?(:compass_config)
  end

  def host
    app.config[:asset_host] || options[:host]
  end

  helpers do 
    # Override default asset url helper to include asset hosts
    #
    # @param [String] path
    # @param [String] prefix
    # @return [String]
    def asset_url(path, prefix="")
      controller = extensions[:asset_host]

      original_output = super
      return original_output unless controller.host

      asset_prefix = if controller.host.is_a?(Proc)
        controller.host.call(original_output)
      elsif controller.host.is_a?(String)
        controller.host
      end

      File.join(asset_prefix, original_output)
    end
  end
end