;;; pkg-reading.el --- RSS reader, OPDS browser, and ebook tools -*- lexical-binding: t -*-

;; Copyright (C) 2026 Cytrogen

;;; Commentary:

;; This module provides:
;; - elfeed + elfeed-protocol for FreshRSS (Fever API)
;; - Custom OPDS browser for Calibre Content Server
;; - nov.el for EPUB reading
;; - pdf-tools for PDF reading
;;
;; Configuration is stored in ~/.emacs.d/reading-feeds.el

;;; Code:

(require 'url)
(require 'xml)
(require 'dom)

;;; ============================================================
;;; Configuration Loading
;;; ============================================================

(defvar my/reading-config nil
  "Reading configuration loaded from external file.")

(defvar my/reading-config-file
  (expand-file-name "reading-feeds.el" user-emacs-directory)
  "Path to the reading configuration file.")

(defun my/reading--load-config ()
  "Load reading configuration from external file."
  (when (file-exists-p my/reading-config-file)
    (load-file my/reading-config-file)))

;; Load config immediately
(my/reading--load-config)

(defun my/reading--get-config (key &optional subkey)
  "Get configuration value for KEY, optionally SUBKEY."
  (let ((section (plist-get my/reading-config key)))
    (if subkey
        (plist-get section subkey)
      section)))

;;; ============================================================
;;; Package Installation
;;; ============================================================

(unless (package-installed-p 'elfeed)
  (package-refresh-contents)
  (package-install 'elfeed))

(unless (package-installed-p 'olivetti)
  (package-install 'olivetti))

(unless (package-installed-p 'elfeed-protocol)
  (package-install 'elfeed-protocol))

(unless (package-installed-p 'nov)
  (package-install 'nov))

(unless (package-installed-p 'pdf-tools)
  (package-install 'pdf-tools))

;;; ============================================================
;;; URL Reading Mode
;;; ============================================================

;; 启用 url-handler-mode，可以直接 C-x C-f 打开 URL
(url-handler-mode 1)

;; 配置 olivetti 居中宽度
(setq olivetti-body-width 80)

(defun my/url-buffer-p ()
  "Check if current buffer was opened from a URL."
  (and buffer-file-name
       (string-match-p "^https?://" buffer-file-name)))

(defun my/setup-url-reading-mode ()
  "Setup comfortable reading mode for URL buffers."
  (when (my/url-buffer-p)
    (visual-line-mode 1)
    (olivetti-mode 1)
    (read-only-mode 1)
    (message "URL reading mode enabled")))

;; 打开 URL 文件时自动启用阅读模式
(add-hook 'find-file-hook #'my/setup-url-reading-mode)

;; 手动切换阅读模式的命令
(defun my/toggle-reading-mode ()
  "Toggle reading mode (visual-line + olivetti)."
  (interactive)
  (if olivetti-mode
      (progn
        (visual-line-mode -1)
        (olivetti-mode -1)
        (message "Reading mode disabled"))
    (visual-line-mode 1)
    (olivetti-mode 1)
    (message "Reading mode enabled")))

;;; ============================================================
;;; EPUB Reader (nov.el)
;;; ============================================================

(require 'nov)
(add-to-list 'auto-mode-alist '("\\.epub\\'" . nov-mode))

(with-eval-after-load 'nov
  (setq nov-text-width t)
  (add-hook 'nov-mode-hook 'visual-line-mode)
  (add-hook 'nov-mode-hook 'olivetti-mode))

;;; ============================================================
;;; PDF Reader (pdf-tools)
;;; ============================================================

(pdf-loader-install)

(with-eval-after-load 'pdf-tools
  (setq pdf-view-use-scaling t))

;;; ============================================================
;;; RSS Reader (elfeed + FreshRSS)
;;; ============================================================

(require 'elfeed)
(require 'elfeed-protocol)

(defun my/reading--setup-elfeed ()
  "Setup elfeed with FreshRSS configuration."
  (my/reading--load-config)
  (let* ((freshrss (my/reading--get-config :freshrss))
         (url (plist-get freshrss :url))
         (api-path (plist-get freshrss :api-path))
         (user (plist-get freshrss :user))
         (password (plist-get freshrss :password)))
    (when (and url user password)
      ;; 基础设置
      (setq elfeed-use-curl t)
      (elfeed-set-timeout 36000)
      (setq elfeed-curl-extra-arguments '("--insecure"))

      ;; 调试日志
      (setq elfeed-protocol-log-trace t)

      ;; 协议设置
      (setq elfeed-protocol-enabled-protocols '(fever))
      ;; FreshRSS 兼容性：不提供有效 item ID，需要只更新未读
      (setq elfeed-protocol-fever-update-unread-only t)
      (setq elfeed-protocol-feeds
            `((,(format "fever+%s://%s@%s"
                        (if (string-prefix-p "https" url) "https" "http")
                        user
                        (replace-regexp-in-string "^https?://" "" url))
               :api-url ,(concat url api-path)
               :password ,password)))

      ;; 重新启用协议（确保 advice 生效）
      (when (fboundp 'elfeed-protocol-disable)
        (elfeed-protocol-disable))
      (elfeed-protocol-enable)

      (message "elfeed configured: %s" (caar elfeed-protocol-feeds)))))

;; 延迟配置
(with-eval-after-load 'elfeed
  (my/reading--setup-elfeed))

(defun my/elfeed ()
  "Start elfeed and update feeds."
  (interactive)
  (my/reading--setup-elfeed)
  (elfeed)
  (elfeed-update))

;;; ============================================================
;;; elfeed + eww Integration
;;; ============================================================

(defun my/elfeed-show-eww ()
  "View current elfeed article in eww browser."
  (interactive)
  (let ((link (elfeed-entry-link elfeed-show-entry)))
    (when link
      (eww link))))

(with-eval-after-load 'elfeed-show
  (define-key elfeed-show-mode-map (kbd "b") #'my/elfeed-show-eww))

(add-hook 'eww-mode-hook #'visual-line-mode)
(add-hook 'eww-mode-hook #'olivetti-mode)

;;; ============================================================
;;; OPDS Browser (Calibre)
;;; ============================================================

(defvar my/opds-current-entries nil
  "Current OPDS entries being displayed.")

(defvar my/opds-history nil
  "Navigation history for OPDS browser.")

(defun my/opds--fetch-url (url &optional callback)
  "Fetch URL and return parsed XML. If CALLBACK, call it with result."
  (let* ((opds-config (my/reading--get-config :opds))
         (user (plist-get opds-config :user))
         (password (plist-get opds-config :password))
         (url-request-extra-headers
          (when (and user password)
            `(("Authorization" .
               ,(concat "Basic "
                        (base64-encode-string
                         (format "%s:%s" user password))))))))
    (if callback
        (url-retrieve url
                      (lambda (_status)
                        (goto-char url-http-end-of-headers)
                        (skip-chars-forward "\r\n \t")
                        (set-buffer-multibyte t)
                        (decode-coding-region (point) (point-max) 'utf-8)
                        (let ((xml (libxml-parse-xml-region (point) (point-max))))
                          (funcall callback xml))))
      (with-current-buffer (url-retrieve-synchronously url)
        (goto-char url-http-end-of-headers)
        (skip-chars-forward "\r\n \t")
        (set-buffer-multibyte t)
        (decode-coding-region (point) (point-max) 'utf-8)
        (prog1 (libxml-parse-xml-region (point) (point-max))
          (kill-buffer))))))

(defvar my/opds--next-page-url nil
  "URL for the next page of OPDS results.")

(defun my/opds--parse-entries (xml)
  "Parse OPDS XML and return list of entries."
  ;; 解析下一页链接
  (let ((links (dom-by-tag xml 'link)))
    (setq my/opds--next-page-url
          (dom-attr (cl-find-if (lambda (link)
                                   (string= "next" (dom-attr link 'rel)))
                                 links)
                    'href)))
  ;; 解析书籍条目
  (let ((entries (dom-by-tag xml 'entry)))
    (mapcar (lambda (entry)
              (let* ((title (dom-text (dom-by-tag entry 'title)))
                     (author (dom-text (dom-by-tag (dom-by-tag entry 'author) 'name)))
                     (links (dom-by-tag entry 'link))
                     (acquisition-link
                      (cl-find-if (lambda (link)
                                    (let ((rel (dom-attr link 'rel))
                                          (type (dom-attr link 'type)))
                                      (or (string-match-p "acquisition" (or rel ""))
                                          (string-match-p "epub\\|pdf" (or type "")))))
                                  links))
                     (nav-link
                      (cl-find-if (lambda (link)
                                    (let ((type (dom-attr link 'type)))
                                      (string-match-p "atom\\|opds" (or type ""))))
                                  links)))
                `(:title ,title
                  :author ,author
                  :download-url ,(when acquisition-link (dom-attr acquisition-link 'href))
                  :download-type ,(when acquisition-link (dom-attr acquisition-link 'type))
                  :nav-url ,(when nav-link (dom-attr nav-link 'href)))))
            entries)))

(defun my/opds--format-entry (entry)
  "Format ENTRY for display."
  (let ((title (plist-get entry :title))
        (author (plist-get entry :author))
        (has-download (plist-get entry :download-url))
        (has-nav (plist-get entry :nav-url)))
    (format "%s%s%s"
            (or title "Unknown")
            (if author (format " - %s" author) "")
            (cond (has-download " [BOOK]")
                  (has-nav " [>]")
                  (t "")))))

(defun my/opds--select-entry (entry)
  "Handle selection of ENTRY."
  (let ((download-url (plist-get entry :download-url))
        (nav-url (plist-get entry :nav-url)))
    (cond
     (download-url
      (my/opds-download-and-open entry))
     (nav-url
      (push (my/reading--get-config :opds :url) my/opds-history)
      (my/opds--browse-url nav-url)))))

(defun my/opds--browse-url (url)
  "Browse OPDS catalog at URL."
  (message "Fetching OPDS catalog...")
  (let* ((base-url (my/reading--get-config :opds :url))
         (full-url (if (string-prefix-p "http" url)
                       url
                     (concat (replace-regexp-in-string "/opds/?$" "" base-url) url))))
    (condition-case err
        (let* ((xml (my/opds--fetch-url full-url))
               (entries (my/opds--parse-entries xml)))
          (setq my/opds-current-entries entries)
          (let* ((choices (mapcar (lambda (e)
                                    (cons (my/opds--format-entry e) e))
                                  entries))
                 ;; 如果有下一页，添加选项
                 (choices (if my/opds--next-page-url
                              (append choices '(("▶ 下一页..." . :next-page)))
                            choices))
                 (selection (completing-read
                             (format "OPDS (%d items%s): "
                                     (length entries)
                                     (if my/opds--next-page-url " + more" ""))
                             choices nil t)))
            (when selection
              (let ((selected (cdr (assoc selection choices))))
                (if (eq selected :next-page)
                    (my/opds--browse-url my/opds--next-page-url)
                  (my/opds--select-entry selected))))))
      (error (message "OPDS error: %s" (error-message-string err))))))

(defun my/opds-browse ()
  "Browse OPDS catalog."
  (interactive)
  (my/reading--load-config)
  (let ((url (my/reading--get-config :opds :url)))
    (if url
        (progn
          (setq my/opds-history nil)
          (my/opds--browse-url url))
      (message "OPDS URL not configured. Edit reading-feeds.el"))))

(defun my/opds-back ()
  "Go back in OPDS navigation history."
  (interactive)
  (if my/opds-history
      (my/opds--browse-url (pop my/opds-history))
    (message "No history")))

(defun my/opds-download-and-open (entry)
  "Download and open ENTRY."
  (let* ((url (plist-get entry :download-url))
         (type (plist-get entry :download-type))
         (title (plist-get entry :title))
         (download-dir (or (my/reading--get-config :download-dir) "~/Books/"))
         (ext (cond ((string-match-p "epub" (or type "")) ".epub")
                    ((string-match-p "pdf" (or type "")) ".pdf")
                    (t ".epub")))
         (filename (concat (replace-regexp-in-string "[^a-zA-Z0-9]+" "_" (or title "book")) ext))
         (filepath (expand-file-name filename download-dir))
         (opds-config (my/reading--get-config :opds))
         (base-url (plist-get opds-config :url))
         (full-url (if (string-prefix-p "http" url)
                       url
                     (concat (replace-regexp-in-string "/opds/?$" "" base-url) url))))
    ;; Ensure download directory exists
    (unless (file-directory-p download-dir)
      (make-directory download-dir t))
    (message "Downloading %s..." title)
    (let* ((user (plist-get opds-config :user))
           (password (plist-get opds-config :password))
           (url-request-extra-headers
            (when (and user password)
              `(("Authorization" .
                 ,(concat "Basic "
                          (base64-encode-string
                           (format "%s:%s" user password))))))))
      (url-copy-file full-url filepath t)
      (message "Downloaded to %s" filepath)
      (find-file filepath))))

(defun my/opds-search ()
  "Search OPDS catalog."
  (interactive)
  (my/reading--load-config)
  (let* ((query (read-string "Search books: "))
         (base-url (my/reading--get-config :opds :url))
         ;; Calibre 搜索格式: /opds/search/关键词
         (search-url (format "%s/search/%s"
                             (replace-regexp-in-string "/opds/?$" "/opds" base-url)
                             (url-hexify-string query))))
    (my/opds--browse-url search-url)))

;;; ============================================================
;;; Interactive Commands
;;; ============================================================

(defun my/reading-reload-config ()
  "Reload reading configuration."
  (interactive)
  (my/reading--load-config)
  (when (featurep 'elfeed)
    (my/reading--setup-elfeed))
  (message "Reading configuration reloaded"))

;;; ============================================================
;;; PDF Tools Enhancement
;;; ============================================================

;; PDF 页码偏移量
(defvar-local my/pdf-page-offset 0
  "当前 PDF 的页码偏移量。书籍页码 = 物理页码 - 偏移量")

(defun my/pdf-set-offset ()
  "设置当前 PDF 的页码偏移量。"
  (interactive)
  (let* ((current-page (pdf-view-current-page))
         (book-page (read-number (format "当前是 PDF 第 %d 页，对应书籍第几页？" current-page)))
         (offset (- current-page book-page)))
    (setq my/pdf-page-offset offset)
    (message "偏移量设为 %d（书籍第1页 = PDF第%d页）" offset (1+ offset))))

(defun my/pdf-goto-page ()
  "跳转到书籍页码（自动应用偏移量）。"
  (interactive)
  (let* ((book-page (read-number "跳转到书籍第几页: "))
         (pdf-page (+ book-page my/pdf-page-offset)))
    (pdf-view-goto-page pdf-page)))

;; 绑定快捷键
(with-eval-after-load 'pdf-view
  (define-key pdf-view-mode-map (kbd "O") 'my/pdf-set-offset)
  (define-key pdf-view-mode-map (kbd "G") 'my/pdf-goto-page))

(provide 'pkg-reading)
;;; pkg-reading.el ends here