From af7367be0cd581cb345756e55b041fa37d99d3a5 Mon Sep 17 00:00:00 2001
From: ChillerDragon <ChillerDragon@gmail.com>
Date: Mon, 24 Jun 2024 11:42:08 +0800
Subject: [PATCH] Drop known chunks. Fixes duplicated chat messages.

---
 lib/chunk.rb            | 11 ++++++++---
 lib/connection.rb       | 20 ++++++++++++++++++++
 lib/teeworlds_client.rb | 17 ++++++++++++++---
 3 files changed, 42 insertions(+), 6 deletions(-)
 create mode 100644 lib/connection.rb

diff --git a/lib/chunk.rb b/lib/chunk.rb
index 46ffa07..1a9b1b2 100644
--- a/lib/chunk.rb
+++ b/lib/chunk.rb
@@ -13,13 +13,14 @@ require_relative 'bytes'
 #
 # https://chillerdragon.github.io/teeworlds-protocol/07/packet_layout.html
 class NetChunk
-  attr_reader :next, :data, :msg, :sys, :flags, :header_raw, :full_raw
+  attr_reader :next, :data, :msg, :sys, :flags, :seq, :header_raw, :full_raw
 
   @@sent_vital_chunks = 0
 
   def initialize(data)
     @next = nil
     @flags = {}
+    @seq = 0
     @size = 0
     parse_header(data[0..2])
     header_size = if flags_vital
@@ -135,8 +136,12 @@ class NetChunk
     size_bytes.map! { |b| b[2..].join }
     @size = size_bytes.join.to_i(2)
 
-    # sequence number
-    # in da third byte but who needs seq?!
+    if @flags[:vital]
+      data = data[0..2].bytes
+      @seq = (data[1] & (0xC0 << 2)) | data[2]
+    else
+      @seq = 0
+    end
   end
 
   # @return [Boolean]
diff --git a/lib/connection.rb b/lib/connection.rb
new file mode 100644
index 0000000..810095a
--- /dev/null
+++ b/lib/connection.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+##
+# Only used for chunks where the sequence number does not match the expected value
+# to decide wether to drop known chunks silently or request resend if something got lost
+#
+# true - if the sequence number is already known and the chunk should be dropped
+# false - if the sequence number is off and we need to request a resend of lost chunks
+#
+# @return [Boolean]
+def seq_in_backroom?(seq, ack)
+  bottom = ack - (NET_MAX_SEQUENCE / 2)
+  if bottom.negative?
+    return true if seq <= ack
+    return true if seq >= (bottom + NET_MAX_SEQUENCE)
+  elsif seq <= ack && seq >= bottom
+    return true
+  end
+  false
+end
diff --git a/lib/teeworlds_client.rb b/lib/teeworlds_client.rb
index aba2b29..fdadb47 100644
--- a/lib/teeworlds_client.rb
+++ b/lib/teeworlds_client.rb
@@ -14,6 +14,7 @@ require_relative 'packer'
 require_relative 'models/player'
 require_relative 'game_client'
 require_relative 'config'
+require_relative 'connection'
 
 class TeeworldsClient
   attr_reader :state, :hooks, :game_client, :verbose_snap
@@ -445,9 +446,19 @@ class TeeworldsClient
     end
     chunks = BigChungusTheChunkGetter.get_chunks(data)
     chunks.each do |chunk|
-      if chunk.flags_vital && !chunk.flags_resend && chunk.msg != NETMSG_NULL
-        @netbase.ack = (@netbase.ack + 1) % NET_MAX_SEQUENCE
-        puts "got ack: #{@netbase.ack}" if @verbose
+      if chunk.flags_vital
+        if chunk.seq == (@netbase.ack + 1) % NET_MAX_SEQUENCE
+          # in sequence
+          @netbase.ack = (@netbase.ack + 1) % NET_MAX_SEQUENCE
+        else
+          puts "warning: got chunk out of sequence! seq=#{chunk.seq} expected_seq=#{(@netbase.ack + 1) % NET_MAX_SEQUENCE}"
+          if seq_in_backroom?(chunk.seq, @netbase.ack)
+            puts '         dropping known chunk ...'
+            next
+          end
+          # TODO: request resend
+          puts '         REQUESTING RESEND NOT IMPLEMENTED'
+        end
       end
       process_chunk(chunk)
     end