#!/usr/bin/env bash

cd "${0%/*}" || exit
PATH+=":${PWD}"
cd - &> /dev/null
source "toolbox.sh" || exit

set -o pipefail

declare -r g_mode_read="READ"
declare -r g_mode_write="WRITE"

terminate_process_group()
{
  kill -TERM -"$(get_own_process_group)"
}

exit_handler()
{
  terminate_process_group
}

int_handler()
{
  terminate_process_group
}

child()
{
  local p_mode="$1"
  local p_file="$2"
  local p_log_file="$3"
  if [ "${p_mode}" = "${g_mode_write}" ]
  then
    dd if=/dev/zero of="${p_file}" bs=8M 2>&1 | stdbuf -o0 grep 'copied' | insert_date | tee "${p_log_file}" || fatal_error_handler
  elif [ "${p_mode}" = "${g_mode_read}" ]
  then
    dd if="${p_file}" of=/dev/null bs=8M 2>&1 | stdbuf -o0 grep 'copied' | insert_date | tee "${p_log_file}" || fatal_error_handler
  else
    fatal_error_handler
  fi
  terminate_process_group
}

get_dd_pid()
{
  local pid_container
  pid_container=($(pgrep -g "$(get_own_process_group)" dd)) || fatal_error_handler || return
  [ "${#pid_container[@]}" = "1" ] || fatal_error_handler || return
  echo "${pid_container[0]}"
}

main()
{
  local p_mode="$1"
  local p_file="$2"
  local p_log_file="$3"
  trap exit_handler EXIT
  trap int_handler SIGINT
  child "${p_mode}" "${p_file}" "${p_log_file}" &
  local dd_pid
  execute_with_retry 5 eval 'dd_pid="$(get_dd_pid)"' || fatal_error_handler || return
  while true
  do
    sleep 1
    kill -USR1 "${dd_pid}" || fatal_error_handler || return
  done
}

LANG="C"
main "$@" || fatal_error_handler