(defun s-repeat (num s)
  ;; extracted from s.el
  "Make a string of S repeated NUM times."
  (let (ss)
    (while (> num 0)
      (setq ss (cons s ss))
      (setq num (1- num)))
    (apply 'concat ss)))

(defun s-concat (&rest strings)
  ;; extracted from s.el
  "Join all the string arguments into one string."
  (apply 'concat strings))

(setq tee-program "
import fcntl
import os
import select
import sys

fd = sys.stdin.fileno()
fl = fcntl.fcntl(fd, fcntl.F_GETFL)
fcntl.fcntl(fd, fcntl.F_SETFL, fl | os.O_NONBLOCK)

filename, = sys.argv[1:]

with open(filename, 'w') as stream:
    while True:
        select.select([sys.stdin], [], [sys.stdin], 0.2)
        data = sys.stdin.read()
        if data == '':
            break
        else:
            stream.write(data)
            stream.flush()
")

(defun repro ()
  (list
     (length (write-to-file (s-repeat 3000 "a")))
     (length (write-to-file (s-repeat 5000 "a")))
     (length (write-to-file (s-concat (s-repeat 3000 "a") "\n" (s-repeat 3000 "a"))))
     ))

(defun write-to-file (input)
  (let (p)

    (if (not (file-exists-p "/tmp/bettertee.py"))
        (write-region tee-program nil "/tmp/bettertee.py"))

    (setq p (start-process "bocp" "*bocp*"
                           "python" "/tmp/bettertee.py" "/tmp/line-repro-bug"))
    (process-send-string p input)
    (process-send-string p "\nnext")
    (process-send-eof p)

    (message (format "Waiting for process to die"))
    (while (process-live-p p)
      (sit-for 0.1))
    (message "Process is dead")
    (get-string-from-file "/tmp/line-repro-bug")
    ))

(defun get-string-from-file (filePath)
  "Return filePath's file content."
  (with-temp-buffer
    (insert-file-contents filePath) (buffer-string)))