;;; helm-elisp.el --- Elisp symbols completion for helm. -*- lexical-binding: t -*-

;; Copyright (C) 2012 ~ 2019 Thierry Volpiatto <thierry.volpiatto@gmail.com>

;; 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/>.

;;; Code:
(require 'cl-lib)
(require 'helm)
(require 'helm-lib)
(require 'helm-help)
(require 'helm-types)
(require 'helm-utils)
(require 'helm-info)
(require 'helm-eval)
(require 'helm-files)

(declare-function 'helm-describe-function "helm-lib")
(declare-function 'helm-describe-variable "helm-lib")
(declare-function 'helm-describe-face "helm-lib")


;;; Customizable values

(defgroup helm-elisp nil
  "Elisp related Applications and libraries for Helm."
  :group 'helm)

(defcustom helm-turn-on-show-completion t
  "Display candidate in `current-buffer' while moving selection when non--nil."
  :group 'helm-elisp
  :type  'boolean)

(defcustom helm-show-completion-min-window-height 7
  "Minimum completion window height used in show completion.
This is used in macro `with-helm-show-completion'."
  :group 'helm-elisp
  :type  'integer)

(defcustom helm-lisp-quoted-function-list
  '(funcall apply mapc cl-mapc mapcar cl-mapcar
    callf callf2 cl-callf cl-callf2 fset
    fboundp fmakunbound symbol-function)
  "List of function where quoted function completion happen.
e.g give only function names after \(funcall '."
  :group 'helm-elisp
  :type '(repeat (choice symbol)))

(defcustom helm-lisp-unquoted-function-list
  '(function defadvice)
  "List of function where unquoted function completion happen.
e.g give only function names after \(function ."
  :group 'helm-elisp
  :type '(repeat (choice symbol)))

(defcustom helm-apropos-fuzzy-match nil
  "Enable fuzzy matching for `helm-apropos' when non-nil."
  :group 'helm-elisp
  :type 'boolean)

(defcustom helm-lisp-fuzzy-completion nil
  "Enable fuzzy matching in emacs-lisp completion when non-nil.
NOTE: This enable fuzzy matching in helm native implementation of
elisp completion, but not on helmized elisp completion, i.e
fuzzy completion is not available in `completion-at-point'."
  :group 'helm-elisp
  :type 'boolean)

(defcustom helm-apropos-function-list '(helm-def-source--emacs-commands
                                        helm-def-source--emacs-functions
                                        helm-def-source--eieio-classes
                                        helm-def-source--eieio-generic
                                        helm-def-source--emacs-variables
                                        helm-def-source--emacs-faces)
  "A list of functions that build helm sources to use in `helm-apropos'."
  :group 'helm-elisp
  :type '(repeat (choice symbol)))

(defcustom helm-apropos-defaut-info-lookup-sources '(helm-source-info-elisp
                                                     helm-source-info-cl
                                                     helm-source-info-eieio)
  "A list of sources to look into when searching info page of a symbol."
  :group 'helm-elisp
  :type '(repeat (choice symbol)))

(defcustom helm-show-completion-display-function
  (if (display-graphic-p)
      #'helm-display-buffer-in-own-frame
    #'helm-show-completion-default-display-function)
  "The function used to display helm completion buffer.

This function is used by `with-helm-show-completion', when nil
fallback to `helm-default-display-buffer'.

Default is to use a separate frame on graphic display and
`helm-show-completion-default-display-function' on non graphic
display."
  :group 'helm-elisp
  :type 'function)

;;; Faces
;;
;;
(defgroup helm-elisp-faces nil
  "Customize the appearance of helm-elisp."
  :prefix "helm-"
  :group 'helm-elisp
  :group 'helm-faces)

(defface helm-lisp-show-completion
    '((t (:background "DarkSlateGray")))
  "Face used for showing candidates in `helm-lisp-completion'."
  :group 'helm-elisp-faces)

(defface helm-lisp-completion-info
    '((t (:foreground "red")))
  "Face used for showing info in `helm-lisp-completion'."
  :group 'helm-elisp-faces)

(defcustom helm-elisp-help-function
  'helm-elisp-show-help
  "Function for displaying help for Lisp symbols."
  :group 'helm-elisp
  :type '(choice (function :tag "Open help for the symbol."
                  helm-elisp-show-help)
                 (function :tag "Show one liner in modeline."
                  helm-elisp-show-doc-modeline)))

(defcustom helm-locate-library-fuzzy-match t
  "Enable fuzzy-matching in `helm-locate-library' when non--nil."
  :type 'boolean
  :group 'helm-elisp)


;;; Show completion.
;;
;; Provide show completion with macro `with-helm-show-completion'.

(defvar helm-show-completion-overlay nil)

;; Called each time cursor move in helm-buffer.
(defun helm-show-completion ()
  (with-helm-current-buffer
    (overlay-put helm-show-completion-overlay
                 'display (substring-no-properties
                           (helm-get-selection)))))

(defun helm-show-completion-init-overlay (beg end)
  (setq helm-show-completion-overlay (make-overlay beg end))
  (overlay-put helm-show-completion-overlay
               'face 'helm-lisp-show-completion))

(defun helm-show-completion-default-display-function (buffer &rest _args)
  "A special resized helm window is used depending on position in BUFFER."
  (with-selected-window (selected-window)
    (if (window-dedicated-p)
        (helm-default-display-buffer buffer)
      (let* ((screen-size  (+ (count-screen-lines (window-start) (point) t)
                              1                         ; mode-line
                              (if header-line-format 1 0))) ; header-line
             (def-size     (- (window-height)
                              helm-show-completion-min-window-height))
             (upper-height (max window-min-height (min screen-size def-size)))
             split-window-keep-point)
        (recenter -1)
        (set-window-buffer (if (active-minibuffer-window)
                               (minibuffer-selected-window)
                               (split-window nil upper-height
                                             helm-split-window-default-side))
                           buffer)))))

(defmacro with-helm-show-completion (beg end &rest body)
  "Show helm candidate in an overlay at point.
BEG and END are the beginning and end position of the current completion
in `helm-current-buffer'.
BODY is an helm call where we want to enable show completion.
If `helm-turn-on-show-completion' is nil do nothing."
  (declare (indent 2) (debug t))
  `(unwind-protect
        (if helm-turn-on-show-completion
            (let ((helm-move-selection-after-hook
                   (append (list 'helm-show-completion)
                           helm-move-selection-after-hook))
                  (helm-split-window-default-side
                   (if (eq helm-split-window-default-side 'same)
                       'below helm-split-window-default-side))
                  helm-split-window-inside-p
                  helm-reuse-last-window-split-state)
              (helm-set-local-variable
               'helm-display-function
               (or helm-show-completion-display-function
                   'helm-default-display-buffer))
              (helm-show-completion-init-overlay ,beg ,end)
              ,@body)
          ,@body)
     (when (and helm-show-completion-overlay
                (overlayp helm-show-completion-overlay))
       (delete-overlay helm-show-completion-overlay))))


;;; Lisp symbol completion.
;;
;;
(defun helm-lisp-completion--predicate-at-point (beg)
  ;; Return a predicate for `all-completions'.
  (let ((fn-sym-p (lambda ()
                    (or
                     (and (eq (char-before) ?\ )
                          (save-excursion
                            (skip-syntax-backward " " (point-at-bol))
                            (memq (symbol-at-point)
                                  helm-lisp-unquoted-function-list)))
                     (and (eq (char-before) ?\')
                          (save-excursion
                            (forward-char -1)
                            (eq (char-before) ?\#)))))))
    (save-excursion
      (goto-char beg)
      (if (or
           ;; Complete on all symbols in non--lisp modes (logs mail etc..)
           (not (memq major-mode '(emacs-lisp-mode
                                   lisp-interaction-mode
                                   inferior-emacs-lisp-mode)))
           (not (or (funcall fn-sym-p)
                    (and (eq (char-before) ?\')
                         (save-excursion
                           (forward-char (if (funcall fn-sym-p) -2 -1))
                           (skip-syntax-backward " " (point-at-bol))
                           (memq (symbol-at-point)
                                 helm-lisp-quoted-function-list)))
                    (eq (char-before) ?\())) ; no paren before str.
           ;; Looks like we are in a let statement.
           (condition-case nil
               (progn (up-list -2) (forward-char 1)
                      (eq (char-after) ?\())
             (error nil)))
          (lambda (sym)
            (or (boundp sym) (fboundp sym) (symbol-plist sym)))
        #'fboundp))))

(defun helm-thing-before-point (&optional limits regexp)
  "Return symbol name before point.
If REGEXP is specified return what REGEXP find before point.
By default match the beginning of symbol before point.
With LIMITS arg specified return the beginning and end position
of symbol before point."
  (save-excursion
    (let (beg
          (end (point))
          (boundary (field-beginning nil nil (point-at-bol))))
      (if (re-search-backward (or regexp "\\_<") boundary t)
          (setq beg (match-end 0))
        (setq beg boundary))
      (unless (= beg end)
        (if limits
            (cons beg end)
          (buffer-substring-no-properties beg end))))))

(defun helm-bounds-of-thing-before-point (&optional regexp)
  "Get the beginning and end position of `helm-thing-before-point'.
Return a cons \(beg . end\)."
  (helm-thing-before-point 'limits regexp))

(defun helm-insert-completion-at-point (beg end str)
  ;; When there is no space after point
  ;; we are completing inside a symbol or
  ;; after a partial symbol with the next arg aside
  ;; without space, in this case mark the region.
  ;; deleting it would remove the
  ;; next arg which is unwanted.
  (delete-region beg end)
  (insert str)
  (let ((pos (cdr (or (bounds-of-thing-at-point 'symbol)
                      ;; needed for helm-dabbrev.
                      (bounds-of-thing-at-point 'filename)))))
    (when (and pos (< (point) pos))
      (push-mark pos t t))))

(defvar helm-lisp-completion--cache nil)
(defvar helm-lgst-len nil)
;;;###autoload
(defun helm-lisp-completion-at-point ()
  "Preconfigured helm for lisp symbol completion at point."
  (interactive)
  (setq helm-lgst-len 0)
  (let* ((target     (helm-thing-before-point))
         (beg        (car (helm-bounds-of-thing-before-point)))
         (end        (point))
         (pred       (and beg (helm-lisp-completion--predicate-at-point beg)))
         (loc-vars   (and (fboundp 'elisp--local-variables)
                          (ignore-errors
                            (mapcar #'symbol-name (elisp--local-variables)))))
         (glob-syms  (and target pred (all-completions target obarray pred)))
         (candidates (append loc-vars glob-syms))
         (helm-quit-if-no-candidate t)
         (helm-execute-action-at-once-if-one t)
         (enable-recursive-minibuffers t))
    (setq helm-lisp-completion--cache (cl-loop for sym in candidates
                                            for len = (length sym)
                                            when (> len helm-lgst-len)
                                            do (setq helm-lgst-len len)
                                            collect sym))
    (if candidates
        (with-helm-show-completion beg end
          ;; Overlay is initialized now in helm-current-buffer.
          (helm
           :sources (helm-build-in-buffer-source "Lisp completion"
                      :data helm-lisp-completion--cache
                      :persistent-action `(helm-lisp-completion-persistent-action .
                                           ,(and (eq helm-elisp-help-function
                                                     'helm-elisp-show-doc-modeline)
                                                 'never-split))
                      :nomark t
                      :match-part (lambda (c) (car (split-string c)))
                      :fuzzy-match helm-lisp-fuzzy-completion
                      :persistent-help (helm-lisp-completion-persistent-help)
                      :filtered-candidate-transformer
                      'helm-lisp-completion-transformer
                      :action (lambda (candidate)
                                (with-helm-current-buffer
                                  (run-with-timer
                                   0.01 nil
                                   'helm-insert-completion-at-point
                                   beg end candidate))))
           :input (if helm-lisp-fuzzy-completion
                      target (concat target " "))
           :resume 'noresume
           :truncate-lines t
           :buffer "*helm lisp completion*"
           :allow-nest t))
      (message "[No Match]"))))

(defun helm-lisp-completion-persistent-action (candidate &optional name)
  "Show documentation for the function.
Documentation is shown briefly in mode-line or completely
in other window according to the value of `helm-elisp-help-function'."
  (funcall helm-elisp-help-function candidate name))

(defun helm-lisp-completion-persistent-help ()
  "Return persistent-help according to the value of `helm-elisp-help-function'"
    (cl-ecase helm-elisp-help-function
      (helm-elisp-show-doc-modeline "Show brief doc in mode-line")
      (helm-elisp-show-help "Toggle show help for the symbol")))

(defun helm-elisp--show-help-1 (candidate &optional name)
  (let ((sym (intern-soft candidate)))
    (cl-typecase sym
      ((and fboundp boundp)
       (if (member name `(,helm-describe-function-function ,helm-describe-variable-function))
           (funcall (intern (format "helm-%s" name)) sym)
           ;; When there is no way to know what to describe
           ;; prefer describe-function.
           (helm-describe-function sym)))
      (fbound  (helm-describe-function sym))
      (bound    (helm-describe-variable sym))
      (face     (helm-describe-face sym)))))

(defun helm-elisp-show-help (candidate &optional name)
  "Show full help for the function CANDIDATE.
Arg NAME specify the name of the top level function
calling helm generic completion (e.g \"describe-function\")
which allow calling the right function when CANDIDATE symbol
refers at the same time to variable and a function."
  (helm-elisp--persistent-help
   candidate 'helm-elisp--show-help-1 name))

(defun helm-elisp-show-doc-modeline (candidate &optional name)
  "Show brief documentation for the function in modeline."
  (let ((cursor-in-echo-area t)
        mode-line-in-non-selected-windows)
    (helm-show-info-in-mode-line
     (propertize
      (helm-get-first-line-documentation
       (intern candidate) name)
      'face 'helm-lisp-completion-info))))

(defun helm-lisp-completion-transformer (candidates _source)
  "Helm candidates transformer for lisp completion."
  (cl-loop for c in candidates
        for sym = (intern c)
        for annot = (cl-typecase sym
                      (command " (Com)")
                      (class   " (Class)")
                      (generic " (Gen)")
                      (fbound  " (Fun)")
                      (bound   " (Var)")
                      (face    " (Face)"))
        for spaces = (make-string (- helm-lgst-len (length c)) ? )
        collect (cons (concat c spaces annot) c) into lst
        finally return (sort lst #'helm-generic-sort-fn)))

(defun helm-get-first-line-documentation (sym &optional name)
  "Return first line documentation of symbol SYM.
If SYM is not documented, return \"Not documented\"."
  (let ((doc (cl-typecase sym
               ((and fboundp boundp)
                (cond ((string= name "describe-function")
                       (documentation sym t))
                      ((string= name  "describe-variable")
                       (documentation-property sym 'variable-documentation t))
                      (t (documentation sym t))))
               (fbound  (documentation sym t))
               (bound   (documentation-property sym 'variable-documentation t))
               (face    (face-documentation sym)))))
    (if (and doc (not (string= doc ""))
             ;; `documentation' return "\n\n(args...)"
             ;; for CL-style functions.
             (not (string-match-p "^\n\n" doc)))
        (car (split-string doc "\n"))
      "Not documented")))

;;; File completion.
;;
;; Complete file name at point.

;;;###autoload
(defun helm-complete-file-name-at-point (&optional force)
  "Preconfigured helm to complete file name at point."
  (interactive)
  (require 'helm-mode)
  (let* ((tap (thing-at-point 'filename))
         beg
         (init (and tap
                    (or force
                        (save-excursion
                          (end-of-line)
                          (search-backward tap (point-at-bol) t)
                          (setq beg (point))
                          (looking-back "[^'`( ]" (1- (point)))))
                    (expand-file-name
                     (substring-no-properties tap))))
         (end  (point))
         (helm-quit-if-no-candidate t)
         (helm-execute-action-at-once-if-one t)
         completion)
    (with-helm-show-completion beg end
      (setq completion (helm-read-file-name "FileName: "
                                            :initial-input init)))
    (when (and completion (not (string= completion "")))
      (delete-region beg end) (insert (if (string-match "^~" tap)
                                          (abbreviate-file-name completion)
                                        completion)))))

;;;###autoload
(defun helm-lisp-indent ()
  ;; It is meant to use with `helm-define-multi-key' which
  ;; does not support args for functions yet, so use `current-prefix-arg'
  ;; for now instead of (interactive "P").
  (interactive)
  (let ((tab-always-indent (or (eq tab-always-indent 'complete)
                               tab-always-indent)))
    (indent-for-tab-command current-prefix-arg)))

;;;###autoload
(defun helm-lisp-completion-or-file-name-at-point ()
  "Preconfigured helm to complete lisp symbol or filename at point.
Filename completion happen if string start after or between a double quote."
  (interactive)
  (let* ((tap (thing-at-point 'filename)))
    (if (and tap (save-excursion
                   (end-of-line)
                   (search-backward tap (point-at-bol) t)
                   (looking-back "[^'`( ]" (1- (point)))))
        (helm-complete-file-name-at-point)
      (helm-lisp-completion-at-point))))


;;; Apropos
;;
;;
(defvar helm-apropos-history nil)

(defun helm-apropos-init (test default)
  "Init candidates buffer for `helm-apropos' sources."
  (require 'helm-help)
  (helm-init-candidates-in-buffer 'global
    (let ((default-symbol (and (stringp default)
                               (intern-soft default)))
          (symbols (all-completions "" obarray test)))
      (if (and default-symbol (funcall test default-symbol))
          (cons default-symbol symbols)
        symbols))))

(defun helm-apropos-init-faces (default)
  "Init candidates buffer for faces for `helm-apropos'."
  (require 'helm-help)
  (with-current-buffer (helm-candidate-buffer 'global)
    (goto-char (point-min))
    (let ((default-symbol (and (stringp default)
                               (intern-soft default)))
          (faces (face-list)))
      (when (and default-symbol (facep default-symbol))
        (insert (concat default "\n")))
      (insert
       (mapconcat #'prin1-to-string
                  (if default
                      (cl-remove-if (lambda (sym) (string= sym default)) faces)
                    faces)
                  "\n")))))

(defun helm-apropos-default-sort-fn (candidates _source)
  (if (string= helm-pattern "")
      candidates
      (sort candidates #'helm-generic-sort-fn)))

(defun helm-apropos-clean-history-variable (candidate)
  (with-helm-current-buffer ; var is maybe local
    (let* ((sym   (intern-soft candidate))
           (cands (symbol-value sym))
           (mkds  (and (listp cands)
                       (helm-comp-read "Delete entry: "
                                       cands :marked-candidates t))))
      (cl-assert (listp mkds) nil "Variable value is not a list")
      (cl-loop for elm in mkds do
               (if (local-variable-p sym)
                   (set (make-local-variable sym)
                        (setq cands (delete elm cands)))
                 (set sym (setq cands (delete elm cands))))))))

(defun helm-apropos-clean-ring (candidate)
  (with-helm-current-buffer ; var is maybe local
    (let* ((sym   (intern-soft candidate))
           (val   (symbol-value sym))
           (cands (and (ring-p val) (ring-elements val)))
           (mkds  (and cands (helm-comp-read
                                "Delete entry: "
                                cands :marked-candidates t))))
      (when mkds
        (cl-loop for elm in mkds do
                 (ring-remove
                  val (helm-position
                       elm
                       (ring-elements val)
                       :test 'equal))
                 and do (if (local-variable-p sym)
                            (set (make-local-variable sym) val)
                          (set sym val)))))))

(defun helm-apropos-action-transformer (actions candidate)
  (let* ((sym (helm-symbolify candidate))
         (val (with-helm-current-buffer (symbol-value sym))))
    (cond ((custom-variable-p sym)
           (append
            actions
            (let ((standard-value (eval (car (get sym 'standard-value)))))
              (unless (equal standard-value (symbol-value sym))
                `(("Reset Variable to default value"
                   . ,(lambda (candidate)
                        (let ((sym (helm-symbolify candidate)))
                          (set sym standard-value)))))))
            '(("Customize variable" .
               (lambda (candidate)
                 (customize-option (helm-symbolify candidate)))))))
          ((and val (with-helm-current-buffer (ring-p (symbol-value sym))))
           (append actions
                   '(("Clean ring" . helm-apropos-clean-ring))))
          ((and (string-match-p "history" candidate) (listp val))
           (append actions
                   '(("Clean variable" .
                      helm-apropos-clean-history-variable))))
          (t actions))))

(defun helm-def-source--emacs-variables (&optional default)
  (helm-build-in-buffer-source "Variables"
    :init (lambda ()
            (helm-apropos-init
             (lambda (x) (and (boundp x) (not (keywordp x)))) default))
    :fuzzy-match helm-apropos-fuzzy-match
    :filtered-candidate-transformer (and (null helm-apropos-fuzzy-match)
                                         'helm-apropos-default-sort-fn)
    :nomark t
    :persistent-action (lambda (candidate)
                         (helm-elisp--persistent-help
                          candidate 'helm-describe-variable))
    :persistent-help "Toggle describe variable"
    :action '(("Describe variable" . helm-describe-variable)
              ("Find variable" . helm-find-variable)
              ("Info lookup" . helm-info-lookup-symbol)
              ("Set variable" . helm-set-variable))
    :action-transformer 'helm-apropos-action-transformer))

(defun helm-def-source--emacs-faces (&optional default)
  "Create `helm' source for faces to be displayed with
`helm-apropos'."
  (helm-build-in-buffer-source "Faces"
    :init (lambda () (helm-apropos-init-faces default))
    :fuzzy-match helm-apropos-fuzzy-match
    :filtered-candidate-transformer
    (append (and (null helm-apropos-fuzzy-match)
                 '(helm-apropos-default-sort-fn))
            (list
             (lambda (candidates _source)
               (cl-loop for c in candidates
                        collect (propertize c 'face (intern c))))))
    :persistent-action (lambda (candidate)
                         (helm-elisp--persistent-help
                          candidate 'helm-describe-face))
    :persistent-help "Toggle describe face"
    :action '(("Describe face" . helm-describe-face)
              ("Find face" . helm-find-face-definition)
              ("Customize face" . (lambda (candidate)
                                    (customize-face (helm-symbolify candidate)))))))

(defun helm-def-source--emacs-commands (&optional default)
  (helm-build-in-buffer-source "Commands"
    :init (lambda ()
            (helm-apropos-init 'commandp default))
    :fuzzy-match helm-apropos-fuzzy-match
    :filtered-candidate-transformer (and (null helm-apropos-fuzzy-match)
                                         'helm-apropos-default-sort-fn)
    :nomark t
    :persistent-action (lambda (candidate)
                         (helm-elisp--persistent-help
                          candidate 'helm-describe-function))
    :persistent-help "Toggle describe command"
    :action '(("Describe function" . helm-describe-function)
              ("Find function" . helm-find-function)
              ("Info lookup" . helm-info-lookup-symbol))))

(defun helm-def-source--emacs-functions (&optional default)
  (helm-build-in-buffer-source "Functions"
    :init (lambda ()
            (helm-apropos-init (lambda (x)
                                 (and (fboundp x)
                                      (not (commandp x))
                                      (not (generic-p x))
                                      (not (class-p x))))
                               default))
    :fuzzy-match helm-apropos-fuzzy-match
    :filtered-candidate-transformer (and (null helm-apropos-fuzzy-match)
                                         'helm-apropos-default-sort-fn)
    :persistent-action (lambda (candidate)
                         (helm-elisp--persistent-help
                          candidate 'helm-describe-function))
    :persistent-help "Toggle describe function"
    :nomark t
    :action '(("Describe function" . helm-describe-function)
              ("Find function" . helm-find-function)
              ("Info lookup" . helm-info-lookup-symbol))))

(defun helm-def-source--eieio-classes (&optional default)
  (helm-build-in-buffer-source "Classes"
    :init (lambda ()
            (helm-apropos-init (lambda (x)
                                 (class-p x))
                               default))
    :fuzzy-match helm-apropos-fuzzy-match
    :filtered-candidate-transformer (and (null helm-apropos-fuzzy-match)
                                         'helm-apropos-default-sort-fn)
    :nomark t
    :persistent-action (lambda (candidate)
                         (helm-elisp--persistent-help
                          candidate 'helm-describe-class))
    :persistent-help "Toggle describe class"
    :action '(("Describe Class" . helm-describe-class)
              ("Find Class" . helm-find-function)
              ("Info lookup" . helm-info-lookup-symbol))))

(defun helm-def-source--eieio-generic (&optional default)
  (helm-build-in-buffer-source "Generic functions"
    :init (lambda ()
            (helm-apropos-init (lambda (x)
                                 (generic-p x))
                               default))
    :fuzzy-match helm-apropos-fuzzy-match
    :filtered-candidate-transformer (and (null helm-apropos-fuzzy-match)
                                         'helm-apropos-default-sort-fn)
    :nomark t
    :persistent-action (lambda (candidate)
                         (helm-elisp--persistent-help
                          candidate 'helm-describe-function))
    :persistent-help "Toggle describe generic function"
    :action '(("Describe function" . helm-describe-function)
              ("Find function" . helm-find-function)
              ("Info lookup" . helm-info-lookup-symbol))))

(defun helm-info-lookup-fallback-source (candidate)
  (let ((sym (helm-symbolify candidate))
        src-name fn)
    (cond ((class-p sym)
           (setq fn #'helm-describe-function
                 src-name "Describe class"))
          ((generic-p sym)
           (setq fn #'helm-describe-function
                 src-name "Describe generic function"))
          ((fboundp sym)
           (setq fn #'helm-describe-function
                 src-name "Describe function"))
          ((facep sym)
           (setq fn #'helm-describe-face
                 src-name "Describe face"))
          (t
           (setq fn #'helm-describe-variable
                 src-name "Describe variable")))
    (helm-build-sync-source src-name
      :candidates (list candidate)
      :persistent-action (lambda (candidate)
                           (helm-elisp--persistent-help
                            candidate fn))
      :persistent-help src-name
      :nomark t
      :action fn)))

(defun helm-info-lookup-symbol-1 (c)
  (let ((helm-execute-action-at-once-if-one 'current-source))
    (helm :sources (append helm-apropos-defaut-info-lookup-sources
                           (list (helm-info-lookup-fallback-source c)))
          :resume 'noresume
          :buffer "*helm lookup*"
          :input c)))

(defun helm-info-lookup-symbol (candidate)
  ;; ???:Running an idle-timer allows not catching RET when exiting
  ;; with the fallback source.
  ;; (run-with-idle-timer 0.01 nil #'helm-info-lookup-symbol-1 candidate)
  (helm-info-lookup-symbol-1 candidate))

;;;###autoload
(defun helm-apropos (default)
  "Preconfigured helm to describe commands, functions, variables and faces.
In non interactives calls DEFAULT argument should be provided as a string,
i.e the `symbol-name' of any existing symbol."
  (interactive (list (thing-at-point 'symbol)))
    (helm :sources
          (mapcar (lambda (func)
                    (funcall func default))
                  helm-apropos-function-list)
          :history 'helm-apropos-history
          :buffer "*helm apropos*"
          :preselect (and default (concat "\\_<" (regexp-quote default) "\\_>"))))


;;; Advices
;;
;;
(defvar helm-source-advice
  (helm-build-sync-source "Function Advice"
    :init (lambda () (require 'advice))
    :candidates 'helm-advice-candidates
    :action (helm-make-actions "Toggle Enable/Disable" 'helm-advice-toggle)
    :persistent-action 'helm-advice-persistent-action
    :nomark t
    :multiline t
    :persistent-help "Toggle describe function / C-u C-j: Toggle advice"))

(defun helm-advice-candidates ()
  (cl-loop for (fname) in ad-advised-functions
        for function = (intern fname)
        append
        (cl-loop for class in ad-advice-classes append
              (cl-loop for advice in (ad-get-advice-info-field function class)
                    for enabled = (ad-advice-enabled advice)
                    collect
                    (cons (format
                           "%s %s %s"
                           (if enabled "Enabled " "Disabled")
                           (propertize fname 'face 'font-lock-function-name-face)
                           (ad-make-single-advice-docstring advice class nil))
                          (list function class advice))))))

(defun helm-advice-persistent-action (func-class-advice)
  (if current-prefix-arg
      (helm-advice-toggle func-class-advice)
    (describe-function (car func-class-advice))))

(defun helm-advice-toggle (func-class-advice)
  (cl-destructuring-bind (function _class advice) func-class-advice
    (cond ((ad-advice-enabled advice)
           (ad-advice-set-enabled advice nil)
           (message "Disabled"))
          (t
           (ad-advice-set-enabled advice t)
           (message "Enabled")))
    (ad-activate function)
    (and helm-in-persistent-action
         (helm-advice-update-current-display-string))))

(defun helm-advice-update-current-display-string ()
  (helm-edit-current-selection
    (let ((newword (cond ((looking-at "Disabled") "Enabled")
                         ((looking-at "Enabled")  "Disabled"))))
      (when newword
        (delete-region (point) (progn (forward-word 1) (point)))
        (insert newword)))))

;;;###autoload
(defun helm-manage-advice ()
  "Preconfigured `helm' to disable/enable function advices."
  (interactive)
  (helm-other-buffer 'helm-source-advice "*helm advice*"))


;;; Locate elisp library
;;
;;
(defun helm-locate-library-scan-list ()
  (cl-loop for dir in load-path
           with load-suffixes = '(".el")
           when (file-directory-p dir)
           append (directory-files
                   dir t (concat (regexp-opt (get-load-suffixes))
                                 "\\'"))))

;;;###autoload
(defun helm-locate-library ()
  "Preconfigured helm to locate elisp libraries."
  (interactive)
  (helm :sources (helm-build-in-buffer-source  "Elisp libraries (Scan)"
                   :data #'helm-locate-library-scan-list
                   :fuzzy-match helm-locate-library-fuzzy-match
                   :keymap helm-generic-files-map
                   :search (unless helm-locate-library-fuzzy-match
                             (lambda (regexp)
                               (re-search-forward
                                (if helm-ff-transformer-show-only-basename
                                    (replace-regexp-in-string
                                     "\\`\\^" "" regexp)
                                    regexp)
                                nil t)))
                   :match-part (lambda (candidate)
                                 (with-helm-buffer
                                   (if helm-ff-transformer-show-only-basename
                                       (helm-basename candidate) candidate)))
                   :filter-one-by-one (lambda (c)
                                        (with-helm-buffer
                                          (if helm-ff-transformer-show-only-basename
                                              (cons (helm-basename c) c) c)))
                   :action (helm-actions-from-type-file))
        :ff-transformer-show-only-basename nil
        :buffer "*helm locate library*"))

(defun helm-set-variable (var)
  "Set VAR value interactively."
  (let* ((sym (helm-symbolify var))
         (val (default-value sym)))
    (set-default sym (eval-minibuffer
                      (format "Set `%s': " var)
                      (if (or (stringp val)
                              (memq val '(nil t))
                              (numberp val))
                          (prin1-to-string val)
                        (format "'%s" (prin1-to-string val)))))))


;;; Elisp Timers.
;;
;;
(defclass helm-absolute-time-timers-class (helm-source-sync helm-type-timers)
  ((candidates :initform timer-list)
   (allow-dups :initform t)
   (candidate-transformer
    :initform
    (lambda (candidates)
      (cl-loop for timer in candidates
               collect (cons (helm-elisp--format-timer timer) timer))))))

(defvar helm-source-absolute-time-timers
  (helm-make-source "Absolute Time Timers" 'helm-absolute-time-timers-class))

(defclass helm-idle-time-timers-class (helm-source-sync helm-type-timers)
  ((candidates :initform timer-idle-list)
   (allow-dups :initform t)
   (candidate-transformer
    :initform
    (lambda (candidates)
      (cl-loop for timer in candidates
               collect (cons (helm-elisp--format-timer timer) timer))))))

(defvar helm-source-idle-time-timers
  (helm-make-source "Idle Time Timers" 'helm-idle-time-timers-class))

(defun helm-elisp--format-timer (timer)
  (format "%s repeat=%s %s(%s)"
          (let ((time (timer--time timer)))
            (if (timer--idle-delay timer)
                (format-time-string "idle-for=%5s" time)
              (format-time-string "%m/%d %T" time)))
          (or (timer--repeat-delay timer) "nil")
          (mapconcat 'identity (split-string
                                (prin1-to-string (timer--function timer))
                                "\n") " ")
          (mapconcat 'prin1-to-string (timer--args timer) " ")))

;;;###autoload
(defun helm-timers ()
  "Preconfigured `helm' for timers."
  (interactive)
  (helm :sources '(helm-source-absolute-time-timers
                   helm-source-idle-time-timers)
        :buffer "*helm timers*"))


;;; Complex command history
;;
;;
(defun helm-btf--usable-p ()
  "Return t if current version of `backtrace-frame' accept 2 arguments."
  (condition-case nil
      (progn (backtrace-frame 1 'condition-case) t)
    (wrong-number-of-arguments nil)))

(if (helm-btf--usable-p)        ; Check if BTF accept more than one arg.
    ;; Emacs 24.4.
    (dont-compile
      (defvar helm-sexp--last-sexp nil)
      ;; This wont work compiled.
      (defun helm-sexp-eval-1 ()
        (interactive)
        (unwind-protect
             (progn
               ;; Trick called-interactively-p into thinking that `cand' is
               ;; an interactive call, See `repeat-complex-command'.
               (add-hook 'called-interactively-p-functions
                         #'helm-complex-command-history--called-interactively-skip)
               (eval (read helm-sexp--last-sexp)))
          (remove-hook 'called-interactively-p-functions
                       #'helm-complex-command-history--called-interactively-skip)))

      (defun helm-complex-command-history--called-interactively-skip (i _frame1 frame2)
        (and (eq 'eval (cadr frame2))
             (eq 'helm-sexp-eval-1
                 (cadr (backtrace-frame (+ i 2) #'called-interactively-p)))
             1))

      (defun helm-sexp-eval (_candidate)
        (call-interactively #'helm-sexp-eval-1)))
  ;; Emacs 24.3
  (defun helm-sexp-eval (cand)
    (let ((sexp (read cand)))
      (condition-case err
          (if (> (length (remove nil sexp)) 1)
              (eval sexp)
            (apply 'call-interactively sexp))
        (error (message "Evaluating gave an error: %S" err)
               nil)))))

(defvar helm-source-complex-command-history
  (helm-build-sync-source "Complex Command History"
    :candidates (lambda ()
                  ;; Use cdr to avoid adding
                  ;; `helm-complex-command-history' here.
                  (cl-loop for i in command-history
                           unless (equal i '(helm-complex-command-history))
                           collect (prin1-to-string i)))
    :action (helm-make-actions
             "Eval" (lambda (candidate)
                      (and (boundp 'helm-sexp--last-sexp)
                           (setq helm-sexp--last-sexp candidate))
                      (let ((command (read candidate)))
                        (unless (equal command (car command-history))
                          (setq command-history (cons command command-history))))
                      (run-with-timer 0.1 nil #'helm-sexp-eval candidate))
             "Edit and eval" (lambda (candidate)
                               (edit-and-eval-command "Eval: " (read candidate))))
    :persistent-action #'helm-sexp-eval
    :multiline t))

;;;###autoload
(defun helm-complex-command-history ()
  "Preconfigured helm for complex command history."
  (interactive)
  (helm :sources 'helm-source-complex-command-history
        :buffer "*helm complex commands*"))

(provide 'helm-elisp)

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

;;; helm-elisp.el ends here
