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;;; jao-pdf.el --- utilities for pdf files           -*- lexical-binding: t; -*-

;; Copyright (C) 2022  jao

;; Author: jao <mail@jao.io>
;; Keywords: docs

;; 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 this program.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; Some niceties for PDFs:
;;
;;   - Using mutools, we can extract the outline of PDFs, and tell back the
;;     section title of a given page.
;;   - Interoperability with zathura.

(require 'jao-doc-session)

;;; PDF info

(declare-function 'pdf-info-outline "pdf-info")

(defvar-local jao-pdf--outline nil)

(defun jao-pdf-is-pdf-file (file)
  "Simply checks the FILE extension."
  (string-match-p ".*\\.pdf$" file))

(defun jao-pdf-title-to-file-name (title)
  "Convert a title, possibly with embedded spaces, to a PDF filename."
  (concat (mapconcat 'downcase (split-string title nil t) "-") ".pdf"))

(defvar jao-pdf--outline-rx
  ".+\\(\t+\\)\"\\(.+\\)\"\t#\\(?:page=\\)?\\([0-9]+\\)")

(defun jao-pdf-outline (file-name)
  "Return an alist describing the given FILE-NAME (or current if nil).
The result is cached as a local buffer variable."
  (if (derived-mode-p 'pdf-view-mode)
      (pdf-info-outline)
    (let* ((outline nil)
           (fn (or file-name (buffer-file-name)))
           (fn (shell-quote-argument (expand-file-name fn))))
      (with-temp-buffer
        (insert (shell-command-to-string (format "mutool show %s outline" fn)))
        (goto-char (point-min))
        (while (re-search-forward jao-pdf--outline-rx nil t)
          (push `((level . ,(length (match-string 1)))
                  (title . ,(match-string 2))
                  (page . ,(string-to-number (match-string 3))))
                outline)))
      (nreverse outline))))

(defun jao-pdf-title (&optional fname)
  (if (or fname (not (derived-mode-p 'doc-view-mode 'pdf-view-mode)))
      (let ((base (file-name-base (or fname (buffer-file-name)))))
        (capitalize (replace-regexp-in-string "-" " " base)))
    (or (jao-pdf-section-title)
        (when buffer-file-name (jao-pdf-title buffer-file-name)))))

(defun jao-pdf-section-title (&optional page file-name)
  (when (not jao-pdf--outline)
    (setq-local jao-pdf--outline (jao-pdf-outline file-name)))
  (let ((page (or page
                  (and (derived-mode-p 'doc-view-mode) (doc-view-current-page))
                  (and (derived-mode-p 'pdf-view) (pdf-view-current-page))))
        (outline jao-pdf--outline)
        (cur-page 0)
        (cur-title (jao-pdf-title (or file-name buffer-file-name "title"))))
    (while (and (car outline) (< cur-page page))
      (setq cur-page (cdr (assoc 'page (car outline))))
      (when (<= cur-page page)
        (setq cur-title (cdr (assoc 'title (car outline)))))
      (setq outline (cdr outline)))
    (replace-regexp-in-string "[[:blank:]]+" " " cur-title)))

;;; zathura interop
(defun jao-pdf-zathura-open-cmd (file page &optional suffix)
  (let ((page (if page (format "-P %s" page) "")))
    (format "zathura %s %s %s" file page (or suffix ""))))

(defun jao-pdf-zathura-file-info (title)
  (when (string-match "\\(.+\\) \\[\\(.+\\) (\\([0-9]+\\)/\\([0-9]+\\))\\]"
                      title)
    (list (expand-file-name (match-string 1 title))
          (string-to-number (match-string 3 title))
          (string-to-number (match-string 4 title))
          (match-string 2 title))))

(defun jao-pdf-goto-zathura-org (title &optional no-ask)
  (when-let* ((info (jao-pdf-zathura-file-info title))
              (pdf-file (car info))
              (file (jao-org-pdf-to-org-file pdf-file))
              (page (cadr info))
              (pageno (or (car (last info)) page)))
    (ignore-errors (jao-afio--goto-docs))
    (let ((exists (file-exists-p file)))
      (find-file file)
      (unless exists (jao-org-insert-doc-skeleton))
      (let* ((fn (file-name-nondirectory pdf-file))
             (desc (jao-pdf-section-title page pdf-file))
             (lnk (format "[[doc:%s::%d][%s]]" fn page desc)))
        (jao-doc-session-mark)
        (if (or (not exists) (and (not no-ask) (y-or-n-p "Insert link?")))
            (insert lnk "\n")
          (kill-new lnk)
          (message "Link to %s (%s) killed" file page))))))

(provide 'jao-pdf)
;;; jao-pdf.el ends here