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;;; mono-complete-backend-capf.el --- DABBREV back-end -*- lexical-binding: t -*-
;; SPDX-License-Identifier: GPL-3.0-or-later
;; Copyright (C) 2023 Campbell Barton
;; URL:
;; Version: 0.1
;;; Commentary:
;; Completion at point function (capf) back-end.
;;; Code:
(require 'mono-complete)
;; ---------------------------------------------------------------------------
;; Custom Variables
(defgroup mono-complete-backend-capf nil
"Word prediction for mono-complete, generated on demand."
:group 'convenience)
(defcustom mono-complete-backend-capf-complete-fn nil
"The completion function.
When nil, defaults are used (depending on the mode)."
:type '(choice (const nil) function))
;; ---------------------------------------------------------------------------
;; Callbacks
(defun mono-complete-backend-capf-setup (config)
"Validate CONFIG."
(let ((complete-fn (plist-get config :complete-fn)))
;; Find a completion function.
(unless complete-fn
((and (fboundp 'eglot-managed-p) (funcall #'eglot-managed-p))
(setq config (plist-put config :complete-fn 'eglot-completion-at-point)))
((eq major-mode 'emacs-lisp-mode)
(setq config (plist-put config :complete-fn 'elisp-completion-at-point)))
(t ; Disable this backend if no functions can be found.
(setq config t)))))
(defun mono-complete-backend-capf-prefix ()
"Return the prefix at point."
(let ((pos-init (point)))
((< (point) pos-init)
(buffer-substring-no-properties pos-init (point)))
(defun mono-complete-backend-capf-complete (config _prefix cache)
"Complete at point based on CONFIG, PREFIX & CACHE."
;; Return a list of strings or nil.
(let ((result nil))
(let ((comp-data (funcall (plist-get config :complete-fn))))
(when comp-data
(pcase-let ((`(,beg ,end ,collection) comp-data))
(completion-in-region beg end collection
(lambda (&rest x)
;; For now just use the first hit.
;; It's possible to select the shortest or something else.
(unless result
(let ((complete (car x)))
;; May be a string or a symbol.
(when (symbolp complete)
(setq complete (symbol-name complete)))
(setq result
(substring-no-properties complete (- end beg)))))
(when result
(setq result (list result)))
(cons result cache)))
;; ---------------------------------------------------------------------------
;; Public Callback
(defun mono-complete-backend-capf ()
"Wrapper for `completion-at-point' using CONFIG."
:setup #'mono-complete-backend-capf-setup
:prefix #'mono-complete-backend-capf-prefix
:complete #'mono-complete-backend-capf-complete))
(provide 'mono-complete-backend-capf)
;; Local Variables:
;; fill-column: 99
;; indent-tabs-mode: nil
;; End:
;;; mono-complete-backend-capf.el ends here