require "action_view"

module Sprockets
  module Helpers
    module RailsHelper
      extend ActiveSupport::Concern
      include ActionView::Helpers::AssetTagHelper

      def asset_paths
        @asset_paths ||= begin
          config     = self.config if respond_to?(:config)
          config   ||= Rails.application.config
          controller = self.controller if respond_to?(:controller)
          paths = RailsHelper::AssetPaths.new(config, controller)
          paths.asset_environment = asset_environment
          paths.asset_prefix      = asset_prefix
          paths
        end
      end

      def javascript_include_tag(*sources)
        options = sources.extract_options!
        debug = options.key?(:debug) ? options.delete(:debug) : debug_assets?
        body  = options.key?(:body)  ? options.delete(:body)  : false

        sources.collect do |source|
          if debug && asset = asset_paths.asset_for(source, 'js')
            asset.to_a.map { |dep|
              javascript_include_tag(dep, options.merge({ :debug => false, :body => true }))
            }
          else
            super(source.to_s, { :src => asset_path(source, 'js', body) }.merge!(options))
          end
        end.join("\n").html_safe
      end

      def stylesheet_link_tag(*sources)
        options = sources.extract_options!
        debug = options.key?(:debug) ? options.delete(:debug) : debug_assets?
        body  = options.key?(:body)  ? options.delete(:body)  : false

        sources.collect do |source|
          if debug && asset = asset_paths.asset_for(source, 'css')
            asset.to_a.map { |dep|
              stylesheet_link_tag(dep, options.merge({ :debug => false, :body => true }))
            }
          else
            super(source.to_s, { :href => asset_path(source, 'css', body, :request) }.merge!(options))
          end
        end.join("\n").html_safe
      end

      def asset_path(source, default_ext = nil, body = false, protocol = nil)
        source = source.logical_path if source.respond_to?(:logical_path)
        path = asset_paths.compute_public_path(source, 'assets', default_ext, true, protocol)
        body ? "#{path}?body=1" : path
      end

    private
      def debug_assets?
        config = Rails.application.config.assets
        config.allow_debugging && (config.debug || params[:debug_assets])
      end

      # Override to specify an alternative prefix for asset path generation.
      # When combined with a custom +asset_environment+, this can be used to
      # implement themes that can take advantage of the asset pipeline.
      #
      # If you only want to change where the assets are mounted, refer to
      # +config.assets.prefix+ instead.
      def asset_prefix
        Rails.application.config.assets.prefix
      end

      # Override to specify an alternative asset environment for asset
      # path generation. The environment should already have been mounted
      # at the prefix returned by +asset_prefix+.
      def asset_environment
        Rails.application.assets
      end

      class AssetPaths < ::ActionView::AssetPaths #:nodoc:
        attr_accessor :asset_environment, :asset_prefix

        def compute_public_path(source, dir, ext=nil, include_host=true, protocol=nil)
          super(source, asset_prefix, ext, include_host, protocol)
        end

        # Return the filesystem path for the source
        def compute_source_path(source, ext)
          asset_for(source, ext)
        end

        def asset_for(source, ext)
          source = source.to_s
          return nil if is_uri?(source)
          source = rewrite_extension(source, nil, ext)
          asset_environment[source]
        end

        def digest_for(logical_path)
          if asset = asset_environment[logical_path]
            return asset.digest_path
          end

          logical_path
        end

        def rewrite_asset_path(source, dir)
          if source[0] == ?/
            source
          else
            source = digest_for(source) if performing_caching?
            source = File.join(dir, source)
            source = "/#{source}" unless source =~ /^\//
            source
          end
        end

        def rewrite_extension(source, dir, ext)
          if ext && File.extname(source).empty?
            "#{source}.#{ext}"
          else
            source
          end
        end

        def performing_caching?
          # When included in Sprockets::Context, we need to ask the
          # top-level config as the controller is not available.
          if config.action_controller.present?
            config.action_controller.perform_caching
          else
            config.perform_caching
          end
        end
      end
    end
  end
end