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(define-module (vcomponent duration)
:use-module (hnh util)
:use-module (hnh util exceptions)
:use-module (datetime)
:use-module (ice-9 peg)
:use-module (ice-9 match)
:use-module (srfi srfi-9 gnu)
:use-module (srfi srfi-1)
:export (duration parse-duration))
(define-immutable-record-type <duration>
(make-duration sign week day dur-time)
duration?
(sign duration-sign)
(week duration-week)
(day duration-day)
(dur-time duration-time))
(define* (duration
key: (sign '+)
week day time)
(when (and week (or day time))
(scm-error 'misc-error "duration"
"Can't give week together with day or time"
#f #f))
(make-duration sign week day time))
(define-public (format-duration duration)
(with-output-to-string
(lambda ()
(unless (eq? '+ (duration-sign duration))
(display (duration-sign duration)))
(display "P")
(aif (duration-week duration)
(format #t "~aW" it)
(begin
(awhen (duration-day duration) (format #t "~aD" it))
(awhen (duration-time duration)
(display "T")
;; if any non-zero,
(unless (= 0 (hour it) (minute it) (second it))
(format #t "~aH" (hour it))
(unless (= 0 (minute it) (second it))
(format #t "~aM" (minute it))
(unless (= 0 (second it))
(format #t "~aS" (second it)))))))))))
(define-peg-pattern number all (+ (range #\0 #\9)))
(define-peg-pattern time-pattern body
(and (ignore "T")
(and (? (capture (and number "H")))
(? (and (? (capture (and number "M")))
(? (capture (and number "S"))))))))
(define-peg-pattern dur-pattern body
(and (capture (? (or "+" "-")))
(and "P"
(or (capture (and number "W"))
(or (capture (and (and number "D")
(? time-pattern)))
(capture time-pattern))))))
(define (parse-duration str)
(let ((m (match-pattern dur-pattern str)))
(unless m
(scm-error 'parse-error "parse-duration"
"~s doesn't appar to be a duration"
(list str)
#f))
(unless (= (peg:end m) (string-length str))
(warning "Garbage at end of duration"))
(let* ((tree (peg:tree m))
(sign (case (string->symbol (car tree))
[(+ -) => identity]
[(P) '+]))
(lst (concatenate
(map (match-lambda
[(('number num) type)
(let ((n (string->number num)))
(case (string->symbol type)
[(W) `(week: ,n)]
[(D) `(day: ,n)]
[(H) `(hour: ,n)]
[(M) `(minute: ,n)]
[(S) `(second: ,n)]
[else (scm-error 'misc-error "parse-duration"
"Invalid key ~a" type #f)]))]
[a
(scm-error 'misc-error "parse-duration"
"~s not on expected form ((number <num>) type)"
(list a) #f)])
(context-flatten (lambda (x) (and (pair? (car x))
(eq? 'number (caar x))))
(cdr (member "P" tree)))
))))
(apply duration
(cons* sign: sign
(let loop ((rem lst))
(if (null? rem)
'()
;; NOTE a potentially prettier way would be
;; to capture the T above, and use that as
;; the delimiter for the time.
(if (memv (car rem) '(hour: minute: second:))
(list time: (apply time rem))
(cons* (car rem) (cadr rem)
(loop (cddr rem)))))))))))
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