# encoding: utf-8
# frozen_string_literal: true

module Carbon
  module Compiler
    module Visitor
      # A visitor base.
      module Base
        # The class methods.
        module ClassMethods
          def matches
            @_matches ||= Concurrent::Hash.new
          end

          def on(nodes)
            matches.merge!(nodes)
          end
        end

        # The instance methods.
        module InstanceMethods
          def accept(node, *params)
            visit(node, *params)
          end

          def visit(node, *params)
            return unless node
            begin
              action = self.class.matches.fetch(node.class)
            rescue KeyError
              visit_missing(node, *params)
            end
            public_send(action, node, *params)
          end

          def visit_missing(node, *)
            fail ArgumentError, "Cannot visit #{node.class}"
          end

          def visit_ignore(node)
            node
          end
        end

        def self.included(base)
          base.include InstanceMethods
          base.extend ClassMethods
        end
      end
    end
  end
end