private: No

;;; vertico.el --- VERTical Interactive COmpletion -*- lexical-binding: t -*-

;; Copyright (C) 2021  Free Software Foundation, Inc.

;; Author: Daniel Mendler <>
;; Maintainer: Daniel Mendler <>
;; Created: 2021
;; Version: 0.13
;; Package-Requires: ((emacs "24.5") (subr-x "26.1.92") (seq "2.22"))
;; Homepage:

;; 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
;; 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 <>.

;;; Commentary:

;; Vertico provides a performant and minimalistic vertical completion UI
;; based on the default completion system. By reusing the built-in
;; facilities, Vertico achieves full compatibility with built-in Emacs
;; completion commands and completion tables.

;;; Code:

(require 'seq)
  (require 'cl-lib)
  (require 'subr-x))

(defgroup vertico nil
  "VERTical Interactive COmpletion."
  :group 'convenience
  :group 'minibuffer
  :prefix "vertico-")

(defcustom vertico-count-format (cons "%-6s " "%s/%s")
  "Format string used for the candidate count."
  :type '(choice (const :tag "No candidate count" nil) (cons string string)))

(defcustom vertico-group-format
  (concat #("    " 0 4 (face vertico-group-separator))
          #(" %s " 0 4 (face vertico-group-title))
          #(" " 0 1 (face vertico-group-separator display (space :align-to right))))
  "Format string used for the group title."
  :type '(choice (const :tag "No group titles" nil) string))

(defcustom vertico-count 10
  "Maximal number of candidates to show."
  :type 'integer)

(defcustom vertico-resize resize-mini-windows
  "How to resize the Vertico minibuffer window.
See `resize-mini-windows' for documentation."
  :type '(choice (const :tag "Fixed" nil)
                 (const :tag "Shrink and grow" t)
                 (const :tag "Grow-only" grow-only)))

(defcustom vertico-cycle nil
  "Enable cycling for `vertico-next' and `vertico-previous'."
  :type 'boolean)

(defcustom vertico-multiline
  (cons #("⤶" 0 1 (face vertico-multiline)) #("…" 0 1 (face vertico-multiline)))
  "Replacements for multiline strings."
  :type '(cons (string :tag "Newline") (string :tag "Truncation")))

(defcustom vertico-sort-function #'vertico-sort-history-length-alpha
  "Default sorting function, which is used if no `display-sort-function' is specified."
  :type `(choice
          (const :tag "No sorting" nil)
          (const :tag "By history, length and alpha" ,#'vertico-sort-history-length-alpha)
          (const :tag "By history and alpha" ,#'vertico-sort-history-alpha)
          (const :tag "By length and alpha" ,#'vertico-sort-length-alpha)
          (const :tag "Alphabetically" ,#'vertico-sort-alpha)
          (function :tag "Custom function")))

(defgroup vertico-faces nil
  "Faces used by Vertico."
  :group 'vertico
  :group 'faces)

(defface vertico-multiline '((t :inherit shadow))
  "Face used to highlight multiline replacement characters.")

(defface vertico-group-title '((t :inherit shadow :slant italic))
  "Face used for the title text of the candidate group headlines.")

(defface vertico-group-separator '((t :inherit shadow :strike-through t))
  "Face used for the separator lines of the candidate groups.")

(defface vertico-current '((t :inherit highlight :extend t))
  "Face used to highlight the currently selected candidate.")

(defvar vertico-map
  (let ((map (make-composed-keymap nil minibuffer-local-map)))
    (define-key map [remap beginning-of-buffer] #'vertico-first)
    (define-key map [remap minibuffer-beginning-of-buffer] #'vertico-first)
    (define-key map [remap end-of-buffer] #'vertico-last)
    (define-key map [remap scroll-down-command] #'vertico-scroll-down)
    (define-key map [remap scroll-up-command] #'vertico-scroll-up)
    (define-key map [remap next-line] #'vertico-next)
    (define-key map [remap previous-line] #'vertico-previous)
    (define-key map [remap next-line-or-history-element] #'vertico-next)
    (define-key map [remap previous-line-or-history-element] #'vertico-previous)
    (define-key map [remap backward-paragraph] #'vertico-previous-group)
    (define-key map [remap forward-paragraph] #'vertico-next-group)
    (define-key map [remap exit-minibuffer] #'vertico-exit)
    (define-key map [remap kill-ring-save] #'vertico-save)
    (define-key map [C-return] #'vertico-exit-input)
    (define-key map "\t" #'vertico-insert)
  "Vertico minibuffer keymap derived from `minibuffer-local-map'.")

(defvar-local vertico--highlight-function #'identity
  "Deferred candidate highlighting function.")

(defvar-local vertico--require-match nil
  "REQUIRE-MATCH parameter of `completing-read'.")

(defvar-local vertico--history-hash nil
  "History hash table.")

(defvar-local vertico--history-base nil
  "Base prefix of `vertico--history-hash'.")

(defvar-local vertico--candidates-ov nil
  "Overlay showing the candidates.")

(defvar-local vertico--count-ov nil
  "Overlay showing the number of candidates.")

(defvar-local vertico--index -1
  "Index of current candidate or negative for prompt selection.")

(defvar-local vertico--input nil
  "Cons of last minibuffer contents and point or t.")

(defvar-local vertico--candidates nil
  "List of candidates.")

(defvar-local vertico--base 0
  "Size of the base string, which is concatenated with the candidate.")

(defvar-local vertico--total 0
  "Length of the candidate list `vertico--candidates'.")

(defvar-local vertico--lock-candidate nil
  "Lock-in current candidate.")

(defvar-local vertico--lock-groups nil
  "Lock-in current group order.")

(defvar-local vertico--all-groups nil
  "List of all group titles.")

(defvar-local vertico--groups nil
  "List of current group titles.")

(defvar-local vertico--default-missing nil
  "Default candidate is missing from candidates list.")

(defun vertico--history-hash ()
  "Recompute history hash table and return it."
  (or vertico--history-hash
      (let* ((index 0)
             (base vertico--history-base)
             (base-size (length base))
             ;; History disabled if `minibuffer-history-variable' eq `t'.
             (hist (and (not (eq minibuffer-history-variable t))
                        (symbol-value minibuffer-history-variable)))
             (hash (make-hash-table :test #'equal :size (length hist))))
        (if (= base-size 0)
            ;; Put history elements into the hash
            (dolist (elem hist)
              (unless (gethash elem hash)
                (puthash elem index hash))
              (setq index (1+ index)))
          ;; Drop base string from history elements, before putting them into the hash
          (dolist (elem hist)
            (when (and (>= (length elem) base-size)
                       (eq t (compare-strings base 0 base-size elem 0 base-size)))
              (setq elem (substring elem base-size))
              (unless (gethash elem hash)
                (puthash elem index hash)))
            (setq index (1+ index))))
        (setq vertico--history-hash hash))))

(defun vertico--length-string< (x y)
  "Sorting predicate which compares X and Y first by length then by `string<'."
  (or (< (length x) (length y))
      (and (= (length x) (length y))
           (string< x y))))

(defun vertico--sort-decorated (list)
  "Sort decorated LIST and remove decorations."
  (setq list (sort list #'car-less-than-car))
  (let ((item list))
    (while item
      (setcar item (cdar item))
      (pop item)))

(defmacro vertico--define-sort (by bsize bindex bpred pred)
  "Generate optimized sorting function.
The function is configured by BY, BSIZE, BINDEX, BPRED and PRED."
  `(defun ,(intern (mapconcat #'symbol-name `(vertico sort ,@by) "-")) (candidates)
     ,(concat "Sort candidates by " (mapconcat #'symbol-name by ", ") ".")
     (let* ((buckets (make-vector ,bsize nil))
            ,@(and (eq (car by) 'history) '((hhash (vertico--history-hash)) (hcands))))
       (dolist (% candidates)
         ,(if (eq (car by) 'history)
              ;; Find recent candidates or fill buckets
              `(if-let (idx (gethash % hhash))
                   (push (cons idx %) hcands)
                 (let ((idx (min ,(1- bsize) ,bindex)))
                   (aset buckets idx (cons % (aref buckets idx)))))
            ;; Fill buckets
            `(let ((idx (min ,(1- bsize) ,bindex)))
               (aset buckets idx (cons % (aref buckets idx))))))
       (nconc ,@(and (eq (car by) 'history) '((vertico--sort-decorated hcands)))
              (cl-mapcan (lambda (bucket) (sort bucket #',bpred))
                         (nbutlast (append buckets nil)))
              ;; Last bucket needs special treatment
              (sort (aref buckets ,(1- bsize)) #',pred)))))

(vertico--define-sort (history length alpha) 32 (length %) string< vertico--length-string<)
(vertico--define-sort (history alpha) 32 (if (eq % "") 0 (/ (aref % 0) 4)) string< string<)
(vertico--define-sort (length alpha) 32 (length %) string< vertico--length-string<)
(vertico--define-sort (alpha) 32 (if (eq % "") 0 (/ (aref % 0) 4)) string< string<)

(defun vertico--affixate (metadata candidates)
  "Annotate CANDIDATES with annotation function specified by METADATA."
  (if-let (aff (or (completion-metadata-get metadata 'affixation-function)
                   (plist-get completion-extra-properties :affixation-function)))
      (funcall aff candidates)
    (if-let (ann (or (completion-metadata-get metadata 'annotation-function)
                     (plist-get completion-extra-properties :annotation-function)))
        (mapcar (lambda (cand)
                  (let ((suffix (or (funcall ann cand) "")))
                    (list cand ""
                          ;; The default completion UI adds the `completions-annotations' face
                          ;; if no other faces are present.
                          (if (text-property-not-all 0 (length suffix) 'face nil suffix)
                            (propertize suffix 'face 'completions-annotations)))))
      (mapcar (lambda (cand) (list cand "" "")) candidates))))

(defun vertico--move-to-front (elem list)
  "Move ELEM to front of LIST."
  (if-let (found (member elem list))
      (let ((head (list (car found))))
        (nconc head (delq (setcar found nil) list)))

;; bug#47711: Deferred highlighting for `completion-all-completions'
;; XXX There is one complication: `completion--twq-all' already adds `completions-common-part'.
;; See below `vertico--candidate'.
(defun vertico--all-completions (&rest args)
  "Compute all completions for ARGS with deferred highlighting."
  (cl-letf* ((orig-pcm (symbol-function #'completion-pcm--hilit-commonality))
             (orig-flex (symbol-function #'completion-flex-all-completions))
             ((symbol-function #'completion-flex-all-completions)
              (lambda (&rest args)
                ;; Unfortunately for flex we have to undo the deferred highlighting, since flex uses
                ;; the completion-score for sorting, which is applied during highlighting.
                (cl-letf (((symbol-function #'completion-pcm--hilit-commonality) orig-pcm))
                  (apply orig-flex args))))
             ;; Defer the following highlighting functions
             (hl #'identity)
             ((symbol-function #'completion-hilit-commonality)
              (lambda (cands prefix &optional base)
                (setq hl (lambda (x) (nconc (completion-hilit-commonality x prefix base) nil)))
                (and cands (nconc cands base))))
             ((symbol-function #'completion-pcm--hilit-commonality)
              (lambda (pattern cands)
                (setq hl (lambda (x)
                           ;; `completion-pcm--hilit-commonality' sometimes throws an internal error
                           ;; for example when entering "/sudo:://u".
                           (condition-case nil
                               (completion-pcm--hilit-commonality pattern x)
                             (t x))))
    ;; Only advise orderless after it has been loaded to avoid load order issues
    (if (and (fboundp 'orderless-highlight-matches) (fboundp 'orderless-pattern-compiler))
        (cl-letf (((symbol-function 'orderless-highlight-matches)
                   (lambda (pattern cands)
                     (let ((regexps (orderless-pattern-compiler pattern)))
                       (setq hl (lambda (x) (orderless-highlight-matches regexps x))))
          (cons (apply #'completion-all-completions args) hl))
      (cons (apply #'completion-all-completions args) hl))))

(defun vertico--sort-function (metadata)
  "Return the sorting function given the completion METADATA."
  (or (completion-metadata-get metadata 'display-sort-function) vertico-sort-function))

(defun vertico--filter-files (files)
  "Filter FILES by `completion-ignored-extensions'."
  (let ((re (concat "\\(?:\\(?:\\`\\|/\\)\\.\\.?/\\|"
                    (regexp-opt completion-ignored-extensions)
    (or (seq-remove (lambda (x) (string-match-p re x)) files) files)))

(defun vertico--recompute-candidates (pt content bounds metadata)
  "Recompute candidates given PT, CONTENT, BOUNDS and METADATA."
  ;; Redisplay the minibuffer such that the input becomes immediately
  ;; visible before the expensive candidate recomputation is performed (Issue #89).
  ;; Do not redisplay during initialization, since this leads to flicker.
  (when (consp vertico--input) (redisplay))
  (pcase-let* ((field (substring content (car bounds) (+ pt (cdr bounds))))
               ;; `minibuffer-completing-file-name' has been obsoleted by the completion category
               (completing-file (eq 'file (completion-metadata-get metadata 'category)))
               (`(,all . ,hl) (vertico--all-completions content
                                                        pt metadata))
               (base (or (when-let (z (last all)) (prog1 (cdr z) (setcdr z nil))) 0))
               (base-str (substring content 0 base))
               (def (or (car-safe minibuffer-default) minibuffer-default))
               (sort (vertico--sort-function metadata))
    ;; Reset the history hash table
    (unless (equal base-str vertico--history-base)
      (setq vertico--history-base base-str vertico--history-hash nil))
    ;; Filter the ignored file extensions. We cannot use modified predicate for this filtering,
    ;; since this breaks the special casing in the `completion-file-name-table' for `file-exists-p'
    ;; and `file-directory-p'.
    (when completing-file
      (setq all (vertico--filter-files all)))
    ;; Sort using the `display-sort-function' or the Vertico sort functions
    (unless (memq sort '(nil identity))
      (setq all (funcall sort all)))
    ;; Move special candidates: "field" appears at the top, before "field/", before default value
    (when (stringp def)
      (setq all (vertico--move-to-front def all)))
    (when (and completing-file (not (string-suffix-p "/" field)))
      (setq all (vertico--move-to-front (concat field "/") all)))
    (setq all (vertico--move-to-front field all))
    (when-let (group-fun (and all (completion-metadata-get metadata 'group-function)))
      (setq groups (vertico--group-by group-fun all) all (car groups)))
    (list base (length all)
          ;; Default value is missing from collection
          (and def (equal content "") (not (member def all)))
          ;; Find position of old candidate in the new list.
          (when vertico--lock-candidate
            (if (< vertico--index 0)
              (seq-position all (nth vertico--index vertico--candidates))))
          all (cadr groups) (or (nth 2 groups) vertico--all-groups) hl)))

(defun vertico--cycle (list n)
  "Rotate LIST to position N."
  (nconc (copy-sequence (nthcdr n list)) (seq-take list n)))

(defun vertico--group-by (fun elems)
  "Group ELEMS by FUN."
  (let ((ht (make-hash-table :test #'equal))
        (titles) (groups))
    ;; Build hash table of groups
    (while elems
      (let* ((title (funcall fun (car elems) nil))
             (group (gethash title ht)))
        (if group
            (setcdr group (setcdr (cdr group) elems)) ;; Append to tail of group
          (puthash title (cons elems elems) ht) ;; New group element (head . tail)
          (push title titles))
        (pop elems)))
    (setq titles (nreverse titles))
    ;; Cycle groups if `vertico--lock-groups' is set
    (when-let (group (and vertico--lock-groups
                          (seq-find (lambda (group) (gethash group ht))
      (setq titles (vertico--cycle titles (seq-position titles group))))
    ;; Build group list
    (dolist (title titles)
      (push (gethash title ht) groups))
    ;; Unlink last tail
    (setcdr (cdar groups) nil)
    (setq groups (nreverse groups))
    ;; Link groups
    (let ((link groups))
      (while (cdr link)
        (setcdr (cdar link) (car (cadr link)))
        (pop link)))
    ;; Check if new groups are found
    (dolist (group vertico--all-groups)
      (remhash group ht))
    (list (caar groups) titles
          (if (hash-table-empty-p ht) vertico--all-groups titles))))

(defun vertico--update-candidates (pt content bounds metadata)
  "Preprocess candidates given PT, CONTENT, BOUNDS and METADATA."
  (pcase ;; bug#38024: Icomplete uses `while-no-input-ignore-events' to repair updating issues
      (let ((while-no-input-ignore-events '(selection-request)))
        (while-no-input (vertico--recompute-candidates pt content bounds metadata)))
    (`nil (abort-recursive-edit))
    (`(,base ,total ,def-missing ,index ,candidates ,groups ,all-groups ,hl)
     (setq vertico--input (cons content pt)
           vertico--index index
           vertico--base base
           vertico--total total
           vertico--highlight-function hl
           vertico--groups groups
           vertico--all-groups all-groups
           vertico--candidates candidates
           vertico--default-missing def-missing)
     ;; If the current index is nil, compute new index. Select the prompt:
     ;; * If there are no candidates
     ;; * If the default is missing from the candidate list.
     ;; * For matching content, as long as the full content after the boundary is empty,
     ;;   including content after point.
     (unless vertico--index
       (setq vertico--lock-candidate nil
             (if (or vertico--default-missing
                     (= 0 vertico--total)
                     (and (= (car bounds) (length content))
                          (test-completion content minibuffer-completion-table
                 -1 0))))))

(defun vertico--flatten-string (prop str)
  "Flatten STR with display or invisible PROP."
  (let ((end (length str)) (pos 0) (chunks))
    (while (< pos end)
      (let ((next (next-single-property-change pos prop str end))
            (val (get-text-property pos prop str)))
         ((and val (eq prop 'display) (stringp val))
          (push val chunks))
         ((not (and val (eq prop 'invisible)))
          (push (substring str pos next) chunks)))
        (setq pos next)))
    (apply #'concat (nreverse chunks))))

(defun vertico--truncate-multiline (cand max-width)
  "Truncate multiline CAND to MAX-WIDTH."
   (thread-last cand
     (replace-regexp-in-string "[\t ]+" " ")
     (replace-regexp-in-string "[\t\n ]*\n[\t\n ]*" (car vertico-multiline))
     (replace-regexp-in-string "\\`[\t\n ]+\\|[\t\n ]+\\'" ""))
   max-width 0 nil (cdr vertico-multiline)))

(defun vertico--format-candidate (cand prefix suffix index _start)
  "Format CAND given PREFIX, SUFFIX and INDEX."
  (setq cand (concat prefix cand suffix "\n")
        cand (vertico--flatten-string 'invisible (vertico--flatten-string 'display cand)))
  (when (= index vertico--index)
    (add-face-text-property 0 (length cand) 'vertico-current 'append cand))

(defun vertico--arrange-candidates (metadata)
  "Arrange candidates given the current METADATA."
  (let ((curr-line 0) (lines))
    ;; Compute group titles
    (let* ((index (min (max 0 (- vertico--index (/ vertico-count 2) (1- (mod vertico-count 2))))
                       (max 0 (- vertico--total vertico-count))))
           (group-fun (completion-metadata-get metadata 'group-function))
           (group-format (and group-fun vertico-group-format (concat vertico-group-format "\n")))
            (thread-last (seq-subseq vertico--candidates index
                                     (min (+ index vertico-count) vertico--total))
              (funcall vertico--highlight-function)
              (vertico--affixate metadata))))
      (dolist (cand candidates)
        (let ((str (car cand)))
          (when-let (new-title (and group-format (funcall group-fun str nil)))
            (unless (equal title new-title)
              (setq title new-title)
              ;; Restore group title highlighting for prefix titles
              (when (string-prefix-p title str)
                (setq title (substring
                             (car (funcall
                                   ;; Remove all properties from the title
                                   (list (propertize str 'face 'vertico-group-title))))
                             0 (length title)))
                 0 (length title) '(face completions-first-difference) title))
              (push (format group-format title) lines))
            (setcar cand (funcall group-fun str 'transform))))
        (when (= index vertico--index)
          (setq curr-line (length lines)))
        (push (cons index cand) lines)
        (setq index (1+ index))))
    ;; Drop excess lines
    (setq lines (nreverse lines))
    (let ((count (length lines)))
      (while (> count vertico-count)
        (if (< curr-line (/ count 2))
            (nbutlast lines)
          (setq curr-line (1- curr-line) lines (cdr lines)))
        (setq count (1- count))))
    ;; Format candidates
    (let ((max-width (- (window-width) 4))
          (line lines) (start))
      (while line
        (pcase (car line)
          (`(,index ,cand ,prefix ,suffix)
           (setq start (or start index))
           (when (string-match-p "\n" cand)
             (setq cand (vertico--truncate-multiline cand max-width)))
           (setcar line (vertico--format-candidate cand prefix suffix index start))))
        (pop line)))

(defun vertico--display-candidates (lines)
  "Update candidates overlay `vertico--candidates-ov' with LINES."
  (move-overlay vertico--candidates-ov (point-max) (point-max))
  (overlay-put vertico--candidates-ov 'after-string
               (apply #'concat #(" " 0 1 (cursor t)) (and lines "\n") lines))
  (vertico--resize-window (length lines)))

(defun vertico--resize-window (height)
  "Resize active minibuffer window to HEIGHT."
  (setq-local truncate-lines (< (point) (* 0.8 (window-width))))
  (unless (frame-root-window-p (active-minibuffer-window))
    (unless vertico-resize
      (setq height (max height vertico-count)))
    (let* ((window-resize-pixelwise t)
           (dp (- (max (cdr (window-text-pixel-size))
                       (* (default-line-height) (1+ height)))
      (when (or (and (> dp 0) (/= height 0))
                (and (< dp 0) (eq vertico-resize t)))
	(window-resize nil dp nil nil 'pixelwise)))))

(defun vertico--format-count ()
  "Format the count string."
  (format (car vertico-count-format)
          (format (cdr vertico-count-format)
                  (cond ((>= vertico--index 0) (1+ vertico--index))
                        ((vertico--allow-prompt-selection-p) "*")
                        (t "!"))

(defun vertico--display-count ()
  "Update count overlay `vertico--count-ov'."
  (when vertico--count-ov
    (move-overlay vertico--count-ov (point-min) (point-min))
    ;; Set priority for compatibility with `minibuffer-depth-indicate-mode'
    (overlay-put vertico--count-ov 'priority 1)
    (overlay-put vertico--count-ov 'before-string (vertico--format-count))))

(defun vertico--prompt-selection ()
  "Highlight the prompt if selected."
  (let ((inhibit-modification-hooks t))
    (if (and (< vertico--index 0) (vertico--allow-prompt-selection-p))
        (add-face-text-property (minibuffer-prompt-end) (point-max) 'vertico-current 'append)
      (remove-text-properties (minibuffer-prompt-end) (point-max) '(face vertico-current)))))

(defun vertico--exhibit ()
  "Exhibit completion UI."
  (let* ((non-essential t)
         (buffer-undo-list t) ; Overlays affect point position and undo list!
         (pt (max 0 (- (point) (minibuffer-prompt-end))))
         (content (minibuffer-contents-no-properties))
         (before (substring content 0 pt))
         (after (substring content pt))
         (metadata (completion-metadata before
         ;; bug#47678: `completion-boundaries` fails for `partial-completion`
         ;; if the cursor is moved between the slashes of "~//".
         ;; See also marginalia.el which has the same issue.
         (bounds (or (condition-case nil
                         (completion-boundaries before
                       (t (cons 0 (length after)))))))
    (unless (or (input-pending-p) (equal vertico--input (cons content pt)))
      (vertico--update-candidates pt content bounds metadata))
    (vertico--display-candidates (vertico--arrange-candidates metadata))))

(defun vertico--allow-prompt-selection-p ()
  "Return t if prompt can be selected."
  (or vertico--default-missing
      (memq vertico--require-match '(nil confirm confirm-after-completion))))

(defun vertico--goto (index)
  "Go to candidate with INDEX."
  (let ((prompt (vertico--allow-prompt-selection-p)))
    (setq vertico--index
          (max (if (or prompt (= 0 vertico--total)) -1 0)
               (min index (1- vertico--total)))
          vertico--lock-candidate (or (>= vertico--index 0) prompt))))

(defun vertico-first ()
  "Go to first candidate, or to the prompt when the first candidate is selected."
  (vertico--goto (if (> vertico--index 0) 0 -1)))

(defun vertico-last ()
  "Go to last candidate."
  (vertico--goto (1- vertico--total)))

(defun vertico-scroll-down (&optional n)
  "Go back by N pages."
  (interactive "p")
  (vertico--goto (max 0 (- vertico--index (* (or n 1) vertico-count)))))

(defun vertico-scroll-up (&optional n)
  "Go forward by N pages."
  (interactive "p")
  (vertico-scroll-down (- (or n 1))))

(defun vertico-next (&optional n)
  "Go forward N candidates."
  (interactive "p")
  (let ((index (+ vertico--index (or n 1))))
      ((not vertico-cycle) index)
      ((= vertico--total 0) -1)
      ((vertico--allow-prompt-selection-p) (1- (mod (1+ index) (1+ vertico--total))))
      (t (mod index vertico--total))))))

(defun vertico-previous (&optional n)
  "Go backward N candidates."
  (interactive "p")
  (vertico-next (- (or n 1))))

(defun vertico--match-p (input)
  "Return t if INPUT is a valid match."
  (or (memq vertico--require-match '(nil confirm-after-completion))
      (equal "" input) ;; The questionable null completion
      (test-completion input
      (if (eq vertico--require-match 'confirm)
          (eq (ignore-errors (read-char "Confirm")) 13)
        (and (message "Match required") nil))))

(defun vertico-exit (&optional arg)
  "Exit minibuffer with current candidate or input if prefix ARG is given."
  (interactive "P")
  (unless arg (vertico-insert))
  (when (vertico--match-p (minibuffer-contents-no-properties))

(defun vertico-next-group (&optional n)
  "Cycle N groups forward.
When the prefix argument is 0, the group order is reset."
  (interactive "p")
  (when (cdr vertico--groups)
    (if (eq n 0)
        (setq vertico--groups nil
              vertico--all-groups nil
              vertico--lock-groups nil)
      (setq vertico--groups
            (vertico--cycle vertico--groups
                            (let ((len (length vertico--groups)))
                              (- len (mod (- (or n 1)) len))))
            (vertico--cycle vertico--all-groups
                            (seq-position vertico--all-groups
                                          (car vertico--groups)))
            vertico--lock-groups t))
    (setq vertico--lock-candidate nil
          vertico--input nil)))

(defun vertico-previous-group (&optional n)
  "Cycle N groups backward.
When the prefix argument is 0, the group order is reset."
  (interactive "p")
  (vertico-next-group (- (or n 1))))

(defun vertico-exit-input ()
  "Exit minibuffer with input."
  (vertico-exit t))

(defun vertico-save ()
  "Save current candidate to kill ring."
  (if (or (use-region-p) (not transient-mark-mode))
      (call-interactively #'kill-ring-save)
    (kill-new (vertico--candidate))))

(defun vertico-insert ()
  "Insert current candidate in minibuffer."
  ;; XXX There is a small bug here, depending on interpretation. When
  ;; completing "~/emacs/master/li|/calc" where "|" is the cursor,
  ;; then the returned candidate only includes the prefix
  ;; "~/emacs/master/lisp/", but not the suffix "/calc". Default
  ;; completion has the same problem when selecting in the
  ;; *Completions* buffer. See bug#48356.
  (when-let (cand (and (>= vertico--index 0) (vertico--candidate)))
    (insert cand)))

(defun vertico--candidate (&optional hl)
  "Return current candidate string with optional highlighting if HL is non-nil."
  (let ((content (minibuffer-contents)))
    (if (>= vertico--index 0)
        (let ((cand (nth vertico--index vertico--candidates)))
          ;;; XXX Drop the completions-common-part face which is added by `completion--twq-all'.
          ;; This is a hack in Emacs and should better be fixed in Emacs itself, the corresponding
          ;; code is already marked with a FIXME. Should this be reported as a bug?
          (remove-text-properties 0 (length cand) '(face completions-common-part) cand)
          (concat (substring content 0 vertico--base)
                  (if hl (car (funcall vertico--highlight-function (list cand))) cand)))
      ;; Remove prompt face
      (remove-text-properties 0 (length content) '(face vertico-current) content)

(defun vertico--setup (require-match)
  "Setup completion UI."
  (setq vertico--input t
        vertico--candidates-ov (make-overlay (point-max) (point-max) nil t t)
        vertico--count-ov (and vertico-count-format
                               (make-overlay (point-min) (point-min) nil t t)))
  (setq-local max-mini-window-height 1.0)
  (setq-local truncate-lines t)
  (setq-local completion-auto-help nil)
  (setq-local completion-show-inline-help nil)
  (setq-local vertico--require-match require-match)
  (use-local-map vertico-map)
  ;; Use -90 to ensure that the exhibit hook runs early such that the
  ;; candidates are available for Consult preview. It works, but besides
  ;; that I'dont have a specific reason for this particular value.
  (add-hook 'post-command-hook #'vertico--exhibit -90 'local))

(defun vertico--advice (orig &rest args)
  "Advice for ORIG completion function, receiving ARGS."
      #'(lambda () (vertico--setup (nth 3 args)))
    ;; XXX When using automatic minibuffer resizing in a graphical
    ;; session with truncate-lines enabled there are often bugs which
    ;; cause the buffer to be resized to a single line bug#46718.
    ;; However in non-graphical sessions disabling automatic
    ;; minibuffer resizing can have the same effect. Further, it is
    ;; insufficient to `setq-local' resize-mini-windows in
    ;; `vertico--setup' on GNU Emacs 24.5.1 for unknown reasons.
    (let ((resize-mini-windows (unless (display-graphic-p) 'grow-only)))
      (apply orig args))))

(define-minor-mode vertico-mode
  "VERTical Interactive COmpletion."
  :global t
  (if vertico-mode
        (advice-add #'completing-read-default :around #'vertico--advice)
        (advice-add #'completing-read-multiple :around #'vertico--advice))
    (advice-remove #'completing-read-default #'vertico--advice)
    (advice-remove #'completing-read-multiple #'vertico--advice)))

;; Emacs 28: Do not show Vertico commands in M-X
(dolist (sym '(vertico-next vertico-next-group vertico-previous vertico-previous-group
                            vertico-scroll-down vertico-scroll-up vertico-exit vertico-insert
                            vertico-exit-input vertico-save vertico-first vertico-last))
  (put sym 'completion-predicate #'vertico--command-p))

(defun vertico--command-p (_sym buffer)
  "Return non-nil if Vertico is active in BUFFER."
  (buffer-local-value 'vertico--input buffer))

(provide 'vertico)
;;; vertico.el ends here