# Extensions namespace
module Middleman::Extensions
  
  # Asset Host module
  module AssetHost
    
    # Setup extension
    class << self
      
      # Once registered
      def registered(app)
        # Default to no host
        app.set :asset_host, false
      
        # Include methods
        app.send :include, InstanceMethods
      end
      
      alias :included :registered
    end
  
    # Asset Host Instance Methods
    module InstanceMethods
      
      # Override default asset url helper to include asset hosts
      #
      # @param [String] path
      # @param [String] prefix
      # @return [String]
      def asset_url(path, prefix="")
        original_output = super
        return original_output unless asset_host

        asset_prefix = if asset_host.is_a?(Proc)
          asset_host.call(original_output)
        elsif asset_host.is_a?(String)
          asset_host
        end
        
        File.join(asset_prefix, original_output)
      end
    end
  end
  
  # Register the extension
  register :asset_host, AssetHost
end