feat(view): add template resolver with layouts and partials

lib/prism/view.rb

@@ -0,0 +1,57 @@
+module Prism
+  class View
+    class TemplateNotFound < StandardError; end
+
+    def initialize(roots)
+      @roots = Array(roots)
+      @namespace_stack = []
+    end
+
+    def render(name, locals: {}, layout: nil)
+      content = render_template(name.to_s, locals)
+      return content unless layout
+      render_template("layouts/#{layout}", locals.merge('content' => content))
+    end
+
+    def render_partial(name, locals: {})
+      render_template(partial_name(qualify(name)), locals)
+    end
+
+    def render_collection(name, collection, locals: {}, as: nil)
+      local_name = (as || Inflector.underscore(name.to_s.split('/').last)).to_s
+      collection.each_with_index.map do |item, index|
+        render_partial(name, locals: locals.merge(local_name => item, "#{local_name}_counter" => index + 1))
+      end.join
+    end
+
+    def resolve(name)
+      @roots.each do |root|
+        path = File.join(root, "#{name}.erb")
+        return path if File.file?(path)
+      end
+      raise TemplateNotFound, "no template #{name.inspect} in #{@roots.join(', ')}"
+    end
+
+    private
+
+    def render_template(name, locals)
+      source = File.read(resolve(name))
+      @namespace_stack.push(File.dirname(name))
+      Template.render(source, locals, self)
+    ensure
+      @namespace_stack.pop
+    end
+
+    def qualify(name)
+      text = name.to_s
+      return text if text.include?('/')
+      namespace = @namespace_stack.last
+      namespace && namespace != '.' ? File.join(namespace, text) : text
+    end
+
+    def partial_name(path)
+      directory, base = File.split(path)
+      directory == '.' ? "_#{base}" : File.join(directory, "_#{base}")
+    end
+  end
+end