;;; find-func.el --- find the definition of the elisp function near point

;; Copyright (C) 1997 Free Software Foundation, Inc.

;; Author: Jens Petersen <petersen@kurims.kyoto-u.ac.jp>
;; Maintainer: petersen@kurims.kyoto-u.ac.jp
;; Keywords: emacs-lisp, help, functions
;; Created: 97/07/25

;; 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 2, 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; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:
;;
;; The funniest thing about this is that I can't imagine why a package
;; so obviously useful as this hasn't been written before!!
;; This probably belongs in "help.el" or somewhere like that.
;;
;; Put this file in your `load-path', byte-compile it and add the
;; following code in your init file:
;;
;; ;;; find-func
;; (load "find-function")
;; (global-set-key [(control ?c) ?f] 'find-function)
;; (global-set-key [(control ?c) ?4 ?f] 'find-function-other-window)
;; (global-set-key [(control ?c) ?5 ?f] 'find-function-other-frame)
;; (global-set-key [(control ?c) ?k] 'find-function-on-key)
;;
;; and away you go!  It does pretty much what you would expect,
;; putting the cursor at the definition of the function at point.
;;
;; The code is adapted from `describe-function', `describe-key'
;; ("help.el") and `fff-find-loaded-emacs-lisp-function' (Noah Friedman's
;; "fff.el").

;;; To do:
;;
;; o custom?
;;
;; o improve handling of advice'd functions? (at the moment it goes to
;; the advice, not the actual definition)

;;;; Code:

;;; User variables:
(defgroup find-function nil
  "Find the definition of the elisp function near point."
  :prefix "find-function"
  :group 'lisp)

(defcustom find-function-function 'function-at-point
  "*The function used by `find-function' to select the function near
point.

For example `function-at-point' or `function-called-at-point'."
  :type 'function
  :group 'find-function)

(defcustom find-function-source-path nil
  "The default list of directories where find-function searches.

If this variable is `nil' then find-function searches `load-path' by
default."
  :type '(repeat directory)
  :group 'find-function)


;;; Functions:

;;;###autoload
(defun find-function-noselect (function &optional path)
  "Returns list (BUFFER POINT) pointing to the definition of FUNCTION.

Finds the Emacs Lisp library containing the definition of FUNCTION
in a buffer and places point before the definition.  The buffer is
not selected.

If the optional argument PATH is given, the library where FUNCTION is
defined is searched in PATH instead of `load-path' (see
`find-function-source-path')."
  (and (subrp (symbol-function function))
       (error "%s is a primitive function" function))
  (if (not function)
      (error "You didn't specify a function"))
  (let ((def (symbol-function function))
	library aliases)
    (while (symbolp def)
      (or (eq def function)
	  (if aliases
	      (setq aliases (concat aliases
				    (format ", which is an alias for %s"
					    (symbol-name def))))
	    (setq aliases (format "an alias for %s" (symbol-name
						       def)))))
      (setq function (symbol-function function)
	    def (symbol-function function)))
    (if aliases
	(message aliases))
    (setq library
	  (cond ((eq (car-safe def) 'autoload)
		 (nth 1 def))
		((describe-function-find-file function))))
    (if (null library)
	(error (format "`%s' is not in `load-history'" function)))
    (if (string-match "\\(\\.elc?\\'\\)" library)
	(setq library (substring library 0 (match-beginning 1))))
    (let* ((path (or path find-function-source-path))
	   (compression (or (rassq 'jka-compr-handler file-name-handler-alist)
			    (member 'crypt-find-file-hook find-file-hooks)))
	   (filename (or (locate-library (concat library ".el")
					 t path)
			 (locate-library library t path)
			 (if compression
			     (or (locate-library (concat library ".el.gz")
						 t path)
				 (locate-library (concat library ".gz")
						 t path))))))
      (if (not filename)
	  (error "The library \"%s\" is not in the path." library))
      (save-excursion
	(set-buffer (find-file-noselect filename))
	(save-match-data
	  (let (;; avoid defconst, defgroup, defvar (any others?)
		(regexp (format "^\\s-*(def[^cgv\W]\\w+\\s-+%s\\s-" function))
		(syntable (syntax-table)))
	    (set-syntax-table emacs-lisp-mode-syntax-table)
	    (goto-char (point-min))
	    (if (prog1
		    (re-search-forward regexp nil t)
		  (set-syntax-table syntable))
		(progn
		  (beginning-of-line)
		  (list (current-buffer) (point)))
	      (error "Cannot find definition of %s" function))))))))

(defun function-at-point ()
  (or (condition-case ()
	  (let ((stab (syntax-table)))
	    (unwind-protect
		(save-excursion
		  (set-syntax-table emacs-lisp-mode-syntax-table)
		  (or (not (zerop (skip-syntax-backward "_w")))
		      (eq (char-syntax (char-after (point))) ?w)
		      (eq (char-syntax (char-after (point))) ?_)
		      (forward-sexp -1))
		  (skip-chars-forward "`'")
		  (let ((obj (read (current-buffer))))
		    (and (symbolp obj) (fboundp obj) obj)))
	      (set-syntax-table stab)))
	(error nil))
      (condition-case ()
	  (save-excursion
	    (save-restriction
	      (narrow-to-region (max (point-min) (- (point) 1000)) (point-max))
	      (backward-up-list 1)
	      (forward-char 1)
	      (let (obj)
		(setq obj (read (current-buffer)))
		(and (symbolp obj) (fboundp obj) obj))))
	(error nil))))

(defun find-function-read-function ()
  "Read and return a function, defaulting to the one near point.

The function named by `find-function-function' is used to select the
default function."
  (let ((fn (funcall find-function-function))
	(enable-recursive-minibuffers t)
	val)
    (setq val (completing-read
	       (if fn
		   (format "Find function (default %s): " fn)
		 "Find function: ")
	       obarray 'fboundp t))
    (list (if (equal val "")
	      fn (intern val)))))

(defun find-function-do-it (function path switch-fn)
  "Find Emacs Lisp FUNCTION in PATH and display it with SWITCH-FN.
Point is saved if FUNCTION is in the current buffer."
  (let ((orig-point (point))
	(buffer-point (find-function-noselect function path)))
    (if buffer-point
	(progn
	  (if (eq (current-buffer) (car buffer-point))
	      (push-mark orig-point))
	  (funcall switch-fn (car buffer-point))
	  (goto-char (elt buffer-point 1))
	  (recenter 0)))))

;;;###autoload
(defun find-function (function &optional path)
  "Find the definition of the function near point in the current window.

Finds the Emacs Lisp library containing the definition of the function
near point (selected by `find-function-function') and places point
before the definition.  Point is saved if FUNCTION is in the current
buffer.

If the optional argument PATH is given, the library where FUNCTION is
defined is searched in PATH instead of `load-path'"
  (interactive (find-function-read-function))
  (find-function-do-it function path 'switch-to-buffer))

;;;###autoload
(defun find-function-other-window (function &optional path)
  "Find the definition of the function near point in the other window.

Finds the Emacs Lisp package containing the definition of the function
near point (selected by `find-function-function') and places point
before the definition.  Point is saved if FUNCTION is in the current
buffer.

If the optional argument PATH is given, the package where FUNCTION is
defined is searched in PATH instead of `load-path'"
  (interactive (find-function-read-function))
  (find-function-do-it function path 'switch-to-buffer-other-window))

;;;###autoload
(defun find-function-other-frame (function &optional path)
  "Find the definition of the function near point in the another frame.

Finds the Emacs Lisp package containing the definition of the function
near point (selected by `find-function-function') and places point
before the definition.  Point is saved if FUNCTION is in the current
buffer.

If the optional argument PATH is given, the package where FUNCTION is
defined is searched in PATH instead of `load-path'"
  (interactive (find-function-read-function))
  (find-function-do-it function path 'switch-to-buffer-other-frame))

;;;###autoload
(defun find-function-on-key (key)
  "Find the function that KEY invokes.  KEY is a string.
Point is saved if FUNCTION is in the current buffer."
  (interactive "kFind function on key: ")
  ;; If this key seq ends with a down event, discard the
  ;; following click or drag event.  Otherwise that would
  ;; erase an eventual message.
  (let ((type (aref key (1- (length key)))))
    (if (listp type) (setq type (car type)))
    (and (symbolp type)
	 (memq 'down (event-modifiers type))
	 (read-event)))
  (save-excursion
    (let ((modifiers (event-modifiers (aref key 0)))
          window position)
      ;; For a mouse button event, go to the button it applies to
      ;; to get the right key bindings.  And go to the right place
      ;; in case the keymap depends on where you clicked.
      (if (or (memq 'click modifiers) (memq 'down modifiers)
              (memq 'drag modifiers))
          (setq window (posn-window (event-start (aref key 0)))
                position (posn-point (event-start (aref key 0)))))
      (if (windowp window)
          (progn
            (set-buffer (window-buffer window))
            (goto-char position)))
      ;; Ok, now look up the key and name the command.
      (let ((defn (key-binding key)))
        (if (or (null defn) (integerp defn))
            (message "%s is undefined" (key-description key))
          (if (consp defn)
              (message (if (windowp window)
			   "%s at that spot runs %s"
			 "%s runs %s")
		       (key-description key) (prin1-to-string defn))
            (find-function-other-window defn)))))))

(provide 'find-func)

;;; find-func.el ends here