;;; semantic/mru-bookmark.el --- Automatic bookmark tracking  -*- lexical-binding: t; -*-

;; Copyright (C) 2007-2021 Free Software Foundation, Inc.

;; Author: Eric M. Ludlam <zappo@gnu.org>

;; This file is part of GNU Emacs.

;; GNU Emacs 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.

;; GNU Emacs 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 GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:
;;
;; Using editing hooks, track the most recently visited or poked tags,
;; and keep a list of them, with the current point in from, and sorted
;; by most recently used.
;;
;; I envision this would be used in place of switch-buffers once
;; someone got the hang of it.
;;
;; I'd also like to see this used to provide some nice defaults for
;; other programs where logical destinations or targets are the tags
;; that have been recently edited.
;;
;; Quick Start:
;;
;; M-x global-semantic-mru-bookmark-mode RET
;;
;; < edit some code >
;;
;; C-x B  <select a tag name> RET
;;
;; In the above, the history is pre-filled with the tags you recently
;; edited in the order you edited them.

;;; Code:

(require 'semantic)
(require 'eieio-base)
(require 'ring)

(declare-function data-debug-new-buffer "data-debug")
(declare-function data-debug-insert-object-slots "eieio-datadebug")
(declare-function semantic-momentary-highlight-tag "semantic/decorate")
(declare-function semantic-tag-similar-p "semantic/tag-ls")

;;; TRACKING CORE
;;
;; Data structure for tracking MRU tag locations

(defclass semantic-bookmark (eieio-named)
  ((tag :initarg :tag
	:type semantic-tag
	:documentation "The TAG this bookmark belongs to.")
   (parent :type (or semantic-tag null)
	   :documentation "The tag that is the parent of :tag.")
   (offset :type number
	 :documentation "The offset from `tag' start that is
somehow interesting.")
   (filename :type string
	     :documentation "String the tag belongs to.
Set this when the tag gets unlinked from the buffer it belongs to.")
   (frequency :type number
	      :initform 0
	      :documentation "Track the frequency this tag is visited.")
   (reason :type symbol
	   :initform t
	   :documentation
	   "The reason this tag is interesting.
Nice values include the following:
 edit - created because the tag text was edited.
 read - created because point lingered in tag text.
 jump - jumped to another tag from this tag.
 mark - created a regular mark in this tag.")
   )
  "A single bookmark.")

(cl-defmethod initialize-instance :after ((sbm semantic-bookmark) &rest _fields)
  "Initialize the bookmark SBM with details about :tag."
  (condition-case nil
      (save-excursion
	(oset sbm filename (semantic-tag-file-name (oref sbm tag)))
	(semantic-go-to-tag (oref sbm tag))
	(oset sbm parent (semantic-current-tag-parent)))
    (error (message "Error bookmarking tag.")))
  )

(cl-defmethod semantic-mrub-visit ((sbm semantic-bookmark))
  "Visit the semantic tag bookmark SBM.
Uses `semantic-go-to-tag' and highlighting."
  (require 'semantic/decorate)
  (with-slots (tag filename) sbm
    ;; Go to the tag
    (when (not (semantic-tag-in-buffer-p tag))
      (let ((fn (or (semantic-tag-file-name tag)
 		    filename)))
 	(set-buffer (find-file-noselect fn))))
    (semantic-go-to-tag (oref sbm tag) (oref sbm parent))
    ;; Go back to the offset.
    (condition-case nil
	(let ((o (oref sbm offset)))
	  (forward-char o))
      (error nil))
    ;; make it visible
    (pop-to-buffer-same-window (current-buffer))
    (semantic-momentary-highlight-tag tag)
    ))

(cl-defmethod semantic-mrub-update ((sbm semantic-bookmark) point reason)
  "Update the existing bookmark SBM.
POINT is some important location.
REASON is a symbol.  See slot `reason' on `semantic-bookmark'."
  (condition-case nil
      (progn
	(with-slots (tag offset frequency) sbm
	  (setq offset (- point (semantic-tag-start tag)))
	  (setq frequency (1+ frequency))
	  )
	(oset sbm reason reason))
    ;; This can fail on XEmacs at miscellaneous times.
    (error nil))
  )

(cl-defmethod semantic-mrub-preflush ((sbm semantic-bookmark))
  "Method called on a tag before the current buffer list of tags is flushed.
If there is a buffer match, unlink the tag."
  (let ((tag (oref sbm tag))
	(parent (when (slot-boundp sbm 'parent)
		  (oref sbm parent))))
    (let ((b (semantic-tag-in-buffer-p tag)))
      (when (and b (eq b (current-buffer)))
	(semantic--tag-unlink-from-buffer tag)))

    (when parent
      (let ((b (semantic-tag-in-buffer-p parent)))
	(when (and b (eq b (current-buffer)))
	  (semantic--tag-unlink-from-buffer parent))))))

(defclass semantic-bookmark-ring ()
  ((ring :initarg :ring
	 :type ring
	 :documentation
	 "List of `semantic-bookmark' objects.
This list is maintained as a list with the first item
being the current location, and the rest being a list of
items that were recently visited.")
   (current-index :initform 0
		  :type number
		  :documentation
		  "The current index into RING for some operation.
User commands use this to move through the ring, or reset.")
   )
  "Track the current MRU stack of bookmarks.
We can't use the built-in ring data structure because we need
to delete some items from the ring when we don't have the data.")

(defvar semantic-mru-bookmark-ring (semantic-bookmark-ring
				    :ring (make-ring 20))
  "The MRU bookmark ring.
This ring tracks the most recent active tags of interest.")

(defun semantic-mrub-find-nearby-tag (point)
  "Find a nearby tag to be pushed for this current location.
Argument POINT is where to find the tag near."
  ;; I thought this was a good idea, but it is not!
  ;;(semantic-fetch-tags) ;; Make sure everything is up-to-date.
  (let ((tag (semantic-current-tag)))
    (when (or (not tag) (semantic-tag-of-class-p tag 'type))
      (let ((nearby (or (semantic-find-tag-by-overlay-next point)
			(semantic-find-tag-by-overlay-prev point))))
	(when nearby (setq tag nearby))))
    tag))

(cl-defmethod semantic-mrub-push ((sbr semantic-bookmark-ring) point
			       &optional reason)
  "Add a bookmark to the ring SBR from POINT.
REASON is why it is being pushed.  See doc for `semantic-bookmark'
for possible reasons.
The resulting bookmark is then sorted within the ring."
  (let* ((ring (oref sbr ring))
	 (tag (semantic-mrub-find-nearby-tag (point)))
	 (idx 0))
    (when tag
      (while (and (not (ring-empty-p ring)) (< idx (ring-size ring)))
	(if (semantic-tag-similar-p (oref (ring-ref ring idx) tag)
				    tag)
	    (ring-remove ring idx))
	(setq idx (1+ idx)))
      ;; Create a new mark
      (let ((sbm (semantic-bookmark (semantic-tag-name tag)
				    :tag tag)))
	;; Take the mark, and update it for the current state.
	(ring-insert ring sbm)
	(semantic-mrub-update sbm point reason))
      )))

(defun semantic-mrub-cache-flush-fcn ()
  "Function called in the `semantic-before-toplevel-cache-flush-hook'.
Cause tags in the ring to become unlinked."
  (let* ((ring (oref semantic-mru-bookmark-ring ring))
	 (len (ring-length ring))
	 (idx 0)
	 )
    (while (< idx len)
      (semantic-mrub-preflush (ring-ref ring idx))
      (setq idx (1+ idx)))))

(add-hook 'semantic-before-toplevel-cache-flush-hook
	  #'semantic-mrub-cache-flush-fcn)

;;; EDIT tracker
;;
(defvar semantic-mrub-last-overlay nil
  "The last overlay bumped by `semantic-mru-bookmark-change-hook-fcn'.")

(defun semantic-mru-bookmark-change-hook-fcn (overlay)
  "Function set into `semantic-edits-new/move-change-hook's.
Argument OVERLAY is the overlay created to mark the change.
This function pushes tags onto the tag ring."
  ;; Dup?
  (when (not (eq overlay semantic-mrub-last-overlay))
    (setq semantic-mrub-last-overlay overlay)
    (semantic-mrub-push semantic-mru-bookmark-ring
			(point)
			'edit)))

;;; MINOR MODE
;;
;; Tracking minor mode.

(defcustom global-semantic-mru-bookmark-mode nil
  "If non-nil, enable `semantic-mru-bookmark-mode' globally.
When this mode is enabled, Emacs keeps track of which tags have
been edited, and you can re-visit them with \\[semantic-mrub-switch-tags]."
  :group 'semantic
  :group 'semantic-modes
  :type 'boolean
  :require 'semantic/util-modes
  :initialize #'custom-initialize-default
  :set (lambda (_sym val)
         (global-semantic-mru-bookmark-mode (if val 1 -1))))

;;;###autoload
(define-minor-mode global-semantic-mru-bookmark-mode
  "Toggle global use of option `semantic-mru-bookmark-mode'."
  :global t :group 'semantic :group 'semantic-modes
  ;; Not needed because it's autoloaded instead.
  ;; :require 'semantic-util-modes
  (semantic-toggle-minor-mode-globally
   'semantic-mru-bookmark-mode (if global-semantic-mru-bookmark-mode 1 -1)))

(defcustom semantic-mru-bookmark-mode-hook nil
  "Hook run at the end of function `semantic-mru-bookmark-mode'."
  :group 'semantic
  :type 'hook)

(defvar semantic-mru-bookmark-mode-map
  (let ((km (make-sparse-keymap)))
    (define-key km "\C-xB" #'semantic-mrub-switch-tags)
    km)
  "Keymap for mru-bookmark minor mode.")

(define-minor-mode semantic-mru-bookmark-mode
  "Minor mode for tracking tag-based bookmarks automatically.
When this mode is enabled, Emacs keeps track of which tags have
been edited, and you can re-visit them with \\[semantic-mrub-switch-tags].

\\{semantic-mru-bookmark-mode-map}

The minor mode can be turned on only if semantic feature is
available and the current buffer was set up for parsing.  Return
non-nil if the minor mode is enabled."
  :keymap semantic-mru-bookmark-mode-map
  (if semantic-mru-bookmark-mode
      (if (not (and (featurep 'semantic) (semantic-active-p)))
	  (progn
            ;; Disable minor mode if semantic stuff not available
            (setq semantic-mru-bookmark-mode nil)
            (error "Buffer %s was not set up for parsing"
                   (buffer-name)))
        (add-hook 'semantic-edits-new-change-functions
                  #'semantic-mru-bookmark-change-hook-fcn nil t)
        (add-hook 'semantic-edits-move-change-hooks
                  #'semantic-mru-bookmark-change-hook-fcn nil t))
    ;; Remove hooks
    (remove-hook 'semantic-edits-new-change-functions
		 #'semantic-mru-bookmark-change-hook-fcn t)
    (remove-hook 'semantic-edits-move-change-hooks
		 #'semantic-mru-bookmark-change-hook-fcn t)))

(semantic-add-minor-mode 'semantic-mru-bookmark-mode
                         "k")

;;; COMPLETING READ
;;
;; Ask the user for a tag in MRU order.
(defun semantic-mrub-read-history nil
  "History of `semantic-mrub-completing-read'.")

(defun semantic-mrub-ring-to-assoc-list (ring)
  "Convert RING into an association list for completion."
  (let ((idx 0)
	(len (ring-length ring))
	(al nil))
    (while (< idx len)
      (let ((r (ring-ref ring idx)))
	(setq al (cons (cons (oref r object-name) r)
		       al)))
      (setq idx (1+ idx)))
    (nreverse al)))

(defun semantic-mrub-completing-read (prompt)
  "Do a `completing-read' on elements from the mru bookmark ring.
Argument PROMPT is the prompt to use when reading."
  (if (ring-empty-p (oref semantic-mru-bookmark-ring ring))
      (error "Semantic Bookmark ring is currently empty"))
  (let* ((ring (oref semantic-mru-bookmark-ring ring))
	 (ans nil)
	 (alist (semantic-mrub-ring-to-assoc-list ring))
	 (first (cdr (car alist)))
	 (semantic-mrub-read-history nil)
	 )
    ;; Don't include the current tag.. only those that come after.
    (if (semantic-equivalent-tag-p (oref first tag)
				   (semantic-current-tag))
	(setq first (cdr (car (cdr alist)))))
    ;; Create a fake history list so we don't have to bind
    ;; M-p and M-n to our special cause.
    (let ((elts (reverse alist)))
      (while elts
	(setq semantic-mrub-read-history
	      (cons (car (car elts)) semantic-mrub-read-history))
	(setq elts (cdr elts))))
    (setq semantic-mrub-read-history (nreverse semantic-mrub-read-history))

    ;; Do the read/prompt
    (let ((prompt (if first (format "%s (%s): " prompt
				    (semantic-format-tag-name
				     (oref first tag) t)
				    )
		    (concat prompt ": ")))
	  )
      (setq ans
	    (completing-read prompt alist nil nil nil 'semantic-mrub-read-history)))
    ;; Calculate the return tag.
    (if (string= ans "")
	(setq ans first)
      ;; Return the bookmark object.
      (setq ans (assoc ans alist))
      (if ans
	  (cdr ans)
	;; no match.  Custom word.  Look it up somewhere?
	nil)
      )))

(defun semantic-mrub-switch-tags (tagmark)
  "Switch tags to TAGMARK.
Selects a new tag via prompt through the mru tag ring.
Jumps to the tag and highlights it briefly."
  (interactive (list (semantic-mrub-completing-read "Switch to tag")))
  (if (not (semantic-bookmark-p tagmark))
      (signal 'wrong-type-argument tagmark))

  (semantic-mrub-push semantic-mru-bookmark-ring
		      (point)
		      'jump)
  (semantic-mrub-visit tagmark)
  )

;;; Debugging
;;
(defun semantic-adebug-mrub ()
  "Display a list of items in the MRU bookmarks list.
Useful for debugging mrub problems."
  (interactive)
  (require 'eieio-datadebug)
  (let* ((out semantic-mru-bookmark-ring))
    (data-debug-new-buffer "*TAG RING ADEBUG*")
    (data-debug-insert-object-slots out "]")
    ))


(provide 'semantic/mru-bookmark)

;; Local variables:
;; generated-autoload-file: "loaddefs.el"
;; generated-autoload-load-name: "semantic/mru-bookmark"
;; End:

;;; semantic/mru-bookmark.el ends here