;; Watch https://asciinema.org/a/631451 for a demo

(defconst my/termux-p (getenv "ANDROID_ROOT"))

(defun my/clipboard-get ()
  "Return the text on the system clipboard.

This function treats Termux systems differently, the clipboard is only
accessible through the termux-clipboard-get commandline interface,
part of the the termux-api package."

  (if my/termux-p
      (shell-command-to-string "termux-clipboard-get")
    (current-kill 0)))

(defun my/get-url-title (url)
  "Attempt to retrieve the title string from the given URL.

Assuming the URL points to an HTML source.

Returns nil if there is a non-200 return status or no title could
be found."
  (let* ((command (format "curl --fail --silent %s" url))
         (html (shell-command-to-string command))
         (regexp (rx (seq "<title>"
                          (group (+ (not (any "<" ">"))))
                          "</title>")))
         (matches (string-match regexp html)))
    (match-string 1 html)))

(defun my/denote/url-clipboard ()
  "Return the URL from the system clipboard, if any."
  (let ((clipboard (my/clipboard-get)))
    (when (org-url-p clipboard)
      clipboard)))

(defvar my/denote/url-functions
  '(thing-at-point-url-at-point my/denote/url-clipboard)
  "List of function symbols to call to get an URL candidate.

Each function should return a string with the URL or a cons
cell (URL . TITLE), where title is either a string or a function
returning a string.")

(defun my/denote/url (url &optional title)
  "Create a new Org-based note based on a URL.

URL can be a string or a cons cell (URL . TITLE). The TITLE, in
turn, can be a string or a function (without arguments) to
retrieve the title.

When called interactively, the candidate URLs are obtained from
the variable `my/denote/url-functions' (e.g. takes the URL from
the clipboard).

In case no TTTLE is passed to this function, or the URL wasn't
paired with a title value, the title is obtained by curl(1) by
looking at the <title> tags."
  (interactive (list
                (let* ((prompt (format-prompt "URL" ""))
                       (candidate-urls (-non-nil (mapcar #'funcall my/denote/url-functions)))
                       (url (if (eql 1 (length candidate-urls))
                                (read-string prompt (caar candidate-urls))
                              (completing-read prompt candidate-urls))))

                  ;; `candidate-urls' is a mix of strings and cons
                  ;; cells. If the selected URL comes from a cons
                  ;; cell, (assoc) will return it. If it comes from a
                  ;; string valuo, (assoc) will return nil. In that
                  ;; case return the URL as is.
                  (or (assoc url candidate-urls #'string=) url))
                nil))
  (denote
   (read-string (format-prompt "Title" "")

                ;; initial input. If no title was passed, see if it
                ;; can be obtained from the URL value (the cdr if the
                ;; url was a cons cell.
                (or
                 title
                 (cond ((and (consp url) (stringp (cdr url))) (cdr url))
                       ((and (consp url) (functionp (cdr url))) (funcall (cdr url)))
                       ((stringp url) (my/get-url-title url)))))
   (denote-keywords-prompt)
   'org
   (denote-subdirectory-prompt))

  (org-set-property "URL" (if (consp url)
                              (car url)
                            url))

  (goto-char (point-max))

  ;; Requires kagi.el at https://codeberg.org/bram85/kagi.el
  (require 'kagi)
  (when (yes-or-no-p "Insert summary?")
    (kagi-summarize-url url t
                        (completing-read
                         (format-prompt "To language" "EN")
                         '("EN" "NL")))))

;;; Elfeed integration

(defun my/elfeed/entry-url ()
  "Return the URL of the current elfeed entry."
  (when-let ((entry (or elfeed-show-entry
                        (elfeed-search-selected :ignore-region))))
    (cons (elfeed-entry-link entry)
          (elfeed-entry-title entry))))

(add-to-list 'my/denote/url-functions #'my/elfeed/entry-url)