-#!/usr/bin/guile
--*- scheme -*-
-!#
-
-;;; srt2vtt --- SRT to WebVTT converter
-;;; Copyright © 2015 David Thompson <davet@gnu.org>
-;;;
-;;; srt2vtt is free software; you can redistribute it and/or modify it
-;;; under the terms of the GNU General Public License as published by
-;;; the Free Software Foundation; either version 3 of the License, or
-;;; (at your option) any later version.
-;;;
-;;; srt2vtt is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
-;;; General Public License for more details.
-;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with srt2vtt. If not, see <http://www.gnu.org/licenses/>.
-
-;;; Commentary:
-;;
-;; Convert SRT formatted subtitles to WebVTT format.
-;;
-;;; Code:
-
-(use-modules (ice-9 format)
- (ice-9 match)
- (ice-9 rdelim)
- (ice-9 regex)
- (srfi srfi-1)
- (srfi srfi-9)
- (srfi srfi-11)
- (srfi srfi-26)
- (srfi srfi-37))
-
-(define-record-type <subtitle>
- (make-subtitle id start end text)
- subtitle?
- (id subtitle-id)
- (start subtitle-start)
- (end subtitle-end)
- (text subtitle-text))
-
-(define parse-time
- (let ((regexp (make-regexp "([0-9]+):([0-9]+):([0-9]+),([0-9]+)")))
- (lambda (s)
- "Parse the SubRip formatted timestamp in the string S into a 4
-element list. Valid input looks like '00:00:03.417'."
- (let ((match (regexp-exec regexp s)))
- (map (cut match:substring match <>) '(1 2 3 4))))))
-
-(define parse-time-span
- (let ((regexp (make-regexp "([0-9:,]+) --> ([0-9:,]+)")))
- (lambda (s)
- "Parse the SubRip formatted time span in the string S and return
-two values: the start time and the end time. Valid input looks like
-'00:00:03.417 --> 00:00:04.936'."
- (let ((match (regexp-exec regexp s)))
- (values (parse-time (match:substring match 1))
- (parse-time (match:substring match 2)))))))
-
-(define (read-sub-rip port)
- "Read a SubRip formatted subtitle from PORT."
- (let-values (((id) (string->number (read-line port)))
- ((start end) (parse-time-span (read-line port)))
- ((lines) (let loop ((lines '()))
- (let ((line (read-line port)))
- (if (or (eof-object? line)
- (and (string-null? line)
- ;; A subtitle may be a blank line!
- (not (null? lines))))
- lines
- (loop (cons line lines)))))))
- (make-subtitle id start end lines)))
-
-(define (read-sub-rips port)
- "Read all SubRip formatted subtitles from PORT."
- (reverse
- (let loop ((subs '()))
- (if (eof-object? (peek-char port))
- subs
- (loop (cons (read-sub-rip port) subs))))))
-
-(define (write-time time port)
- "Write TIME as a WebVTT formatted timestamp to PORT."
- (match time
- ((h m s ms)
- (format port "~a:~a:~a.~a" h m s ms))))
-
-(define (write-web-vtt subtitle port)
- "Write SUBTITLE as a WebVTT formatted subtitle to PORT."
- (match subtitle
- (($ <subtitle> id start end text)
- (format port "~a~%" id)
- (write-time start port)
- (display " --> " port)
- (write-time end port)
- (newline port)
- (format port "~a~%" (string-join text "\n"))
- (newline port))))
-
-(define (write-web-vtts subtitles port)
- "Write all SUBTITLES as WebVTT formatted subtitles to PORT."
- (format port "WEBVTT~%~%")
- (for-each (cut write-web-vtt <> port) subtitles))
-
-(define (convert input-port output-port)
- "Read the SubRip formatted subtitles from INPUT-PORT and write the
-WebVTT equivalents to OUTPUT-PORT."
- (write-web-vtts (read-sub-rips input-port) output-port))
-
-(define (show-help-and-exit)
- (format #t "Usage: srt2vtt [OPTIONS]
-Convert SubRip formatted subtitles to WebVTT format.~%")
- (display "
- -h, --help display this help and exit")
- (display "
- -v, --version display version and exit")
- (display "
- -i, --input=FILE-NAME read input from FILE-NAME")
- (display "
- -o, --output=FILE-NAME write output to FILE-NAME")
- (newline)
- (exit 0))
-
-(define (show-version-and-exit)
- (format #t "srt2vtt 0.1~%")
- (exit 0))
-
-(define (show-usage-and-exit)
- (format #t "Try `srt2vtt --help' for more information.~%")
- (exit 1))
-
-(define (show-wrong-args-and-exit)
- (format #t "Invalid arguments~%")
- (show-usage-and-exit))
-
-(define %default-args
- `((input . ,(current-input-port))
- (output . ,(current-output-port))))
-
-(define %options
- (list (option '(#\h "help") #f #f
- (lambda (opt name arg args)
- (show-help-and-exit)))
- (option '(#\v "version") #f #f
- (lambda (opt name arg args)
- (show-version-and-exit)))
- (option '(#\i "input") #t #f
- (lambda (opt name arg args)
- (alist-cons 'input arg args)))
- (option '(#\o "output") #t #f
- (lambda (opt name arg args)
- (alist-cons 'output arg args)))))
-
-(define (make-call-with-port-or-file file-proc)
- "Create a new procedure that accepts two arguments: a port or file,
-and a procedure. When the returned procedure is called with a port as
-the first argument, the second argument is simply applied with that
-port. If the first argument is a string, the second argument is
-applied with the port corresponding to the file name contained in the
-string as opened by FILE-PROC."
- (lambda (port-or-file proc)
- (if (port? port-or-file)
- (proc port-or-file)
- (file-proc port-or-file proc))))
-
-(define call-with-port-or-input-file
- (make-call-with-port-or-file call-with-input-file))
-
-(define call-with-port-or-output-file
- (make-call-with-port-or-file call-with-output-file))
-
-(define (parse-opts args)
- "Parse the list of ARGS and return a list of option/value pairs.
-When an option isn't specified in ARGS, it defaults to the value in
-'%default-args'."
- (args-fold args
- %options
- (lambda (opt name arg args)
- (error "Unrecognized option '~a'" name))
- (lambda (arg args)
- (error "Extraneous argument '~a'" arg))
- %default-args))
-
-(define (main args)
- "srt2vtt entry point."
- (let ((opts (parse-opts args)))
- (call-with-port-or-input-file (assoc-ref opts 'input)
- (lambda (input-port)
- (call-with-port-or-output-file (assoc-ref opts 'output)
- (lambda (output-port)
- (convert input-port output-port)))))))
-
-(match (command-line)
- ((arg0 args ...)
- (main args)))