;;; finder.el --- topic & keyword-based code finder  -*- lexical-binding: t -*-

;; Copyright (C) 1992, 1997-1999, 2001-2022 Free Software Foundation,
;; Inc.

;; Author: Eric S. Raymond <esr@snark.thyrsus.com>
;; Created: 16 Jun 1992
;; Keywords: help

;; 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:

;; This mode uses the Keywords library header to provide code-finding
;; services by keyword.

;;; Code:

(require 'package)
(require 'lisp-mnt)
(require 'find-func) ;for find-library(-suffixes)
(require 'finder-inf nil t)

;; These are supposed to correspond to top-level customization groups,
;; says rms.
(defvar finder-known-keywords
  '((abbrev	. "abbreviation handling, typing shortcuts, and macros")
    (bib	. "bibliography processors")
    (c		. "C and related programming languages")
    (calendar	. "calendar and time management tools")
    (comm	. "communications, networking, and remote file access")
    (convenience . "convenience features for faster editing")
    (data	. "editing data (non-text) files")
    (docs	. "Emacs documentation facilities")
    (emulations	. "emulations of other editors")
    (extensions	. "Emacs Lisp language extensions")
    (faces	. "fonts and colors for text")
    (files      . "file editing and manipulation")
    (frames     . "Emacs frames and window systems")
    (games	. "games, jokes and amusements")
    (hardware	. "interfacing with system hardware")
    (help	. "Emacs help systems")
    (hypermedia . "links between text or other media types")
    (i18n	. "internationalization and character-set support")
    (internal	. "code for Emacs internals, build process, defaults")
    (languages	. "specialized modes for editing programming languages")
    (lisp	. "Lisp support, including Emacs Lisp")
    (local	. "code local to your site")
    (maint	. "Emacs development tools and aids")
    (mail	. "email reading and posting")
    (matching	. "searching, matching, and sorting")
    (mouse	. "mouse support")
    (multimedia . "images and sound")
    (news	. "USENET news reading and posting")
    (outlines   . "hierarchical outlining and note taking")
    (processes	. "processes, subshells, and compilation")
    (terminals	. "text terminals (ttys)")
    (tex	. "the TeX document formatter")
    (tools	. "programming tools")
    (unix	. "UNIX feature interfaces and emulators")
    (vc		. "version control")
    (wp		. "word processing"))
  "Association list of the standard \"Keywords:\" headers.
Each element has the form (KEYWORD . DESCRIPTION).")

(defvar finder-mode-map
  (let ((map (make-sparse-keymap)))
    (define-key map " "	'finder-select)
    (define-key map "f"	'finder-select)
    (define-key map [follow-link] 'mouse-face)
    (define-key map [mouse-2]	'finder-mouse-select)
    (define-key map "\C-m"	'finder-select)
    (define-key map "?"	'finder-summary)
    (define-key map "n" 'next-line)
    (define-key map "p" 'previous-line)
    (define-key map "q"	'finder-exit)
    (define-key map "d"	'finder-list-keywords)
    map)
  "Keymap used in `finder-mode'.")

(easy-menu-define finder-mode-menu finder-mode-map
  "Menu for `finder-mode'."
  '("Finder"
    ["Select" finder-select
     :help "Select item on current line in a finder buffer"]
    ["List keywords" finder-list-keywords
     :help "Display descriptions of the keywords in the Finder buffer"]
    ["Summary" finder-summary
     :help "Summary item on current line in a finder buffer"]
    ["Quit" finder-exit
     :help "Exit Finder mode"]))

(defvar finder-mode-syntax-table
  (let ((st (make-syntax-table emacs-lisp-mode-syntax-table)))
    (modify-syntax-entry ?\; ".   " st)
    st)
  "Syntax table used while in `finder-mode'.")

(defvar finder-headmark nil
  "Internal Finder mode variable, local in Finder buffer.")

;;; Code for regenerating the keyword list.

(defvar finder-keywords-hash nil
  "Hash table mapping keywords to lists of package names.
Keywords and package names both should be symbols.")

(defvar generated-finder-keywords-file "finder-inf.el"
  "The function `finder-compile-keywords' writes keywords into this file.")

;; Skip autogenerated files, because they will never contain anything
;; useful, and because in parallel builds of Emacs they may get
;; modified while we are trying to read them.
;; https://lists.gnu.org/r/emacs-pretest-bug/2007-01/msg00469.html
;; ldefs-boot is not auto-generated, but has nothing useful.
(defvar finder-no-scan-regexp "\\(^\\.#\\|\\(loaddefs\\|ldefs-boot\\|\
cus-load\\|finder-inf\\|esh-groups\\|subdirs\\|leim-list\\)\\.el$\\)"
  "Regexp matching file names not to scan for keywords.")

(autoload 'autoload-rubric "autoload")

(defconst finder--builtins-descriptions
  ;; I have no idea whether these are supposed to be capitalized
  ;; and/or end in a full-stop.  Existing file headers are inconsistent,
  ;; but mainly seem to not do so.
  '((emacs . "the extensible text editor")
    (nxml . "a new XML mode"))
  "Alist of built-in package descriptions.
Entries have the form (PACKAGE-SYMBOL . DESCRIPTION).
When generating `package--builtins', this overrides what the description
would otherwise be.")

(defvar finder--builtins-alist
  '(("calc" . calc)
    ("ede"  . ede)
    ("erc"  . erc)
    ("eshell" . eshell)
    ("gnus" . gnus)
    ("international" . emacs)
    ("language" . emacs)
    ("mh-e" . mh-e)
    ("semantic" . semantic)
    ("analyze" . semantic)
    ("bovine" . semantic)
    ("decorate" . semantic)
    ("symref" . semantic)
    ("wisent" . semantic)
    ;; This should really be ("nxml" . nxml-mode), because nxml-mode.el
    ;; is the main file for the package.  Then we would not need an
    ;; entry in finder--builtins-descriptions.  But I do not know if
    ;; it is safe to change this, in case it is already in use.
    ("nxml" . nxml)
    ("org"  . org)
    ("srecode" . srecode)
    ("term" . emacs)
    ("url"  . url))
  "Alist of built-in package directories.
Each element should have the form (DIR . PACKAGE), where DIR is a
directory name and PACKAGE is the name of a package (a symbol).
When generating `package--builtins', Emacs assumes any file in
DIR is part of the package PACKAGE.")

(defconst finder-buffer "*Finder*"
  "Name of the Finder buffer.")

(defun finder-compile-keywords (&rest dirs)
  "Regenerate list of built-in Emacs packages.
This recomputes `package--builtins' and `finder-keywords-hash',
and prints them into the file `generated-finder-keywords-file'.

Optional DIRS is a list of Emacs Lisp directories to compile
from; the default is `load-path'."
  ;; Allow compressed files also.
  (setq package--builtins nil)
  (setq finder-keywords-hash (make-hash-table :test 'eq))
  (let* ((el-file-regexp "\\`\\([^=].*\\)\\.el\\(\\.\\(gz\\|Z\\)\\)?\\'")
         (file-count 0)
         (files (cl-loop for d in (or dirs load-path)
                         when (file-exists-p (directory-file-name d))
                         append (mapcar
                                 (lambda (f)
                                   (cons d f))
                                 (directory-files d nil el-file-regexp))))
         (progress (make-progress-reporter
                    (byte-compile-info "Scanning files for finder")
                    0 (length files)))
	 base-name summary keywords package version entry desc)
    (dolist (elem files)
      (let* ((d (car elem))
             (f (cdr elem))
             (package-override
	      (intern-soft
	       (cdr-safe
	        (assoc (file-name-nondirectory
                        (directory-file-name d))
		       finder--builtins-alist)))))
        (progress-reporter-update progress (setq file-count (1+ file-count)))
        (unless (or (string-match finder-no-scan-regexp f)
		    (null (setq base-name
			        (and (string-match el-file-regexp f)
				     (intern (match-string 1 f))))))
          ;; (memq base-name processed))
          ;; There are multiple files in the tree with the same
          ;; basename.  So skipping files based on basename means you
          ;; randomly (depending on which order the files are
          ;; traversed in) miss some packages.
          ;; https://debbugs.gnu.org/14010
          ;; You might think this could lead to two files providing
          ;; the same package, but it does not, because the duplicates
          ;; are (at time of writing) all due to files in cedet, which
          ;; end up with package-override set.  FIXME this is
          ;; obviously fragile.  Make the (eq base-name package) case
          ;; below issue a warning if package-override is nil?
          ;;	    (push base-name processed)
	  (with-temp-buffer
	    (insert-file-contents (expand-file-name f d))
	    (setq keywords (mapcar #'intern (lm-keywords-list))
		  package  (or package-override
			       (let ((str (lm-header "package")))
			         (if str (intern str)))
			       base-name)
		  summary  (or (cdr
			        (assq package finder--builtins-descriptions))
			       (lm-synopsis))
		  version  (lm-header "version")))
	  (when summary
	    (setq version (or (ignore-errors (version-to-list version))
                              (alist-get package package--builtin-versions)))
	    (setq entry (assq package package--builtins))
	    (cond ((null entry)
		   (push (cons package
                               (package-make-builtin version summary))
		         package--builtins))
		  ;; The idea here is that eg calc.el gets to define
		  ;; the description of the calc package.
		  ;; This does not work for eg nxml-mode.el.
		  ((eq base-name package)
		   (setq desc (cdr entry))
		   (aset desc 0 version)
		   (aset desc 2 summary)))
	    (dolist (kw keywords)
	      (puthash kw
		       (cons package
			     (delq package
				   (gethash kw finder-keywords-hash)))
		       finder-keywords-hash))))))
    (progress-reporter-done progress))
  (setq package--builtins
	(sort package--builtins
	      (lambda (a b) (string< (symbol-name (car a))
				     (symbol-name (car b))))))

  (with-current-buffer
      (find-file-noselect generated-finder-keywords-file)
    (setq buffer-undo-list t)
    (erase-buffer)
    (insert (autoload-rubric generated-finder-keywords-file
                             "keyword-to-package mapping" t))
    (search-backward "")
    ;; FIXME: Now that we have package--builtin-versions, package--builtins is
    ;; only needed to get the list of unversioned packages and to get the
    ;; summary description of each package.
    (insert "(setq package--builtins '(\n")
    (dolist (package package--builtins)
      (insert "  ")
      (prin1 package (current-buffer))
      (insert "\n"))
    (insert "))\n\n")
    ;; Insert hash table.
    (insert "(setq finder-keywords-hash\n      ")
    (prin1 finder-keywords-hash (current-buffer))
    (insert ")\n")
    (basic-save-buffer)))

(defun finder-compile-keywords-make-dist ()
  "Regenerate `finder-inf.el' for the Emacs distribution."
  (apply #'finder-compile-keywords command-line-args-left)
  (kill-emacs))

;;; Now the retrieval code

(defun finder-insert-at-column (column &rest strings)
  "Insert, at column COLUMN, other args STRINGS."
  (if (>= (current-column) column) (insert "\n"))
  (move-to-column column t)
  (apply #'insert strings))

(defvar finder-help-echo nil)

(defun finder-mouse-face-on-line ()
  "Put `mouse-face' and `help-echo' properties on the previous line."
  (save-excursion
    (forward-line -1)
    ;; If finder-insert-at-column moved us to a new line, go back one more.
    (if (looking-at "[ \t]") (forward-line -1))
    (unless finder-help-echo
      (setq finder-help-echo
	    (let* ((keys1 (where-is-internal 'finder-select
					     finder-mode-map))
		   (keys (nconc (where-is-internal
				 'finder-mouse-select finder-mode-map)
				keys1)))
	      (concat (mapconcat #'key-description keys ", ")
		      ": select item"))))
    (add-text-properties
     (line-beginning-position) (line-end-position)
     '(mouse-face highlight
		  help-echo finder-help-echo))))

(defun finder-unknown-keywords ()
  "Return an alist of unknown keywords and number of their occurrences.
Unknown keywords are those present in `finder-keywords-hash' but
not `finder-known-keywords'."
  (let (alist)
    (maphash (lambda (kw packages)
	       (unless (assq kw finder-known-keywords)
		 (push (cons kw (length packages)) alist)))
	     finder-keywords-hash)
    (sort alist (lambda (a b) (string< (car a) (car b))))))

;;;###autoload
(defun finder-list-keywords ()
  "Display descriptions of the keywords in the Finder buffer."
  (interactive)
  (if (get-buffer finder-buffer)
      (pop-to-buffer finder-buffer)
    (pop-to-buffer (get-buffer-create finder-buffer))
    (finder-mode)
    (let ((inhibit-read-only t))
      (erase-buffer)
      (dolist (assoc finder-known-keywords)
	(let ((keyword (car assoc)))
	  (insert (propertize (symbol-name keyword)
			      'font-lock-face 'font-lock-constant-face))
	  (finder-insert-at-column 14 (concat (cdr assoc) "\n"))
	  (finder-mouse-face-on-line)))
      (goto-char (point-min))
      (setq finder-headmark (point)
	    buffer-read-only t)
      (set-buffer-modified-p nil)
      (balance-windows)
      (finder-summary))))

(defun finder-list-matches (key)
  (let* ((id (intern key))
	 (packages (gethash id finder-keywords-hash)))
    (unless packages
      (error "No packages matching key `%s'" key))
    (let ((package-list-unversioned t))
      (package-show-package-list packages))))

(define-button-type 'finder-xref 'action #'finder-goto-xref)

(defun finder-goto-xref (button)
  "Jump to a Lisp file for the BUTTON at point."
  (let* ((file (button-get button 'xref))
         (lib (locate-library file)))
    (if lib (finder-commentary lib)
      (message "Unable to locate `%s'" file))))

;;;###autoload
(defun finder-commentary (file)
  "Display FILE's commentary section.
FILE should be in a form suitable for passing to `locate-library'."
  (interactive
   (list
    (completing-read "Library name: "
		     (apply-partially 'locate-file-completion-table
                                      (or find-library-source-path load-path)
                                      (find-library-suffixes)))))
  (let ((str (lm-commentary (find-library-name file))))
    (or str (error "Can't find any Commentary section"))
    ;; This used to use *Finder* but that would clobber the
    ;; directory of categories.
    (pop-to-buffer "*Finder-package*")
    (setq buffer-read-only nil
          buffer-undo-list t)
    (erase-buffer)
    (insert str)
    (goto-char (point-min))
    (while (re-search-forward "\\<\\([-[:alnum:]]+\\.el\\)\\>" nil t)
      (if (locate-library (match-string 1))
          (make-text-button (match-beginning 1) (match-end 1)
                            'xref (match-string-no-properties 1)
                            'help-echo "Read this file's commentary"
                            :type 'finder-xref)))
    (goto-char (point-min))
    (setq buffer-read-only t)
    (set-buffer-modified-p nil)
    (shrink-window-if-larger-than-buffer)
    (finder-mode)
    (finder-summary)))

(defun finder-current-item ()
  (let ((key (save-excursion
	       (beginning-of-line)
	       (current-word))))
    (if (or (and finder-headmark (< (point) finder-headmark))
	    (zerop (length key)))
	(error "No keyword or filename on this line")
      key)))

(defun finder-select ()
  "Select item on current line in a Finder buffer."
  (interactive nil finder-mode)
  (let ((key (finder-current-item)))
      (if (string-match "\\.el$" key)
	  (finder-commentary key)
	(finder-list-matches key))))

(defun finder-mouse-select (event)
  "Select item in a Finder buffer with the mouse."
  (interactive "e")
  (with-current-buffer (window-buffer (posn-window (event-start event)))
    (goto-char (posn-point (event-start event)))
    (finder-select)))

;;;###autoload
(defun finder-by-keyword ()
  "Find packages matching a given keyword."
  ;; FIXME: Why does this function exist?  Should it just be an alias?
  (interactive)
  (finder-list-keywords))

(define-derived-mode finder-mode nil "Finder"
  "Major mode for browsing package documentation.
\\<finder-mode-map>
\\[finder-select]	more help for the item on the current line
\\[finder-exit]	exit Finder mode and kill the Finder buffer."
  :syntax-table finder-mode-syntax-table
  :interactive nil
  (setq buffer-read-only t
	buffer-undo-list t)
  (setq-local finder-headmark nil))

(defun finder-summary ()
  "Summarize basic Finder commands."
  (interactive nil finder-mode)
  (message "%s"
   (substitute-command-keys
    "\\<finder-mode-map>\\[finder-select] = select, \
\\[finder-mouse-select] = select, \\[finder-list-keywords] = to \
finder directory, \\[finder-exit] = quit, \\[finder-summary] = help")))

(defun finder-exit ()
  "Exit Finder mode.
Quit the window and kill all Finder-related buffers."
  (interactive nil finder-mode)
  (quit-window t)
  (dolist (buf (list finder-buffer "*Finder-package*"))
    (and (get-buffer buf) (kill-buffer buf))))

(defun finder-unload-function ()
  "Unload the Finder library."
  (with-demoted-errors (unload-feature 'finder-inf t))
  ;; continue standard unloading
  nil)


(provide 'finder)

;;; finder.el ends here