# Usage: daemonize <name> [<command> [...<args>]]
#
# Starts the command in the background with an exclusive lock on $name.
#
# If no command is passed, it uses the name as the command.
#
# Logs are in .direnv/$name.log
#
# To kill the process, run `kill $(< .direnv/$name.pid)`.
daemonize() {
  local name=$1
  shift
  local pid_file=$(direnv_layout_dir)/$name.pid
  local log_file=$(direnv_layout_dir)/$name.log

  if [[ $# -lt 1 ]]; then
    cmd=$name
  else
    cmd=$1
    shift
  fi

  if ! has "$cmd"; then
    echo "ERROR: $cmd not found"
    return 1
  fi

  mkdir -p "$(direnv_layout_dir)"

  # Open pid_file on file descriptor 200
  exec 200>"$pid_file"

  # Check that we have exclusive access
  if ! flock --nonblock 200; then
    echo "daemonize[$name] is already running as pid $(< "$pid_file")"
    return
  fi

  # Start the process in the background. This requires two forks to escape the
  # control of bash.

  # First fork
  (
    # Second fork
    (
      echo "daemonize[$name:$BASHPID]: starting $cmd $*" >&2

      # Record the PID for good measure
      echo "$BASHPID" >&200

      # Redirect standard file descriptors
      exec 0</dev/null
      exec 1>"$log_file"
      exec 2>&1
      # Used by direnv
      exec 3>&-
      exec 4>&-

      # Run command
      exec "$cmd" "$@"
    ) &
  ) &

  # Release that file descriptor
  exec 200>&-
}