Add support for relative base uri. (#42)

Author: ioquatix

lib/utopia/content/document.rb

@@ -38,6 +38,27 @@ def initialize(request, attributes = {})
 				super()
 			end
 
+			# @returns [Path] The original request path, if known.
+			def request_path
+				Path[request.env["REQUEST_PATH"]]
+			end
+			
+			protected def current_base_uri_path
+				self.current.node.uri_path
+			end
+			
+			# Compute the relative path from the curent base uri (e.g. the node being rendered) to the request uri. This path can be used to ensure resources are loaded relative to a given path.
+			#
+			# | Relative To   | Request Path           | Base URI     |
+			# |---------------|------------------------|--------------|
+			# | "/page"       | "/index"               | ""           |
+			# | "/blog/entry" | "/blog/2025/05/my-cat" | "../.."      |
+			#
+			# @returns [String] the base uri for the current page.
+			def base_uri(relative_to = self.current_base_uri_path)
+				Path[relative_to].dirname.shortest_path(request_path)
+			end
+			
 			def [] key
 				@attributes[key]
 			end

setup/site/pages/_page.xnode

@@ -9,7 +9,7 @@
 			<title>Utopia</title>
 		<?r end ?>
 
-		<base href="#{first.node.uri_path}"/>
+		<base href="#{document.base_uri}"/>
 		<meta name="viewport" content="width=device-width, initial-scale=1"/>
 
 		<link href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css" rel="stylesheet" integrity="sha384-wvfXpqpZZVQGK6TAh5PVlGOfQNHSoD2xbE+QkPxCAFlNEevoEH3Sl0sibVcOQVnN" crossorigin="anonymous" />

test/utopia/content/document.rb

@@ -4,9 +4,12 @@
 # Copyright, 2017-2025, by Samuel Williams.
 
 require "utopia/content/document"
+require "rack/request"
 
 describe Utopia::Content::Document do
-	let(:document) {subject.new(nil, {})}
+	let(:env) {Hash["REQUEST_PATH" => "/index"]}
+	let(:request) {Rack::Request.new(env)}
+	let(:document) {subject.new(request, {})}
 
 	it "should generate valid self-closing markup" do
 		node = proc do |document, state|
@@ -40,4 +43,18 @@
 
 		expect{document.render_node(node)}.to raise_exception(Utopia::Content::UnbalancedTagError, message: be =~ /tag span/)
 	end
+	
+	it "generates an empty base uri" do
+		relative_to = Utopia::Path["/page"]
+		expect(document.base_uri(relative_to)).to be == Utopia::Path[""]
+	end
+	
+	with "nested request path" do
+		let(:env) {Hash["REQUEST_PATH" => "/nested/index"]}
+		
+		it "generates a relative base uri" do
+			relative_to = Utopia::Path["/page"]
+			expect(document.base_uri(relative_to)).to be == Utopia::Path[".."]
+		end
+	end
 end