slex.rb

# frozen_string_literal: false
#
#   irb/slex.rb - simple lex analyzer
#   	$Release Version: 0.9.6$
#   	$Revision$
#   	by Keiju ISHITSUKA(keiju@ruby-lang.org)
#
# --
#
#
#

require "e2mmap"
require "irb/notifier"

# :stopdoc:
module IRB
  class SLex

    extend Exception2MessageMapper
    def_exception :ErrNodeNothing, "node nothing"
    def_exception :ErrNodeAlreadyExists, "node already exists"

    DOUT = Notifier::def_notifier("SLex::")
    D_WARN = DOUT::def_notifier(1, "Warn: ")
    D_DEBUG = DOUT::def_notifier(2, "Debug: ")
    D_DETAIL = DOUT::def_notifier(4, "Detail: ")

    DOUT.level = Notifier::D_NOMSG

    def initialize
      @head = Node.new("")
    end

    def def_rule(token, preproc = nil, postproc = nil, &block)
      D_DETAIL.pp token

      postproc = block if block_given?
      create(token, preproc, postproc)
    end

    def def_rules(*tokens, &block)
      if block_given?
        p = block
      end
      for token in tokens
        def_rule(token, nil, p)
      end
    end

    def preproc(token, proc)
      node = search(token)
      node.preproc=proc
    end

    #$BMW%A%'%C%/(B?
    def postproc(token)
      node = search(token, proc)
      node.postproc=proc
    end

    def search(token)
      @head.search(token.split(//))
    end

    def create(token, preproc = nil, postproc = nil)
      @head.create_subnode(token.split(//), preproc, postproc)
    end

    def match(token)
      case token
      when Array
      when String
        return match(token.split(//))
      else
        return @head.match_io(token)
      end
      ret = @head.match(token)
      D_DETAIL.exec_if{D_DETAIL.printf "match end: %s:%s\n", ret, token.inspect}
      ret
    end

    def inspect
      format("<SLex: @head = %s>", @head.inspect)
    end

    #----------------------------------------------------------------------
    #
    #   class Node -
    #
    #----------------------------------------------------------------------
    class Node
      # if postproc is nil, this node is an abstract node.
      # if postproc is non-nil, this node is a real node.
      def initialize(preproc = nil, postproc = nil)
        @Tree = {}
        @preproc = preproc
        @postproc = postproc
      end

      attr_accessor :preproc
      attr_accessor :postproc

      def search(chrs, opt = nil)
        return self if chrs.empty?
        ch = chrs.shift
        if node = @Tree[ch]
          node.search(chrs, opt)
        else
          if opt
            chrs.unshift ch
            self.create_subnode(chrs)
          else
            SLex.fail ErrNodeNothing
          end
        end
      end

      def create_subnode(chrs, preproc = nil, postproc = nil)
        if chrs.empty?
          if @postproc
            D_DETAIL.pp node
            SLex.fail ErrNodeAlreadyExists
          else
            D_DEBUG.puts "change abstract node to real node."
            @preproc = preproc
            @postproc = postproc
          end
          return self
        end

        ch = chrs.shift
        if node = @Tree[ch]
          if chrs.empty?
            if node.postproc
              DebugLogger.pp node
              DebugLogger.pp self
              DebugLogger.pp ch
              DebugLogger.pp chrs
              SLex.fail ErrNodeAlreadyExists
            else
              D_WARN.puts "change abstract node to real node"
              node.preproc = preproc
              node.postproc = postproc
            end
          else
            node.create_subnode(chrs, preproc, postproc)
          end
        else
          if chrs.empty?
            node = Node.new(preproc, postproc)
          else
            node = Node.new
            node.create_subnode(chrs, preproc, postproc)
          end
          @Tree[ch] = node
        end
        node
      end

      #
      # chrs: String
      #       character array
      #       io must have getc()/ungetc(); and ungetc() must be
      #       able to be called arbitrary number of times.
      #
      def match(chrs, op = "")
        D_DETAIL.print "match>: ", chrs, "op:", op, "\n"
        if chrs.empty?
          if @preproc.nil? || @preproc.call(op, chrs)
            DOUT.printf(D_DETAIL, "op1: %s\n", op)
            @postproc.call(op, chrs)
          else
            nil
          end
        else
          ch = chrs.shift
          if node = @Tree[ch]
            if ret = node.match(chrs, op+ch)
              return ret
            else
              chrs.unshift ch
              if @postproc and @preproc.nil? || @preproc.call(op, chrs)
                DOUT.printf(D_DETAIL, "op2: %s\n", op.inspect)
                ret = @postproc.call(op, chrs)
                return ret
              else
                return nil
              end
            end
          else
            chrs.unshift ch
            if @postproc and @preproc.nil? || @preproc.call(op, chrs)
              DOUT.printf(D_DETAIL, "op3: %s\n", op)
              @postproc.call(op, chrs)
              return ""
            else
              return nil
            end
          end
        end
      end

      def match_io(io, op = "")
        if op == ""
          ch = io.getc
          if ch == nil
            return nil
          end
        else
          ch = io.getc_of_rests
        end
        if ch.nil?
          if @preproc.nil? || @preproc.call(op, io)
            D_DETAIL.printf("op1: %s\n", op)
            @postproc.call(op, io)
          else
            nil
          end
        else
          if node = @Tree[ch]
            if ret = node.match_io(io, op+ch)
              ret
            else
              io.ungetc ch
              if @postproc and @preproc.nil? || @preproc.call(op, io)
                DOUT.exec_if{D_DETAIL.printf "op2: %s\n", op.inspect}
                @postproc.call(op, io)
              else
                nil
              end
            end
          else
            io.ungetc ch
            if @postproc and @preproc.nil? || @preproc.call(op, io)
              D_DETAIL.printf("op3: %s\n", op)
              @postproc.call(op, io)
            else
              nil
            end
          end
        end
      end
    end
  end
end
# :startdoc:

if $0 == __FILE__
  case $1
  when "1"
    tr = SLex.new
    print "0: ", tr.inspect, "\n"
    tr.def_rule("=") {print "=\n"}
    print "1: ", tr.inspect, "\n"
    tr.def_rule("==") {print "==\n"}
    print "2: ", tr.inspect, "\n"

    print "case 1:\n"
    print tr.match("="), "\n"
    print "case 2:\n"
    print tr.match("=="), "\n"
    print "case 3:\n"
    print tr.match("=>"), "\n"

  when "2"
    tr = SLex.new
    print "0: ", tr.inspect, "\n"
    tr.def_rule("=") {print "=\n"}
    print "1: ", tr.inspect, "\n"
    tr.def_rule("==", proc{false}) {print "==\n"}
    print "2: ", tr.inspect, "\n"

    print "case 1:\n"
    print tr.match("="), "\n"
    print "case 2:\n"
    print tr.match("=="), "\n"
    print "case 3:\n"
    print tr.match("=>"), "\n"
  end
  exit
end