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(define-module (transform strings)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-19)
#:use-module (ice-9 match)
#:use-module (ice-9 string-fun)
#:use-module (ice-9 textual-ports)
#:export (string-blank?
time-unix->string
string-blank?
string-split-substring
delete-substrings
replace-substrings
sanitize-rdf-string
snake->lower-camel
string-capitalize-first))
(define (time-unix->string seconds . maybe-format)
"Given an integer saying the number of seconds since the Unix
epoch (1970-01-01 00:00:00), SECONDS, format it as a human readable
date and time-string, possible using the MAYBE-FORMAT."
(letrec ([time-unix->time-utc
(lambda (seconds)
(add-duration
(date->time-utc (make-date 0 0 0 0 1 1 1970 0))
(make-time time-duration 0 seconds)))])
(apply date->string
(time-utc->date (time-unix->time-utc seconds))
maybe-format)))
(define (string-blank? str)
"Return non-#f if STR consists only of whitespace characters."
(string-every char-set:whitespace str))
(define (string-split-substring str substr)
"Split the string @var{str} into a list of substrings delimited by the
substring @var{substr}."
(define substrlen (string-length substr))
(define strlen (string-length str))
(define (loop index start)
(cond
((>= start strlen) (list ""))
((not index) (list (substring str start)))
(else
(cons (substring str start index)
(let ((new-start (+ index substrlen)))
(loop (string-contains str substr new-start)
new-start))))))
(cond
((string-contains str substr) => (lambda (idx) (loop idx 0)))
(else (list str))))
(define (delete-substrings str . substrings)
"Delete SUBSTRINGS, a list of strings, from STR."
(fold (lambda (substring result)
(string-replace-substring result substring ""))
str
substrings))
(define (replace-substrings str replacement-alist)
"Replace substrings in STR according to REPLACEMENT-ALIST, an
association list mapping substrings to their replacements."
(fold (match-lambda*
(((substring . replacement) str)
(string-replace-substring str substring replacement)))
str
replacement-alist))
(define (sanitize-rdf-string str)
(replace-substrings
(string-trim-both str)
'(("\r" . "\\r")
("\n" . "\\n")
("\"" . "'")
("\v" . "")
("\xad" . "")
("\x28" . "")
("\x29" . "")
("\xa0" . " ")
("\x02" . "")
("\x01" . ""))))
(define (snake->lower-camel str)
(let ((char-list (string->list str)))
(call-with-output-string
(lambda (port)
(put-char port (char-downcase (string-ref str 0)))
(map (lambda (char previous-char)
(unless (char=? char #\_)
(put-char port (if (char=? previous-char #\_)
(char-upcase char)
char))))
(drop char-list 1)
char-list)))))
(define (string-capitalize-first string)
(string-titlecase
(string-downcase string) 0 1))
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