Nofollow link rendering + archive.org integration for Hugo

render-link.html

{{- $linkurl := .Destination }}
{{- $relval := ""}}
{{- $targetval := ""}}
{{- $classval := "" }}
{{- if strings.HasPrefix $linkurl "http" }}
    {{- $targetval = printf "%s %s"  $targetval "_blank" }}
    {{- $relval = printf "%s %s" $relval "noopener" }}
    {{- $classval = printf "%s %s" $classval "external" }}
{{- end -}}
{{- if strings.HasSuffix $linkurl "#?" }} 
    {{- $relval = printf "%s %s" $relval "nofollow" }}
    {{- $urlparts := split $linkurl "#" -}}
    {{- $linkurl = index $urlparts 0}}
{{- end -}}
<a href="{{ $linkurl | safeURL }}"
    {{- with .Title}} title="{{ trim . " " }}"{{ end -}}
    {{- with $relval}} rel="{{ trim . " " }}"{{ end -}}
    {{- with $targetval}} target="{{ trim . " " }}"{{ end -}}
    {{- with $classval}} class="{{ trim . " " }}"{{ end -}}
>{{ .Text | safeHTML }}</a>
{{- if strings.HasPrefix $linkurl "http" }}
    {{- if gt (sub now.Year .Page.Date.Year) 5 }} 
    {{- $relval = printf "%s %s" $relval "nofollow" }}
    (<a href="https://web.archive.org/web/{{ .Page.Date.Year }}*/{{ $linkurl }}"
        {{- with $relval}} rel="{{ trim . " " }}"{{ end -}}
        {{- with $targetval}} target="{{ trim . " " }}"{{ end -}}
        {{- with $classval}} class="{{ trim . " " }}"{{ end -}}
        >archive.org</a>)
    {{- end -}}
{{- end -}}

• Links like http://example.com/page#? are rendered with rel=nofollow
• External links are class=external, target=_blank, rel=noopener
• Links on posts older than 5 years additionally get an archive.org link for external links