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;;; Commentary:
;;; @var{flow-text} take a (multiline) string, and justifies
;;; its contents. All linebreaks are treated as hard line breaks.
;;; Code:
(define-module (text flow)
:use-module (hnh util)
:use-module (text util)
:use-module (srfi srfi-1)
:use-module (srfi srfi-71)
:use-module (srfi srfi-88)
:export (flow-text))
;; str -> (str)
(define* (flow-text str key: (width 70))
(flatten
(map (lambda (line) (justify-line line width: width))
(lines str))))
;; Splits and justifies the given line to @var{width:}.
;; Returns a list of justified strings.
;; str -> (str)
(define* (justify-line line key: (width 70))
(let recur ((lst (words line)))
(let ((head tail (span
(let ((w 0))
(lambda (word) ; Take words until we are above the limit.
(< (set/r! w = (+ 1 (true-string-length word)))
width)))
lst)))
(cond ((null? tail) (list (unwords head))) ; Don't justify last line.
((null? head)
;; an empty head implies that we found a word longer
;; than our max width. Add it as is and continue
;; (while crying).
(cons (car tail) (recur (cdr tail))))
(else (cons (justify-line-helper head width: width)
(recur tail)))))))
;; (str) -> str
(define* (justify-line-helper words key: (width 70))
(let* ((phrase-length (true-string-length (string-concatenate/shared words)))
(needed-spaces (- width phrase-length))
(slots (1- (length words)))
(space-list
(let loop ((n needed-spaces) (d slots))
(unless (zero? d)
(let ((v (round (/ n d))))
(cons v (loop (- n v)
(1- d))))))))
(string-concatenate/shared
(merge words (map (lambda (n) (make-string n #\space))
space-list)
(let ((f #t)) (lambda _ (set/r! f = not)))))))
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