;;; anki-editor.el --- Make Anki Cards in Org-mode
;;
;; Copyright (C) 2018 Louie Tan <louietanlei@gmail.com>
;;
;; Filename: anki-editor.el
;; Description: Make Anki Cards in Org-mode
;; Author: Louie Tan
;; Version: 0.2.0
;; Package-Requires: ((emacs "25"))
;; URL: https://github.com/louietan/anki-editor
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;;; Commentary:
;;
;;  This package is for people who use Anki as SRS but would like to
;;  make cards in Org-mode.
;;
;;  With this package, you can make cards from something like:
;;  (which is inspired by `org-dirll')
;;
;;  * Computing                    :deck:
;;  ** Item                        :note:
;;     :PROPERTIES:
;;     :ANKI_NOTE_TYPE: Basic
;;     :END:
;;  *** Front
;;      How to hello world in elisp ?
;;  *** Back
;;      #+BEGIN_SRC emacs-lisp
;;      (message "Hello, world!")
;;      #+END_SRC
;;
;;  This package leverages Org-mode's built-in HTML backend to
;;  generate HTML for contents of note fields with specific syntax
;;  (e.g. latex) translated to Anki style, then save the note to Anki.
;;
;;  For this package to work, you have to setup these external dependencies:
;;  - curl
;;  - AnkiConnect, an Anki addon that runs an HTTP server to expose
;;                 Anki functions as RESTful APIs
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; This program 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.
;;
;; This program 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 <http://www.gnu.org/licenses/>.
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;;; Code:

(require 'json)
(require 'org-element)
(require 'ox)

(defconst anki-editor-prop-note-type :ANKI_NOTE_TYPE)
(defconst anki-editor-prop-note-tags :ANKI_TAGS)
(defconst anki-editor-prop-note-id :ANKI_NOTE_ID)
(defconst anki-editor-prop-failure-reason :ANKI_FAILURE_REASON)
(defconst anki-editor-buffer-html-output "*AnkiEditor HTML Output*")

(defgroup anki-editor nil
  "Customizations for anki-editor."
  :group 'org)

(defcustom anki-editor-note-tag
  "note"
  "Headings with this tag will be considered as notes.")

(defcustom anki-editor-deck-tag
  "deck"
  "Headings with this tag will be considered as decks.")

(defcustom anki-editor-break-consecutive-braces-in-latex
  nil
  "If non-nil, consecutive `}' will be automatically separated by spaces to prevent early-closing of cloze.
See https://apps.ankiweb.net/docs/manual.html#latex-conflicts.")

(defcustom anki-editor-anki-connect-listening-address
  "127.0.0.1"
  "The network address AnkiConnect is listening.")

(defcustom anki-editor-anki-connect-listening-port
  "8765"
  "The port number AnkiConnect is listening.")


;;; AnkiConnect

(defun anki-editor--anki-connect-invoke (action version &optional params)
  "Invoke AnkiConnect with ACTION, VERSION and PARAMS."
  (let* ((data `(("action" . ,action)
                 ("version" . ,version)))
         (request-body (json-encode
                        (if params
                            (push `("params" . ,params) data)
                          data)))
         (request-tempfile (make-temp-file "emacs-anki-editor")))

    (with-temp-file request-tempfile
      (setq buffer-file-coding-system 'utf-8)
      (set-buffer-multibyte t)
      (insert request-body))

    (let* ((raw-resp (shell-command-to-string
                      (format "curl %s:%s --silent -X POST --data-binary @%s"
                              (shell-quote-argument anki-editor-anki-connect-listening-address)
                              (shell-quote-argument anki-editor-anki-connect-listening-port)
                              (shell-quote-argument request-tempfile))))
           resp error)
      (condition-case err
          (let ((json-array-type 'list))
            (setq resp (json-read-from-string raw-resp)
                  error (alist-get 'error resp)))
        (error (setq error
                     (format "Unexpected error communicating with AnkiConnect: %s, the response was %s"
                             (error-message-string err)
                             (prin1-to-string raw-resp)))))
      `((result . ,(alist-get 'result resp))
        (error . ,error)))))

(defmacro anki-editor--anki-connect-invoke-result (&rest args)
  "Invoke AnkiConnect with ARGS, return the result from response or raise an error."
  `(let* ((resp (anki-editor--anki-connect-invoke ,@args))
          (rslt (alist-get 'result resp))
          (err (alist-get 'error resp)))
     (when err (error err))
     rslt))

(defun anki-editor--anki-connect-map-note (note)
  "Convert NOTE to the form that AnkiConnect accepts."
  (let-alist note
    (list (cons "id" .note-id)
          (cons "deckName" .deck)
          (cons "modelName" .note-type)
          (cons "fields" .fields)
          ;; Convert tags to a vector since empty list is identical to nil
          ;; which will become None in Python, but AnkiConnect requires it
          ;; to be type of list.
          (cons "tags" (vconcat .tags)))))

(defun anki-editor--anki-connect-heading-to-note (heading)
  "Convert HEADING to a note in the form that AnkiConnect accepts."
  (anki-editor--anki-connect-map-note
   (anki-editor--heading-to-note heading)))

;;; Commands

;;;###autoload
(defun anki-editor-submit ()
  "Send notes in current buffer to Anki.

For each note heading, if there's no note id in property drawer,
create a note, otherwise, update fields and tags of the existing
note.

If one fails, the failure reason will be set in property drawer
of that heading."
  (interactive)
  (let ((total 0)
        (failed 0)
        current-deck)
    (org-map-entries
     (lambda ()
       (let ((current-tags (org-get-tags)))
         (cond
          ((member anki-editor-deck-tag current-tags)
           (setq current-deck (nth 4 (org-heading-components))))
          ((member anki-editor-note-tag current-tags)
           (progn
             (setq total (1+ total))
             (message "Processing note at %d..." (point))
             (anki-editor--clear-failure-reason)
             (condition-case err
                 (anki-editor--process-note-heading current-deck)
               (error (progn
                        (setq failed (1+ failed))
                        (anki-editor--set-failure-reason (error-message-string err))))))))))
     (mapconcat 'identity `(,anki-editor-deck-tag ,anki-editor-note-tag) "|"))

    (message (with-output-to-string
               (princ (format "Submitted %d notes, with %d failed." total failed))
               (when (> failed 0)
                 (princ " Check property drawers for failure reasons."))))))

;;;###autoload
(defun anki-editor-insert-deck (&optional prefix)
  "Insert a deck heading.
With PREFIX, only insert the deck name at point."
  (interactive "P")
  (message "Fetching decks...")
  (let ((decks (sort (anki-editor--anki-connect-invoke-result "deckNames" 5) #'string-lessp))
        deckname)
    (setq deckname (completing-read "Choose a deck: " decks))
    (if prefix
        (insert deckname)
      (let (inserted)
        (anki-editor--visit-ancestor-headings
         (lambda ()
           (when (member anki-editor-deck-tag (org-get-tags))
             (anki-editor--insert-deck-heading deckname)
             (setq inserted t))))

        (unless inserted
          (anki-editor--insert-deck-heading deckname))))))

;;;###autoload
(defun anki-editor-insert-note ()
  "Insert the skeleton of a note.

The contents to be insrted are structured with a note heading
along with subheadings that correspond to fields.

Where the note is inserted depends on where the point is.

When the point is somewhere inside a note heading, the new note
is inserted below this note with same heading level.

Or when the point is outside any note heading but inside a
heading that isn't tagged with 'deck' but under a deck heading,
the new note is one level lower to and is inserted at the bottom
of this heading.

Or when the point is inside a deck heading, the behavior is the
same as above.

Otherwise, it's inserted below current heading at point."
  (interactive)
  (message "Fetching note types...")
  (let ((note-types (sort (anki-editor--anki-connect-invoke-result "modelNames" 5) #'string-lessp))
        note-type note-heading fields)
    (setq note-type (completing-read "Choose a note type: " note-types))
    (message "Fetching note fields...")
    (setq fields (anki-editor--anki-connect-invoke-result "modelFieldNames" 5 `((modelName . ,note-type)))
          note-heading (read-from-minibuffer "Enter the heading: " "Item"))

    ;; find and go to the best position, then insert the note
    (let ((cur-point (point))
          pt-of-grp
          inserted)
      (anki-editor--visit-ancestor-headings
       (lambda ()
         (let ((tags (org-get-tags)))
           (cond
            ;; if runs into a note heading, inserts the note heading with
            ;; the same level
            ((member anki-editor-note-tag tags)
             (progn
               (anki-editor--insert-note-skeleton note-heading note-type fields)
               (setq inserted t)
               t))
            ;; if runs into a deck heading, inserts the note heading one
            ;; level lower to current deck heading or to the group
            ;; heading that was visited before
            ((member anki-editor-deck-tag tags)
             (progn
               (when pt-of-grp (goto-char pt-of-grp))
               (anki-editor--insert-note-skeleton note-heading note-type fields t)
               (setq inserted t)
               t))
            ;; otherwise, consider it as a group heading and save its
            ;; point for further consideration, then continue
            (t (progn
                 (unless pt-of-grp (setq pt-of-grp (point)))
                 nil))))))
      (unless inserted
        (goto-char cur-point)
        (anki-editor--insert-note-skeleton note-heading note-type fields)))))

;;;###autoload
(defun anki-editor-insert-tags ()
  "Insert tags at point with autocompletion."
  (interactive)
  (let ((tags (sort (anki-editor--anki-connect-invoke-result "getTags" 5) #'string-lessp)))
    (while t (insert (format " %s" (completing-read "Choose a tag: " tags))))))

;;;###autoload
(defun anki-editor-cloze-region (&optional arg)
  "Cloze region with number ARG."
  (interactive "p")
  (unless (region-active-p) (error "No active region"))
  (let ((region (buffer-substring (region-beginning) (region-end)))
        (hint (read-from-minibuffer "Hint (optional): ")))
    (save-excursion
      (delete-region (region-beginning) (region-end))
      (insert (with-output-to-string
                (princ (format "{{c%d::%s" (or arg 1) region))
                (unless (string-empty-p (string-trim hint)) (princ (format "::%s" hint)))
                (princ "}}"))))))

;;;###autoload
(defun anki-editor-export-heading-contents-to-html ()
  "Export the contents of the heading at point to HTML."
  (interactive)
  (let* ((tree (org-element-at-point))
         (contents (or (and (org-element-property :contents-begin tree)
                            (org-element-property :contents-end tree)
                            (buffer-substring (org-element-property :contents-begin tree)
                                              (org-element-property :contents-end tree)))
                       "")))
    (if (or (null tree)
            (not (eq (org-element-type tree) 'headline)))
        (error "No element at point or it's not a heading")
      (when (buffer-live-p (get-buffer anki-editor-buffer-html-output))
        (kill-buffer anki-editor-buffer-html-output))
      (switch-to-buffer-other-window (get-buffer-create anki-editor-buffer-html-output))
      (insert (org-export-string-as contents anki-editor--ox-anki-html-backend t)))))

;;;###autoload
(defun anki-editor-convert-region-to-html ()
  "Convert and replace region to HTML."
  (interactive)
  (org-export-replace-region-by anki-editor--ox-anki-html-backend))

;;;###autoload
(defun anki-editor-anki-connect-upgrade ()
  "Upgrade AnkiConnect to the latest version.

This will display a confirmation dialog box in Anki asking if you
want to continue.  The upgrading is done by downloading the latest
code in the master branch of its Github repo.

This is useful when new version of this package depends on the
bugfixes or new features of AnkiConnect."
  (interactive)
  (when (yes-or-no-p "NOTE: This will download the latest codebase of AnkiConnect to your system, which is not guaranteed to be safe or stable. Generally, you don't need this command, this is useful only when new version of this package requires the updates of AnkiConnect that are not released yet. Do you still want to continue?")
    (let ((result (anki-editor--anki-connect-invoke-result "upgrade" 5)))
      (when (and (booleanp result) result)
        (message "AnkiConnect has been upgraded, you might have to restart Anki to make it in effect.")))))

;;; Core Functions

(defun anki-editor--insert-deck-heading (deckname)
  "Insert a deck heading with DECKNAME."
  (org-insert-heading-respect-content)
  (insert deckname)
  (anki-editor--set-tags-fix anki-editor-deck-tag))

(defun anki-editor--process-note-heading (deck)
  "Process note heading at point.
DECK is used when the action is note creation."
  (unless deck (error "No deck specified"))

  (let (note-elem note)
    (setq note-elem (org-element-at-point)
          note-elem (let ((content (buffer-substring
                                    (org-element-property :begin note-elem)
                                    (org-element-property :end note-elem))))
                      (with-temp-buffer
                        (org-mode)
                        (insert content)
                        (car (org-element-contents (org-element-parse-buffer)))))
          note (anki-editor--heading-to-note note-elem))
    (push `(deck . ,deck) note)
    (anki-editor--save-note note)))

(defun anki-editor--insert-note-skeleton (heading note-type fields &optional demote)
  "Insert a note skeleton with HEADING, NOTE-TYPE and FIELDS.
If DEMOTE is t, demote the inserted note heading."
  (org-insert-heading-respect-content)
  (when demote (org-do-demote))
  (insert heading)
  (anki-editor--set-tags-fix anki-editor-note-tag)
  (org-set-property (substring (symbol-name anki-editor-prop-note-type) 1) note-type)
  (dolist (field fields)
    (save-excursion
      (org-insert-heading-respect-content)
      (org-do-demote)
      (insert field))))

(defun anki-editor--save-note (note)
  "Request AnkiConnect for updating or creating NOTE."
  (if (= (alist-get 'note-id note) -1)
      (anki-editor--create-note note)
    (anki-editor--update-note note)))

(defun anki-editor--create-note (note)
  "Request AnkiConnect for creating NOTE."
  (let* ((response (anki-editor--anki-connect-invoke
                    "addNote" 5 `((note . ,(anki-editor--anki-connect-map-note note)))))
         (result (alist-get 'result response))
         (err (alist-get 'error response)))
    (if result
        ;; put ID of newly created note in property drawer
        (org-set-property (substring (symbol-name anki-editor-prop-note-id) 1)
                          (format "%d" (alist-get 'result response)))
      (error (or err "Sorry, the operation was unsuccessful and detailed information is unavailable.")))))

(defun anki-editor--update-note (note)
  "Request AnkiConnect for updating fields and tags of NOTE."
  (anki-editor--anki-connect-invoke-result
   "updateNoteFields" 5 `((note . ,(anki-editor--anki-connect-map-note note))))

  ;; update tags
  (let (existing-note added-tags removed-tags)
    (setq existing-note (car (anki-editor--anki-connect-invoke-result
                              "notesInfo" 5 `(("notes" . (,(alist-get 'note-id note))))))
          added-tags (cl-set-difference (alist-get 'tags note) (alist-get 'tags existing-note) :test #'string-equal)
          removed-tags (cl-set-difference (alist-get 'tags existing-note) (alist-get 'tags note) :test #'string-equal))

    (when added-tags
      (anki-editor--anki-connect-invoke-result
       "addTags" 5 `(("notes" . (,(alist-get 'note-id note)))
                     ("tags" . ,(mapconcat #'identity added-tags " ")))))
    (when removed-tags
      (anki-editor--anki-connect-invoke-result
       "removeTags" 5 `(("notes" . (,(alist-get 'note-id note)))
                        ("tags" . ,(mapconcat #'identity removed-tags " ")))))))

(defun anki-editor--set-failure-reason (reason)
  "Set failure reason to REASON in property drawer at point."
  (org-entry-put nil (substring (symbol-name anki-editor-prop-failure-reason) 1) reason))

(defun anki-editor--clear-failure-reason ()
  "Clear failure reason in property drawer at point."
  (org-entry-delete nil (substring (symbol-name anki-editor-prop-failure-reason) 1)))

(defun anki-editor--heading-to-note (heading)
  "Construct an alist representing a note for HEADING."
  (let (note-id note-type tags fields)
    (setq note-id (org-element-property anki-editor-prop-note-id heading)
          note-type (org-element-property anki-editor-prop-note-type heading)
          tags (org-element-property anki-editor-prop-note-tags heading)
          fields (mapcar #'anki-editor--heading-to-note-field (anki-editor--get-subheadings heading)))

    (unless note-type (error "Missing note type"))
    (unless fields (error "Missing fields"))

    `((note-id . ,(string-to-number (or note-id "-1")))
      (note-type . ,note-type)
      (tags . ,(and tags (split-string tags " ")))
      (fields . ,fields))))

(defun anki-editor--heading-to-note-field (heading)
  "Convert HEADING to field data, a cons cell, the car of which is the field name, the cdr of which is contens represented in HTML."
  (let ((field-name (substring-no-properties
                     (org-element-property
                      :raw-value
                      heading)))
        (contents (org-element-contents heading)))
    `(,field-name . ,(org-export-string-as
                      (org-element-interpret-data contents)
                      anki-editor--ox-anki-html-backend t))))

;;; Org Export Backend

(defconst anki-editor--ox-anki-html-backend
  (org-export-create-backend
   :parent 'html
   :transcoders '((latex-fragment . anki-editor--ox-latex)
                  (latex-environment . anki-editor--ox-latex))))

(defconst anki-editor--anki-latex-syntax-map
  `((,(format "^%s" (regexp-quote "$$")) . "[$$]")
    (,(format "%s$" (regexp-quote "$$")) . "[/$$]")
    (,(format "^%s" (regexp-quote "$")) . "[$]")
    (,(format "%s$" (regexp-quote "$")) . "[/$]")
    (,(format "^%s" (regexp-quote "\\(")) . "[$]")
    (,(format "%s$" (regexp-quote "\\)")) . "[/$]")
    (,(format "^%s" (regexp-quote "\\[")) . "[$$]")
    (,(format "%s$" (regexp-quote "\\]")) . "[/$$]")))

(defun anki-editor--wrap-latex (content)
  "Wrap CONTENT with Anki-style latex markers."
  (format "[latex]%s[/latex]" content))

(defun anki-editor--ox-latex (latex contents info)
  "Transcode LATEX from Org to HTML.
CONTENTS is nil.  INFO is a plist holding contextual information."
  (let* ((code (org-element-property :value latex))
         (copy code))
    ;; translate delimiters
    (dolist (map anki-editor--anki-latex-syntax-map)
      (setq code (replace-regexp-in-string (car map) (cdr map) code t t)))

    (when (equal copy code)
      (setq code (anki-editor--wrap-latex
                  (if (eq (org-element-type latex) 'latex-fragment)
                      code
                    (format "\n<pre>\n%s</pre>\n"
                            (org-remove-indentation code))))))

    (if anki-editor-break-consecutive-braces-in-latex
        (replace-regexp-in-string "}}" "} } " code)
      code)))

;;; Utilities

(defun anki-editor--set-tags-fix (tags)
  "Set tags to TAGS and fix tags on the fly."
  (org-set-tags-to tags)
  (org-fix-tags-on-the-fly))

(defun anki-editor--get-subheadings (heading)
  "Get all the subheadings of HEADING."
  (org-element-map (org-element-contents heading)
      'headline 'identity nil nil 'headline))

(defun anki-editor--visit-ancestor-headings (visitor &optional level)
  "Move point to and call VISITOR at each ancestor heading from point.
Don't pass LEVEL, it's only used in recursion.
Stops when VISITOR returns t or point reaches the beginning of buffer."
  (let (stop)
    (when (org-at-heading-p)
      (let ((cur-level (car (org-heading-components))))
        (when (or (null level) (< cur-level level))
          (setq level cur-level
                stop (funcall visitor)))))
    (when (and (not stop) (/= (point) (point-min)))
      (org-previous-visible-heading 1)
      (anki-editor--visit-ancestor-headings visitor level))))


(provide 'anki-editor)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; anki-editor.el ends here