BEGIN {
  RS = "\x0c"
  FS = "\n"
}

/^message{/ {
  id = ""
  depth = -1
  split($1, a, " ")
  for (i in a) {
    if (id && depth >= 0)
      continue
    if (substr(a[i], 1, 3) == "id:")
      id = substr(a[i], 4)
    else if (substr(a[i], 1, 6) == "depth:")
      depth = substr(a[i], 7) + 0
  }
}
/^header{/ {
  subj = ""
  for (i=3; i<=NF; i++) {
    if (substr($i, 1, 9) == "Subject: ") {
      subj = substr($i, 10)
      break
      }
    }
  printf "%s\t%s\t%"(2*depth)"s%s\n", id, subj, "", $2
}