# frozen_string_literal: true

# rubocop:disable Metrics/ModuleLength
module RuboCop
  module AST
    # Provides methods for traversing an AST.
    # Does not transform an AST; for that, use Parser::AST::Processor.
    # Override methods to perform custom processing. Remember to call `super`
    # if you want to recursively process descendant nodes.
    module Traversal
      def walk(node)
        return if node.nil?

        send(:"on_#{node.type}", node)
        nil
      end

      NO_CHILD_NODES    = %i[true false nil int float complex
                             rational str sym regopt self lvar
                             ivar cvar gvar nth_ref back_ref cbase
                             arg restarg blockarg shadowarg
                             kwrestarg zsuper lambda redo retry
                             forward_args forwarded_args
                             match_var match_nil_pattern].freeze
      ONE_CHILD_NODE    = %i[splat kwsplat block_pass not break next
                             preexe postexe match_current_line defined?
                             arg_expr pin match_rest if_guard unless_guard
                             match_with_trailing_comma].freeze
      MANY_CHILD_NODES  = %i[dstr dsym xstr regexp array hash pair
                             mlhs masgn or_asgn and_asgn
                             undef alias args super yield or and
                             while_post until_post iflipflop eflipflop
                             match_with_lvasgn begin kwbegin return
                             in_match case_match in_pattern match_alt
                             match_as array_pattern array_pattern_with_tail
                             hash_pattern const_pattern].freeze
      SECOND_CHILD_ONLY = %i[lvasgn ivasgn cvasgn gvasgn optarg kwarg
                             kwoptarg].freeze

      NO_CHILD_NODES.each do |type|
        module_eval("def on_#{type}(node); end", __FILE__, __LINE__)
      end

      ONE_CHILD_NODE.each do |type|
        module_eval(<<~RUBY, __FILE__, __LINE__ + 1)
          def on_#{type}(node)
            if (child = node.children[0])
              send(:"on_\#{child.type}", child)
            end
          end
        RUBY
      end

      MANY_CHILD_NODES.each do |type|
        module_eval(<<~RUBY, __FILE__, __LINE__ + 1)
          def on_#{type}(node)
            node.children.each { |child| send(:"on_\#{child.type}", child) }
            nil
          end
        RUBY
      end

      SECOND_CHILD_ONLY.each do |type|
        # Guard clause is for nodes nested within mlhs
        module_eval(<<~RUBY, __FILE__, __LINE__ + 1)
          def on_#{type}(node)
            if (child = node.children[1])
              send(:"on_\#{child.type}", child)
            end
          end
        RUBY
      end

      def on_const(node)
        return unless (child = node.children[0])

        send(:"on_#{child.type}", child)
      end

      def on_casgn(node)
        children = node.children
        if (child = children[0]) # always const???
          send(:"on_#{child.type}", child)
        end
        return unless (child = children[2])

        send(:"on_#{child.type}", child)
      end

      def on_class(node)
        children = node.children
        child = children[0] # always const???
        send(:"on_#{child.type}", child)
        if (child = children[1])
          send(:"on_#{child.type}", child)
        end
        return unless (child = children[2])

        send(:"on_#{child.type}", child)
      end

      def on_def(node)
        children = node.children
        on_args(children[1])
        return unless (child = children[2])

        send(:"on_#{child.type}", child)
      end

      def on_send(node)
        node.children.each_with_index do |child, i|
          next if i == 1

          send(:"on_#{child.type}", child) if child
        end
        nil
      end

      alias on_csend on_send

      def on_op_asgn(node)
        children = node.children
        child = children[0]
        send(:"on_#{child.type}", child)
        child = children[2]
        send(:"on_#{child.type}", child)
      end

      def on_defs(node)
        children = node.children
        child = children[0]
        send(:"on_#{child.type}", child)
        on_args(children[2])
        return unless (child = children[3])

        send(:"on_#{child.type}", child)
      end

      def on_if(node)
        children = node.children
        child = children[0]
        send(:"on_#{child.type}", child)
        if (child = children[1])
          send(:"on_#{child.type}", child)
        end
        return unless (child = children[2])

        send(:"on_#{child.type}", child)
      end

      def on_while(node)
        children = node.children
        child = children[0]
        send(:"on_#{child.type}", child)
        return unless (child = children[1])

        send(:"on_#{child.type}", child)
      end

      alias on_until  on_while
      alias on_module on_while
      alias on_sclass on_while

      def on_block(node)
        children = node.children
        child = children[0]
        send(:"on_#{child.type}", child) # can be send, zsuper...
        on_args(children[1])
        return unless (child = children[2])

        send(:"on_#{child.type}", child)
      end

      def on_case(node)
        node.children.each do |child|
          send(:"on_#{child.type}", child) if child
        end
        nil
      end

      alias on_rescue  on_case
      alias on_resbody on_case
      alias on_ensure  on_case
      alias on_for     on_case
      alias on_when    on_case
      alias on_irange  on_case
      alias on_erange  on_case
    end
  end
end
# rubocop:enable Metrics/ModuleLength