#lang racket/base

;; Copyright (c) 2018 Joel Dueck.
;;
;; Licensed under the Apache License, Version 2.0 (the "License");
;; you may not use this file except in compliance with the License.
;; A copy of the License is included with this source code, in the
;; file "LICENSE.txt".
;; You may also obtain a copy of the License at
;;
;;       http://www.apache.org/licenses/LICENSE-2.0
;;
;; Unless required by applicable law or agreed to in writing, software
;; distributed under the License is distributed on an "AS IS" BASIS,
;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
;; See the License for the specific language governing permissions and
;; limitations under the License.
;;
;; Author contact information:
;;   joel@jdueck.net
;;   https://joeldueck.com
;; -------------------------------------------------------------------------

;; Convenience functions for YYYY-MM-DD date strings

(require gregor
         racket/string)

(provide (all-defined-out))

;; These functions ignore everything after the first space!
(define (ymd->dateformat ymd-string dateformat)
  (~t (iso8601->date (car (string-split ymd-string))) dateformat))

(define (ymd->english ymd-string)
  (ymd->dateformat ymd-string "MMMM d, yyyy"))

(module+ test
  (require rackunit)
  (check-equal? (ymd->english "2018-08-12") "August 12, 2018")
  (check-equal? (ymd->dateformat "2018-08-12" "d MMM YYYY") "12 Aug 2018")

  ;; How we handle weird input
  (check-equal? (ymd->english "2018-08-12 everything after 1st space ignored") "August 12, 2018")
  (check-equal? (ymd->english "2018-08 omitting the day") "August 1, 2018")
  (check-equal? (ymd->english "2018 omitting month and day") "January 1, 2018")
  (check-equal? (ymd->dateformat "2018-08-12" "123") "123")

  ;; Stuff we just don't handle
  (check-exn exn:gregor:parse? (lambda () (ymd->english "2018-xyz"))))
