require 'ripper'
require 'ripper_ruby_parser/syntax_error'

module RipperRubyParser
  # Variant of Ripper's SexpBuilderPP parser class that inserts comments as
  # Sexps into the built parse tree.
  class CommentingRipperParser < Ripper::SexpBuilderPP
    def initialize *args
      super
      @comment = nil
      @comment_stack = []
      @in_symbol = false
    end

    def parse
      result = suppress_warnings { super }
      raise 'Ripper parse failed.' unless result

      Sexp.from_array(result)
    end

    def on_comment tok
      @comment ||= ''
      @comment += tok
      super
    end

    def on_kw tok
      case tok
      when 'class', 'def', 'module'
        unless @in_symbol
          @comment_stack.push [tok.to_sym, @comment]
          @comment = nil
        end
      end
      super
    end

    def on_module *args
      commentize(:module, super)
    end

    def on_class *args
      commentize(:class, super)
    end

    def on_sclass *args
      commentize(:class, super)
    end

    def on_def *args
      commentize(:def, super)
    end

    def on_defs *args
      commentize(:def, super)
    end

    def on_qsymbols_add list, elem
      super list, [:dyna_symbol, [elem]]
    end

    def on_symbols_add list, elem
      super list, [:dyna_symbol, elem]
    end

    def on_words_add list, elem
      if elem.count == 1
        super
      else
        super list, [:string_content, *elem]
      end
    end

    def on_op(token)
      @seen_space = false
      super
    end

    def on_sp(_token)
      @seen_space = true
      super
    end

    def on_int(_token)
      @space_before = @seen_space
      super
    end

    def on_float(_token)
      @space_before = @seen_space
      super
    end

    NUMBER_LITERAL_TYPES = [:@int, :@float]

    def on_unary(op, value)
      if !@space_before && op == :-@ && NUMBER_LITERAL_TYPES.include?(value.first)
        type, literal, lines = value
        if literal[0] == '-'
          super
        else
          [type, "-#{literal}", lines]
        end
      else
        super
      end
    end

    def on_symbeg *args
      @in_symbol = true
      super
    end

    def on_symbol *args
      @in_symbol = false
      super
    end

    def on_embexpr_beg *args
      @in_symbol = false
      super
    end

    def on_dyna_symbol *args
      @in_symbol = false
      super
    end

    def on_parse_error *args
      raise SyntaxError, *args
    end

    def on_class_name_error *args
      raise SyntaxError, *args
    end

    def on_alias_error *args
      raise SyntaxError, *args
    end

    def on_assign_error *args
      raise SyntaxError, *args
    end

    def on_param_error *args
      raise SyntaxError, *args
    end

    private

    def commentize name, exp
      raise "Comment stack empty in #{name} event" if @comment_stack.empty?
      tok, comment = @comment_stack.pop
      @comment = nil
      unless tok == name
        raise "Expected on_#{tok} event, got on_#{name}"
      end
      [:comment, comment || '', exp]
    end

    def suppress_warnings
      old_verbose = $VERBOSE
      $VERBOSE = nil
      result = yield
      $VERBOSE = old_verbose
      result
    end
  end
end