summaryrefslogtreecommitdiff
path: root/extensions/corfu-history.el
blob: b64ae8c71d696f79e471478367683dbad00cdcba (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
;;; corfu-history.el --- Sorting by history for Corfu -*- lexical-binding: t -*-

;; Copyright (C) 2022  Free Software Foundation, Inc.

;; Author: Daniel Mendler <mail@daniel-mendler.de>
;; Maintainer: Daniel Mendler <mail@daniel-mendler.de>
;; Created: 2022
;; Version: 0.1
;; Package-Requires: ((emacs "27.1") (corfu "0.32"))
;; Homepage: https://github.com/minad/corfu

;; This file is part of GNU Emacs.

;; 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 <https://www.gnu.org/licenses/>.

;;; Commentary:

;; Enable `corfu-history-mode' to sort candidates by their history
;; position. Maintain a list of recently selected candidates. In order
;; to save the history across Emacs sessions, enable `savehist-mode' and
;; add `corfu-history' to `savehist-additional-variables'.
;;
;; (corfu-history-mode 1)
;; (savehist-mode 1)
;; (add-to-list 'savehist-additional-variables 'corfu-history)

;;; Code:

(require 'corfu)
(eval-when-compile
  (require 'cl-lib))

(defcustom corfu-history-length nil
  "Corfu history length."
  :type '(choice (const nil) integer)
  :group 'corfu)

(defvar corfu-history--hash nil
  "Hash table of Corfu candidates.")

(defvar corfu-history nil
  "History of Corfu candidates.")

(defun corfu-history--sort-predicate (x y)
  "Sorting predicate which compares X and Y."
  (or (< (cdr x) (cdr y))
      (and (= (cdr x) (cdr y))
           (corfu--length-string< (car x) (car y)))))

(defun corfu-history--sort (candidates)
  "Sort CANDIDATES by history."
  (unless corfu-history--hash
    (setq corfu-history--hash (make-hash-table :test #'equal :size (length corfu-history)))
    (cl-loop for elem in corfu-history for index from 0 do
             (unless (gethash elem corfu-history--hash)
               (puthash elem index corfu-history--hash))))
  ;; Decorate each candidate with (index<<13) + length. This way we sort first by index and then by
  ;; length. We assume that the candidates are shorter than 2**13 characters and that the history is
  ;; shorter than 2**16 entries.
  (cl-loop for cand on candidates do
           (setcar cand (cons (car cand)
                              (+ (ash (gethash (car cand) corfu-history--hash #xFFFF) 13)
                                 (length (car cand))))))
  (setq candidates (sort candidates #'corfu-history--sort-predicate))
  (cl-loop for cand on candidates do (setcar cand (caar cand)))
  candidates)

(defun corfu-history--insert (&rest _)
  "Advice for `corfu--insert'."
  (when (>= corfu--index 0)
    (add-to-history 'corfu-history
                    (substring-no-properties
                     (nth corfu--index corfu--candidates))
                    corfu-history-length)
    (setq corfu-history--hash nil)))

;;;###autoload
(define-minor-mode corfu-history-mode
  "Update Corfu history and sort completions by history."
  :global t
  :group 'corfu
  (cond
   (corfu-history-mode
    (setq corfu-sort-function #'corfu-history--sort)
    (advice-add #'corfu--insert :before #'corfu-history--insert))
   (t
    (setq corfu-sort-function #'corfu-sort-length-alpha)
    (advice-remove #'corfu--insert #'corfu-history--insert))))

(provide 'corfu-history)
;;; corfu-history.el ends here