emacs/lisp/gnus/mm-url.el

;;; mm-url.el --- a wrapper of url functions/commands for Gnus  -*- lexical-binding: t; -*-

;; Copyright (C) 2001-2023 Free Software Foundation, Inc.

;; Author: Shenghuo Zhu <zsh@cs.rochester.edu>

;; This file is part of GNU Emacs.

;; GNU Emacs 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.

;; GNU Emacs 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 GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; Some code is stolen from w3 and url packages. Some are moved from
;; nnweb.

;; TODO: Support POST, cookie.

;;; Code:

(eval-when-compile (require 'cl-lib))

(require 'mm-util)
(require 'gnus)

(defvar url-current-object)

(defgroup mm-url nil
  "A wrapper of url package and external url command for Gnus."
  :group 'gnus)

(defcustom mm-url-use-external nil
  "If non-nil, use external grab program `mm-url-program'."
  :version "22.1"
  :type 'boolean)

(defvar mm-url-predefined-programs
  '((wget "wget" "--user-agent=mm-url" "-q" "-O" "-")
    (w3m  "w3m" "-dump_source")
    (lynx "lynx" "-source")
    (curl "curl" "--silent" "--user-agent" "mm-url" "--location")))

(defcustom mm-url-program
  (cond
   ((executable-find "wget") 'wget)
   ((executable-find "w3m") 'w3m)
   ((executable-find "lynx") 'lynx)
   ((executable-find "curl") 'curl)
   (t "GET"))
  "The url grab program.
Likely values are `wget', `w3m', `lynx' and `curl'."
  :version "22.1"
  :type '(choice
	  (symbol :tag "wget" wget)
	  (symbol :tag "w3m" w3m)
	  (symbol :tag "lynx" lynx)
	  (symbol :tag "curl" curl)
	  (string :tag "other")))

(defcustom mm-url-arguments nil
  "The arguments for `mm-url-program'."
  :version "22.1"
  :type '(repeat string))


;;; Internal variables

;; Stolen from w3.
(defvar mm-url-html-entities
  '(
    ;;(excl        .  33)
    (quot        .  34)
    ;;(num         .  35)
    ;;(dollar      .  36)
    ;;(percent     .  37)
    (amp         .  38)
    (rsquo       .  39)			; should be U+8217
    ;;(apos        .  39)
    ;;(lpar        .  40)
    ;;(rpar        .  41)
    ;;(ast         .  42)
    ;;(plus        .  43)
    ;;(comma       .  44)
    ;;(period      .  46)
    ;;(colon       .  58)
    ;;(semi        .  59)
    (lt          .  60)
    ;;(equals      .  61)
    (gt          .  62)
    ;;(quest       .  63)
    ;;(commat      .  64)
    ;;(lsqb        .  91)
    ;;(rsqb        .  93)
    (uarr        .  94)			; should be U+8593
    ;;(lowbar      .  95)
    (lsquo       .  96)			; should be U+8216
    (lcub        . 123)
    ;;(verbar      . 124)
    (rcub        . 125)
    (tilde       . 126)
    (nbsp        . 160)
    (iexcl       . 161)
    (cent        . 162)
    (pound       . 163)
    (curren      . 164)
    (yen         . 165)
    (brvbar      . 166)
    (sect        . 167)
    (uml         . 168)
    (copy        . 169)
    (ordf        . 170)
    (laquo       . 171)
    (not         . 172)
    (shy         . 173)
    (reg         . 174)
    (macr        . 175)
    (deg         . 176)
    (plusmn      . 177)
    (sup2        . 178)
    (sup3        . 179)
    (acute       . 180)
    (micro       . 181)
    (para        . 182)
    (middot      . 183)
    (cedil       . 184)
    (sup1        . 185)
    (ordm        . 186)
    (raquo       . 187)
    (frac14      . 188)
    (frac12      . 189)
    (frac34      . 190)
    (iquest      . 191)
    (Agrave      . 192)
    (Aacute      . 193)
    (Acirc       . 194)
    (Atilde      . 195)
    (Auml        . 196)
    (Aring       . 197)
    (AElig       . 198)
    (Ccedil      . 199)
    (Egrave      . 200)
    (Eacute      . 201)
    (Ecirc       . 202)
    (Euml        . 203)
    (Igrave      . 204)
    (Iacute      . 205)
    (Icirc       . 206)
    (Iuml        . 207)
    (ETH         . 208)
    (Ntilde      . 209)
    (Ograve      . 210)
    (Oacute      . 211)
    (Ocirc       . 212)
    (Otilde      . 213)
    (Ouml        . 214)
    (times       . 215)
    (Oslash      . 216)
    (Ugrave      . 217)
    (Uacute      . 218)
    (Ucirc       . 219)
    (Uuml        . 220)
    (Yacute      . 221)
    (THORN       . 222)
    (szlig       . 223)
    (agrave      . 224)
    (aacute      . 225)
    (acirc       . 226)
    (atilde      . 227)
    (auml        . 228)
    (aring       . 229)
    (aelig       . 230)
    (ccedil      . 231)
    (egrave      . 232)
    (eacute      . 233)
    (ecirc       . 234)
    (euml        . 235)
    (igrave      . 236)
    (iacute      . 237)
    (icirc       . 238)
    (iuml        . 239)
    (eth         . 240)
    (ntilde      . 241)
    (ograve      . 242)
    (oacute      . 243)
    (ocirc       . 244)
    (otilde      . 245)
    (ouml        . 246)
    (divide      . 247)
    (oslash      . 248)
    (ugrave      . 249)
    (uacute      . 250)
    (ucirc       . 251)
    (uuml        . 252)
    (yacute      . 253)
    (thorn       . 254)
    (yuml        . 255)

    ;; Special handling of these
    (frac56      . "5/6")
    (frac16      . "1/6")
    (frac45      . "4/5")
    (frac35      . "3/5")
    (frac25      . "2/5")
    (frac15      . "1/5")
    (frac23      . "2/3")
    (frac13      . "1/3")
    (frac78      . "7/8")
    (frac58      . "5/8")
    (frac38      . "3/8")
    (frac18      . "1/8")

    ;; The following 5 entities are not mentioned in the HTML 2.0
    ;; standard, nor in any other HTML proposed standard of which I
    ;; am aware.  I am not even sure they are ISO entity names.  ***
    ;; Hence, some arrangement should be made to give a bad HTML
    ;; message when they are seen.
    (ndash       .  45)
    (mdash       .  45)
    (emsp        .  32)
    (ensp        .  32)
    (sim         . 126)
    (le          . "<=")
    (agr         . "alpha")
    (rdquo       . "''")
    (ldquo       . "``")
    (trade       . "(TM)")
    ;; To be done
    ;; (shy      . ????) ; soft hyphen
    )
  "An assoc list of entity names and how to actually display them.")

(defconst mm-url-unreserved-chars
  '(
    ?a ?b ?c ?d ?e ?f ?g ?h ?i ?j ?k ?l ?m ?n ?o ?p ?q ?r ?s ?t ?u ?v ?w ?x ?y ?z
    ?A ?B ?C ?D ?E ?F ?G ?H ?I ?J ?K ?L ?M ?N ?O ?P ?Q ?R ?S ?T ?U ?V ?W ?X ?Y ?Z
    ?0 ?1 ?2 ?3 ?4 ?5 ?6 ?7 ?8 ?9
    ?- ?_ ?. ?! ?~ ?* ?' ?\( ?\))
  "A list of characters that are _NOT_ reserved in the URL spec.
This is taken from RFC 2396.")

(defun mm-url-load-url ()
  "Load `url-insert-file-contents'."
  (unless (condition-case ()
	      (progn
		(require 'url-handlers)
		(require 'url-parse)
		(require 'url-vars))
	    (error nil))
    (require 'url)))

;;;###autoload
(defun mm-url-insert-file-contents (url)
  "Insert file contents of URL.
If `mm-url-use-external' is non-nil, use `mm-url-program'."
  (if mm-url-use-external
      (progn
	(if (string-match "^file:/+" url)
	    (insert-file-contents (substring url (1- (match-end 0))))
	  (mm-url-insert-file-contents-external url))
	(goto-char (point-min))
	(setq url-current-object (url-generic-parse-url url))
	(list url (buffer-size)))
    (mm-url-load-url)
    (let ((name buffer-file-name)
	  result)
      (setq result (url-insert-file-contents url))
      (save-excursion
	(goto-char (point-min))
	(while (re-search-forward "\r 1000\r ?" nil t)
	  (replace-match "")))
      (setq buffer-file-name name)
      (when (listp result)
	(setq url-current-object
	      (url-generic-parse-url (car result))))
      result)))

;;;###autoload
(defun mm-url-insert-file-contents-external (url)
  "Insert file contents of URL using `mm-url-program'."
  (let (program args)
    (if (symbolp mm-url-program)
	(let ((item (cdr (assq mm-url-program mm-url-predefined-programs))))
	  (setq program (car item)
		args (append (cdr item) (list url))))
      (setq program mm-url-program
	    args (append mm-url-arguments (list url))))
    (unless (eq 0 (apply #'call-process program nil t nil args))
      (error "Couldn't fetch %s" url))))

(defvar mm-url-timeout 30
  "The number of seconds before timing out an URL fetch.")

(defvar mm-url-retries 10
  "The number of retries after timing out when fetching an URL.")

(defun mm-url-insert (url &optional follow-refresh)
  "Insert the contents from an URL in the current buffer.
If FOLLOW-REFRESH is non-nil, redirect refresh url in META."
  (let ((times mm-url-retries)
	(done nil)
	(first t)
	result)
    (while (and (not (zerop (cl-decf times)))
		(not done))
      (with-timeout (mm-url-timeout)
	(unless first
	  (message "Trying again (%s)..." (- mm-url-retries times)))
	(setq first nil)
	(if follow-refresh
	    (save-restriction
	      (narrow-to-region (point) (point))
	      (mm-url-insert-file-contents url)
	      (goto-char (point-min))
	      (when (re-search-forward
		     "<meta[ \t\r\n]*http-equiv=\"Refresh\"[^>]*URL=\\([^\"]+\\)\"" nil t)
		(let ((url (match-string 1)))
		  (delete-region (point-min) (point-max))
		  (setq result (mm-url-insert url t)))))
	  (setq result (mm-url-insert-file-contents url)))
	(setq done t)))
    result))

(defun mm-url-decode-entities ()
  "Decode all HTML entities."
  (goto-char (point-min))
  (while (re-search-forward "&\\(#[0-9]+\\|#x[0-9a-f]+\\|[a-z]+[0-9]*\\);"
			    nil t)
    (let* ((entity (match-string 1))
	   (elem (if (eq (aref entity 0) ?\#)
		     (let ((c
			    ;; Hex number: &#x3212
			    (if (eq (aref entity 1) ?x)
				(string-to-number (substring entity 2)
						  16)
			      ;; Decimal number: &#23
			      (string-to-number (substring entity 1)))))
		       (setq c (or (cdr (assq c mm-extra-numeric-entities))
				   (mm-ucs-to-char c)))
		       (if (characterp c) c ?#))
		   (or (cdr (assq (intern entity)
				  mm-url-html-entities))
		       ?#))))
      (unless (stringp elem)
	(setq elem (char-to-string elem)))
      (replace-match elem t t))))

(defun mm-url-decode-entities-nbsp ()
  "Decode all HTML entities and &nbsp; to a space."
  (let ((mm-url-html-entities (cons '(nbsp . 32) mm-url-html-entities)))
    (mm-url-decode-entities)))

(defun mm-url-decode-entities-string (string)
  (with-temp-buffer
    (insert string)
    (mm-url-decode-entities)
    (buffer-string)))

(defun mm-url-form-encode-xwfu (chunk)
  "Escape characters in a string for application/x-www-form-urlencoded.
Blasphemous crap because someone didn't think %20 was good enough for encoding
spaces.  Die Die Die."
  ;; This will get rid of the 'attributes' specified by the file type,
  ;; which are useless for an application/x-www-form-urlencoded form.
  (if (consp chunk)
      (setq chunk (cdr chunk)))

  (if chunk
      (mapconcat
       (lambda (char)
	 (cond
	  ((= char ?  ) "+")
	  ((memq char mm-url-unreserved-chars) (char-to-string char))
	  (t (upcase (format "%%%02x" char)))))
       (encode-coding-string chunk (car (find-coding-systems-string chunk)))
       "")))

(defun mm-url-encode-www-form-urlencoded (pairs)
  "Return PAIRS encoded for forms."
  (mapconcat
   (lambda (data)
     (concat (mm-url-form-encode-xwfu (car data)) "="
	     (mm-url-form-encode-xwfu (cdr data))))
   pairs "&"))

(autoload 'mml-compute-boundary "mml")

(defun mm-url-encode-multipart-form-data (data &optional boundary)
  "Return DATA encoded in multipart/form-data.
DATA is a list where the elements can have the following form:
  (\"NAME\" . \"VALUE\")
  (\"submit\")
  (\"file\" . ((\"name\" . \"NAME\")
             (\"filename\" . \"FILENAME\")
             (\"content-type\" . \"CONTENT-TYPE\")
             (\"filedata\" . \"FILEDATA\")))
Lowercase strings above are literals and uppercase are not."
  ;; RFC1867
  ;; Get a good boundary.
  (unless boundary
    (setq boundary (mml-compute-boundary '())))
  (with-temp-buffer
    (set-buffer-multibyte nil)
    (dolist (elem data)
      (let ((name (car elem))
	    (value (cdr elem)))
	(insert "--" boundary "\r\n")
	(cond
	 ((equal name "file")
	  (insert (format
		   "Content-Disposition: form-data; name=%S; filename=%S\r\n"
		   (or (cdr (assoc "name" value)) name)
		   (cdr (assoc "filename" value))))
	  (insert "Content-Transfer-Encoding: binary\r\n")
	  (insert (format "Content-Type: %s\r\n\r\n"
			  (or (cdr (assoc "content-type" value))
			      "text/plain")))
	  (let ((filedata (cdr (assoc "filedata" value))))
	    (cond
	     ((stringp filedata)
	      (insert filedata))
	     ;; How can this possibly be useful?
	     ((integerp filedata)
	      (insert (number-to-string filedata))))))
	 ((equal name "submit")
	  (insert
	   "Content-Disposition: form-data; name=\"submit\"\r\n\r\nSubmit\r\n"))
	 (t
	  (insert (format "Content-Disposition: form-data; name=%S\r\n\r\n"
			  name))
	  (insert value)))
	(unless (bolp)
	  (insert "\r\n"))))
    (insert "--" boundary "--\r\n")
    (buffer-string)))

(defun mm-url-remove-markup ()
  "Remove all HTML markup, leaving just plain text."
  (goto-char (point-min))
  (while (search-forward "<!--" nil t)
    (delete-region (match-beginning 0)
                   (or (search-forward "-->" nil t)
                       (point-max))))
  (goto-char (point-min))
  (while (re-search-forward "<[^>]+>" nil t)
    (replace-match "" t t)))

(provide 'mm-url)

;;; mm-url.el ends here