;;; fuel-help.el -- accessing Factor's help system -*- lexical-binding: t -*-

;; Copyright (C) 2008, 2009, 2010 Jose Antonio Ortega Ruiz
;; See https://factorcode.org/license.txt for BSD license.

;; Author: Jose Antonio Ortega Ruiz <jao@gnu.org>
;; Keywords: languages, fuel, factor
;; Start date: Wed Dec 03, 2008 21:41

;;; Comentary:

;; Modes and functions interfacing Factor's 'see' and 'help'
;; utilities, as well as an ElDoc-based autodoc mode.

;;; Code:

(require 'fuel-edit)
(require 'fuel-eval)
(require 'fuel-markup)
(require 'fuel-autodoc)
(require 'fuel-completion)
(require 'fuel-popup)
(require 'fuel-menu)
(require 'fuel-base)
(require 'factor-mode)

(require 'button)

;;; Customization:

;;;###autoload
(defgroup fuel-help nil
  "Options controlling FUEL's help system."
  :group 'fuel)

(defcustom fuel-help-always-ask t
  "When enabled, always ask for confirmation in help prompts."
  :type 'boolean
  :group 'fuel-help)

(defcustom fuel-help-history-cache-size 50
  "Maximum number of pages to keep in the help browser cache."
  :type 'integer
  :group 'fuel-help)

(defcustom fuel-help-bookmarks nil
  "Bookmars. Maintain this list using the help browser."
  :type 'list
  :group 'fuel-help)

;;; Help browser history:

(defun fuel-help--make-history ()
  (list nil                                        ; current
        (make-ring fuel-help-history-cache-size)   ; previous
        (make-ring fuel-help-history-cache-size))) ; next

(defsubst fuel-help--history-current ()
  (car fuel-help--history))

(defun fuel-help--history-push (link)
  (unless (equal link (car fuel-help--history))
    (let ((next (fuel-help--history-next)))
      (unless (equal link next)
        (when next (fuel-help--history-previous))
        (ring-insert (nth 1 fuel-help--history) (car fuel-help--history))
        (setcar fuel-help--history link))))
  link)

(defun fuel-help--history-next (&optional forget-current)
  (when (not (ring-empty-p (nth 2 fuel-help--history)))
    (when (and (car fuel-help--history) (not forget-current))
      (ring-insert (nth 1 fuel-help--history) (car fuel-help--history)))
    (setcar fuel-help--history (ring-remove (nth 2 fuel-help--history) 0))))

(defun fuel-help--history-previous (&optional forget-current)
  (when (not (ring-empty-p (nth 1 fuel-help--history)))
    (when (and (car fuel-help--history) (not forget-current))
      (ring-insert (nth 2 fuel-help--history) (car fuel-help--history)))
    (setcar fuel-help--history (ring-remove (nth 1 fuel-help--history) 0))))

(defvar fuel-help--history (fuel-help--make-history))

;; https://github.com/jaor/geiser/issues/7
(eval-after-load "session.el"
  '(add-to-list 'session-globals-exclude 'fuel-help--history))


;;; Page cache:

(defun fuel-help--history-current-content ()
  (fuel-help--cache-get (car fuel-help--history)))

(defvar fuel-help--cache (make-hash-table :weakness 'key :test 'equal))

(defsubst fuel-help--cache-get (name)
  (gethash name fuel-help--cache))

(defsubst fuel-help--cache-insert (name str)
  (puthash name str fuel-help--cache))

(defsubst fuel-help--cache-clear ()
  (clrhash fuel-help--cache))


;;; Fuel help buffer and internals:

(defun fuel-help--buffer ()
  (or (get-buffer "*fuel help*")
      (with-current-buffer (get-buffer-create "*fuel help*")
        (fuel-help-mode)
        (fuel-popup-mode)
        (current-buffer))))

(defvar fuel-help--prompt-history nil)

(defvar-local fuel-help--buffer-link nil)

(defun fuel-help--read-word ()
  (let* ((def (factor-symbol-at-point))
         (prompt (format "See help on%s: " (if def (format " (%s)" def) "")))
         (ask (or (not def) fuel-help-always-ask)))
    (if ask
        (fuel-completion--read-word prompt
                                        def
                                        'fuel-help--prompt-history
                                        t)
      def)))

(defun fuel-help--word-help (&optional word display-only print-message)
  (let ((def (or word (fuel-help--read-word))))
    (when def
      (let ((cmd `(:fuel* (,def ,'fuel-word-help)
                          ,(factor-current-vocab)
                          ,(factor-usings))))
        (when print-message
          (message "Looking up '%s' ..." def))
        (let* ((ret (fuel-eval--send/wait cmd))
               (res (fuel-eval--retort-result ret)))
          (if (not res)
              (when print-message
                (message "No help for '%s'" def))
            (fuel-help--insert-contents
             (list def def 'word) res display-only)))))))

(defun fuel-help--get-article (name label)
  (message "Retrieving article ...")
  (let* ((name (if (listp name) (cons :seq name) name))
         (cmd `(:fuel* ((,name fuel-get-article)) "fuel" t))
         (ret (fuel-eval--send/wait cmd))
         (res (fuel-eval--retort-result ret)))
    (if (not res)
        (message "Article '%s' not found" label)
      (fuel-help--insert-contents (list name label 'article) res)
      (message ""))))

(defun fuel-help--get-vocab (name)
  (message "Retrieving help vocabulary for vocabulary '%s' ..." name)
  (let* ((cmd `(:fuel* ((,name fuel-vocab-help)) "fuel" (,name)))
         (ret (fuel-eval--send/wait cmd))
         (res (fuel-eval--retort-result-safe ret)))
    (if (not res)
        (message "No help available for vocabulary '%s'" name)
      (fuel-help--insert-contents (list name name 'vocab) res)
      (message ""))))

(defun fuel-help--get-vocab/author (author)
  (message "Retrieving vocabularies by %s ..." author)
  (let* ((cmd `(:fuel* ((,author fuel-get-vocabs/author)) "fuel" t))
         (ret (fuel-eval--send/wait cmd))
         (res (fuel-eval--retort-result ret)))
    (if (not res)
        (message "No vocabularies by %s" author)
      (fuel-help--insert-contents (list author author 'author) res)
      (message ""))))

(defun fuel-help--get-vocab/tag (tag)
  (message "Retrieving vocabularies tagged '%s' ..." tag)
  (let* ((cmd `(:fuel* ((,tag fuel-get-vocabs/tag)) "fuel" t))
         (ret (fuel-eval--send/wait cmd))
         (res (fuel-eval--retort-result ret)))
    (if (not res)
        (message "No vocabularies tagged '%s'" tag)
      (fuel-help--insert-contents (list tag tag 'tag) res)
      (message ""))))

(defun fuel-help--follow-link (link label type &optional no-cache)
  (let* ((llink (list link label type))
         (cached (and (not no-cache) (fuel-help--cache-get llink))))
    (if (not cached)
        (let ((fuel-help-always-ask nil))
          (cond ((eq type 'word) (fuel-help--word-help link))
                ((eq type 'article) (fuel-help--get-article link label))
                ((eq type 'vocab) (fuel-help--get-vocab link))
                ((eq type 'author) (fuel-help--get-vocab/author label))
                ((eq type 'tag) (fuel-help--get-vocab/tag label))
                ((eq type 'bookmarks) (fuel-help-display-bookmarks))
                (t (error "Links of type %s not yet implemented" type))))
      (fuel-help--insert-contents llink cached))))

(defun fuel-help--insert-contents (key content &optional display-only)
  (let ((hb (fuel-help--buffer))
        (inhibit-read-only t)
        (font-lock-verbose nil))
    (with-current-buffer hb
      (erase-buffer)
      (if (stringp content)
          (insert content)
        (fuel-markup--print content)
        (fuel-markup--insert-newline)
        (delete-blank-lines)
        (fuel-help--cache-insert key (buffer-string)))
      (fuel-help--history-push key)
      (setq fuel-help--buffer-link key)
      (set-buffer-modified-p nil)
      (goto-char (point-min))
      (fuel-popup--display nil display-only))))

;;; Bookmarks:

(defun fuel-help-bookmark-page ()
  "Add current help page to bookmarks."
  (interactive)
  (let ((link fuel-help--buffer-link))
    (unless link (error "No link associated to this page"))
    (add-to-list 'fuel-help-bookmarks link)
    (customize-save-variable 'fuel-help-bookmarks fuel-help-bookmarks)
    (message "Bookmark '%s' saved" (cadr link))))

(defun fuel-help-delete-bookmark ()
  "Delete link at point from bookmarks."
  (interactive)
  (let ((link (fuel-markup--link-at-point)))
    (unless link (error "No link at point"))
    (unless (member link fuel-help-bookmarks)
      (error "'%s' is not bookmarked" (cadr link)))
    (customize-save-variable 'fuel-help-bookmarks
                             (remove link fuel-help-bookmarks))
    (message "Bookmark '%s' delete" (cadr link))
    (fuel-help-display-bookmarks)))

(defun fuel-help-display-bookmarks ()
  "Display bookmarked pages."
  (interactive)
  (let ((links (mapcar (lambda (l) (cons '$subsection l)) fuel-help-bookmarks)))
    (unless links (error "No links to display"))
    (fuel-help--insert-contents '("bookmarks" "Bookmars" bookmarks)
                                `(article "Bookmarks" ,links))))


;;; Interactive help commands:

(defun fuel-help (&optional print-message)
  "Show extended help about the word or vocabulary at point, using a
help buffer."
  (interactive "p")
  (if (factor-on-vocab)
      (fuel-help-vocab (factor-symbol-at-point))
    (fuel-help--word-help nil nil print-message)))

(defun fuel-help-vocab (vocab)
  "Ask for a vocabulary name and show its help page."
  (interactive (list (fuel-completion--read-vocab nil)))
  (fuel-help--get-vocab vocab))

(defun fuel-help-next (&optional forget-current)
  "Go to next page in help browser.
With prefix, the current page is deleted from history."
  (interactive "P")
  (let ((item (fuel-help--history-next forget-current)))
    (unless item (error "No next page"))
    (apply 'fuel-help--follow-link item)))

(defun fuel-help-previous (&optional forget-current)
  "Go to previous page in help browser.
With prefix, the current page is deleted from history."
  (interactive "P")
  (let ((item (fuel-help--history-previous forget-current)))
    (unless item (error "No previous page"))
    (apply 'fuel-help--follow-link item)))

(defun fuel-help-kill-page ()
  "Kill current page if a previous or next one exists."
  (interactive)
  (condition-case nil
      (fuel-help-previous t)
    (error (fuel-help-next t))))

(defun fuel-help-refresh ()
  "Refresh the contents of current page."
  (interactive)
  (when fuel-help--buffer-link
    (apply 'fuel-help--follow-link (append fuel-help--buffer-link '(t)))))

(defun fuel-help-clean-history ()
  "Clean up the help browser cache of visited pages."
  (interactive)
  (fuel-help--cache-clear)
  (setq fuel-help--history (fuel-help--make-history))
  (fuel-help-refresh)
  (message "Browsing history cleaned"))

(defun fuel-help-edit ()
  "Edit the current article or word help."
  (interactive)
  (let ((link (car fuel-help--buffer-link))
        (type (nth 2 fuel-help--buffer-link)))
    (cond ((eq type 'word) (fuel-edit-word-doc-at-point nil link))
          ((member type '(article vocab)) (fuel-edit--edit-article link))
          (t (error "No document associated with this page")))))


;;;; Help mode map:

(defvar fuel-help-mode-map
  (let ((map (make-sparse-keymap)))
    (suppress-keymap map)
    (set-keymap-parent map button-buffer-map)
    map))

(fuel-menu--defmenu fuel-help fuel-help-mode-map
  ("Help on word..." "h" fuel-help)
  ("Help on vocab..." "v" fuel-help-vocab)
  ("Apropos..." "a" fuel-apropos)
  --
  ("Bookmark this page" "ba" fuel-help-bookmark-page)
  ("Delete bookmark" "bd" fuel-help-delete-bookmark)
  ("Show bookmarks..." "bb" fuel-help-display-bookmarks)
  ("Clean browsing history" "c" fuel-help-clean-history)
  --
  ("Edit word or vocab at point" "\M-." fuel-edit-word-at-point)
  ("Edit help file" "e" fuel-help-edit)
  --
  ("Next page" "n" fuel-help-next)
  ("Previous page" ("p" "l") fuel-help-previous)
  ("Refresh page" "r" fuel-help-refresh)
  ("Kill page" "k" fuel-help-kill-page)
  --
  ("Scroll page up" ((kbd "SPC"))  scroll-up)
  ("Scroll page down" ((kbd "S-SPC")) scroll-down)
  --
  ("Switch to listener" "\C-c\C-z" run-factor))

;;; IN: support

(defun fuel-help--find-in-buffer-link ()
  (when (and fuel-help--buffer-link
             (equal (nth 2 fuel-help--buffer-link) 'vocab))
    (car fuel-help--buffer-link)))

(defun fuel-help--find-in ()
  (save-excursion
    (or (factor-find-in)
        (fuel-help--find-in-buffer-link)
        (and (goto-char (point-min))
             (re-search-forward "Vocabulary: \\(.+\\)$" nil t)
             (match-string-no-properties 1)))))

;;; Help mode definition:

;;;###autoload
(define-derived-mode fuel-help-mode special-mode "FUEL Help"
  "Major mode for browsing Factor documentation.
\\{fuel-help-mode-map}"
  :syntax-table factor-mode-syntax-table
  (setq factor-current-vocab-function 'fuel-help--find-in)
  (setq fuel-markup--follow-link-function 'fuel-help--follow-link))

(provide 'fuel-help)
;;; fuel-help.el ends here