custom-date-formater.json

{
  "name": "Apply Date Format by Field Name",
  "description": "Allows applying a custom date format to a source by matching field names",
  "inputs": [
    { 
      "name": "source",
      "description": "Source to update",
      "type": "source-id"
    }
  ],
  "outputs": [
    {
      "name": "updated-src",
      "description": "A link to the updated source with the modified date-time fields",
      "type": "source-id"
    }
  ]
}

custom-date-formater.whizzml

;
; Compare the field name to a list of patterns. Return
; true/false if it matches any
;

(define (field-matches? fieldname patterns)
  (loop (els patterns)
    (if (= els []) false
      (let (el (head els) rest (tail els)) 
        (if (contains-string? el fieldname) true (recur rest))))))
    

;
; Given a source id or record, update the field optypes by searching
; for matching field names in each of the input arrays. 
;
(define (custom-date-format source field-match date-format)
  (let 
    (source-rec (fetch source)
     src-field-ids (keys (get source-rec "fields"))
     optype-map
       (loop (ids src-field-ids update-map {})
         (if (= ids []) update-map
           (let 
             (this (head ids)
              rest (tail ids)
              field-name (get-in source-rec ["fields" this "name"]))
             (if
                (field-matches? field-name field-match)
                (recur rest (assoc update-map this {"optype" "datetime" "time_formats" [date-format] }))
                (recur rest update-map))))))
    (update-and-wait source {"fields" optype-map})))
    
(define updated-src (custom-date-format source ["Date"] "dd-MMM-YYYY HH:mm:ss"))