enhance: truncate super long lines in code files rendered in pdf

Set a hard limit of 1000 characters, and truncate everything in the same
line after the limit is reached. Otherwise we could get PDF files with
hundreds of pages which is completely unreadable.

app/helpers/file_helper.rb

@@ -531,14 +531,20 @@ def task_submission_identifier_path_with_timestamp(type, task, timestamp)
     "#{task_submission_identifier_path(type, task)}/#{timestamp.to_s}"
   end
 
-  # Apply line wrapping to a given file. The default 160-character limit is about two lines in the rendered PDF.
+  # Apply line wrapping to a given file.
+  # The default 160-character limit is about two lines in the rendered PDF.
+  # There is also a hard limit of 1000 characters, anything longer will be truncated to 1000 characters.
   def line_wrap(path, width: 160)
+    hard_limit = 1000
     dir = File.dirname(path)
     basename = File.basename(path)
+    temp_file = Tempfile.new('truncated_file')
     output = File.join(dir, "WRAPPED-#{basename}")
     begin
-      logger.debug "Running fold on #{path} to limit line width to #{width}"
-      system("fold --width #{width} #{path.shellescape} > #{output}", exception: true)
+      logger.debug "Applying hard column width limit of #{hard_limit} to #{path}"
+      system("cut -c-#{hard_limit} #{path.shellescape} > #{temp_file.path}", exception: true)
+      logger.debug "Applying line wrapping on #{temp_file.path} to limit line width to #{width}"
+      system("fold --width #{width} #{temp_file.path} > #{output}", exception: true)
       # compare input and output files, replace the output with a symlink if they are identical
       system "diff #{path.shellescape} #{output} > /dev/null"
       case $CHILD_STATUS.exitstatus
@@ -547,13 +553,16 @@ def line_wrap(path, width: 160)
         File.unlink(output)
         File.symlink(path, output)
       when 1
-        logger.debug "File #{path} contains lines longer than #{width}, line wrapping will be applied"
+        logger.debug "File #{path} contains lines longer than #{width}, line wrapping has been applied"
       else
         raise "Error comparing original and line-wrapped files!"
       end
     rescue => e
-      logger.error "Failed to run fold on #{path} to limit line width to #{width}. Rescued with error:\n\t#{e.message}"
+      logger.error "Failed to apply line wrapping on #{path}. Rescued with error:\n\t#{e.message}"
     end
+  ensure
+    temp_file.close
+    temp_file.unlink
   end
   # Export functions as module functions
   module_function :accept_file

app/views/task/task_pdf.pdf.erb

@@ -121,7 +121,7 @@ No Tutor % Supervisor's Name
   %>
     <% unless File.symlink?(wrapped_file) %>
 \begin{tcolorbox}[colback=blue!5!white,colframe=blue!75!black]
-  This file has additional line breaks applied by <%= @doubtfire_product_name %> because they contain lines longer than the configured limit. The orginal submission can be retrieved via the "Download Uploaded Files" function.
+  This file has additional line breaks applied by <%= @doubtfire_product_name %> because they contain lines longer than the configured limit. Lines over 1000 characters long have been truncated to limit PDF page count. The orginal submission can be retrieved via the "Download Uploaded Files" function.
 \end{tcolorbox}
     <% end %>
 \inputminted[breaklines,linenos,breakanywhere,tabsize=4]{<%= pygments_lang %>}{<%= wrapped_file %>}