Emacs HTML entities un/escaping

html-entities.el

(defvar user/html-entity-to-unicode-alist
  '(("Aacute" . "Á") ("aacute" . "á") ("Acirc" . "Â") ("acirc" . "â") ("acute" . "´") ("AElig" . "Æ") ("aelig" . "æ") ("Agrave" . "À") ("agrave" . "à") ("alefsym" . "ℵ") ("Alpha" . "Α") ("alpha" . "α") ("amp" . "&") ("and" . "∧") ("ang" . "∠") ("apos" . "'") ("aring" . "å") ("Aring" . "Å") ("asymp" . "≈") ("atilde" . "ã") ("Atilde" . "Ã") ("auml" . "ä") ("Auml" . "Ä") ("bdquo" . "„") ("Beta" . "Β") ("beta" . "β") ("brvbar" . "¦") ("bull" . "•") ("cap" . "∩") ("ccedil" . "ç") ("Ccedil" . "Ç") ("cedil" . "¸") ("cent" . "¢") ("Chi" . "Χ") ("chi" . "χ") ("circ" . "ˆ") ("clubs" . "♣") ("cong" . "≅") ("copy" . "©") ("crarr" . "↵") ("cup" . "∪") ("curren" . "¤") ("Dagger" . "‡") ("dagger" . "†") ("darr" . "↓") ("dArr" . "⇓") ("deg" . "°") ("Delta" . "Δ") ("delta" . "δ") ("diams" . "♦") ("divide" . "÷") ("eacute" . "é") ("Eacute" . "É") ("ecirc" . "ê") ("Ecirc" . "Ê") ("egrave" . "è") ("Egrave" . "È") ("empty" . "∅") ("emsp" . " ") ("ensp" . " ") ("Epsilon" . "Ε") ("epsilon" . "ε") ("equiv" . "≡") ("Eta" . "Η") ("eta" . "η") ("eth" . "ð") ("ETH" . "Ð") ("euml" . "ë") ("Euml" . "Ë") ("euro" . "€") ("exist" . "∃") ("fnof" . "ƒ") ("forall" . "∀") ("frac12" . "½") ("frac14" . "¼") ("frac34" . "¾") ("frasl" . "⁄") ("Gamma" . "Γ") ("gamma" . "γ") ("ge" . "≥") ("gt" . ">") ("harr" . "↔") ("hArr" . "⇔") ("hearts" . "♥") ("hellip" . "…") ("iacute" . "í") ("Iacute" . "Í") ("icirc" . "î") ("Icirc" . "Î") ("iexcl" . "¡") ("igrave" . "ì") ("Igrave" . "Ì") ("image" . "ℑ") ("infin" . "∞") ("int" . "∫") ("Iota" . "Ι") ("iota" . "ι") ("iquest" . "¿") ("isin" . "∈") ("iuml" . "ï") ("Iuml" . "Ï") ("Kappa" . "Κ") ("kappa" . "κ") ("Lambda" . "Λ") ("lambda" . "λ") ("lang" . "〈") ("laquo" . "«") ("larr" . "←") ("lArr" . "⇐") ("lceil" . "⌈") ("ldquo" . "“") ("le" . "≤") ("lfloor" . "⌊") ("lowast" . "∗") ("loz" . "◊") ("lrm" . "") ("lsaquo" . "‹") ("lsquo" . "‘") ("lt" . "<") ("macr" . "¯") ("mdash" . "—") ("micro" . "µ") ("middot" . "·") ("minus" . "−") ("Mu" . "Μ") ("mu" . "μ") ("nabla" . "∇") ("nbsp" . "") ("ndash" . "–") ("ne" . "≠") ("ni" . "∋") ("not" . "¬") ("notin" . "∉") ("nsub" . "⊄") ("ntilde" . "ñ") ("Ntilde" . "Ñ") ("Nu" . "Ν") ("nu" . "ν") ("oacute" . "ó") ("Oacute" . "Ó") ("ocirc" . "ô") ("Ocirc" . "Ô") ("OElig" . "Œ") ("oelig" . "œ") ("ograve" . "ò") ("Ograve" . "Ò") ("oline" . "‾") ("omega" . "ω") ("Omega" . "Ω") ("Omicron" . "Ο") ("omicron" . "ο") ("oplus" . "⊕") ("or" . "∨") ("ordf" . "ª") ("ordm" . "º") ("oslash" . "ø") ("Oslash" . "Ø") ("otilde" . "õ") ("Otilde" . "Õ") ("otimes" . "⊗") ("ouml" . "ö") ("Ouml" . "Ö") ("para" . "¶") ("part" . "∂") ("permil" . "‰") ("perp" . "⊥") ("Phi" . "Φ") ("phi" . "φ") ("Pi" . "Π") ("pi" . "π") ("piv" . "ϖ") ("plusmn" . "±") ("pound" . "£") ("Prime" . "″") ("prime" . "′") ("prod" . "∏") ("prop" . "∝") ("Psi" . "Ψ") ("psi" . "ψ") ("quot" . "\"") ("radic" . "√") ("rang" . "〉") ("raquo" . "»") ("rarr" . "→") ("rArr" . "⇒") ("rceil" . "⌉") ("rdquo" . "”") ("real" . "ℜ") ("reg" . "®") ("rfloor" . "⌋") ("Rho" . "Ρ") ("rho" . "ρ") ("rlm" . "") ("rsaquo" . "›") ("rsquo" . "’") ("sbquo" . "‚") ("scaron" . "š") ("Scaron" . "Š") ("sdot" . "⋅") ("sect" . "§") ("shy" . "") ("Sigma" . "Σ") ("sigma" . "σ") ("sigmaf" . "ς") ("sim" . "∼") ("spades" . "♠") ("sub" . "⊂") ("sube" . "⊆") ("sum" . "∑") ("sup" . "⊃") ("sup1" . "¹") ("sup2" . "²") ("sup3" . "³") ("supe" . "⊇") ("szlig" . "ß") ("Tau" . "Τ") ("tau" . "τ") ("there4" . "∴") ("Theta" . "Θ") ("theta" . "θ") ("thetasym" . "ϑ") ("thinsp" . " ") ("thorn" . "þ") ("THORN" . "Þ") ("tilde" . "˜") ("times" . "×") ("trade" . "™") ("uacute" . "ú") ("Uacute" . "Ú") ("uarr" . "↑") ("uArr" . "⇑") ("ucirc" . "û") ("Ucirc" . "Û") ("ugrave" . "ù") ("Ugrave" . "Ù") ("uml" . "¨") ("upsih" . "ϒ") ("Upsilon" . "Υ") ("upsilon" . "υ") ("uuml" . "ü") ("Uuml" . "Ü") ("weierp" . "℘") ("Xi" . "Ξ") ("xi" . "ξ") ("yacute" . "ý") ("Yacute" . "Ý") ("yen" . "¥") ("yuml" . "ÿ") ("Yuml" . "Ÿ") ("Zeta" . "Ζ") ("zeta" . "ζ") ("zwj" . "") ("zwnj" . ""))
  "Alist that maps HTML entity names to equivalent unicode characters")

(defvar user/html-entity-to-unicode-hash nil
  "Hash table mapping HTML entities to unicode characters")

(defvar user/html-unicode-to-entity-hash nil
  "Hash table mapping unicode characters to HTML entities")

(let ((entity-list-length (length user/html-entity-to-unicode-alist)))
  (setq user/html-entity-to-unicode-hash (make-hash-table :test 'equal :size entity-list-length))
  (loop for (key . val) in user/html-entity-to-unicode-alist
        do (puthash key val user/html-entity-to-unicode-hash))
  
  (setq user/html-unicode-to-entity-hash (make-hash-table :test 'equal :size entity-list-length))
  (loop for (val . key) in user/html-entity-to-unicode-alist
        do (puthash key val user/html-unicode-to-entity-hash)))

(defun user/html-entity-to-unicode (entity)
  (gethash entity user/html-entity-to-unicode-hash))

(defun user/html-unicode-to-entity (unicode)
  (gethash unicode user/html-unicode-to-entity-hash))

(defun user/html-string-entities-to-unicode (string)
  (replace-regexp-in-string "&[[:word:]]+;"
                            (lambda (s)
                              (or (user/html-entity-to-unicode (substring s 1 -1)) s))
                            string))

(defun user/html-string-unicode-to-entities (string)
  (replace-regexp-in-string "[^[:word:]]"
                            (lambda (s)
                              (or (user/html-unicode-to-entity s) s))
                            string))

(defun user/html-escape (&optional start end)
  "Escape characters to HTML entities in the current buffer between start and end, which default to the whole buffer"
  (interactive "r")
  (unless start (setq start (point-min)))
  (unless end (setq end (point-max)))
  (save-excursion
    (save-restriction
      (narrow-to-region start end)
      (goto-char (point-min))
      (while (re-search-forward "\\([^[:word:]]\\)" nil t)
        (let* ((match (match-string 1))
               (entity (user/html-unicode-to-entity (match-string 1))))
          (when entity
              (setq entity (concat "&" entity ";")))
          (replace-match (or entity match) nil nil))))))

(defun user/html-unescape (&optional start end)
  "Unescape HTML entities to characters in the current buffer between start and end, which default to the whole buffer"
  (interactive "r")
  (unless start (setq start (point-min)))
  (unless end (setq end (point-max)))
  (save-excursion
    (save-restriction
      (narrow-to-region start end)
      (goto-char (point-min))
      (while (re-search-forward "\\(&\\([[:word:]]+\\);\\)" nil t)
        (replace-match (or (user/html-entity-to-unicode (match-string 2))
                           (match-string 1))
                       nil nil)))))