feat(view): add erb template compiler with html escaping

lib/prism/template.rb

@@ -0,0 +1,54 @@
+module Prism
+  module Template
+    module_function
+
+    def render(source, locals = {}, view = nil)
+      code = compile(source)
+      scope = Context.new(view).__binding
+      locals.each { |name, value| scope.local_variable_set(name.to_sym, value) }
+      scope.eval(code, '(prism template)')
+    end
+
+    def compile(source)
+      buffer = +"__out = +''\n"
+      source.split(/(<%.*?%>)/m).each do |chunk|
+        if chunk.start_with?('<%==')
+          buffer << "__out << (#{chunk[4...-2]}).to_s\n"
+        elsif chunk.start_with?('<%=')
+          buffer << "__out << escape_html((#{chunk[3...-2]}).to_s)\n"
+        elsif chunk.start_with?('<%')
+          buffer << "#{chunk[2...-2]}\n"
+        else
+          buffer << "__out << #{chunk.inspect}\n"
+        end
+      end
+      buffer << "__out\n"
+      buffer
+    end
+
+    class Context
+      def initialize(view = nil)
+        @view = view
+      end
+
+      def escape_html(text)
+        CGI.escapeHTML(text)
+      end
+      alias_method :h, :escape_html
+
+      def partial(name, locals: {})
+        raise 'no view attached to this template' unless @view
+        @view.render_partial(name, locals: locals)
+      end
+
+      def render_collection(name, collection, locals: {}, as: nil)
+        raise 'no view attached to this template' unless @view
+        @view.render_collection(name, collection, locals: locals, as: as)
+      end
+
+      def __binding
+        binding
+      end
+    end
+  end
+end