Implementing the Cache-Status header field in VCL (WIP)

cache-status.vcl

declare local var.cache_status STRING;
declare local var.cache_status_visible BOOL;
set var.cache_status = server.identity;
set var.cache_status_visible = true;

if (fastly_info.state ~ "^NONE") {
  set var.cache_status_visible = false;
} 
elsif (fastly_info.state ~ "^HIT-SYNTH-") {
  set var.cache_status_visible = false;
}
elsif (fastly_info.state ~ "^(PASS|HITPASS)-") {
  set var.cache_status = var.cache_status ";fwd=bypass";
}
elsif (fastly_info.state ~ "^HIT") {
  set var.cache_status = var.cache_status ";hit";
}
elsif (fastly_info.state ~ "^MISS-") {
  if (stale.exists) {
    set var.cache_status = var.cache_status ";fwd=stale";
  } else {
    set var.cache_status = var.cache_status ";fwd=miss";
  }
}
else {
  set var.cache_status_visible = false;  
}

if (fastly_info.state ~ "-REFRESH") {
  set var.cache_status = var.cache_status ";fwd=stale;fwd-status=304";
}

if (req.http.tmp-ttl) {
  set var.cache_status = var.cache_status ";ttl=" regsub(req.http.tmp-ttl, "\..*$", "");
  unset req.http.tmp-ttl;
}

if (fastly_info.state ~ "-WAIT") {
  set var.cache_status = var.cache_status ";collapsed";
}

if (var.cache_status_visible) {
  if (!resp.http.Cache-Status) {
    set resp.http.Cache-Status = var.cache_status;
  } else {
    set resp.http.Cache-Status = resp.http.Cache-Status ", " var.cache_status;
  }
}