;;; company-auto-expand-mode.el --- auto expand company-mode selection candidate

;; Author: Yu Guang

;;; Commentary:
;;
;;  The core code is very simple; just shrink company candidate brefore every command
;;  and expand company candidate again after every command;
;;  dispaly at here maybe useful for someone.

;; (defun company-auto-expand-frontend (command)
;;   (cl-case command
;;     (pre-command
;;      (delete-region company-point (point))
;;      (when (eq this-command 'self-insert-command)
;;        (company-complete-selection)))
;;     (post-command
;;      (company--insert-candidate
;;       (nth company-selection company-candidates)))))

;; Have a minor bug when work together with company-pseudo-tooltip-unless-just-one-frontend-with-delay
;; you could use (if (and (not (overlayp company-preview-overlay)) (not company--auto-expand-inline)))
;; replace this line (if (not (overlayp company-preview-overlay)) in company-pseudo-....-with-delay.


;;; code:

(require 'company)

(defgroup company-auto-expand-mode nil
  "auto expand company-mode selection candidate"
  :group 'company)

(defcustom company-auto-expand-navigate-command
  'company-select-next
  "which command will active company-auto-expand"
  :type 'symbol
  :group 'company-auto-expand-mode)


;; ---------------------------------------------------------------------------------------------------

(defvar-local company-auto-expand-active nil)
(defvar-local company--auto-expand-inline nil)

(defun company-auto-expand-frontend (command)
  (when company-auto-expand-active
    (cl-case command
      (pre-command
       (company--shrink-selection)
       (when (and this-command
		  (company-auto-expand-finish-commmand this-command))
	 (company-complete-selection)))
      (post-command
       (company--expand-selection))
      (hide
       (setq-local company-auto-expand-active nil)))))

(defun company--expand-selection ()
  (unless company--auto-expand-inline
    (let (company-auto-expand-active
	  (company--candidate (nth company-selection
				 company-candidates)))
      (company-call-frontends 'pre-command)
      (company--insert-candidate company--candidate)
      (let ((company-prefix (substring-no-properties
    			   company--candidate)))
	(company-call-frontends 'post-command)))
    (when (overlayp company-preview-overlay)
      (company-preview-hide))
    (setq-local company--auto-expand-inline t)))

(defun company--shrink-selection ()
  (when company--auto-expand-inline
    (delete-region company-point (point))
    (setq-local company--auto-expand-inline nil)))

;; ----------------------
(defun company-auto-expand-finish-commmand (command)
  (or (eq command 'self-insert-command)
      (not (lookup-command-in-keymap-p command company-active-map))))
;; TODO: more efficient
(defun lookup-command-in-keymap-p (command keymap)
  (when (equal command
	    (catch 'lookup-p
	      (do-lookup-command-in-keymap-p command keymap)))
    t))

(defun do-lookup-command-in-keymap-p (command keymap)
  (when (consp keymap)
    (let ((sub-keymap (cdr keymap)))
      (if (eq command sub-keymap)
	  (throw 'lookup-p command)
	(when (listp sub-keymap)
	  (mapc (lambda (ssub-keymap)
		  (do-lookup-command-in-keymap-p command ssub-keymap))
		sub-keymap))))))

;; ---------------------------------------------------------------------------------------------------
;; TODO: shoud more common
(defun company-auto-expand-navigate-advice (orig-command &optional arg)
  (interactive "p")
  (if company-auto-expand-active
      (let ((current-prefix-arg arg))
	(call-interactively orig-command))
    (setq-local company-auto-expand-active t)))


;;;###autoload
(define-minor-mode company-auto-expand-mode
  "A minor mode for company-mode, turn on will auto expand selection candidate.
Usage: add company-auto-expand-frontend to company-frontends (should place behind
pseudo-tooltip and preview) and turn on this minor mode when use company-mode."
  nil nil nil
  :global t
  (if company-auto-expand-mode
      (if company-mode
	  (advice-add company-auto-expand-navigate-command
		      :around #'company-auto-expand-navigate-advice)
	(message "Only Turn-on company-auto-expand-mode when company-mode ON")
	(company-auto-expand-mode -1))
    (when (advice-member-p #'company-auto-expand-navigate-advice
			   company-auto-expand-navigate-command)
      (advice-remove company-auto-expand-navigate-command
		     #'company-auto-expand-navigate-advice))))


(provide 'company-auto-expand-mode)
;;; company-auto-expand-mode.el ends here