From cc98dc22298de0e5fe8e4fbee504af752f054563 Mon Sep 17 00:00:00 2001
From: Sebastian Serth <Sebastian.Serth@hpi.de>
Date: Sun, 10 Oct 2021 15:12:45 +0200
Subject: [PATCH] Split WebSocket event in multiple lines before processing

---
 lib/runner/connection.rb                     | 24 ++++++++++++--------
 lib/runner/strategy/docker_container_pool.rb | 10 ++++----
 lib/runner/strategy/poseidon.rb              |  4 ++--
 3 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/lib/runner/connection.rb b/lib/runner/connection.rb
index 659d769f..bca9cfea 100644
--- a/lib/runner/connection.rb
+++ b/lib/runner/connection.rb
@@ -78,16 +78,22 @@ class Runner::Connection
 
   def on_message(raw_event)
     Rails.logger.debug { "#{Time.zone.now.getutc}: Receiving from #{@socket.url}: #{raw_event.data.inspect}" }
-    event = decode(raw_event)
-    return unless BACKEND_OUTPUT_SCHEMA.valid?(event)
+    # The WebSocket connection might group multiple lines. For further processing, we require all lines
+    # to be processed separately. Therefore, we split the lines by each newline character not part of an enclosed
+    # substring either in single or double quotes (e.g., within a JSON)
+    # Inspired by https://stackoverflow.com/questions/13040585/split-string-by-spaces-properly-accounting-for-quotes-and-backslashes-ruby
+    raw_event.data.scan(/(?:"(?:\\.|[^"])*"|'(?:\\.|[^'])*'|[^"\n])+/).each do |event_data|
+      event = decode(event_data)
+      next unless BACKEND_OUTPUT_SCHEMA.valid?(event)
 
-    event = event.deep_symbolize_keys
-    message_type = event[:type].to_sym
-    if WEBSOCKET_MESSAGE_TYPES.include?(message_type)
-      __send__("handle_#{message_type}", event)
-    else
-      @error = Runner::Error::UnexpectedResponse.new("Unknown WebSocket message type: #{message_type}")
-      close(:error)
+      event = event.deep_symbolize_keys
+      message_type = event[:type].to_sym
+      if WEBSOCKET_MESSAGE_TYPES.include?(message_type)
+        __send__("handle_#{message_type}", event)
+      else
+        @error = Runner::Error::UnexpectedResponse.new("Unknown WebSocket message type: #{message_type}")
+        close(:error)
+      end
     end
   end
 
diff --git a/lib/runner/strategy/docker_container_pool.rb b/lib/runner/strategy/docker_container_pool.rb
index bddf75af..aae831cd 100644
--- a/lib/runner/strategy/docker_container_pool.rb
+++ b/lib/runner/strategy/docker_container_pool.rb
@@ -121,9 +121,9 @@ class Runner::Strategy::DockerContainerPool < Runner::Strategy
       "#{data}\n"
     end
 
-    def decode(raw_event)
-      case raw_event.data
-        when /@#{@strategy.container_id[0..11]}/
+    def decode(event_data)
+      case event_data
+        when /(@#{@strategy.container_id[0..11]}|#exit)/
           # Assume correct termination for now and return exit code 0
           # TODO: Can we use the actual exit code here?
           @exit_code = 0
@@ -135,11 +135,11 @@ class Runner::Strategy::DockerContainerPool < Runner::Strategy
         when /\*\*\*\*\*\*\*\*\*\*\*\*\* Module/
           # Identification of PyLint output, change stream back to stdout and return event
           @stream = 'stdout'
-          {'type' => @stream, 'data' => raw_event.data}
+          {'type' => @stream, 'data' => event_data}
         when /#{@strategy.command}/
         when /bash: cmd:canvasevent: command not found/
         else
-          {'type' => @stream, 'data' => raw_event.data}
+          {'type' => @stream, 'data' => event_data}
       end
     end
   end
diff --git a/lib/runner/strategy/poseidon.rb b/lib/runner/strategy/poseidon.rb
index 90699400..7eeef0aa 100644
--- a/lib/runner/strategy/poseidon.rb
+++ b/lib/runner/strategy/poseidon.rb
@@ -151,8 +151,8 @@ class Runner::Strategy::Poseidon < Runner::Strategy
   end
 
   class Connection < Runner::Connection
-    def decode(raw_event)
-      JSON.parse(raw_event.data)
+    def decode(event_data)
+      JSON.parse(event_data)
     rescue JSON::ParserError => e
       @error = Runner::Error::UnexpectedResponse.new("The WebSocket message from Poseidon could not be decoded to JSON: #{e.inspect}")
       close(:error)