;;; my-epub.el -- epub utils -*- lexical-binding: t -*-

;; Copyright (C) 2025  Free Software Foundation, Inc.

;; Author: Yuchen Pei <id@ypei.org>
;; Package-Requires: ((emacs "30.1"))

;; This file is part of dotted.

;; dotted is free software: you can redistribute it and/or modify it under
;; the terms of the GNU Affero General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; dotted 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 Affero General
;; Public License for more details.

;; You should have received a copy of the GNU Affero General Public
;; License along with dotted.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; epub utils.

;;; Code:


(defun my-epub-content-file-name (file-name)
  (with-temp-buffer
    (if (eq 0 (call-process "unzip" nil t nil
                            "-p" file-name "META-INF/container.xml"))
        (let ((dom (libxml-parse-xml-region (point-min) (point-max))))
          (dom-attr
           (dom-by-tag
            (dom-by-tag (dom-by-tag dom 'container) 'rootfiles)
            'rootfile)
           'full-path))
      (message "Failed to extract container.xml: %s" (buffer-string))
      nil)))

(defun my-epub-metadata (file-name)
  "Get metadata of an epub file."
  (when-let ((content-file-name (my-epub-content-file-name file-name)))
    (with-temp-buffer
      (call-process "unzip" nil t nil "-p" file-name content-file-name)
      (let* ((dom (libxml-parse-xml-region (point-min) (point-max)))
             (metadata (dom-by-tag dom 'metadata))
             (title (dom-text (dom-by-tag metadata 'title)))
             (authors (dom-texts (dom-by-tag metadata 'creator) ", "))
             (identifier
              (replace-regexp-in-string
               "[^0-9,]" ""
               (dom-texts
                (seq-filter
                 (lambda (node)
                   (or (equal "ISBN" (dom-attr node 'scheme))
                       (string-match-p "^[0-9]+$" (dom-text node))))
                 (dom-by-tag metadata 'identifier))
                ",")))
             (date (replace-regexp-in-string
                    "[^0-9]" ""
                    (dom-text (dom-by-tag metadata 'date))))
             (year (substring date 0 (min 4 (length date)))))
        `((title . ,title)
          (authors . ,authors)
          (year . ,year)
          (identifier . ,identifier))
        ;; (pp metadata)
        ))
    ))

;; generate epub
(defun my-epub-create (dir title author)
  "Create an epub by concatenating htmls in DIR."
  (let* ((name
          (file-name-nondirectory (directory-file-name dir)))
         (tmpdir
          (make-temp-file (format "/tmp/%s.epub." name) t))
         (files (directory-files dir nil directory-files-no-dot-files-regexp)))
    (my-epub--create-mimetype tmpdir)
    (my-epub--create-container tmpdir)
    (my-epub--create-opf tmpdir files title author)
    (my-epub--create-toc tmpdir files title)
    (my-epub--add-html
     tmpdir
     (directory-files dir t directory-files-no-dot-files-regexp))
    (my-epub--zip tmpdir name)
    ))

(defun my-epub--create-mimetype (dir)
  (with-temp-buffer
    (insert "application/epub+zip")
    (write-file (file-name-concat dir "mimetype"))))

(defun my-epub--create-container (dir)
  (with-temp-buffer
    (insert
     "<?xml version=\"1.0\"?>
<container version=\"1.0\" xmlns=\"urn:oasis:names:tc:opendocument:xmlns:container\">
    <rootfiles>
        <rootfile full-path=\"OEBPS/content.opf\" media-type=\"application/oebps-package+xml\"/>
   </rootfiles>
</container>")
    (make-directory
     (file-name-concat dir "META-INF"))
    (write-file (file-name-concat dir "META-INF/container.xml"))))

(defun my-epub--create-opf (dir files title author)
  (with-temp-buffer
    (insert
     "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" "\n")
    (dom-print
     `(package
       ((unique-identifier . "BookID")
        (version . "2.0"))
       (metadata nil
                 (title nil ,title)
                 (creator nil ,author)
                 (language nil "en")
                 (identifier
                  ((id . "BookID"))
                  "Hello ID"))
       (manifest
        nil
        (item ((id . "ncx")
               (href . "toc.ncx")
               (media-type . "application/x-dtbncx+xml")))
        ,@(seq-map
           (lambda (file)
             `(item ((id . ,file)
                     (href . ,file)
                     (media-type . "application/xhtml+xml"))))
           files))
       (spine
        ((toc . "ncx"))
        ,@(seq-map
           (lambda (file)
             `(itemref ((idref . ,file))))
           files)))
     t t)
    (make-directory
     (file-name-concat dir "OEBPS"))
    (write-file (file-name-concat dir "OEBPS/content.opf"))
    (message (buffer-string))))

(defun my-epub--create-toc (dir files title)
  (with-temp-buffer
    (insert "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" "\n")
    (dom-print
     `(ncx nil
           (docTitle nil
                     (text nil ,title))
           (navMap
            nil
            ,@(seq-map
               (lambda (file)
                 `(navPoint nil
                            (content ((src . ,file)))))
               files)))
     t t)
    (write-file (file-name-concat dir "OEBPS/toc.ncx"))))

(defun my-epub--add-html (dir files)
  (seq-do
   (lambda (file)
     (copy-file file (file-name-concat dir "OEBPS/")))
   files))

(defun my-epub--zip (dir name)
  (let ((default-directory dir))
    (call-process "zip" nil nil nil "-r" (format "/tmp/%s.epub" name) ".")))

(provide 'my-epub)
;;; my-epub.el ends here