Initial Meow MUD client

2026-09-17 01:08:16 +02:00
commit 5e6d9138c4
9 changed files with 1123 additions and 0 deletions
@@ -0,0 +1,148 @@
+module MeowClient
+  module Telnet
+    IAC = 255
+    DONT = 254
+    DO = 253
+    WONT = 252
+    WILL = 251
+    SB = 250
+    SE = 240
+
+    ECHO = 1
+    SUPPRESS_GO_AHEAD = 3
+    TERMINAL_TYPE = 24
+    TTYPE_IS = 0
+    TTYPE_SEND = 1
+
+    Result = Struct.new(:data, :replies, :events, keyword_init: true)
+
+    class Parser
+      attr_reader :remote_echo
+
+      def initialize
+        @state = :data
+        @negotiation_command = nil
+        @subnegotiation_option = nil
+        @subnegotiation = +"".b
+        @remote_echo = false
+        @remote_options = {}
+        @local_options = {}
+      end
+
+      def feed(bytes)
+        output = +"".b
+        replies = []
+        events = []
+        bytes.to_s.b.each_byte do |byte|
+          case @state
+          when :data
+            if byte == IAC
+              @state = :iac
+            else
+              output << byte
+            end
+          when :iac
+            handle_iac(byte, output)
+          when :negotiation
+            reply, event = negotiate(@negotiation_command, byte)
+            replies << reply if reply != nil
+            events << event if event != nil
+            @state = :data
+          when :sb_option
+            @subnegotiation_option = byte
+            @subnegotiation.clear
+            @state = :sb
+          when :sb
+            if byte == IAC
+              @state = :sb_iac
+            else
+              @subnegotiation << byte
+            end
+          when :sb_iac
+            if byte == IAC
+              @subnegotiation << IAC
+              @state = :sb
+            elsif byte == SE
+              reply, event = finish_subnegotiation
+              replies << reply if reply != nil
+              events << event if event != nil
+              @state = :data
+            else
+              @state = :data
+            end
+          end
+        end
+        Result.new(:data => output, :replies => replies, :events => events)
+      end
+
+      private
+
+      def handle_iac(byte, output)
+        case byte
+        when IAC
+          output << IAC
+          @state = :data
+        when WILL, WONT, DO, DONT
+          @negotiation_command = byte
+          @state = :negotiation
+        when SB
+          @state = :sb_option
+        else
+          @state = :data
+        end
+      end
+
+      def packet(command, option)
+        [IAC, command, option].pack("C*")
+      end
+
+      def negotiate(command, option)
+        case command
+        when WILL
+          enabled = [ECHO, SUPPRESS_GO_AHEAD].include?(option)
+          changed = @remote_options[option] != enabled
+          @remote_options[option] = enabled
+          return [nil, nil] unless changed
+          if option == ECHO
+            @remote_echo = enabled
+            return [packet(enabled ? DO : DONT, option), [:remote_echo, enabled]]
+          end
+          [packet(enabled ? DO : DONT, option), nil]
+        when WONT
+          changed = @remote_options[option] != false
+          @remote_options[option] = false
+          if option == ECHO
+            @remote_echo = false
+            return [packet(DONT, option), [:remote_echo, false]] if changed
+          end
+          [changed ? packet(DONT, option) : nil, nil]
+        when DO
+          enabled = [SUPPRESS_GO_AHEAD, TERMINAL_TYPE].include?(option)
+          changed = @local_options[option] != enabled
+          @local_options[option] = enabled
+          [changed ? packet(enabled ? WILL : WONT, option) : nil, nil]
+        when DONT
+          changed = @local_options[option] != false
+          @local_options[option] = false
+          [changed ? packet(WONT, option) : nil, nil]
+        else
+          [nil, nil]
+        end
+      end
+
+      def finish_subnegotiation
+        if @subnegotiation_option == TERMINAL_TYPE &&
+            @local_options[TERMINAL_TYPE] == true &&
+            @subnegotiation.getbyte(0) == TTYPE_SEND
+          body = [IAC, SB, TERMINAL_TYPE, TTYPE_IS].pack("C*") + "MEOW".b
+          return [body + [IAC, SE].pack("C*"), [:terminal_type, "MEOW"]]
+        end
+        [nil, [:subnegotiation, @subnegotiation_option]]
+      ensure
+        @subnegotiation_option = nil
+        @subnegotiation.clear
+      end
+    end
+  end
+end
+