A simple minor-mode to automatically enforce a "one-sentence per
line" style in text files.

;; Installation

Place the file `electric-ospl.el' somewhere on your `load-path',
and `require` it (note, autoloading is also supported).  Enable
`electric-ospl-mode' anywhere where you want to follow a
"one-sentence per line" style, for instance, by adding to various
mode hooks (I use `text-mode-hook' personally).

Additionally, a globalized minor mode, `global-electric-ospl-mode'
is available, which will activate the mode based on the value of
`electric-ospl-global-modes' (see below).

;; Configuration

There are a couple of options which can be used to modify behavior
(and speed) of the mode.  The variables noted with (CUSTOM) *must*
be customized using either the customize interface or (on Emacs
29.1 or later) `setopt', because a setter is used to cache the
regular expressions.

- The first is `electric-ospl-regexps' (CUSTOM), which sets the
  list of regular expressions defining how a sentence ends.

- The next is `electric-ospl-ignored-abbreviations' (CUSTOM), which
  is a (case-sensitive) list of abbrevations ending in a period
  that are not necessarily considered the end of a sentence.

- Next, efficiency may be modified by changing
  `electric-ospl-maximum-lookback-chars', which determines how far
  to look back to find the end of a sentence.

 - Additionally, the `electric-ospl-sentence-end-functions' hook
   determines if point is currently at the end of a sentence.  It
   defaults to using the regexp returned by `sentence-end' but may
   be extended to use sentence-end determination logic provided by
   other packages.

 - Finally, you can configure ignoring of OSPL in certain
   circumstances using the
   `electric-ospl-ignore-electric-functions' hook.  This variable
   defaults to ignoring when the last thing was in the ignored
   abbreviations list.  It is used by checking, one-by-one for a
   function which returns non-nil.  An example use is below.

(add-hook 'LaTeX-mode-hook (defun my/latex-ospl-config ()
                             (add-hook 'electric-ospl-ignore-electric-functions
                                       (defun my/ignore-ospl-in-some-latex-envs ()
                                         (cl-member (LaTeX-current-environment)
                                                    '("tabular" "tabularx" "tikzpicture")))
                                       -100 t)))

Additionally, where the globalized mode is enabled is configured
using `electric-ospl-global-modes', which has the following
semantics.

- If t, it will be enabled in all modes (except for special modes,
  ephemeral buffers, or the minibuffer).

- If nil, it will not be enabled in any modes.

- If the first symbol is `not', `electric-ospl-mode' will not be
  enabled in buffers with the listed major modes or descending from
  the listed major modes.

- Otherwise, it will be enabled only in the listed modes.

It may also be configured using the
`electric-ospl-allowed-override-commands' variable, which defines
which bindings for SPC may be overridden.  If the current binding
for SPC is not in `electric-ospl-allowed-override-commands', then
the mode will not be activated locally.  This defaults to
`self-insert-command' and `org-self-insert-command'.

;; Acknowledgments

This code is based significantly on Jan Seeger's `twauctex'
(https://github.com/jeeger/twauctex).  I've made effort to simplify
the logic and make it so that it's usable in modes other than
`LaTeX-mode'.

;; Errors and Patches

If you find an error or have a patch to improve this package, please
send an email to `~swflint/emacs-utilities@lists.sr.ht`.