1 files changed, 146 insertions, 0 deletions
diff --git a/actionpack/lib/action_view/asset_paths.rb b/actionpack/lib/action_view/asset_paths.rb
new file mode 100644
index 0000000000..96d8fd0dfe
--- /dev/null
+++ b/actionpack/lib/action_view/asset_paths.rb
@@ -0,0 +1,146 @@
+require 'zlib'
+require 'active_support/core_ext/file'
+
+module ActionView
+  class AssetPaths #:nodoc:
+    attr_reader :config, :controller
+
+    def initialize(config, controller = nil)
+      @config = config
+      @controller = controller
+    end
+
+    # Add the extension +ext+ if not present. Return full or scheme-relative URLs otherwise untouched.
+    # Prefix with <tt>/dir/</tt> if lacking a leading +/+. Account for relative URL
+    # roots. Rewrite the asset path for cache-busting asset ids. Include
+    # asset host, if configured, with the correct request protocol.
+    #
+    # When include_host is true and the asset host does not specify the protocol
+    # the protocol parameter specifies how the protocol will be added.
+    # When :relative (default), the protocol will be determined by the client using current protocol
+    # When :request, the protocol will be the request protocol
+    # Otherwise, the protocol is used (E.g. :http, :https, etc)
+    def compute_public_path(source, dir, ext = nil, include_host = true, protocol = nil)
+      source = source.to_s
+      return source if is_uri?(source)
+
+      source = rewrite_extension(source, dir, ext) if ext
+      source = rewrite_asset_path(source, dir)
+      source = rewrite_relative_url_root(source, relative_url_root) if has_request?
+      source = rewrite_host_and_protocol(source, protocol) if include_host
+      source
+    end
+
+    # Return the filesystem path for the source
+    def compute_source_path(source, dir, ext)
+      source = rewrite_extension(source, dir, ext) if ext
+      File.join(config.assets_dir, dir, source)
+    end
+
+    def is_uri?(path)
+      path =~ %r{^[-a-z]+://|^cid:|^//}
+    end
+
+  private
+
+    def rewrite_extension(source, dir, ext)
+      raise NotImplementedError
+    end
+
+    def rewrite_asset_path(source, path = nil)
+      raise NotImplementedError
+    end
+
+    def rewrite_relative_url_root(source, relative_url_root)
+      relative_url_root && !source.starts_with?("#{relative_url_root}/") ? "#{relative_url_root}#{source}" : source
+    end
+
+    def has_request?
+      controller.respond_to?(:request)
+    end
+
+    def rewrite_host_and_protocol(source, protocol = nil)
+      host = compute_asset_host(source)
+      if host && !is_uri?(host)
+        if (protocol || default_protocol) == :request && !has_request?
+          host = nil
+        else
+          host = "#{compute_protocol(protocol)}#{host}"
+        end
+      end
+      host.nil? ? source : "#{host}#{source}"
+    end
+
+    def compute_protocol(protocol)
+      protocol ||= default_protocol
+      case protocol
+      when :relative
+        "//"
+      when :request
+        unless @controller
+          invalid_asset_host!("The protocol requested was :request. Consider using :relative instead.")
+        end
+        @controller.request.protocol
+      else
+        "#{protocol}://"
+      end
+    end
+
+    def default_protocol
+      protocol = @config.action_controller.default_asset_host_protocol if @config.action_controller.present?
+      protocol ||= @config.default_asset_host_protocol
+      protocol || (has_request? ? :request : :relative)
+    end
+
+    def invalid_asset_host!(help_message)
+      raise ActionController::RoutingError, "This asset host cannot be computed without a request in scope. #{help_message}"
+    end
+
+    # Pick an asset host for this source. Returns +nil+ if no host is set,
+    # the host if no wildcard is set, the host interpolated with the
+    # numbers 0-3 if it contains <tt>%d</tt> (the number is the source hash mod 4),
+    # or the value returned from invoking call on an object responding to call
+    # (proc or otherwise).
+    def compute_asset_host(source)
+      if host = asset_host_config
+        if host.respond_to?(:call)
+          args = [source]
+          arity = arity_of(host)
+          if arity > 1 && !has_request?
+            invalid_asset_host!("Remove the second argument to your asset_host Proc if you do not need the request.")
+          end
+          args << current_request if (arity > 1 || arity < 0) && has_request?
+          host.call(*args)
+        else
+          (host =~ /%d/) ? host % (Zlib.crc32(source) % 4) : host
+        end
+      end
+    end
+
+    def relative_url_root
+      config = controller.config if controller.respond_to?(:config)
+      config ||= config.action_controller if config.action_controller.present?
+      config ||= config
+      config.relative_url_root
+    end
+
+    def asset_host_config
+      if config.action_controller.present?
+        config.action_controller.asset_host
+      else
+        config.asset_host
+      end
+    end
+
+    # Returns the current request if one exists.
+    def current_request
+      controller.request if has_request?
+    end
+
+    # Returns the arity of a callable
+    def arity_of(callable)
+      callable.respond_to?(:arity) ? callable.arity : callable.method(:call).arity
+    end
+
+  end
+end