;;; sync-file.el --- a viewing mode for books and novels.  -*- lexical-binding: t; -*-

;; Copyright (C) 2019 Robert Rose

;; Author: Robert Rose <overclucker@gmail.com>
;; Keywords: lisp sync file
;; Version: 0.0.1
;; Package-Requires ((emacs "24"))

;; This program 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.

;; This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; Allows you to syncronize files by newest file date. Directories arent currently handled,
;; as I have no need for that functionaliity at this point. Parent directories will always
;; be created if they dont exist. Some conditions that may occur haven't been covered, such
;; as write permissions and attributes. If one of the files is a regular file and the other
;; is a directory, strange behaviours may occur. Another thing to note is that file names
;; can make use of TRAMP, which makes remote sync and root file access possible.
;; e.g.,
;; (let ((files
;;        '(("~/foo/file1.txt" . "/ssh:use@host:~/foo/file1.txt")
;; 	    ("~/foo/file2.txt" . "/ssh:use@host:~/foo/file2.txt")
;; 	    ("~/foo/file3.txt" . "/ssh:use@host:~/foo/file3.txt")) ))
;;   (sync-files files))

;;; Code:

(defun copy-file-make-parents (name newname)
  "Copy file and make parent directories if neccessary."
  (let* ((parent (file-name-directory (file-name-directory newname))))
    (unless (file-directory-p parent)
      (make-directory parent t))
    (copy-file name newname t)))

(defun sync-file (f1 f2)
  "Syncronize newest to oldest file. Parent directories will be created."
  (cond ((and (file-exists-p f1) (file-exists-p f2))
	 (cond ((file-newer-than-file-p f1 f2)
		(copy-file f1 f2 t))
	       ((file-newer-than-file-p f2 f1)
		(copy-file f2 f1 t)) ))
	((and (file-exists-p f1) (not (file-exists-p f2)))
	 (copy-file-make-parents f1 f2) )
	((and (file-exists-p f2) (not (file-exists-p f1)))
	 (copy-file-make-parents f2 f1)) ))

(defun sync-files (files)
  "Syncronize newest to oldest files. Parent directories will be created.
`files' should be in the form (cons f1 f2)."
  (dolist (file files)
     (sync-file (car file) (cdr file))))

(provide 'sync-file)

;;; sync-file.el ends here