1 files changed, 101 insertions, 0 deletions
diff --git a/transform/strings.scm b/transform/strings.scm
new file mode 100644
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--- /dev/null
+++ b/transform/strings.scm
@@ -0,0 +1,101 @@
+(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))
+