module Prism
  # A compiler is a visitor that returns the value of each node as it visits.
  # This is as opposed to a visitor which will only walk the tree. This can be
  # useful when you are trying to compile a tree into a different format.
  #
  # For example, to build a representation of the tree as s-expressions, you
  # could write:
  #
  #     class SExpressions < Prism::Compiler
  #       def visit_arguments_node(node) = [:arguments, super]
  #       def visit_call_node(node) = [:call, super]
  #       def visit_integer_node(node) = [:integer]
  #       def visit_program_node(node) = [:program, super]
  #     end
  #
  #     Prism.parse("1 + 2").value.accept(SExpressions.new)
  #     # => [:program, [[[:call, [[:integer], [:arguments, [[:integer]]]]]]]]
  #
  class Compiler < Visitor
    # Visit an individual node.
    def visit(node)
      node&.accept(self)
    end

    # Visit a list of nodes.
    def visit_all(nodes)
      nodes.map { |node| node&.accept(self) }
    end

    # Visit the child nodes of the given node.
    def visit_child_nodes(node)
      node.compact_child_nodes.map { |node| node.accept(self) }
    end

    <%- nodes.each_with_index do |node, index| -%>
<%= "\n" if index != 0 -%>
    # Compile a <%= node.name %> node
    alias visit_<%= node.human %> visit_child_nodes
    <%- end -%>
  end
end
