;;; geiser-doc.el -- accessing scheme-provided documentation  -*- lexical-binding: t; -*-

;; Copyright (C) 2009-2016, 2021-2022 Jose Antonio Ortega Ruiz

;; This program is free software; you can redistribute it and/or
;; modify it under the terms of the Modified BSD License. You should
;; have received a copy of the license along with this program. If
;; not, see <http://www.xfree86.org/3.3.6/COPYRIGHT2.html#5>.

;; Start date: Sat Feb 14, 2009 14:09


;;; Code:

(require 'geiser-edit)
(require 'geiser-impl)
(require 'geiser-completion)
(require 'geiser-autodoc)
(require 'geiser-eval)
(require 'geiser-syntax)
(require 'geiser-menu)
(require 'geiser-popup)
(require 'geiser-custom)
(require 'geiser-base)

(require 'button)
(eval-when-compile (require 'subr-x))


;;; Customization:

(defgroup geiser-doc nil
  "Options for documentation buffers."
  :group 'geiser)

(geiser-custom--defface doc-title
  'bold geiser-doc "article titles in documentation buffers")

(geiser-custom--defface doc-link
  'link geiser-doc "links in documentation buffers")

(geiser-custom--defface doc-button
  'button geiser-doc "buttons in documentation buffers")


;;; Implementation
(geiser-impl--define-caller geiser-doc--external-help external-help
                            (symbol module)
  "By default, Geiser will display help about an identifier in a
help buffer, after collecting the associated signature and
docstring. You can provide an alternative function for displaying
help (e.g. browse an HTML page) implementing this method.")

(geiser-impl--define-caller geiser-doc--display-docstring
    display-docstring (ret)
  "This method receives the result of calling the geiser scheme
procedure symbol-documentation and should display it in the
current buffer.  By default, geiser looks for the value of the
key docstring in the result, assumed to be an alist, and inserts
it verbatim at point if it's a string.  Providing an
implementation of this method may be useful if displaying the
info returned by the scheme side (display-docstring) needs more
elaboration on emacs' side.  This method should return a truthy
value if the default action should be skipped.")


;;; Documentation browser history:

(defvar geiser-doc-history-size 50)
(defvar geiser-doc--history nil)

(defun geiser-doc--make-history ()
  (list nil                                   ; current
        (make-ring geiser-doc-history-size)   ; previous
        (make-ring geiser-doc-history-size))) ; next

(setq geiser-doc--history (geiser-doc--make-history))

(defsubst geiser-doc--history-current ()
  (car geiser-doc--history))

(defsubst geiser-doc--history-previous-link ()
  (ring-ref (cadr geiser-doc--history) 0))

(defsubst geiser-doc--history-next-link ()
  (ring-ref (car (cddr geiser-doc--history)) 0))

(defun geiser-doc--history-push (link)
  (unless (or (null link) (equal link (geiser-doc--history-current)))
    (when (not (null (geiser-doc--history-current)))
      (let ((next (geiser-doc--history-next)))
        (unless (equal link next)
          (when next (geiser-doc--history-previous))
          (ring-insert (nth 1 geiser-doc--history)
                       (car geiser-doc--history)))))
    (setcar geiser-doc--history link))
  link)

(defsubst geiser-doc--history-next-p ()
  (not (ring-empty-p (nth 2 geiser-doc--history))))

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

(defsubst geiser-doc--history-previous-p ()
  (not (ring-empty-p (nth 1 geiser-doc--history))))

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


;;; Links

(defsubst geiser-doc--make-link (target module impl)
  (list target module impl))

(defsubst geiser-doc--link-target (link)
  (nth 0 link))

(defsubst geiser-doc--link-module (link)
  (nth 1 link))

(defsubst geiser-doc--link-impl (link)
  (nth 2 link))

(defun geiser-doc--follow-link (link)
  (let ((target (geiser-doc--link-target link))
        (module (geiser-doc--link-module link))
        (impl (geiser-doc--link-impl link)))
    (when (and (or target module) impl)
      (with--geiser-implementation impl
        (if (null target)
            (geiser-doc-module module impl)
          (let ((geiser-eval--get-module-function (lambda (x) module)))
            (geiser-doc-symbol target module impl)))))))

(defvar-local geiser-doc--buffer-link nil)

(defsubst geiser-doc--implementation ()
  (geiser-doc--link-impl geiser-doc--buffer-link))

(defun geiser-doc--button-action (button)
  (let ((link (button-get button 'geiser-link)))
    (when link (geiser-doc--follow-link link))))

(define-button-type 'geiser-doc--button
  'action 'geiser-doc--button-action
  'follow-link t)

(defun geiser-doc--make-module-button (beg end module impl)
  (let ((link (geiser-doc--make-link nil module impl))
        (help (format "Help for module %s" module)))
    (make-text-button beg end :type 'geiser-doc--button
                      'face 'geiser-font-lock-doc-link
                      'geiser-link link
                      'help-echo help)))

(defun geiser-doc--insert-button (target module impl &optional sign)
  (let* ((link (geiser-doc--make-link target module impl))
         (sign (when sign (if (listp sign) sign (list target))))
         (text (format "%s" (or (and sign (geiser-autodoc--str* sign))
                                target
                                module)))
         (help (format "%smodule %s"
                       (if target (format "%s in " target) "")
                       (or module "<unknown>"))))
    (insert-text-button text
                        :type 'geiser-doc--button
                        'face 'geiser-font-lock-doc-link
                        'geiser-link link
                        'help-echo help)))

(defun geiser-doc-goto-source ()
  "Go to the definition of this item."
  (interactive)
  (when-let (link geiser-doc--buffer-link)
    (with--geiser-implementation (geiser-doc--link-impl link)
      (if-let (target (geiser-doc--link-target link))
          (geiser-edit-symbol target nil (point-marker))
        (geiser-edit-module (geiser-doc--link-module link))))))

(defun geiser-doc-goto-manual ()
  "Go to the manual for this item."
  (interactive)
  (when-let (link geiser-doc--buffer-link)
    (let ((tm (geiser-doc--link-target link))
          (mod (geiser-doc--link-module link))
          (impl (geiser-doc--link-impl link)))
      (geiser-doc--external-help impl (or tm mod) mod))))

(defun geiser-doc--xbutton-action (button)
  (let ((k (button-get button 'x-kind)))
    (cond ((eq 'source k) (geiser-doc-goto-source))
          ((eq 'manual k) (geiser-doc-goto-manual)))))

(define-button-type 'geiser-doc--xbutton
  'action 'geiser-doc--xbutton-action
  'face 'geiser-font-lock-doc-button
  'follow-link t)

(defun geiser-doc--insert-xbutton (&optional manual)
  (let ((label (if manual "[manual]" "[source]"))
        (help (if manual "Look up in Scheme manual" "Go to definition")))
    (insert-text-button label
                        :type 'geiser-doc--xbutton
                        'help-echo help
                        'x-kind (if manual 'manual 'source))))

(defun geiser-doc--insert-xbuttons (impl)
  (when (geiser-impl--method 'external-help impl)
    (geiser-doc--insert-xbutton t)
    (insert " "))
  (geiser-doc--insert-xbutton))

(defun geiser-doc--insert-nav-button (next)
  (let* ((lnk (if next (geiser-doc--history-next-link)
                (geiser-doc--history-previous-link)))
         (what (geiser-doc--link-target lnk))
         (what (or what (geiser-doc--link-module lnk)))
         (action (if next '(lambda (b) (geiser-doc-next))
                   '(lambda (b) (geiser-doc-previous)))))
    (insert-text-button (if next "[forward]" "[back]")
                        'action action
                        'help-echo (format "Previous help item (%s)" what)
                        'face 'geiser-font-lock-doc-button
                        'follow-link t)))


;;; Auxiliary functions:

(defun geiser-doc--manual-available-p ()
  (geiser-impl--method 'external-help geiser-impl--implementation))

(defun geiser-doc--module (&optional mod impl)
  (let ((impl (or impl (geiser-doc--link-impl geiser-doc--buffer-link)))
        (mod (or mod (geiser-doc--link-module geiser-doc--buffer-link))))
    (geiser-impl--call-method 'find-module impl mod)))

(defun geiser-doc--insert-title (title)
  (let ((p (point)))
    (insert (format "%s" title))
    (fill-paragraph nil)
    (let ((indent-line-function 'lisp-indent-line))
      (indent-region p (point)))
    (put-text-property p (point) 'face 'geiser-font-lock-doc-title)
    (newline)))

(defun geiser-doc--insert-list (title lst module impl)
  (when lst
    (geiser-doc--insert-title title)
    (newline)
    (dolist (w lst)
      (let ((name (car w))
            (signature (cdr (assoc "signature" w)))
            (info (cdr (assoc "info" w))))
        (insert "\t- ")
        (if module
            (geiser-doc--insert-button name module impl signature)
          (geiser-doc--insert-button nil name impl))
        (when info (insert (format "  %s" info)))
        (newline)))
    (newline)))

(defun geiser-doc--insert-footer (impl)
  (newline 2)
  (geiser-doc--insert-xbuttons impl)
  (let* ((prev (and (geiser-doc--history-previous-p) 8))
         (nxt (and (geiser-doc--history-next-p) 10))
         (len (max 1 (- (window-width)
                        (- (point) (line-beginning-position))
                        (or prev 0)
                        (or nxt 0)))))
    (when (or prev nxt)
      (insert (make-string len ?\ )))
    (when prev
      (geiser-doc--insert-nav-button nil)
      (insert " "))
    (when nxt
      (geiser-doc--insert-nav-button t))))


;;; Documentation browser and mode:

(defun geiser-doc-edit-symbol-at-point ()
  "Open definition of symbol at point."
  (interactive)
  (let* ((impl (geiser-doc--implementation))
         (module (geiser-doc--module)))
    (unless (and impl module)
      (error "I don't know what module this buffer refers to."))
    (with--geiser-implementation impl
      (geiser-edit-symbol-at-point))))

(defvar geiser-doc-mode-map
  (let ((map (make-sparse-keymap)))
    (suppress-keymap map)
    (set-keymap-parent map button-buffer-map)
    map)
  "Keymap for `geiser-doc-mode'.")

(declare-function geiser-repl--switch-to-repl "geiser-repl")

(defun geiser-doc-switch-to-repl ()
  (interactive)
  (geiser-repl--switch-to-repl))

(geiser-menu--defmenu doc geiser-doc-mode-map
  ("Next link" ("n") forward-button)
  ("Previous link" ("p") backward-button)
  ("Next section" ("N") geiser-doc-next-section)
  ("Previous section" ("P") geiser-doc-previous-section)
  --
  ("Next page" ("f") geiser-doc-next "Next item"
   :enable (geiser-doc--history-next-p))
  ("Previous page" ("b") geiser-doc-previous "Previous item"
   :enable (geiser-doc--history-previous-p))
  --
  ("Go to REPL" ("z" "\C-cz" "\C-c\C-z") geiser-doc-switch-to-repl)
  ("Refresh" ("g" "r") geiser-doc-refresh "Refresh current page")
  --
  ("Edit symbol" ("." "\M-.") geiser-doc-edit-symbol-at-point
   :enable (geiser--symbol-at-point))
  ("View source" ("s") geiser-doc-goto-source)
  ("View manual" ("m" "h") geiser-doc-goto-manual)
  --
  ("Kill item" "k" geiser-doc-kill-page "Kill this page")
  ("Clear history" "c" geiser-doc-clean-history)
  --
  (custom "Browser options" geiser-doc)
  --
  ("Quit" nil View-quit))

(define-derived-mode geiser-doc-mode nil "Geiser Doc"
  "Major mode for browsing scheme documentation.
\\{geiser-doc-mode-map}"
  (buffer-disable-undo)
  (setq truncate-lines t)
  (set-syntax-table scheme-mode-syntax-table)
  (setq geiser-eval--get-module-function 'geiser-doc--module)
  (setq buffer-read-only t))

(geiser-popup--define doc "*Geiser Documentation*" geiser-doc-mode)


;;; Commands:

(defun geiser-doc--get-docstring (symbol module)
  (geiser-eval--send/result
   `(:eval (:ge symbol-documentation ',symbol) ,module)))

(defun geiser-doc--get-module-exports (module)
  (geiser-eval--send/result
   `(:eval (:ge module-exports '(:module ,module)) :f)))

(defun geiser-doc--buttonize-modules (impl)
  (save-excursion
    (goto-char (point-min))
    (while (re-search-forward "in module \\([^.\n]+\\)[.\n ]" nil t)
      (geiser-doc--make-module-button (match-beginning 1)
                                      (match-end 1)
                                      (geiser-doc--module (match-string 1)
                                                          impl)
                                      impl))))

(defun geiser-doc--render-docstring (docstring symbol &optional module impl)
  (erase-buffer)
  (geiser-doc--insert-title
   (geiser-autodoc--str* (cdr (assoc "signature" docstring))))
  (newline)
  (or (geiser-doc--display-docstring impl docstring)
      (insert (or (cdr (assoc "docstring" docstring)) "")))
  (geiser-doc--buttonize-modules impl)
  (setq geiser-doc--buffer-link
        (geiser-doc--history-push (geiser-doc--make-link symbol
                                                         module
                                                         impl)))
  (geiser-doc--insert-footer impl)
  (goto-char (point-min)))

(defun geiser-doc-symbol (symbol &optional module impl)
  (let* ((impl (or impl geiser-impl--implementation))
         (module (geiser-doc--module (or module (geiser-eval--get-module))
                                     impl)))
    (let ((ds (geiser-doc--get-docstring symbol module)))
      (if (or (not ds) (not (listp ds)))
          (message "No documentation available for '%s'" symbol)
        (geiser-doc--with-buffer
          (geiser-doc--render-docstring ds symbol module impl))
        (geiser-doc--pop-to-buffer)))))

(defun geiser-doc-symbol-at-point (&optional arg)
  "Get docstring for symbol at point.
With prefix argument, ask for symbol (with completion)."
  (interactive "P")
  (let ((symbol (or (and (not arg) (geiser--symbol-at-point))
                    (geiser-completion--read-symbol
                     "Symbol: " (geiser--symbol-at-point)))))
    (when symbol (geiser-doc-symbol symbol))))

(defun geiser-doc-manual-for-symbol (symbol)
  (geiser-doc--external-help geiser-impl--implementation
                             symbol
                             (geiser-eval--get-module)))

(defun geiser-doc-look-up-manual (&optional arg)
  "Look up manual for symbol at point.
With prefix argument, ask for the lookup symbol (with completion)."
  (interactive "P")
  (unless (geiser-doc--manual-available-p)
    (error "No manual available"))
  (let ((symbol (or (and (not arg) (geiser--symbol-at-point))
                    (geiser-completion--read-symbol "Symbol: "))))
    (geiser-doc-manual-for-symbol symbol)))

(defconst geiser-doc--sections '(("Procedures:" "procs")
                                 ("Syntax:" "syntax")
                                 ("Variables:" "vars")
                                 ("Submodules:" "modules" t)))

(defconst geiser-doc--sections-re
  (format "^%s\n" (regexp-opt (mapcar 'car geiser-doc--sections))))

(defun geiser-doc-module (&optional module impl)
  "Display information about a given module."
  (interactive)
  (let* ((impl (or impl geiser-impl--implementation))
         (module (geiser-doc--module (or module
                                         (geiser-completion--read-module))
                                     impl))
         (msg (format "Retrieving documentation for %s ..." module))
         (exports (progn
                    (message "%s" msg)
                    (geiser-doc--get-module-exports module))))
    (if (not exports)
        (message "No information available for %s" module)
      (geiser-doc--with-buffer
        (erase-buffer)
        (geiser-doc--insert-title (format "%s" module))
        (newline)
        (dolist (g geiser-doc--sections)
          (geiser-doc--insert-list (car g)
                                   (cdr (assoc (cadr g) exports))
                                   (and (not (cddr g)) module)
                                   impl))
        (setq geiser-doc--buffer-link
              (geiser-doc--history-push
               (geiser-doc--make-link nil module impl)))
        (geiser-doc--insert-footer impl)
        (goto-char (point-min)))
      (message "%s done" msg)
      (geiser-doc--pop-to-buffer))))

(defun geiser-doc-next-section ()
  "Move to next section in this page."
  (interactive)
  (forward-line)
  (re-search-forward geiser-doc--sections-re nil t)
  (forward-line -1))

(defun geiser-doc-previous-section ()
  "Move to previous section in this page."
  (interactive)
  (re-search-backward geiser-doc--sections-re nil t))

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

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

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

(defun geiser-doc-refresh ()
  "Refresh the contents of current page."
  (interactive)
  (when geiser-doc--buffer-link
    (geiser-doc--follow-link geiser-doc--buffer-link)))

(defun geiser-doc-clean-history ()
  "Clean up the document browser history."
  (interactive)
  (when (y-or-n-p "Clean browsing history? ")
    (setq geiser-doc--history (geiser-doc--make-history))
    (geiser-doc-refresh))
  (message ""))



(provide 'geiser-doc)