;;; auto-version.el --- Automatic x.y.z version -*- lexical-binding: t -*-
;;
;; Author: Emanuel Berg <incal@dataswamp.org>
;; Created: 2024-08-01
;; Keywords: convenience, lisp, tools
;; License: GPL3+
;; Package-Requires: ((emacs "25.1"))
;; URL: https://dataswamp.org/~incal/elpa/auto-version.el
;; Version: 1.16.3
;;
;;; Commentary:
;;
;; __________________________________________________________
;; ^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`
;;
;;         auto-version.el -- automatic x.y.z version
;;
;; __________________________________________________________
;; `^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^
;;
;; Automatic version number uptick.
;;
;; The version number looks like this:
;;
;;   x.y.z
;;
;; Uptick is by default 20 for x and y. Increments to z are
;; by 1 every update. z resets and increments y; y resets
;; and increments x. x doesn't reset or increment:
;;
;;   0 <= z < 20
;;   0 <= y < 20
;;   0 <= x
;;
;; ----------------------------------------------------------
;;
;; To enable in Emacs Lisp buffers:
;;
;; (keymap-set emacs-lisp-mode-map "C-x C-s" #'auto-version-save)
;;
;; ----------------------------------------------------------
;;
;; The most important function, see its docstring:
;;   `auto-version'
;;
;; Automates version update for every save, all transparent:
;;   `auto-version-save'
;;
;; Extra material. How many updates is there in a version?
;; Plus version compare, and more.
;;   `auto-version--updates'
;;   `auto-version<'
;;
;; ----------------------------------------------------------
;;
;; If you want to update the version at most once a day set:
;;   `auto-version--max-once-a-day'
;;
;; ----------------------------------------------------------
;;
;;; Code:

(require 'cl-lib)

(defvar auto-version--max-once-a-day nil
  "Non-nil and `auto-version' increments version(s) at most once a day.")

(defun auto-version-save (&rest arg)
  "Uptick version and save, see `auto-version'.

Also see `auto-version--max-once-a-day'.

ARG are passed on to `save-buffer', you can
use this just as you did `save-buffer'."
  (interactive "p")
  (let ((buffer-undo-list t)
        (today (format-time-string "%F")))
    (if (not auto-version--max-once-a-day)
        (auto-version)
      (when (and auto-version--max-once-a-day
                 (not (and (stringp auto-version--max-once-a-day)
                           (string= today auto-version--max-once-a-day))))
        (auto-version)
        (setq auto-version--max-once-a-day today)) ))
    (save-buffer arg))

(defun auto-version (&optional yz-max label)
  "Uptick the x.y.z version number if present.
y and z overtick at YZ-MAX, default 20.

LABEL is prepended to the version search string, it defaults
to \"^;; Version: \" in Elisp buffers and otherwise to
\"\\\\W\".

Also see: `auto-version-save'"
  (interactive)
  (or yz-max (setq yz-max 20))
  (or label (setq label (if (eq major-mode 'emacs-lisp-mode)
                            "^;; Version: "
                          "\\W")))
  (when (buffer-modified-p)
    (save-mark-and-excursion
      (goto-char (point-min))
      (when (re-search-forward
              (format "%s\\([0-9]+.[0-9]+.[0-9]+\\)\\b" label)
              nil t)
        (pcase-let ((`(,x ,y ,z) (version-to-list (match-string 1))))
          (when (zerop (setq z (mod (cl-incf z) yz-max)))
            (when (zerop (setq y (mod (cl-incf y) yz-max)))
              (cl-incf x)))
          (let ((ver (format "%d.%d.%d" x y z)))
            (replace-match ver nil nil nil 1)
            ver))))))

(defun auto-version< (ver1 ver2 &optional otick1 otick2)
  "Do VER1 has less updates than VER2?

OTICK1 and OTICK2 defaults to 20 for both."
  (interactive
    (list
      (read-string "version 1 [x.y.z]: ")
      (read-string "version 2 [a.b.c]: ")
      (read-number "version 1 overtick" 20)
      (read-number "version 2 overtick" 20)))
  (or otick1 (setq otick1 20))
  (or otick2 (setq otick2 20))
  (let* ((up1 (auto-version--updates ver1 otick1))
        (up2 (auto-version--updates ver2 otick2))
        (res (< up1 up2)))
    (prog1
        res
      (message "updates %s: %d [%s]\nupdates %s: %d" ver1 up1 res ver2 up2))))

(defun auto-version--updates (ver &optional overtick)
  "Translate VER into the number of updates it represents.
Overtick is OVERTICK for y and z, default 20.

For example, version 0.0.1 is the first update or update number 1;
and version 7.4.19 is already at update number 2899.

\(+ (* 7 (expt 20 2)) (* 4 (expt 20 1)) (* 19 (expt 20 0)))"
  (interactive (list
                 (read-string "Version: ")
                 (read-number "Overtick: " 20)))
  (or overtick (setq overtick 20))
  (let* ((vel (version-to-list ver)))
    (cl-loop
      with ups = 0
      for i downfrom (1- (length vel))
      for d in vel do
        (cl-incf ups (* d (expt overtick i)))
      finally return ups)))

(provide 'auto-version)
;;; auto-version.el ends here