;;; helm-lib.el --- Helm routines. -*- lexical-binding: t -*-

;; Copyright (C) 2015 ~ 2019  Thierry Volpiatto <thierry.volpiatto@gmail.com>

;; Author: Thierry Volpiatto <thierry.volpiatto@gmail.com>
;; URL: http://github.com/emacs-helm/helm

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

;;; Commentary:
;; All helm functions that don't require specific helm code should go here.

;;; Code:

(require 'cl-lib)

(declare-function wdired-change-to-dired-mode "wdired.el")
(declare-function wdired-do-symlink-changes "wdired.el")
(declare-function wdired-do-perm-changes "wdired.el")
(declare-function wdired-get-filename "wdired.el")
(declare-function wdired-do-renames "wdired.el")
(declare-function wdired-flag-for-deletion "wdired.el")
(declare-function wdired-normalize-filename "wdired.el")
(declare-function dired-mark-remembered "dired.el")
(declare-function dired-log-summary "dired.el")
(declare-function dired-current-directory "dired.el")
(declare-function ansi-color--find-face "ansi-color.el")
(declare-function ansi-color-apply-sequence "ansi-color.el")
(declare-function helm-get-sources "helm.el")
(declare-function helm-marked-candidates "helm.el")
(declare-function helm-follow-mode-p "helm.el")
(declare-function helm-attr "helm.el")
(declare-function helm-attrset "helm.el")
(declare-function org-open-at-point "org.el")
(declare-function org-content "org.el")
(declare-function org-mark-ring-goto "org.el")
(declare-function org-mark-ring-push "org.el")
(declare-function helm-interpret-value "helm.el")
(declare-function helm-get-current-source "helm.el")
(declare-function helm-source--cl--print-table "helm-source.el")
(defvar helm-sources)
(defvar helm-initial-frame)
(defvar helm-current-position)
(defvar wdired-old-marks)
(defvar wdired-keep-marker-rename)
(defvar wdired-allow-to-change-permissions)
(defvar wdired-allow-to-redirect-links)
(defvar helm-persistent-action-display-window)
(defvar completion-flex-nospace)

;;; User vars.
;;
(defcustom helm-file-globstar t
  "Same as globstar bash shopt option.
When non--nil a pattern beginning with two stars will expand recursively.
Directories expansion is not supported yet."
  :group 'helm
  :type 'boolean)

(defcustom helm-yank-text-at-point-function nil
  "The function used to forward point with `helm-yank-text-at-point'.
With a nil value, fallback to default `forward-word'.
The function should take one arg, an integer like `forward-word'.
NOTE: Using `forward-symbol' here is not very useful as it is already
provided by \\<helm-map>\\[next-history-element]."
  :type  'function
  :group 'helm)

(defcustom helm-scroll-amount nil
  "Scroll amount when scrolling other window in a helm session.
It is used by `helm-scroll-other-window'
and `helm-scroll-other-window-down'.

If you prefer scrolling line by line, set this value to 1."
  :group 'helm
  :type 'integer)

(defcustom helm-help-full-frame t
  "Display help window in full frame when non nil.

Even when `nil' probably the same result (full frame)
can be reach by tweaking `display-buffer-alist' but it is
much more convenient to use a simple boolean value here."
  :type 'boolean
  :group 'helm-help)

(defvar helm-ff--boring-regexp nil)
(defun helm-ff--setup-boring-regex (var val)
  (set var val)
  (setq helm-ff--boring-regexp
          (cl-loop with last = (car (last val))
                   for r in (butlast val)
                   if (string-match "\\$\\'" r)
                   concat (concat r "\\|") into result
                   else concat (concat r "$\\|") into result
                   finally return
                   (concat result last
                           (if (string-match "\\$\\'" last) "" "$")))))

(defcustom helm-boring-file-regexp-list
  (mapcar (lambda (f)
            (let ((rgx (regexp-quote f)))
              (if (string-match-p "[^/]$" f)
                  ;; files: e.g .o => \\.o$
                  (concat rgx "$")
                ;; directories: e.g .git/ => \.git\\(/\\|$\\)
                (concat (substring rgx 0 -1) "\\(/\\|$\\)"))))
          completion-ignored-extensions)
  "A list of regexps matching boring files.

This list is build by default on `completion-ignored-extensions'.
The directory names should end with \"/?\" e.g. \"\\.git/?\" and the
file names should end with \"$\" e.g. \"\\.o$\".

These regexps may be used to match the entire path, not just the file
name, so for example to ignore files with a prefix \".bak.\", use
\"\\.bak\\..*$\" as the regexp.

NOTE: When modifying this, be sure to use customize interface or the
customize functions e.g. `customize-set-variable' and NOT `setq'."
  :group 'helm-files
  :type  '(repeat (choice regexp))
  :set 'helm-ff--setup-boring-regex)

(defcustom helm-describe-function-function 'describe-function
  "Function used to describe functions in Helm."
  :group 'helm-elisp
  :type 'function)

(defcustom helm-describe-variable-function 'describe-variable
  "Function used to describe variables in Helm."
  :group 'helm-elisp
  :type 'function)


;;; Internal vars
;;
(defvar helm-yank-point nil)
(defvar helm-pattern ""
  "The input pattern used to update the helm buffer.")
(defvar helm-buffer "*helm*"
  "Buffer showing completions.")
(defvar helm-current-buffer nil
  "Current buffer when `helm' is invoked.")
(defvar helm-suspend-update-flag nil)
(defvar helm-action-buffer "*helm action*"
  "Buffer showing actions.")


;;; Compatibility
;;
(defun helm-add-face-text-properties (beg end face &optional append object)
  "Add the face property to the text from START to END.
It is a compatibility function which behave exactly like
`add-face-text-property' if available otherwise like `add-text-properties'.
When only `add-text-properties' is available APPEND is ignored."
  (if (fboundp 'add-face-text-property)
      (add-face-text-property beg end face append object)
      (add-text-properties beg end `(face ,face) object)))

;; Override `wdired-finish-edit'.
;; Fix emacs bug in `wdired-finish-edit' where
;; Wdired is not handling the case where `dired-directory' is a cons
;; cell instead of a string.
(defun helm--advice-wdired-finish-edit ()
  (interactive)
  (wdired-change-to-dired-mode)
  (let ((changes nil)
	(errors 0)
	files-deleted
	files-renamed
	some-file-names-unchanged
	file-old file-new tmp-value)
    (save-excursion
      (when (and wdired-allow-to-redirect-links
		 (fboundp 'make-symbolic-link))
	(setq tmp-value (wdired-do-symlink-changes))
	(setq errors (cdr tmp-value))
	(setq changes (car tmp-value)))
      (when (and wdired-allow-to-change-permissions
		 (boundp 'wdired-col-perm)) ; could have been changed
	(setq tmp-value (wdired-do-perm-changes))
	(setq errors (+ errors (cdr tmp-value)))
	(setq changes (or changes (car tmp-value))))
      (goto-char (point-max))
      (while (not (bobp))
	(setq file-old (wdired-get-filename nil t))
	(when file-old
	  (setq file-new (wdired-get-filename))
          (if (equal file-new file-old)
	      (setq some-file-names-unchanged t)
            (setq changes t)
            (if (not file-new)		;empty filename!
                (push file-old files-deleted)
	      (when wdired-keep-marker-rename
		(let ((mark (cond ((integerp wdired-keep-marker-rename)
				   wdired-keep-marker-rename)
				  (wdired-keep-marker-rename
				   (cdr (assoc file-old wdired-old-marks)))
				  (t nil))))
		  (when mark
		    (push (cons (substitute-in-file-name file-new) mark)
			  wdired-old-marks))))
              (push (cons file-old (substitute-in-file-name file-new))
                    files-renamed))))
	(forward-line -1)))
    (when files-renamed
      (setq errors (+ errors (wdired-do-renames files-renamed))))
    (if changes
	(progn
	  ;; If we are displaying a single file (rather than the
	  ;; contents of a directory), change dired-directory if that
	  ;; file was renamed.  (This ought to be generalized to
	  ;; handle the multiple files case, but that's less trivial)
          ;; fixit [1].
	  (cond ((and (stringp dired-directory)
                      (not (file-directory-p dired-directory))
                      (null some-file-names-unchanged)
                      (= (length files-renamed) 1))
                 (setq dired-directory (cdr (car files-renamed))))
                ;; Fix [1] i.e dired buffers created with
                ;; (dired '(foo f1 f2 f3)).
                ((and (consp dired-directory)
                      (cdr dired-directory)
                      files-renamed)
                 (setcdr dired-directory
                         ;; Replace in `dired-directory' files that have
                         ;; been modified with their new name keeping
                         ;; the ones that are unmodified at the same place.
                         (cl-loop with old-to-rename = (mapcar 'car files-renamed)
                                  for f in (cdr dired-directory)
                                  if (member f old-to-rename)
                                  collect (assoc-default f files-renamed)
                                  else collect f))))
	  ;; Re-sort the buffer if all went well.
	  (unless (> errors 0) (revert-buffer))
	  (let ((inhibit-read-only t))
	    (dired-mark-remembered wdired-old-marks)))
      (let ((inhibit-read-only t))
	(remove-text-properties (point-min) (point-max)
				'(old-name nil end-name nil old-link nil
					   end-link nil end-perm nil
					   old-perm nil perm-changed nil))
	(message "(No changes to be performed)")))
    (when files-deleted
      (wdired-flag-for-deletion files-deleted))
    (when (> errors 0)
      (dired-log-summary (format "%d rename actions failed" errors) nil)))
  (set-buffer-modified-p nil)
  (setq buffer-undo-list nil))

;; Override `wdired-get-filename'.
;; Fix emacs bug in `wdired-get-filename' which returns the current
;; directory concatened with the filename i.e
;; "/home/you//home/you/foo" when filename is absolute in dired
;; buffer.
;; In consequence Wdired try to rename files even when buffer have
;; been modified and corrected, e.g delete one char and replace it so
;; that no change to file is done.
;; This also lead to ask confirmation for every files even when not
;; modified and when `wdired-use-interactive-rename' is nil.
(defun helm--advice-wdired-get-filename (&optional no-dir old)
  ;; FIXME: Use dired-get-filename's new properties.
  (let (beg end file)
    (save-excursion
      (setq end (line-end-position))
      (beginning-of-line)
      (setq beg (next-single-property-change (point) 'old-name nil end))
      (unless (eq beg end)
	(if old
	    (setq file (get-text-property beg 'old-name))
	  ;; In the following form changed `(1+ beg)' to `beg' so that
	  ;; the filename end is found even when the filename is empty.
	  ;; Fixes error and spurious newlines when marking files for
	  ;; deletion.
	  (setq end (next-single-property-change beg 'end-name))
	  (setq file (buffer-substring-no-properties (1+ beg) end)))
	;; Don't unquote the old name, it wasn't quoted in the first place
        (and file (setq file (condition-case _err
                                 ;; emacs-25+
                                 (apply #'wdired-normalize-filename
                                        (list file (not old)))
                               (wrong-number-of-arguments
                                ;; emacs-24
                                (wdired-normalize-filename file))))))
      (if (or no-dir old (and file (file-name-absolute-p file)))
	  file
	(and file (> (length file) 0)
             (expand-file-name file (dired-current-directory)))))))

;;; Override `push-mark'
;;
;; Fix duplicates in `mark-ring' and `global-mark-ring' and update
;; buffers in `global-mark-ring' to recentest mark.
(defun helm--advice-push-mark (&optional location nomsg activate)
  (unless (null (mark t))
    (let ((marker (copy-marker (mark-marker))))
      (setq mark-ring (cons marker (delete marker mark-ring))))
    (when (> (length mark-ring) mark-ring-max)
      ;; Move marker to nowhere.
      (set-marker (car (nthcdr mark-ring-max mark-ring)) nil)
      (setcdr (nthcdr (1- mark-ring-max) mark-ring) nil)))
  (set-marker (mark-marker) (or location (point)) (current-buffer))
  ;; Now push the mark on the global mark ring.
  (setq global-mark-ring (cons (copy-marker (mark-marker))
                               ;; Avoid having multiple entries
                               ;; for same buffer in `global-mark-ring'.
                               (cl-loop with mb = (current-buffer)
                                        for m in global-mark-ring
                                        for nmb = (marker-buffer m)
                                        unless (eq mb nmb)
                                        collect m)))
  (when (> (length global-mark-ring) global-mark-ring-max)
    (set-marker (car (nthcdr global-mark-ring-max global-mark-ring)) nil)
    (setcdr (nthcdr (1- global-mark-ring-max) global-mark-ring) nil))
  (or nomsg executing-kbd-macro (> (minibuffer-depth) 0)
      (message "Mark set"))
  (when (or activate (not transient-mark-mode))
    (set-mark (mark t)))
  nil)

(defcustom helm-advice-push-mark t
  "Override `push-mark' with a version avoiding duplicates when non nil."
  :group 'helm
  :type 'boolean
  :set (lambda (var val)
         (set var val)
         (if val
             (advice-add 'push-mark :override #'helm--advice-push-mark)
           (advice-remove 'push-mark #'helm--advice-push-mark))))

;; This the version of Emacs-27 written by Stefan
(defun helm-advice--ffap-read-file-or-url (prompt guess)
  (or guess (setq guess default-directory))
  (if (ffap-url-p guess)
      (read-string prompt guess nil nil t)
    (unless (ffap-file-remote-p guess)
      (setq guess (abbreviate-file-name (expand-file-name guess))))
    (read-file-name prompt (file-name-directory guess) nil nil
                    (file-name-nondirectory guess))))

;;; Macros helper.
;;
(defmacro helm-with-gensyms (symbols &rest body)
  "Bind the SYMBOLS to fresh uninterned symbols and eval BODY."
  (declare (indent 1))
  `(let ,(mapcar (lambda (s)
                   ;; Use cl-gensym here instead of make-symbol
                   ;; to ensure a symbol that have a live that go
                   ;; beyond the live of its macro have different name.
                   ;; i.e symbols created with `with-helm-temp-hook'
                   ;; should have random names.
                   `(,s (cl-gensym (symbol-name ',s))))
                 symbols)
     ,@body))

;;; Command loop helper
;;
(defun helm-this-command ()
  "Returns the actual command in action.
Like `this-command' but return the real command,
and not `exit-minibuffer' or other unwanted functions."
  (cl-loop with bl = '(helm-maybe-exit-minibuffer
                       helm-confirm-and-exit-minibuffer
                       helm-exit-minibuffer
                       exit-minibuffer)
           for count from 1 to 50
           for btf = (backtrace-frame count)
           for fn = (cl-second btf)
           if (and
               ;; In some case we may have in the way an
               ;; advice compiled resulting in byte-code,
               ;; ignore it (Issue #691).
               (symbolp fn)
               (commandp fn)
               (not (memq fn bl)))
           return fn
           else
           if (and (eq fn 'call-interactively)
                   (> (length btf) 2))
           return (cadr (cdr btf))))


;;; Iterators
;;
(cl-defmacro helm-position (item seq &key test all)
  "A simple and faster replacement of CL `position'.

Returns ITEM first occurence position found in SEQ.
When SEQ is a string, ITEM have to be specified as a char.
Argument TEST when unspecified default to `eq'.
When argument ALL is non--nil return a list of all ITEM positions
found in SEQ."
  (let ((key (if (stringp seq) 'across 'in)))
    `(cl-loop with deftest = 'eq
              for c ,key ,seq
              for index from 0
              when (funcall (or ,test deftest) c ,item)
              if ,all collect index into ls
              else return index
              finally return ls)))

(defun helm-iter-list (seq)
  "Return an iterator object from SEQ."
  (let ((lis seq))
    (lambda ()
      (let ((elm (car lis)))
        (setq lis (cdr lis))
        elm))))

(defun helm-iter-circular (seq)
  "Infinite iteration on SEQ."
  (let ((lis seq))
     (lambda ()
       (let ((elm (car lis)))
         (setq lis (pcase lis (`(,_ . ,ll) (or ll seq))))
         elm))))

(cl-defun helm-iter-sub-next-circular (seq elm &key (test 'eq))
  "Infinite iteration of SEQ starting at ELM."
  (let* ((pos      (1+ (helm-position elm seq :test test)))
         (sub      (append (nthcdr pos seq) (cl-subseq seq 0 pos)))
         (iterator (helm-iter-circular sub)))
    (lambda ()
      (helm-iter-next iterator))))

(defun helm-iter-next (iterator)
  "Return next elm of ITERATOR."
  (and iterator (funcall iterator)))


;;; Anaphoric macros.
;;
(defmacro helm-aif (test-form then-form &rest else-forms)
  "Anaphoric version of `if'.
Like `if' but set the result of TEST-FORM in a temporary variable called `it'.
THEN-FORM and ELSE-FORMS are then excuted just like in `if'."
  (declare (indent 2) (debug t))
  `(let ((it ,test-form))
     (if it ,then-form ,@else-forms)))

(defmacro helm-awhile (sexp &rest body)
  "Anaphoric version of `while'.
Same usage as `while' except that SEXP is bound to
a temporary variable called `it' at each turn.
An implicit nil block is bound to the loop so usage
of `cl-return' is possible to exit the loop."
  (declare (indent 1) (debug t))
  (helm-with-gensyms (flag)
    `(let ((,flag t))
       (cl-block nil
         (while ,flag
           (helm-aif ,sexp
               (progn ,@body)
             (setq ,flag nil)))))))

(defmacro helm-acond (&rest clauses)
  "Anaphoric version of `cond'.
In each clause of CLAUSES, the result of the car of clause
is stored in a temporary variable called `it' and usable in the cdr
of this same clause.  Each `it' variable is independent of its clause.
The usage is the same as `cond'."
  (declare (debug cond))
  (unless (null clauses)
    (helm-with-gensyms (sym)
      (let ((clause1 (car clauses)))
        `(let ((,sym ,(car clause1)))
           (helm-aif ,sym
               (if (cdr ',clause1)
                   (progn ,@(cdr clause1))
                 it)
             (helm-acond ,@(cdr clauses))))))))

(defmacro helm-aand (&rest conditions)
  "Anaphoric version of `and'.
Each condition is bound to a temporary variable called `it' which is
usable in next condition."
  (declare (debug (&rest form)))
  (cond ((null conditions) t)
        ((null (cdr conditions)) (car conditions))
        (t `(helm-aif ,(car conditions)
                (helm-aand ,@(cdr conditions))))))

(defmacro helm-acase (expr &rest clauses)
  "A simple anaphoric `cl-case' implementation handling strings.
EXPR is bound to a temporary variable called `it' which is usable in
CLAUSES to refer to EXPR.
NOTE: Duplicate keys in CLAUSES are deliberately not handled.

\(fn EXPR (KEYLIST BODY...)...)"
  (declare (indent 1) (debug (form &rest (sexp body))))
  (unless (null clauses)
    (let ((clause1 (car clauses)))
      `(let ((key ',(car clause1))
             (it ,expr))
         (if (or (equal it key)
                 (and (listp key) (member it key))
                 (eq key t))
             (progn ,@(cdr clause1))
           (helm-acase it ,@(cdr clauses)))))))

;;; Fuzzy matching routines
;;
(defsubst helm--mapconcat-pattern (pattern)
  "Transform string PATTERN in regexp for further fuzzy matching.
e.g helm.el$
    => \"[^h]*h[^e]*e[^l]*l[^m]*m[^.]*[.][^e]*e[^l]*l$\"
    ^helm.el$
    => \"helm[.]el$\"."
  (let ((ls (split-string-and-unquote pattern "")))
    (if (string= "^" (car ls))
        ;; Exact match.
        (mapconcat (lambda (c)
                     (if (and (string= c "$")
                              (string-match "$\\'" pattern))
                         c (regexp-quote c)))
                   (cdr ls) "")
        ;; Fuzzy match.
        (mapconcat (lambda (c)
                     (if (and (string= c "$")
                              (string-match "$\\'" pattern))
                         c (format "[^%s]*%s" c (regexp-quote c))))
                   ls ""))))

(defsubst helm--collect-pairs-in-string (string)
  (cl-loop for str on (split-string string "" t) by 'cdr
           when (cdr str)
           collect (list (car str) (cadr str))))

;;; Help routines.
;;
(defun helm-help-internal (bufname insert-content-fn)
  "Show long message during `helm' session in BUFNAME.
INSERT-CONTENT-FN is the function that insert
text to be displayed in BUFNAME."
  (let ((winconf (current-frame-configuration))
        (hframe (selected-frame)))
    (with-selected-frame helm-initial-frame
      (select-frame-set-input-focus helm-initial-frame)
      (unwind-protect
           (progn
             (setq helm-suspend-update-flag t)
             (set-buffer (get-buffer-create bufname))
             (switch-to-buffer bufname)
             (when helm-help-full-frame (delete-other-windows))
             (delete-region (point-min) (point-max))
             (org-mode)
             (org-mark-ring-push) ; Put mark at bob
             (save-excursion
               (funcall insert-content-fn))
             (buffer-disable-undo)
             (helm-help-event-loop))
        (raise-frame hframe)
        (setq helm-suspend-update-flag nil)
        (set-frame-configuration winconf)))))

(defun helm-help-scroll-up (amount)
  (condition-case _err
      (scroll-up-command amount)
    (beginning-of-buffer nil)
    (end-of-buffer nil)))

(defun helm-help-scroll-down (amount)
  (condition-case _err
      (scroll-down-command amount)
    (beginning-of-buffer nil)
    (end-of-buffer nil)))

(defun helm-help-next-line ()
  (condition-case _err
      (call-interactively #'next-line)
    (beginning-of-buffer nil)
    (end-of-buffer nil)))

(defun helm-help-previous-line ()
  (condition-case _err
      (call-interactively #'previous-line)
    (beginning-of-buffer nil)
    (end-of-buffer nil)))

(defun helm-help-toggle-mark ()
  (if (region-active-p)
      (deactivate-mark)
      (push-mark nil nil t)))

;; For movement of cursor in help buffer we need to call interactively
;; commands for impaired people using a synthetizer (#1347).
(defun helm-help-event-loop ()
  (let ((prompt (propertize
                 "[SPC,C-v,next:ScrollUp  b,M-v,prior:ScrollDown TAB:Cycle M-TAB:All C-s/r:Isearch q:Quit]"
                 'face 'helm-helper))
        scroll-error-top-bottom
        (iter-org-state (helm-iter-circular '(1 (16) (64)))))
    (helm-awhile (read-key prompt)
      (cl-case it
        ((?\C-v ? next) (helm-help-scroll-up helm-scroll-amount))
        ((?\M-v ?b prior) (helm-help-scroll-down helm-scroll-amount))
        (?\C-s (isearch-forward))
        (?\C-r (isearch-backward))
        (?\C-a (call-interactively #'move-beginning-of-line))
        (?\C-e (call-interactively #'move-end-of-line))
        ((?\C-f right) (call-interactively #'forward-char))
        ((?\C-b left) (call-interactively #'backward-char))
        ((?\C-n down) (helm-help-next-line))
        ((?\C-p up) (helm-help-previous-line))
        (?\M-a (call-interactively #'backward-sentence))
        (?\M-e (call-interactively #'forward-sentence))
        (?\M-f (call-interactively #'forward-word))
        (?\M-b (call-interactively #'backward-word))
        (?\M-> (call-interactively #'end-of-buffer))
        (?\M-< (call-interactively #'beginning-of-buffer))
        (?\C-  (helm-help-toggle-mark))
        (?\t   (org-cycle))
        (?\C-m (ignore-errors (call-interactively #'org-open-at-point)))
        (?\C-& (ignore-errors (call-interactively #'org-mark-ring-goto)))
        (?\C-% (call-interactively #'org-mark-ring-push))
        (?\M-\t (pcase (helm-iter-next iter-org-state)
                  ((pred numberp) (org-content))
                  ((and state) (org-cycle state))))
        (?\M-w (copy-region-as-kill
                (region-beginning) (region-end))
               (deactivate-mark))
        (?q    (cl-return))
        (t     (ignore))))))


;;; Multiline transformer
;;
(defun helm-multiline-transformer (candidates _source)
  (cl-loop with offset = (helm-interpret-value
                          (assoc-default 'multiline (helm-get-current-source)))
           for i in candidates
           if (numberp offset)
           collect (cons (helm--multiline-get-truncated-candidate i offset) i)
           else collect i))

(defun helm--multiline-get-truncated-candidate (candidate offset)
  "Truncate CANDIDATE when its length is > than OFFSET."
  (with-temp-buffer
    (insert candidate)
    (goto-char (point-min))
    (if (and offset
             (> (buffer-size) offset))
        (let ((end-str "[...]"))
          (concat
           (buffer-substring
            (point)
            (save-excursion
              (forward-char offset)
              (setq end-str (if (looking-at "\n")
                                end-str (concat "\n" end-str)))
              (point)))
           end-str))
        (buffer-string))))

;;; List processing
;;
(defun helm-flatten-list (seq &optional omit-nulls)
  "Return a list of all single elements of sublists in SEQ."
  (let (result)
    (cl-labels ((flatten (seq)
                  (cl-loop
                        for elm in seq
                        if (and (or elm
                                    (null omit-nulls))
                                (or (atom elm)
                                    (functionp elm)
                                    (and (consp elm)
                                         (cdr elm)
                                         (atom (cdr elm)))))
                        do (push elm result)
                        else do (flatten elm))))
      (flatten seq))
    (nreverse result)))

(defun helm-mklist (obj)
  "If OBJ is a list \(but not lambda\), return itself.
Otherwise make a list with one element."
  (if (and (listp obj) (not (functionp obj)))
      obj
    (list obj)))

(cl-defun helm-fast-remove-dups (seq &key (test 'eq))
  "Remove duplicates elements in list SEQ.

This is same as `remove-duplicates' but with memoisation.
It is much faster, especially in large lists.
A test function can be provided with TEST argument key.
Default is `eq'.
NOTE: Comparison of special elisp objects (e.g. markers etc...) fails
because their printed representations which are stored in hash-table
can't be compared with with the real object in SEQ.
This is a bug in `puthash' which store the printable representation of
object instead of storing the object itself, this to provide at the
end a printable representation of hashtable itself."
  (cl-loop with cont = (make-hash-table :test test)
           for elm in seq
           unless (gethash elm cont)
           collect (puthash elm elm cont)))

(defsubst helm--string-join (strings &optional separator)
  "Join all STRINGS using SEPARATOR."
  (mapconcat 'identity strings separator))

(defun helm--concat-regexps (regexp-list)
  "Return a regexp which matches any of the regexps in REGEXP-LIST."
  (if regexp-list
      (concat "\\(?:" (helm--string-join regexp-list "\\)\\|\\(?:") "\\)")
    "\\<\\>"))                          ; Match nothing

(defun helm-skip-entries (seq black-regexp-list &optional white-regexp-list)
  "Remove entries which matches one of REGEXP-LIST from SEQ."
  (let ((black-regexp (helm--concat-regexps black-regexp-list))
        (white-regexp (helm--concat-regexps white-regexp-list)))
    (cl-loop for i in seq
             unless (and (stringp i)
                         (string-match-p black-regexp i)
                         (null
                          (string-match-p white-regexp i)))
             collect i)))

(defun helm-boring-directory-p (directory black-list)
  "Check if one regexp in BLACK-LIST match DIRECTORY."
  (helm-awhile (helm-basedir (directory-file-name
                              (expand-file-name directory)))
    (when (string= it "/") (cl-return nil))
    (when (cl-loop for r in black-list
                   thereis (string-match-p
                            r (directory-file-name directory)))
      (cl-return t))
    (setq directory it)))

(defun helm-shadow-entries (seq regexp-list)
  "Put shadow property on entries in SEQ matching a regexp in REGEXP-LIST."
  (let ((face 'italic))
    (cl-loop for i in seq
          if (cl-loop for regexp in regexp-list
                   thereis (and (stringp i)
                                (string-match regexp i)))
          collect (propertize i 'face face)
          else collect i)))

(defun helm-remove-if-not-match (regexp seq)
  "Remove all elements of SEQ that don't match REGEXP."
  (cl-loop for s in seq
           for str = (cond ((symbolp s)
                            (symbol-name s))
                           ((consp s)
                            (car s))
                           (t s))
           when (string-match-p regexp str)
           collect s))

(defun helm-remove-if-match (regexp seq)
  "Remove all elements of SEQ that match REGEXP."
  (cl-loop for s in seq
           for str = (cond ((symbolp s)
                            (symbol-name s))
                           ((consp s)
                            (car s))
                           (t s))
           unless (string-match-p regexp str)
           collect s))

(defun helm-transform-mapcar (function args)
  "`mapcar' for candidate-transformer.

ARGS is (cand1 cand2 ...) or ((disp1 . real1) (disp2 . real2) ...)

\(helm-transform-mapcar 'upcase '(\"foo\" \"bar\"))
=> (\"FOO\" \"BAR\")
\(helm-transform-mapcar 'upcase '((\"1st\" . \"foo\") (\"2nd\" . \"bar\")))
=> ((\"1st\" . \"FOO\") (\"2nd\" . \"BAR\"))
"
  (cl-loop for arg in args
        if (consp arg)
        collect (cons (car arg) (funcall function (cdr arg)))
        else
        collect (funcall function arg)))

(defun helm-append-at-nth (seq elm index)
  "Append ELM at INDEX in SEQ."
  (let ((len (length seq)))
    (cond ((> index len) (setq index len))
          ((< index 0) (setq index 0)))
    (if (zerop index)
        (append elm seq)
      (cl-loop for i in seq
               for count from 1 collect i
               when (= count index)
               if (listp elm) append elm
               else collect elm))))

(defun helm-source-by-name (name &optional sources)
  "Get a Helm source in SOURCES by NAME.

Optional argument SOURCES is a list of Helm sources which default to
`helm-sources'."
  (cl-loop with src-list = (if sources
                               (cl-loop for src in sources
                                        collect (if (listp src)
                                                    src
                                                    (symbol-value src)))
                               helm-sources)
           for source in src-list
           thereis (and (string= name (assoc-default 'name source)) source)))

(defun helm-make-actions (&rest args)
  "Build an alist with (NAME . ACTION) elements with each pairs in ARGS.
Where NAME is a string or a function returning a string or nil and ACTION
a function.
If NAME returns nil the pair is skipped.

\(fn NAME ACTION ...)"
  (cl-loop for (name fn) on args by #'cddr
           when (functionp name)
           do (setq name (funcall name))
           when name
           collect (cons name fn)))

;;; Strings processing.
;;
(defun helm-stringify (elm)
  "Return the representation of ELM as a string.
ELM can be a string, a number or a symbol."
  (cl-typecase elm
    (string elm)
    (number (number-to-string elm))
    (symbol (symbol-name elm))))

(defun helm-substring (str width)
  "Return the substring of string STR from 0 to WIDTH.
Handle multibyte characters by moving by columns."
  (with-temp-buffer
    (save-excursion
      (insert str))
    (move-to-column width)
    (buffer-substring (point-at-bol) (point))))

(defun helm-substring-by-width (str width &optional endstr)
  "Truncate string STR to end at column WIDTH.
Similar to `truncate-string-to-width'.
Add ENDSTR at end of truncated STR.
Add spaces at end if needed to reach WIDTH when STR is shorter than WIDTH."
  (cl-loop for ini-str = str
        then (substring ini-str 0 (1- (length ini-str)))
        for sw = (string-width ini-str)
        when (<= sw width) return
        (concat ini-str endstr (make-string (- width sw) ? ))))

(defun helm-string-multibyte-p (str)
  "Check if string STR contains multibyte characters."
  (cl-loop for c across str
        thereis (> (char-width c) 1)))

(defun helm-get-pid-from-process-name (process-name)
  "Get pid from running process PROCESS-NAME."
  (cl-loop with process-list = (list-system-processes)
        for pid in process-list
        for process = (assoc-default 'comm (process-attributes pid))
        when (and process (string-match process-name process))
        return pid))

(defun helm-ff-find-printers ()
  "Return a list of available printers on Unix systems."
  (when (executable-find "lpstat")
    (let ((printer-list (with-temp-buffer
                          (call-process "lpstat" nil t nil "-a")
                          (split-string (buffer-string) "\n"))))
      (cl-loop for p in printer-list
            for printer = (car (split-string p))
            when printer
            collect printer))))

(defun helm-region-active-p ()
  (and transient-mark-mode mark-active (/= (mark) (point))))

(defun helm-quote-whitespace (candidate)
  "Quote whitespace, if some, in string CANDIDATE."
  (replace-regexp-in-string " " "\\\\ " candidate))

(defun helm-current-line-contents ()
  "Current line string without properties."
  (buffer-substring-no-properties (point-at-bol) (point-at-eol)))

(defun helm--replace-regexp-in-buffer-string (regexp rep str &optional fixedcase literal subexp start)
  "Replace REGEXP by REP in string STR.

Same as `replace-regexp-in-string' but handle properly REP as
function with SUBEXP specified.

e.g

    (helm--replace-regexp-in-buffer-string \"e\\\\(m\\\\)acs\" 'upcase \"emacs\" t nil 1)
    => \"eMacs\"

    (replace-regexp-in-string \"e\\\\(m\\\\)acs\" 'upcase \"emacs\" t nil 1)
    => \"eEMACSacs\"

Also START argument behave as expected unlike
`replace-regexp-in-string'.

e.g

    (helm--replace-regexp-in-buffer-string \"f\" \"r\" \"foofoo\" t nil nil 3)
    => \"fooroo\"

    (replace-regexp-in-string \"f\" \"r\" \"foofoo\" t nil nil 3)
    => \"roo\"

Unlike `replace-regexp-in-string' this function is buffer-based
implemented i.e replacement is computed inside a temp buffer, so
REGEXP should be used differently than with
`replace-regexp-in-string'.

NOTE: This function is used internally for
`helm-ff-query-replace-on-filenames' and builded for this.
You should use `replace-regexp-in-string' instead unless the behavior
of this function is really needed."
  (with-temp-buffer
    (insert str)
    (goto-char (or start (point-min)))
    (while (re-search-forward regexp nil t)
      (replace-match (cond ((and (functionp rep) subexp)
                            (funcall rep (match-string subexp)))
                           ((functionp rep)
                            (funcall rep str))
                           (t rep))
                     fixedcase literal nil subexp))
    (buffer-string)))

(defun helm-url-unhex-string (str)
  "Same as `url-unhex-string' but ensure STR is completely decoded."
  (setq str (or str ""))
  (with-temp-buffer
    (save-excursion (insert str))
    (while (re-search-forward "%[A-Za-z0-9]\\{2\\}" nil t)
      (replace-match (byte-to-string (string-to-number
                                      (substring (match-string 0) 1)
                                      16))
                     t t)
      ;; Restart from beginning until string is completely decoded.
      (goto-char (point-min)))
    (decode-coding-string (buffer-string) 'utf-8)))

(defun helm-read-answer (prompt answer-list)
  "Prompt user for an answer.
Arg PROMPT is the prompt to present user the different possible
answers, ANSWER-LIST is a list of strings.
If user enter an answer which is one of ANSWER-LIST return this
answer, otherwise keep prompting for a valid answer.
Note that answer should be a single char, only short answer are
accepted.

Example:

    (let ((answer (helm-read-answer
                    \"answer [y,n,!,q]: \"
                    '(\"y\" \"n\" \"!\" \"q\"))))
      (pcase answer
          (\"y\" \"yes\")
          (\"n\" \"no\")
          (\"!\" \"all\")
          (\"q\" \"quit\")))

"
  (helm-awhile (string
                (read-key (propertize prompt 'face 'minibuffer-prompt)))
    (if (member it answer-list)
        (cl-return it)
      (message "Please answer by %s" (mapconcat 'identity answer-list ", "))
      (sit-for 1))))

;;; Symbols routines
;;
(defun helm-symbolify (str-or-sym)
  "Get symbol of STR-OR-SYM."
  (if (symbolp str-or-sym)
      str-or-sym
    (intern str-or-sym)))

(defun helm-symbol-name (obj)
  (if (or (and (consp obj) (functionp obj))
          (byte-code-function-p obj))
      "Anonymous"
      (symbol-name obj)))

(defun helm-describe-class (class)
  "Display documentation of Eieio CLASS, a symbol or a string."
  (advice-add 'cl--print-table :override #'helm-source--cl--print-table)
  (unwind-protect
       (let ((helm-describe-function-function 'describe-function))
         (helm-describe-function class))
    (advice-remove 'cl--print-table #'helm-source--cl--print-table)))

(defun helm-describe-function (func)
  "Display documentation of FUNC, a symbol or string."
  (cl-letf (((symbol-function 'message) #'ignore))
    (funcall helm-describe-function-function (helm-symbolify func))))

(defun helm-describe-variable (var)
  "Display documentation of VAR, a symbol or a string."
  (cl-letf (((symbol-function 'message) #'ignore))
    (funcall helm-describe-variable-function (helm-symbolify var))))

(defun helm-describe-face (face)
  "Display documentation of FACE, a symbol or a string."
  (let ((faces (helm-marked-candidates)))
    (cl-letf (((symbol-function 'message) #'ignore))
      (describe-face (if (cdr faces)
                         (mapcar 'helm-symbolify faces)
                         (helm-symbolify face))))))

(defun helm-elisp--persistent-help (candidate fun &optional name)
  "Used to build persistent actions describing CANDIDATE with FUN.
Argument NAME is used internally to know which command to use when
symbol CANDIDATE refers at the same time to variable and a function.
See `helm-elisp-show-help'."
  (let ((hbuf (get-buffer (help-buffer))))
    (cond  ((helm-follow-mode-p)
            (if name
                (funcall fun candidate name)
                (funcall fun candidate)))
           ((or (and (helm-attr 'help-running-p)
                     (string= candidate (helm-attr 'help-current-symbol))))
            (progn
              ;; When started from a help buffer,
              ;; Don't kill this buffer as it is helm-current-buffer.
              (unless (equal hbuf helm-current-buffer)
                (kill-buffer hbuf)
                (set-window-buffer (get-buffer-window hbuf)
                                   ;; It is generally
                                   ;; helm-current-buffer but it may
                                   ;; be another buffer when helm have
                                   ;; been started from a dedicated window.
                                   (if helm--buffer-in-new-frame-p
                                       helm-current-buffer
                                     helm-persistent-action-window-buffer)))
              (helm-attrset 'help-running-p nil))
            ;; Force running update hook to may be delete
            ;; helm-persistent-action-display-window, this is done in
            ;; helm-persistent-action-display-window (the function). 
            (unless helm--buffer-in-new-frame-p
              (helm-update (regexp-quote (helm-get-selection)))))
           (t
            (if name
                (funcall fun candidate name)
                (funcall fun candidate))
            (helm-attrset 'help-running-p t)))
    (helm-attrset 'help-current-symbol candidate)))

(defun helm-find-function (func)
  "FUNC is symbol or string."
  (find-function (helm-symbolify func)))

(defun helm-find-variable (var)
  "VAR is symbol or string."
  (find-variable (helm-symbolify var)))

(defun helm-find-face-definition (face)
  "FACE is symbol or string."
  (find-face-definition (helm-symbolify face)))

(defun helm-kill-new (candidate &optional replace)
  "CANDIDATE is symbol or string.
See `kill-new' for argument REPLACE."
  (kill-new (helm-stringify candidate) replace))


;;; Modes
;;
(defun helm-same-major-mode-p (start-buffer alist)
  "Decide if current-buffer is related to START-BUFFER.
Argument ALIST is an alist of associated major modes."
  ;; START-BUFFER is the current-buffer where we start searching.
  ;; Determine the major-mode of START-BUFFER as `cur-maj-mode'.
  ;; Each time the loop go in another buffer we try from this buffer
  ;; to determine if its `major-mode' is:
  ;; - same as the `cur-maj-mode'
  ;; - derived from `cur-maj-mode' and from
  ;;   START-BUFFER if its mode is derived from the one in START-BUFFER.
  ;; - have an assoc entry (major-mode . cur-maj-mode)
  ;; - have an rassoc entry (cur-maj-mode . major-mode)
  ;; - check if one of these entries inherit from another one in
  ;;   `alist'.
  (let* ((cur-maj-mode  (with-current-buffer start-buffer major-mode))
         (maj-mode      major-mode)
         (c-assoc-mode  (assq cur-maj-mode alist))
         (c-rassoc-mode (rassq cur-maj-mode alist))
         (o-assoc-mode  (assq major-mode alist))
         (o-rassoc-mode (rassq major-mode alist))
         (cdr-c-assoc-mode (cdr c-assoc-mode))
         (cdr-o-assoc-mode (cdr o-assoc-mode)))
    (or (eq major-mode cur-maj-mode)
        (derived-mode-p cur-maj-mode)
        (with-current-buffer start-buffer
          (derived-mode-p maj-mode))
        (or (eq cdr-c-assoc-mode major-mode)
            (eq (car c-rassoc-mode) major-mode)
            (eq (cdr (assq cdr-c-assoc-mode alist))
                major-mode)
            (eq (car (rassq cdr-c-assoc-mode alist))
                major-mode))
        (or (eq cdr-o-assoc-mode cur-maj-mode)
            (eq (car o-rassoc-mode) cur-maj-mode)
            (eq (cdr (assq cdr-o-assoc-mode alist))
                cur-maj-mode)
            (eq (car (rassq cdr-o-assoc-mode alist))
                cur-maj-mode)))))

;;; Files routines
;;
(defun helm-file-name-sans-extension (filename)
  "Same as `file-name-sans-extension' but remove all extensions."
  (helm-aif (file-name-sans-extension filename)
      ;; Start searching at index 1 for files beginning with a dot (#1335).
      (if (string-match "\\." (helm-basename it) 1)
          (helm-file-name-sans-extension it)
          it)))

(defun helm-basename (fname &optional ext)
  "Print FNAME  with any  leading directory  components removed.
If specified, also remove filename extension EXT.
Arg EXT can be specified as a string with or without dot,
in this case it should match file-name-extension.
It can also be non-nil (`t') in this case no checking
of file-name-extension is done and the extension is removed
unconditionally."
  (let ((non-essential t))
    (if (and ext (or (string= (file-name-extension fname) ext)
                     (string= (file-name-extension fname t) ext)
                     (eq ext t))
             (not (file-directory-p fname)))
        (file-name-sans-extension (file-name-nondirectory fname))
      (file-name-nondirectory (directory-file-name fname)))))

(defun helm-basedir (fname)
  "Return the base directory of filename ending by a slash."
  (helm-aif (and fname
                 (or (and (string= fname "~") "~")
                     (file-name-directory fname)))
      (file-name-as-directory it)))

(defun helm-current-directory ()
  "Return current-directory name at point.
Useful in dired buffers when there is inserted subdirs."
  (expand-file-name
   (if (eq major-mode 'dired-mode)
       (dired-current-directory)
       default-directory)))

(defun helm-shadow-boring-files (files)
  "Files matching `helm-boring-file-regexp' will be
displayed with the `file-name-shadow' face if available."
  (helm-shadow-entries files helm-boring-file-regexp-list))

(defun helm-skip-boring-files (files)
  "Files matching `helm-boring-file-regexp' will be skipped."
  (helm-skip-entries files helm-boring-file-regexp-list))

(defun helm-skip-current-file (files)
  "Current file will be skipped."
  (remove (buffer-file-name helm-current-buffer) files))

(defun helm-w32-pathname-transformer (args)
  "Change undesirable features of windows pathnames to ones more acceptable to
other candidate transformers."
  (if (eq system-type 'windows-nt)
      (helm-transform-mapcar
       (lambda (x)
         (replace-regexp-in-string
          "/cygdrive/\\(.\\)" "\\1:"
          (replace-regexp-in-string "\\\\" "/" x)))
       args)
    args))

(defun helm-w32-prepare-filename (file)
  "Convert filename FILE to something usable by external w32 executables."
  (replace-regexp-in-string ; For UNC paths
   "/" "\\"
   (replace-regexp-in-string ; Strip cygdrive paths
    "/cygdrive/\\(.\\)" "\\1:"
    file nil nil) nil t))

(defun helm-w32-shell-execute-open-file (file)
  (with-no-warnings
    (w32-shell-execute "open" (helm-w32-prepare-filename file))))

;; Same as `vc-directory-exclusion-list'.
(defvar helm-walk-ignore-directories
  '("SCCS/" "RCS/" "CVS/" "MCVS/" ".svn/" ".git/" ".hg/" ".bzr/"
    "_MTN/" "_darcs/" "{arch}/" ".gvfs/"))

(defsubst helm--dir-file-name (file dir)
  (expand-file-name
   (substring file 0 (1- (length file))) dir))

(defsubst helm--dir-name-p (str)
  (char-equal (aref str (1- (length str))) ?/))

(cl-defun helm-walk-directory (directory &key (path 'basename)
                                           directories
                                           match skip-subdirs
                                           noerror)
  "Walk through DIRECTORY tree.

Argument PATH can be one of basename, relative, full, or a function
called on file name, default to basename.

Argument DIRECTORIES when `t' return also directories names,
otherwise skip directories names, with a value of `only' returns
only subdirectories, i.e files are skipped.

Argument MATCH is a regexp matching files or directories.

Argument SKIP-SUBDIRS when `t' will skip `helm-walk-ignore-directories'
otherwise if it is given as a list of directories, this list will be used
instead of `helm-walk-ignore-directories'.

Argument NOERROR when `t' will skip directories which are not accessible."
  (let ((fn (cl-case path
               (basename 'file-name-nondirectory)
               (relative 'file-relative-name)
               (full     'identity)
               (t        path)))) ; A function.
    (setq skip-subdirs (if (listp skip-subdirs)
                           skip-subdirs
                           helm-walk-ignore-directories))
    (cl-labels ((ls-rec (dir)
                  (unless (file-symlink-p dir)
                    (cl-loop for f in (sort (file-name-all-completions "" dir)
                                            'string-lessp)
                             unless (member f '("./" "../"))
                             ;; A directory.
                             ;; Use `helm--dir-file-name' to remove the final slash.
                             ;; Needed to avoid infloop on directory symlinks.
                             if (and (helm--dir-name-p f)
                                     (helm--dir-file-name f dir))
                             nconc
                             (unless (or (member f skip-subdirs)
                                         (and noerror
                                              (not (file-accessible-directory-p it))))
                               (if (and directories
                                        (or (null match)
                                            (string-match match f)))
                                   (nconc (list (concat (funcall fn it) "/"))
                                          (ls-rec it))
                                   (ls-rec it)))
                             ;; A regular file.
                             else nconc
                             (when (and (null (eq directories 'only))
                                        (or (null match) (string-match match f)))
                               (list (funcall fn (expand-file-name f dir))))))))
      (ls-rec directory))))

(defun helm-file-expand-wildcards (pattern &optional full)
  "Same as `file-expand-wildcards' but allow recursion.
Recursion happen when PATTERN starts with two stars.
Directories expansion is not supported."
  (let ((bn (helm-basename pattern))
        (case-fold-search nil))
    (if (and helm-file-globstar
             (string-match "\\`\\*\\{2\\}\\(.*\\)" bn))
        (helm-walk-directory (helm-basedir pattern)
                             :path (cl-case full
                                     (full 'full)
                                     (relative 'relative)
                                     ((basename nil) 'basename)
                                     (t 'full))
                             :directories nil
                             :match (wildcard-to-regexp bn)
                             :skip-subdirs t)
        (file-expand-wildcards pattern full))))

;;; helm internals
;;
(defun helm-set-pattern (pattern &optional noupdate)
  "Set minibuffer contents to PATTERN.
if optional NOUPDATE is non-nil, helm buffer is not changed."
  (with-selected-window (or (active-minibuffer-window) (minibuffer-window))
    (delete-minibuffer-contents)
    (insert pattern))
  (when noupdate
    (setq helm-pattern pattern)))

(defun helm-minibuffer-completion-contents ()
  "Return the user input in a minibuffer before point as a string.
That is what completion commands operate on."
  (buffer-substring (field-beginning) (point)))

(defmacro with-helm-buffer (&rest body)
  "Eval BODY inside `helm-buffer'."
  (declare (indent 0) (debug t))
  `(with-current-buffer (helm-buffer-get)
     ,@body))

(defmacro with-helm-current-buffer (&rest body)
  "Eval BODY inside `helm-current-buffer'."
  (declare (indent 0) (debug t))
  `(with-current-buffer (or (and (buffer-live-p helm-current-buffer)
                                 helm-current-buffer)
                            (setq helm-current-buffer
                                  (current-buffer)))
     ,@body))

(defun helm-buffer-get ()
  "Return `helm-action-buffer' if shown otherwise `helm-buffer'."
  (if (helm-action-window)
      helm-action-buffer
    helm-buffer))

(defun helm-window ()
  "Window of `helm-buffer'."
  (get-buffer-window (helm-buffer-get) 0))

(defun helm-action-window ()
  "Window of `helm-action-buffer'."
  (get-buffer-window helm-action-buffer 'visible))

(defmacro with-helm-window (&rest body)
  "Be sure BODY is excuted in the helm window."
  (declare (indent 0) (debug t))
  `(with-selected-window (helm-window)
     ,@body))

(defmacro helm-without-follow (&rest body)
  "Ensure BODY runs without following.
I.e. when using `helm-next-line' and friends in BODY."
  (declare (indent 0) (debug t))
  `(cl-letf (((symbol-function 'helm-follow-mode-p)
             (lambda (&optional _) nil)))
    (let (helm-follow-mode-persistent)
      (progn ,@body))))

;; Completion styles related functions
;;
(defun helm--setup-completion-styles-alist ()
  (cl-pushnew '(helm helm-completion-try-completion
                     helm-completion-all-completions
                     "helm multi completion style.")
              completion-styles-alist
              :test 'equal)
  (unless (assq 'flex completion-styles-alist)
    ;; Add helm-fuzzy style only if flex is not available.
    (cl-pushnew '(helm-flex helm-flex-completion-try-completion
                            helm-flex-completion-all-completions
                            "helm flex completion style.\nProvide flex matching for emacs-26.")
                completion-styles-alist
                :test 'equal)))

(defvar helm-blacklist-completion-styles '(emacs21 emacs22))
(defun helm--prepare-completion-styles (&optional nomode)
  "Return a suitable list of styles for `completion-styles'."
  ;; For `helm-completion-style' and `helm-completion-styles-alist'.
  (require 'helm-mode)
  (if (memq helm-completion-style '(helm helm-fuzzy))
      ;; Keep default settings, but probably nil is fine as well.
      '(basic partial-completion emacs22)
    (or
     (pcase (and (null nomode)
                 (with-helm-current-buffer
                   (cdr (assq major-mode helm-completion-styles-alist))))
       (`(,_l . ,ll) ll))
     ;; We need to have flex always behind helm, otherwise
     ;; when matching against e.g. '(foo foobar foao frogo bar
     ;; baz) with pattern "foo" helm style if before flex will
     ;; return foo and foobar only defeating flex that would
     ;; return foo foobar foao and frogo.
     (let* ((wflex (car (or (assq 'flex completion-styles-alist)
                            (assq 'helm-flex completion-styles-alist))))
            (styles (append (and (memq wflex completion-styles)
                                 (list wflex))
                            (cl-loop for s in completion-styles
                                     unless (or (memq s helm-blacklist-completion-styles)
                                                (memq wflex completion-styles))
                                     collect s))))
       (helm-append-at-nth
        styles '(helm)
        (if (memq wflex completion-styles)
            1 0))))))

(defun helm-dynamic-completion (collection predicate &optional point metadata nomode)
  "Build a function listing the possible completions of `helm-pattern' in COLLECTION.

Only the elements of COLLECTION that satisfy PREDICATE are considered.
Argument POINT is same as in `completion-all-completions' and is
meaningful only when using some kind of `completion-at-point'.
The return value is a list of completions that may be sorted by the
sort function provided by the completion-style in use (emacs-27 only),
otherwise (emacs-26) the sort function have to be provided if needed
either with a FCT function in source or by passing the sort function
with METADATA e.g. (metadata (display-sort-function . foo)).

Example:

    (helm :sources (helm-build-sync-source \"test\"
                     :candidates (helm-dynamic-completion
                                  '(foo bar baz foab)
                                  'symbolp)
                     :match-dynamic t)
          :buffer \"*helm test*\")

When argument NOMODE is non nil don't use `completion-styles' as
specified in `helm-completion-styles-alist'."
  (lambda ()
    (let* ((completion-styles
            (helm--prepare-completion-styles nomode))
           (completion-flex-nospace t)
           (compsfn (lambda (str pred _action)
                      (let* ((comps (completion-all-completions
                                     str
                                     (if (functionp collection)
                                         (funcall collection str predicate t)
                                       collection)
                                     pred
                                     (or point 0)
                                     (or metadata '(metadata))))
                             (last-data (last comps))
                             (sort-fn (completion-metadata-get
                                       metadata 'display-sort-function))
                             all)
                        (when (cdr last-data)
                          (setcdr last-data nil))
                        (setq all (copy-sequence comps))
                        (if sort-fn (funcall sort-fn all) all)))))
      ;; Ensure circular objects are removed.
      (complete-with-action t compsfn helm-pattern predicate))))

;; Yank text at point.
;;
;;
(defun helm-yank-text-at-point (arg)
  "Yank text at point in `helm-current-buffer' into minibuffer."
  (interactive "p")
  (with-helm-current-buffer
    (let ((fwd-fn (or helm-yank-text-at-point-function #'forward-word))
          diff)
      ;; Start to initial point if C-w have never been hit.
      (unless helm-yank-point
        (setq helm-yank-point (car helm-current-position)))
      (save-excursion
        (goto-char helm-yank-point)
        (helm-set-pattern
         (if (< arg 0)
             (with-temp-buffer
               (insert helm-pattern)
               (let ((end (point-max)))
                 (goto-char end)
                 (funcall fwd-fn -1)
                 (setq diff (- end (point)))
                 (delete-region (point) end)
                 (buffer-string)))
             (funcall fwd-fn arg)
             (concat
              ;; Allow yankink beyond eol allow inserting e.g long
              ;; urls in mail buffers.
              helm-pattern (replace-regexp-in-string
                            "\\`\n" ""
                            (buffer-substring-no-properties
                             helm-yank-point (point))))))
        (setq helm-yank-point (if diff (- (point) diff) (point)))))))
(put 'helm-yank-text-at-point 'helm-only t)

(defun helm-undo-yank-text-at-point ()
  "Undo last entry added by `helm-yank-text-at-point'."
  (interactive)
  (helm-yank-text-at-point -1))
(put 'helm-undo-yank-text-at-point 'helm-only t)

(defun helm-reset-yank-point ()
  (setq helm-yank-point nil))

(add-hook 'helm-cleanup-hook 'helm-reset-yank-point)
(add-hook 'helm-after-initialize-hook 'helm-reset-yank-point)

;;; Ansi
;;
;;
(defvar helm--ansi-color-regexp
  "\033\\[\\(K\\|[0-9;]*m\\)")
(defvar helm--ansi-color-drop-regexp
  "\033\\[\\([ABCDsuK]\\|[12][JK]\\|=[0-9]+[hI]\\|[0-9;]*[Hf]\\)")
(defun helm--ansi-color-apply (string)
  "A version of `ansi-color-apply' immune to upstream changes.

Similar to the emacs-24.5 version without support to `ansi-color-context'
which is buggy in emacs.

Modify also `ansi-color-regexp' by using own variable `helm--ansi-color-regexp'
that match whole STRING.

This is needed to provide compatibility for both emacs-25 and emacs-24.5
as emacs-25 version of `ansi-color-apply' is partially broken."
  (let ((start 0)
        codes end escape-sequence
        result colorized-substring)
    ;; Find the next escape sequence.
    (while (setq end (string-match helm--ansi-color-regexp string start))
      (setq escape-sequence (match-string 1 string))
      ;; Colorize the old block from start to end using old face.
      (when codes
        (put-text-property
         start end 'font-lock-face (ansi-color--find-face codes) string))
      (setq colorized-substring (substring string start end)
            start (match-end 0))
      ;; Eliminate unrecognized ANSI sequences.
      (while (string-match helm--ansi-color-drop-regexp colorized-substring)
        (setq colorized-substring
              (replace-match "" nil nil colorized-substring)))
      (push colorized-substring result)
      ;; Create new face, by applying escape sequence parameters.
      (setq codes (ansi-color-apply-sequence escape-sequence codes)))
    ;; If the rest of the string should have a face, put it there.
    (when codes
      (put-text-property
       start (length string)
       'font-lock-face (ansi-color--find-face codes) string))
    ;; Save the remainder of the string to the result.
    (if (string-match "\033" string start)
        (push (substring string start (match-beginning 0)) result)
        (push (substring string start) result))
    (apply 'concat (nreverse result))))

(provide 'helm-lib)

;; Local Variables:
;; byte-compile-warnings: (not obsolete)
;; coding: utf-8
;; indent-tabs-mode: nil
;; End:

;;; helm-lib ends here
