#!/usr/bin/guile \
--debug -e main -s
!#

(use-modules (ice-9 regex)
             (ice-9 getopt-long))

;; start-inline: (grumbel helper)
(use-modules (ice-9 optargs))

(define (file:for-each-line filename thunk)
  (with-input-from-file filename
    (lambda ()
      (let loop ((line (read-line)))
        (cond ((not (eof-object? line))
               (thunk line)
               (loop (read-line))))))))

(define* (println #:key (port #f) . rest)
  (cond (port
         (for-each (lambda (el) (display el port))
                   rest))
        (else
         (for-each display
                   rest)))
  (newline))
;; stop-inline:  (grumbel helper)

(define *subtitle-line-regex* (make-regexp "^\\{([0-9]+)\\}\\{([0-9]+)\\}(.*)$"))

(define (scale-subtitle factor offset line)
  (let ((ret (regexp-exec *subtitle-line-regex* line)))
    (cond ((not ret)
           (error 'parse-error "Parse error with line: " line))
          (else
           (let ((start (string->number (match:substring ret 1)))
                 (end   (string->number (match:substring ret 2)))
                 (text                  (match:substring ret 3)))
             (println "{" (inexact->exact (+ (* factor start) offset)) "}" 
                      "{" (inexact->exact (+ (* factor end)   offset)) "}"
                      text))))))

(define (scale-subtitle-file filename scale offset)
  (file:for-each-line 
   filename
   (lambda (line) (scale-subtitle scale offset line))))

(define (print-help)
  (display "\
subscale.scm [options] FILENAME
  -h, --help            Display this help
  -s, --scale NUMBER    Scale the numbers by NUMBER
  -o, --offset NUMBER   Offset the frame references by NUMBER
  --output FILENAME     Write result to filename, instead of stdout

"))

(define (main args)
  (let* ((option-spec '((scale  (single-char #\s) (value #t))
                        (offset (single-char #\o) (value #t))
                        (output (value #t))
                        (help   (single-char #\h) (value #f))))
         (options     (getopt-long args option-spec))
         (scale       (string->number (option-ref options 'scale  "1")))
         (offset      (string->number (option-ref options 'offset "0")))
         (output-file (option-ref options 'output #f))
         (help-wanted (option-ref options 'help #f))
         (rest        (option-ref options '() #f)))

    (cond ((or help-wanted (not (= (length rest) 1)))
           (print-help))
          (else
           (cond (output-file
                  (with-output-to-file output-file
                    (lambda ()
                      (scale-subtitle-file (car rest) scale offset))))
                 (else 
                  (scale-subtitle-file (car rest) scale offset)))))))

;; Avalon: --offset 220

;; EOF ;;