+
+ def telephone_link(key, value)
+ # does it look like a phone number? eg "+1 (234) 567-8901 " ?
+ return nil unless value =~ /^\s*\+[\d\s\(\)\/\.-]{6,25}\s*$/
+
+ # remove all whitespace instead of encoding it http://tools.ietf.org/html/rfc3966#section-5.1.1
+ # "+1 (234) 567-8901 " -> "+1(234)567-8901"
+ valueNoWhitespace = value.gsub(/\s+/, '')
+
+ return "tel:#{valueNoWhitespace}"
+ end