Xah Talk Show 2025-06-03 Ep663 emacs lisp coding, HTML show duplicate links

• https://youtu.be/eUTze3dJoIY

• timestamp
• 11:30 on marriage age gap

• is it bad for men to marry older women
• https://youtu.be/eUTze3dJoIY?t=688

• Emacs: Xah Fly Keys 📦
• Emacs: Xah HTML Mode 📦
• Ergonomic Keyboard Layouts

• Elisp: Sequence. Sort, Reverse

• The Nature of the Unix Philosophy
• The Unix-Haters Handbook
• The X-Windows Disaster (X11) (1994. Don Hopkins)

• Origin of Unix Pipe

• Dragon Book (Compiler) Table of Contents
• Parsing Techniques, Dick Grune, Table of Contents

;; -*- coding: utf-8; lexical-binding: t; -*-

(defun xahhtml-show-duplicate-links ()
  "Highlight and print any duplicate links in current html file.

Also, push mark at each of the duplicate link position, so you can `universal-argument' `set-mark-command' to jump to it.

Created: 2024-07-22
Version: 2025-06-03"
  (interactive)
  (let (xbeg xend xlink
             (xlinksTable (make-hash-table :test 'equal)))
    (seq-setq (xbeg xend)
              (if (region-active-p)
                  (vector (region-beginning) (region-end))
                (vector (point-min) (point-max))))
    (save-restriction
      (narrow-to-region xbeg xend)

      ;; algorithm
      ;; first, built hashtable.
      ;; Find each link, then for each, extract the link, if it is local, then expand to file absolute path.
      ;; this is the key for hashtable.
      ;; add that to hashtable.
      ;; if already exist, add to the value of that key.
      ;; the value of hashtable is a list of vectors [pos-beg pos-end]
      ;; where the position is the href value

      ;; now, find the duplicate. algo.
      ;; go thru hashtable
      ;; if a value has a list of length more than 1, it means that link is repeated.
      ;; for each of those, hight them. by the begin end positions in the value.

      (save-excursion
        (goto-char (point-min))
        (while (search-forward "href=\"" nil t)
          (let (xfpath-beg xfpath-end xhrefval)
            (let ((xboundary (bounds-of-thing-at-point 'filename)))
              (seq-setq (xfpath-beg xfpath-end) (list (car xboundary) (cdr xboundary))))

            (setq xhrefval (buffer-substring-no-properties xfpath-beg xfpath-end))
            (setq xlink
                  (if (string-match "\\`http" xhrefval)
                      xhrefval
                    (expand-file-name xhrefval default-directory)))
            (let ((xresult (gethash xlink xlinksTable)))
              (if xresult
                  (progn
                    (puthash xlink
                             (cons (vector xfpath-beg xfpath-end) xresult)
                             xlinksTable))
                (progn
                  (puthash xlink (list (vector xfpath-beg xfpath-end)) xlinksTable)))))))

      ;; now go thru hashtable
      ;; if a key's value has length 2 or more
      ;; highlight it in buffer

      (maphash
       (lambda (_ xv)
         (if (eq (length xv) 1)
             nil
           (let ((xsorted (sort xv :key (lambda (xx) (aref xx 0)))))
             ;; color first occurances
             (let ((xfirst (pop xsorted)))
               (overlay-put (make-overlay (aref xfirst 0) (aref xfirst 1)) 'face 'hi-yellow))
             ;; color rest occurances
             (mapc
              (lambda (x)
                (overlay-put (make-overlay (aref x 0) (aref x 1)) 'face 'hi-green))
              xsorted))))
       xlinksTable)
      ;; (message "result is [%s]" xlinksTable)
      (message "donnnn"))))