Change browse-url advice for older releases

[elpher.git] / elpher.el

diff --git a/elpher.el b/elpher.el
index 56c5996..f94b33f 100644 (file)
--- a/elpher.el
+++ b/elpher.el
@@ -1,13 +1,28 @@
-;;; elpher.el --- A friendly gopher and gemini client  -*- lexical-binding:t -*-
-
-;; Copyright (C) 2019 Tim Vaughan
+;;; elpher.el --- A friendly gopher and gemini client  -*- lexical-binding: t -*-
+
+;; Copyright (C) 2021 Jens Östlund <jostlund@gmail.com>
+;; Copyright (C) 2021 F. Jason Park <jp@neverwas.me>
+;; Copyright (C) 2021 Christopher Brannon <chris@the-brannons.com>
+;; Copyright (C) 2021 Omar Polo <op@omarpolo.com>
+;; Copyright (C) 2021 Noodles! <nnoodle@chiru.no>
+;; Copyright (C) 2020-2021 Alex Schroeder <alex@gnu.org>
+;; Copyright (C) 2020 Zhiwei Chen <chenzhiwei03@kuaishou.com>
+;; Copyright (C) 2020 condy0919 <condy0919@gmail.com>
+;; Copyright (C) 2020 Alexis <flexibeast@gmail.com>
+;; Copyright (C) 2020 Étienne Deparis <etienne@depar.is>
+;; Copyright (C) 2020 Simon Nicolussi <sinic@sinic.name>
+;; Copyright (C) 2020 Michel Alexandre Salim <michel@michel-slm.name>
+;; Copyright (C) 2020 Koushk Roy <kroy@twilio.com>
+;; Copyright (C) 2020 Vee <vee@vnsf.xyz>
+;; Copyright (C) 2020 Simon South <simon@simonsouth.net>
+;; Copyright (C) 2019-2020 Tim Vaughan <plugd@thelambdalab.xyz>

 
 ;; Author: Tim Vaughan <plugd@thelambdalab.xyz>
 ;; Created: 11 April 2019
 
 ;; Author: Tim Vaughan <plugd@thelambdalab.xyz>
 ;; Created: 11 April 2019

-;; Version: 2.7.9
+;; Version: 2.11.0

 ;; Keywords: comm gopher
 ;; Keywords: comm gopher

-;; Homepage: http://thelambdalab.xyz/elpher
-;; Package-Requires: ((emacs "26"))
+;; Homepage: https://alexschroeder.ch/cgit/elpher
+;; Package-Requires: ((emacs "27.1"))

 
 ;; This file is not part of GNU Emacs.
 
 
 ;; This file is not part of GNU Emacs.
 


@@ -48,7 +63,7 @@
 
 ;; Elpher is under active development.  Any suggestions for
 ;; improvements are welcome, and can be made on the official
 
 ;; Elpher is under active development.  Any suggestions for
 ;; improvements are welcome, and can be made on the official

-;; project page, gopher://thelambdalab.xyz/1/projects/elpher/.
+;; project page, https://alexschroeder.ch/cgit/elpher.

 
 ;;; Code:
 
 
 ;;; Code:
 


@@ -63,14 +78,32 @@
 (require 'url-util)
 (require 'subr-x)
 (require 'dns)
 (require 'url-util)
 (require 'subr-x)
 (require 'dns)

-(require 'ansi-color)

 (require 'nsm)
 (require 'nsm)

-
+(require 'gnutls)
+(require 'socks)
+
+;;; ANSI colors or XTerm colors
+
+(or (require 'xterm-color nil t)
+    (require 'ansi-color))
+
+(defalias 'elpher-color-filter-apply
+  (if (fboundp 'xterm-color-filter)
+      (lambda (s)
+        (let ((xterm-color-render nil))
+          (xterm-color-filter s)))
+    'ansi-color-filter-apply)
+  "A function to filter out ANSI escape sequences.")
+(defalias 'elpher-color-apply
+  (if (fboundp 'xterm-color-filter)
+      'xterm-color-filter
+    'ansi-color-apply)
+  "A function to apply ANSI escape sequences.")

 
 ;;; Global constants
 ;;
 
 
 ;;; Global constants
 ;;
 

-(defconst elpher-version "2.7.9"
+(defconst elpher-version "2.11.0"

   "Current version of elpher.")
 
 (defconst elpher-margin-width 6
   "Current version of elpher.")
 
 (defconst elpher-margin-width 6


@@ -99,18 +132,31 @@
   "Association list from types to getters, renderers, margin codes and index faces.")
 
 
   "Association list from types to getters, renderers, margin codes and index faces.")
 
 

+;;; Internal variables
+;;
+
+;; buffer-local
+(defvar elpher--gemini-page-headings nil
+  "List of headings on the page.")
+
+(defvar elpher--gemini-page-links nil
+  "List of links on the page.")
+
+(defvar elpher--gemini-page-links-cache (make-hash-table :test 'equal)
+  "Hash of addresses and page links.")
+

 ;;; Customization group
 ;;
 
 (defgroup elpher nil
 ;;; Customization group
 ;;
 
 (defgroup elpher nil

-  "A gopher client."
+  "A gopher and gemini client."

   :group 'applications)
 
 ;; General appearance and customizations
 
 (defcustom elpher-open-urls-with-eww nil
   "If non-nil, open URL selectors using eww.
   :group 'applications)
 
 ;; General appearance and customizations
 
 (defcustom elpher-open-urls-with-eww nil
   "If non-nil, open URL selectors using eww.

-Otherwise, use the system browser via the BROWSE-URL function."
+Otherwise, use the system browser via the `browse-url' function."

   :type '(boolean))
 
 (defcustom elpher-use-header t
   :type '(boolean))
 
 (defcustom elpher-use-header t


@@ -119,8 +165,9 @@ Otherwise, use the system browser via the BROWSE-URL function."
 
 (defcustom elpher-auto-disengage-TLS nil
   "If non-nil, automatically disengage TLS following an unsuccessful connection.
 
 (defcustom elpher-auto-disengage-TLS nil
   "If non-nil, automatically disengage TLS following an unsuccessful connection.

-While enabling this may seem convenient, it is also potentially dangerous as it
-allows switching from an encrypted channel back to plain text without user input."
+While enabling this may seem convenient, it is also potentially
+dangerous as it allows switching from an encrypted channel back to
+plain text without user input."

   :type '(boolean))
 
 (defcustom elpher-connection-timeout 5
   :type '(boolean))
 
 (defcustom elpher-connection-timeout 5


@@ -133,6 +180,21 @@ The default behaviour is to use the ansi-color package to interpret these
 sequences."
   :type '(boolean))
 
 sequences."
   :type '(boolean))
 

+(defcustom elpher-certificate-directory
+  (file-name-as-directory (locate-user-emacs-file "elpher-certificates"))
+  "Specify the name of the directory where client certificates will be stored.
+These certificates may be used for establishing authenticated TLS connections."
+  :type '(directory))
+
+(defcustom elpher-openssl-command "openssl"
+  "The command used to launch openssl when generating TLS client certificates."
+  :type '(file))
+
+(defcustom elpher-default-url-type "gopher"
+  "Default URL type (i.e. scheme) to assume if not explicitly given."
+  :type '(choice (const "gopher")
+                 (const "gemini")))
+

 (defcustom elpher-gemini-TLS-cert-checks nil
   "If non-nil, verify gemini server TLS certs using the default security level.
 Otherwise, certificate verification is disabled.
 (defcustom elpher-gemini-TLS-cert-checks nil
   "If non-nil, verify gemini server TLS certs using the default security level.
 Otherwise, certificate verification is disabled.


@@ -167,6 +229,16 @@ This can be useful when browsing from a computer that supports IPv6, because
 some servers which do not support IPv6 can take a long time to time-out."
   :type '(boolean))
 
 some servers which do not support IPv6 can take a long time to time-out."
   :type '(boolean))
 

+(defcustom elpher-socks-always nil
+  "If non-nil, elpher will establish network connections over a SOCKS proxy.
+Otherwise, the SOCKS proxy is only used for connections to onion services."
+  :type '(boolean))
+
+(defcustom elpher-gemini-number-links nil
+  "If non-nil, number links in gemini pages when rendering.
+Links can be accessed by pressing `v' ('visit') followed by the link number."
+  :type '(boolean))
+

 ;; Face customizations
 
 (defgroup elpher-faces nil
 ;; Face customizations
 
 (defgroup elpher-faces nil


@@ -198,7 +270,7 @@ some servers which do not support IPv6 can take a long time to time-out."
   "Face used for html type directory records.")
 
 (defface elpher-gemini
   "Face used for html type directory records.")
 
 (defface elpher-gemini

-  '((t :inherit font-lock-regexp-grouping-backslash))
+  '((t :inherit font-lock-constant-face))

   "Face used for Gemini type directory records.")
 
 (defface elpher-other-url
   "Face used for Gemini type directory records.")
 
 (defface elpher-other-url


@@ -241,6 +313,10 @@ some servers which do not support IPv6 can take a long time to time-out."
   '((t :inherit fixed-pitch))
   "Face used for pre-formatted gemini text blocks.")
 
   '((t :inherit fixed-pitch))
   "Face used for pre-formatted gemini text blocks.")
 

+(defface elpher-gemini-quoted
+  '((t :inherit font-lock-doc-face))
+  "Face used for gemini quoted texts.")
+

 ;;; Model
 ;;
 
 ;;; Model
 ;;
 


@@ -261,13 +337,17 @@ some servers which do not support IPv6 can take a long time to time-out."
             (setf (url-filename url)
                   (url-unhex-string (url-filename url)))
             (unless (url-type url)
             (setf (url-filename url)
                   (url-unhex-string (url-filename url)))
             (unless (url-type url)

-              (setf (url-type url) "gopher"))
+              (setf (url-type url) elpher-default-url-type))
+            (unless (url-host url)
+              (let ((p (split-string (url-filename url) "/" nil nil)))
+                (setf (url-host url) (car p))
+                (setf (url-filename url)
+                      (if (cdr p)
+                          (concat "/" (mapconcat #'identity (cdr p) "/"))
+                        ""))))

             (when (or (equal "gopher" (url-type url))
                       (equal "gophers" (url-type url)))
               ;; Gopher defaults
             (when (or (equal "gopher" (url-type url))
                       (equal "gophers" (url-type url)))
               ;; Gopher defaults

-              (unless (url-host url)
-                (setf (url-host url) (url-filename url))
-                (setf (url-filename url) ""))

               (when (or (equal (url-filename url) "")
                         (equal (url-filename url) "/"))
                 (setf (url-filename url) "/1")))
               (when (or (equal (url-filename url) "")
                         (equal (url-filename url) "/"))
                 (setf (url-filename url) "/1")))


@@ -275,9 +355,23 @@ some servers which do not support IPv6 can take a long time to time-out."
               ;; Gemini defaults
               (if (equal (url-filename url) "")
                   (setf (url-filename url) "/"))))
               ;; Gemini defaults
               (if (equal (url-filename url) "")
                   (setf (url-filename url) "/"))))

-          url)
+          (elpher-remove-redundant-ports url))

       (set-match-data data))))
 
       (set-match-data data))))
 

+(defun elpher-remove-redundant-ports (address)
+  "Remove redundant port specifiers from ADDRESS.
+Here 'redundant' means that the specified port matches the default
+for that protocol, eg 70 for gopher."
+  (if (and (not (elpher-address-special-p address))
+           (eq (url-portspec address) ; (url-port) is too slow!
+               (pcase (url-type address)
+                 ("gemini" 1965)
+                 ((or "gopher" "gophers") 70)
+                 ("finger" 79)
+                 (_ -1))))
+      (setf (url-portspec address) nil))
+  address)
+

 (defun elpher-make-gopher-address (type selector host port &optional tls)
   "Create an ADDRESS object using gopher directory record attributes.
 The basic attributes include: TYPE, SELECTOR, HOST and PORT.
 (defun elpher-make-gopher-address (type selector host port &optional tls)
   "Create an ADDRESS object using gopher directory record attributes.
 The basic attributes include: TYPE, SELECTOR, HOST and PORT.


@@ -307,9 +401,9 @@ requiring gopher-over-TLS."
 
 (defun elpher-address-to-url (address)
   "Get string representation of ADDRESS, or nil if ADDRESS is special."
 
 (defun elpher-address-to-url (address)
   "Get string representation of ADDRESS, or nil if ADDRESS is special."

-  (if (not (elpher-address-special-p address))
-      (url-encode-url (url-recreate-url address))
-    nil))
+  (if (elpher-address-special-p address)
+      nil
+    (url-encode-url (url-recreate-url address))))

 
 (defun elpher-address-type (address)
   "Retrieve type of ADDRESS object.
 
 (defun elpher-address-type (address)
   "Retrieve type of ADDRESS object.


@@ -416,8 +510,8 @@ If no address is defined, returns 0.  (This is for compatibility with the URL li
   "Set the address corresponding to PAGE to NEW-ADDRESS."
   (setcar (cdr page) new-address))
 
   "Set the address corresponding to PAGE to NEW-ADDRESS."
   (setcar (cdr page) new-address))
 

-(defvar elpher-current-page nil)
-(defvar elpher-history nil)
+(defvar elpher-current-page nil) ; buffer local
+(defvar elpher-history nil)      ; buffer local

 
 (defun elpher-visit-page (page &optional renderer no-history)
   "Visit PAGE using its own renderer or RENDERER, if non-nil.
 
 (defun elpher-visit-page (page &optional renderer no-history)
   "Visit PAGE using its own renderer or RENDERER, if non-nil.


@@ -429,15 +523,20 @@ unless NO-HISTORY is non-nil."
               (equal (elpher-page-address elpher-current-page)
                      (elpher-page-address page)))
     (push elpher-current-page elpher-history))
               (equal (elpher-page-address elpher-current-page)
                      (elpher-page-address page)))
     (push elpher-current-page elpher-history))

-  (setq elpher-current-page page)
+  (setq-local elpher-current-page page)

   (let* ((address (elpher-page-address page))
          (type (elpher-address-type address))
   (let* ((address (elpher-page-address page))
          (type (elpher-address-type address))

-         (type-record (cdr (assoc type elpher-type-map))))
+         (type-record (cdr (assoc type elpher-type-map)))
+         (page-links nil))

     (if type-record
     (if type-record

-        (funcall (car type-record)
-                 (if renderer
-                     renderer
-                   (cadr type-record)))
+        (progn
+          (funcall (car type-record)
+                   (if renderer
+                       renderer
+                     (cadr type-record)))
+          (setq page-links (gethash address elpher--gemini-page-links-cache))
+          (if page-links
+              (setq elpher--gemini-page-links page-links)))

       (elpher-visit-previous-page)
       (pcase type
         (`(gopher ,type-char)
       (elpher-visit-previous-page)
       (pcase type
         (`(gopher ,type-char)


@@ -453,7 +552,7 @@ unless NO-HISTORY is non-nil."
     (if previous-page
         (elpher-visit-page previous-page nil t)
       (error "No previous page"))))
     (if previous-page
         (elpher-visit-page previous-page nil t)
       (error "No previous page"))))

-      
+

 (defun elpher-reload-current-page ()
   "Reload the current page, discarding any existing cached content."
   (elpher-cache-content (elpher-page-address elpher-current-page) nil)
 (defun elpher-reload-current-page ()
   "Reload the current page, discarding any existing cached content."
   (elpher-cache-content (elpher-page-address elpher-current-page) nil)


@@ -475,6 +574,9 @@ unless NO-HISTORY is non-nil."
 ;;; Buffer preparation
 ;;
 
 ;;; Buffer preparation
 ;;
 

+(defvar elpher-buffer-name "*elpher*"
+  "The default name of the Elpher buffer.")
+

 (defun elpher-update-header ()
   "If `elpher-use-header' is true, display current page info in window header."
   (if elpher-use-header
 (defun elpher-update-header ()
   "If `elpher-use-header' is true, display current page info in window header."
   (if elpher-use-header


@@ -491,14 +593,31 @@ unless NO-HISTORY is non-nil."
 
 (defmacro elpher-with-clean-buffer (&rest args)
   "Evaluate ARGS with a clean *elpher* buffer as current."
 
 (defmacro elpher-with-clean-buffer (&rest args)
   "Evaluate ARGS with a clean *elpher* buffer as current."

-  (list 'with-current-buffer "*elpher*"
-        '(elpher-mode)
-        (append (list 'let '((inhibit-read-only t))
-                      '(setq-local network-security-level
-                                   (default-value 'network-security-level))
-                      '(erase-buffer)
-                      '(elpher-update-header))
-                args)))
+  `(with-current-buffer elpher-buffer-name
+     (unless (eq major-mode 'elpher-mode)
+       ;; avoid resetting buffer-local variables
+       (elpher-mode))
+     (let ((inhibit-read-only t))
+       (setq-local network-security-level
+                   (default-value 'network-security-level))
+       (erase-buffer)
+       (elpher-update-header)
+       ,@args)))
+
+(defun elpher-buffer-message (string &optional line)
+  "Replace first line in elpher buffer with STRING.
+If LINE is non-nil, replace that line instead."
+  (with-current-buffer elpher-buffer-name
+    (let ((inhibit-read-only t))
+      (goto-char (point-min))
+      (if line
+          (forward-line line))
+      (let ((data (match-data)))
+        (unwind-protect
+            (progn
+              (re-search-forward "^.*$")
+              (replace-match string))
+          (set-match-data data))))))

 
 
 ;;; Text Processing
 
 
 ;;; Text Processing


@@ -518,7 +637,7 @@ unless NO-HISTORY is non-nil."
   "Preprocess text selector response contained in STRING.
 This involes decoding the character representation, and clearing
 away CRs and any terminating period."
   "Preprocess text selector response contained in STRING.
 This involes decoding the character representation, and clearing
 away CRs and any terminating period."

-  (elpher-decode (replace-regexp-in-string "\n\.\n$" "\n"
+  (elpher-decode (replace-regexp-in-string "\n\\.\n$" "\n"

                                            (replace-regexp-in-string "\r" "" string))))
 
 
                                            (replace-regexp-in-string "\r" "" string))))
 
 


@@ -536,12 +655,18 @@ ERROR can be either an error object or a string."
            "Press 'u' to return to the previous page.")))
 
 
            "Press 'u' to return to the previous page.")))
 
 

-;;; Gopher selector retrieval
+;;; General network communication

 ;;
 
 (defvar elpher-network-timer nil
   "Timer used for network connections.")
 
 ;;
 
 (defvar elpher-network-timer nil
   "Timer used for network connections.")
 

+(defvar elpher-use-tls nil
+  "If non-nil, use TLS to communicate with gopher servers.")
+
+(defvar elpher-client-certificate nil
+  "If non-nil, contains client certificate details to use for TLS connections.")
+

 (defun elpher-process-cleanup ()
   "Immediately shut down any extant elpher process and timers."
   (let ((p (get-process "elpher-process")))
 (defun elpher-process-cleanup ()
   "Immediately shut down any extant elpher process and timers."
   (let ((p (get-process "elpher-process")))


@@ -549,101 +674,273 @@ ERROR can be either an error object or a string."
   (if (timerp elpher-network-timer)
       (cancel-timer elpher-network-timer)))
 
   (if (timerp elpher-network-timer)
       (cancel-timer elpher-network-timer)))
 

-(defvar elpher-use-tls nil
-  "If non-nil, use TLS to communicate with gopher servers.")
+(defun elpher-get-host-response (address default-port query-string response-processor
+                                         &optional use-tls force-ipv4)
+  "Generic function for retrieving data from ADDRESS.
+
+When ADDRESS lacks a specific port, DEFAULT-PORT is used instead.
+QUERY-STRING is a string sent to the host specified by ADDRESS to
+illicet a response.  This response is passed as an argument to the
+function RESPONSE-PROCESSOR.
+
+If non-nil, USE-TLS specifies that the connection is to be made over
+TLS.  If set to gemini, the certificate verification will be disabled
+unless `elpher-gemini-TLS-cert-checks' is non-nil.
+
+If non-nil, FORCE-IPV4 causes the network connection to be made over
+ipv4 only.  (The default behaviour when this is not set depends on
+the host operating system and the local network capabilities."
+  (if (and use-tls (not (gnutls-available-p)))
+      (error "Use of TLS requires Emacs to be compiled with GNU TLS support")
+    (unless (< (elpher-address-port address) 65536)
+      (error "Cannot establish network connection: port number > 65536"))
+    (when (and (eq use-tls 'gemini) (not elpher-gemini-TLS-cert-checks))
+      (setq-local network-security-level 'low)
+      (setq-local gnutls-verify-error nil))
+    (condition-case nil
+        (let* ((kill-buffer-query-functions nil)
+               (port (elpher-address-port address))
+               (service (if (> port 0) port default-port))
+               (host (elpher-address-host address))
+               (socks (or elpher-socks-always (string-suffix-p ".onion" host)))
+               (response-string-parts nil)
+               (bytes-received 0)
+               (hkbytes-received 0)
+               (timer (run-at-time elpher-connection-timeout nil
+                                   (lambda ()
+                                     (elpher-process-cleanup)
+                                     (cond
+                                        ; Try again with IPv4
+                                      ((not (or force-ipv4 socks))
+                                       (message "Connection timed out.  Retrying with IPv4.")
+                                       (elpher-get-host-response address default-port
+                                                                 query-string
+                                                                 response-processor
+                                                                 use-tls t))
+                                      ((and use-tls
+                                            (not (eq use-tls 'gemini))
+                                            (or elpher-auto-disengage-TLS
+                                                (y-or-n-p
+                                                 "TLS connetion failed.  Disable TLS mode and retry? ")))
+                                       (setq elpher-use-tls nil)
+                                       (elpher-get-host-response address default-port
+                                                                 query-string
+                                                                 response-processor
+                                                                 nil force-ipv4))
+                                      (t
+                                       (elpher-network-error address "Connection time-out."))))))
+               (gnutls-params (list :type 'gnutls-x509pki :hostname host
+                                    :keylist (elpher-get-current-keylist address)))
+               (proc (if socks (socks-open-network-stream "elpher-process" nil host service)
+                       (make-network-process :name "elpher-process"
+                                             :host host
+                                             :family (and force-ipv4 'ipv4)
+                                             :service service
+                                             :buffer nil
+                                             :nowait t
+                                             :tls-parameters
+                                             (and use-tls
+                                                  (cons 'gnutls-x509pki
+                                                        (apply #'gnutls-boot-parameters
+                                                               gnutls-params)))))))
+          (setq elpher-network-timer timer)
+          (set-process-coding-system proc 'binary 'binary)
+          (set-process-query-on-exit-flag proc nil)
+          (elpher-buffer-message (concat "Connecting to " host "..."
+                                         " (press 'u' to abort)"))
+          (set-process-filter proc
+                              (lambda (_proc string)
+                                (when timer
+                                  (cancel-timer timer)
+                                  (setq timer nil))
+                                (setq bytes-received (+ bytes-received (length string)))
+                                (let ((new-hkbytes-received (/ bytes-received 102400)))
+                                  (when (> new-hkbytes-received hkbytes-received)
+                                    (setq hkbytes-received new-hkbytes-received)
+                                    (elpher-buffer-message
+                                     (concat "("
+                                             (number-to-string (/ hkbytes-received 10.0))
+                                             " MB read)")
+                                     1)))
+                                (setq response-string-parts
+                                      (cons string response-string-parts))))
+          (set-process-sentinel proc
+                                (lambda (proc event)
+                                  (when timer
+                                    (cancel-timer timer))
+                                  (condition-case the-error
+                                      (cond
+                                       ((string-prefix-p "open" event)    ; request URL
+                                        (elpher-buffer-message
+                                         (concat "Connected to " host ". Receiving data..."
+                                                 " (press 'u' to abort)"))
+                                        (let ((inhibit-eol-conversion t))
+                                          (process-send-string proc query-string)))
+                                       ((string-prefix-p "deleted" event)) ; do nothing
+                                       ((and (not response-string-parts)
+                                             (not (or elpher-ipv4-always force-ipv4 socks)))
+                                        ; Try again with IPv4
+                                        (message "Connection failed. Retrying with IPv4.")
+                                        (elpher-get-host-response address default-port
+                                                                  query-string
+                                                                  response-processor
+                                                                  use-tls t))
+                                       (response-string-parts
+                                        (elpher-with-clean-buffer
+                                         (insert "Data received.  Rendering..."))
+                                        (funcall response-processor
+                                                 (apply #'concat (reverse response-string-parts)))
+                                        (elpher-restore-pos))
+                                       (t
+                                        (error "No response from server")))
+                                    (error
+                                     (elpher-network-error address the-error)))))
+          (when socks
+            (if use-tls (apply #'gnutls-negotiate :process proc gnutls-params))
+            (funcall (process-sentinel proc) proc "open\n")))
+      (error
+       (error "Error initiating connection to server")))))
+
+
+;;; Client-side TLS Certificate Management
+;;
+
+(defun elpher-generate-certificate (common-name key-file cert-file &optional temporary)
+  "Generate a key and a self-signed client TLS certificate using openssl.
+
+The Common Name field of the certificate is set to COMMON-NAME.  The
+arguments KEY-FILE and CERT-FILE should contain the absolute paths of
+the key and certificate files to write.

 
 

-(defun elpher-get-selector (address renderer &optional force-ipv4)
-  "Retrieve selector specified by ADDRESS, then render it using RENDERER.
-If FORCE-IPV4 is non-nil, explicitly look up and use IPv4 address corresponding
-to ADDRESS."
-  (when (equal (elpher-address-protocol address) "gophers")
-    (if (gnutls-available-p)
-        (when (not elpher-use-tls)
-          (setq elpher-use-tls t)
-          (message "Engaging TLS gopher mode."))
-      (error "Cannot retrieve TLS gopher selector: GnuTLS not available")))
-  (unless (< (elpher-address-port address) 65536)
-    (error "Cannot retrieve gopher selector: port number > 65536"))
-  (defvar gnutls-verify-error)
-  (condition-case nil
-      (let* ((kill-buffer-query-functions nil)
-             (gnutls-verify-error nil) ; We use the NSM for verification
-             (port (elpher-address-port address))
-             (host (elpher-address-host address))
-             (selector-string-parts nil)
-             (bytes-received 0)
-             (hkbytes-received 0)
-             (proc (open-network-stream "elpher-process"
-                                        nil
-                                        (if (or elpher-ipv4-always force-ipv4)
-                                            (dns-query host)
-                                          host)
-                                        (if (> port 0) port 70)
-                                        :type (if elpher-use-tls 'tls 'plain)
-                                        :nowait t))
-             (timer (run-at-time elpher-connection-timeout
-                                 nil
-                                 (lambda ()
-                                   (pcase (process-status proc)
-                                     ('failed
-                                      (if (and (not (equal (elpher-address-protocol address)
-                                                           "gophers"))
-                                               elpher-use-tls
-                                               (or elpher-auto-disengage-TLS
-                                                   (yes-or-no-p "Could not establish encrypted connection.  Disable TLS mode?")))
-                                          (progn
-                                            (message "Disabling TLS mode.")
-                                            (setq elpher-use-tls nil)
-                                            (elpher-get-selector address renderer))
-                                        (elpher-network-error address "Could not establish encrypted connection")))
-                                     ('connect
-                                      (elpher-process-cleanup)
-                                      (unless (or elpher-ipv4-always force-ipv4)
-                                        (message "Connection timed out. Retrying with IPv4 address.")
-                                        (elpher-get-selector address renderer t))))))))
-        (setq elpher-network-timer timer)
-        (set-process-coding-system proc 'binary)
-        (set-process-filter proc
-                            (lambda (_proc string)
-                              (when timer
-                                (cancel-timer timer)
-                                (setq timer nil))
-                              (setq bytes-received (+ bytes-received (length string)))
-                              (let ((new-hkbytes-received (/ bytes-received 102400)))
-                                (when (> new-hkbytes-received hkbytes-received)
-                                  (setq hkbytes-received new-hkbytes-received)
-                                  (with-current-buffer "*elpher*"
-                                    (let ((inhibit-read-only t))
-                                      (goto-char (point-min))
-                                      (beginning-of-line 2)
-                                      (delete-region (point) (point-max))
-                                      (insert "("
-                                              (number-to-string (/ hkbytes-received 10.0))
-                                              " MB read)")))))
-                              (setq selector-string-parts
-                                    (cons string selector-string-parts))))
-        (set-process-sentinel proc
-                              (lambda (_proc event)
-                                (condition-case the-error
-                                    (cond
-                                     ((string-prefix-p "deleted" event))
-                                     ((string-prefix-p "open" event)
-                                      (let ((inhibit-eol-conversion t))
-                                        (process-send-string
-                                         proc
-                                         (concat (elpher-gopher-address-selector address)
-                                                 "\r\n"))))
-                                     (t
-                                      (when timer
-                                        (cancel-timer timer)
-                                        (setq timer nil))
-                                      (funcall renderer (apply #'concat
-                                                               (reverse selector-string-parts)))
-                                      (elpher-restore-pos)))
-                                  (error
-                                   (elpher-network-error address the-error))))))
-    (error
-     (error "Error initiating connection to server"))))
+If TEMPORARY is non-nil, the certificate will be given an exporation
+period of one day, and the key and certificate files will be deleted
+when the certificate is no longer needed for the current session.
+
+Otherwise, the certificate will be given a 100 year expiration period
+and the files will not be deleted.
+
+The function returns a list containing the current host name, the
+temporary flag, and the key and cert file names in the form required
+by `gnutls-boot-parameters`."
+  (let ((exp-key-file (expand-file-name key-file))
+        (exp-cert-file (expand-file-name cert-file)))
+    (condition-case nil
+        (progn
+          (call-process elpher-openssl-command nil nil nil
+                        "req" "-x509" "-newkey" "rsa:2048"
+                        "-days" (if temporary "1" "36500")
+                        "-nodes"
+                        "-subj" (concat "/CN=" common-name)
+                        "-keyout" exp-key-file
+                        "-out" exp-cert-file)
+          (list (elpher-address-host (elpher-page-address elpher-current-page))
+                temporary exp-key-file exp-cert-file))
+      (error
+       (message "Check that openssl is installed, or customize `elpher-openssl-command`.")
+       (error "Program 'openssl', required for certificate generation, not found")))))
+
+(defun elpher-generate-throwaway-certificate ()
+  "Generate and return details of a throwaway certificate.
+The key and certificate files will be deleted when they are no
+longer needed for this session."
+  (let* ((file-base (make-temp-name "elpher"))
+         (key-file (concat temporary-file-directory file-base ".key"))
+         (cert-file (concat temporary-file-directory file-base ".crt")))
+    (elpher-generate-certificate file-base key-file cert-file t)))
+
+(defun elpher-generate-persistent-certificate (file-base common-name)
+  "Generate and return details of a persistent certificate.
+The argument FILE-BASE is used as the base for the key and certificate
+files, while COMMON-NAME specifies the common name field of the
+certificate.
+
+The key and certificate files are written to in `elpher-certificate-directory'."
+  (let* ((key-file (concat elpher-certificate-directory file-base ".key"))
+         (cert-file (concat elpher-certificate-directory file-base ".crt")))
+    (elpher-generate-certificate common-name key-file cert-file)))
+
+(defun elpher-get-existing-certificate (file-base)
+  "Return a certificate object corresponding to an existing certificate.
+It is assumed that the key files FILE-BASE.key and FILE-BASE.crt exist in
+the directory `elpher-certificate-directory'."
+  (let* ((key-file (concat elpher-certificate-directory file-base ".key"))
+         (cert-file (concat elpher-certificate-directory file-base ".crt")))
+    (list (elpher-address-host (elpher-page-address elpher-current-page))
+          nil
+          (expand-file-name key-file)
+          (expand-file-name cert-file))))
+
+(defun elpher-install-and-use-existing-certificate (key-file-src cert-file-src file-base)
+  "Install a key+certificate file pair in `elpher-certificate-directory'.
+The strings KEY-FILE-SRC and CERT-FILE-SRC are the existing key and
+certificate files to install.  The argument FILE-BASE is used as the
+base for the installed key and certificate files."
+  (let* ((key-file (concat elpher-certificate-directory file-base ".key"))
+         (cert-file (concat elpher-certificate-directory file-base ".crt")))
+    (if (or (file-exists-p key-file)
+            (file-exists-p cert-file))
+        (error "A certificate with base name %s is already installed" file-base))
+    (copy-file key-file-src key-file)
+    (copy-file cert-file-src cert-file)
+    (list (elpher-address-host (elpher-page-address elpher-current-page))
+          nil
+          (expand-file-name key-file)
+          (expand-file-name cert-file))))
+
+(defun elpher-list-existing-certificates ()
+  "Return a list of the persistent certificates in `elpher-certificate-directory'."
+  (unless (file-directory-p elpher-certificate-directory)
+    (make-directory elpher-certificate-directory))
+  (mapcar
+   (lambda (file)
+     (file-name-sans-extension file))
+   (directory-files elpher-certificate-directory nil "\\.key$")))
+
+(defun elpher-forget-current-certificate ()
+  "Causes any current certificate to be forgotten.)
+In the case of throwaway certificates, the key and certificate files
+are also deleted."
+  (interactive)
+  (when elpher-client-certificate
+    (unless (and (called-interactively-p 'any)
+                 (not (y-or-n-p (concat "Really forget client certificate? "
+                                        "(Throwaway certificates will be deleted.)"))))
+      (when (cadr elpher-client-certificate)
+        (delete-file (elt elpher-client-certificate 2))
+        (delete-file (elt elpher-client-certificate 3)))
+      (setq elpher-client-certificate nil)
+      (if (called-interactively-p 'any)
+          (message "Client certificate forgotten.")))))
+
+(defun elpher-get-current-keylist (address)
+  "Retrieve the `gnutls-boot-parameters'-compatable keylist.
+
+This is obtained from the client certificate described by
+`elpher-current-certificate', if one is available and the host for
+that certificate matches the host in ADDRESS.
+
+If `elpher-current-certificate' is non-nil, and its host name doesn't
+match that of ADDRESS, the certificate is forgotten."
+  (if elpher-client-certificate
+      (if (string= (car elpher-client-certificate)
+                   (elpher-address-host address))
+          (list (cddr elpher-client-certificate))
+        (elpher-forget-current-certificate)
+        (message "Disabling client certificate for new host")
+        nil)
+    nil))
+
+
+;;; Gopher selector retrieval
+;;
+
+(defun elpher-get-gopher-response (address renderer)
+  "Get response string from gopher server at ADDRESS and render using RENDERER."
+  (elpher-get-host-response address 70
+                            (concat (elpher-gopher-address-selector address) "\r\n")
+                            renderer
+                            (or (string= (elpher-address-protocol address) "gophers")
+                                elpher-use-tls)))

 
 (defun elpher-get-gopher-page (renderer)
   "Getter function for gopher pages.
 
 (defun elpher-get-gopher-page (renderer)
   "Getter function for gopher pages.


@@ -658,7 +955,7 @@ once they are retrieved from the gopher server."
       (elpher-with-clean-buffer
        (insert "LOADING... (use 'u' to cancel)\n"))
       (condition-case the-error
       (elpher-with-clean-buffer
        (insert "LOADING... (use 'u' to cancel)\n"))
       (condition-case the-error

-          (elpher-get-selector address renderer)
+          (elpher-get-gopher-response address renderer)

         (error
          (elpher-network-error address the-error))))))
 
         (error
          (elpher-network-error address the-error))))))
 


@@ -707,7 +1004,7 @@ displayed.  The _WINDOW argument is currently unused."
                (address (elpher-page-address page)))
           (format "mouse-1, RET: open '%s'" (if (elpher-address-special-p address)
                                                 address
                (address (elpher-page-address page)))
           (format "mouse-1, RET: open '%s'" (if (elpher-address-special-p address)
                                                 address

-                                              (url-recreate-url address))))))))
+                                              (elpher-address-to-url address))))))))

 
 (defun elpher-insert-index-record (display-string &optional address)
   "Function to insert an index record into the current buffer.
 
 (defun elpher-insert-index-record (display-string &optional address)
   "Function to insert an index record into the current buffer.


@@ -719,7 +1016,7 @@ If ADDRESS is not supplied or nil the record is rendered as an
     (if type-map-entry
         (let* ((margin-code (elt type-map-entry 2))
                (face (elt type-map-entry 3))
     (if type-map-entry
         (let* ((margin-code (elt type-map-entry 2))
                (face (elt type-map-entry 3))

-               (filtered-display-string (ansi-color-filter-apply display-string))
+               (filtered-display-string (elpher-color-filter-apply display-string))

                (page (elpher-make-page filtered-display-string address)))
           (elpher-insert-margin margin-code)
           (insert-text-button filtered-display-string
                (page (elpher-make-page filtered-display-string address)))
           (elpher-insert-margin margin-code)
           (insert-text-button filtered-display-string


@@ -757,7 +1054,7 @@ If ADDRESS is not supplied or nil the record is rendered as an
 ;; Text rendering
 
 (defconst elpher-url-regex
 ;; Text rendering
 
 (defconst elpher-url-regex

-  "\\([a-zA-Z]+\\)://\\([a-zA-Z0-9.\-]*[a-zA-Z0-9\-]\\|\[[a-zA-Z0-9:]+\]\\)\\(:[0-9]+\\)?\\(/\\([0-9a-zA-Z\-_~?/@|:.%#=&]*[0-9a-zA-Z\-_~?/@|#]\\)?\\)?"
+  "\\([a-zA-Z]+\\)://\\([a-zA-Z0-9.-]*[a-zA-Z0-9-]\\|\\[[a-zA-Z0-9:]+\\]\\)\\(:[0-9]+\\)?\\(/\\([0-9a-zA-Z_~?/@|:.%#=&-]*[0-9a-zA-Z_~?/@|#-]\\)?\\)?"

   "Regexp used to locate and buttinofy URLs in text files loaded by elpher.")
 
 (defun elpher-buttonify-urls (string)
   "Regexp used to locate and buttinofy URLs in text files loaded by elpher.")
 
 (defun elpher-buttonify-urls (string)


@@ -768,24 +1065,24 @@ If ADDRESS is not supplied or nil the record is rendered as an
     (while (re-search-forward elpher-url-regex nil t)
       (let ((page (elpher-make-page (substring-no-properties (match-string 0))
                                     (elpher-address-from-url (match-string 0)))))
     (while (re-search-forward elpher-url-regex nil t)
       (let ((page (elpher-make-page (substring-no-properties (match-string 0))
                                     (elpher-address-from-url (match-string 0)))))

-          (make-text-button (match-beginning 0)
-                            (match-end 0)
-                            'elpher-page  page
-                            'action #'elpher-click-link
-                            'follow-link t
-                            'help-echo #'elpher--page-button-help
-                            'face 'button)))
+        (make-text-button (match-beginning 0)
+                          (match-end 0)
+                          'elpher-page  page
+                          'action #'elpher-click-link
+                          'follow-link t
+                          'help-echo #'elpher--page-button-help
+                          'face 'button)))

     (buffer-string)))
 
 (defconst elpher-ansi-regex "\x1b\\[[^m]*m"
     (buffer-string)))
 
 (defconst elpher-ansi-regex "\x1b\\[[^m]*m"

-  "Wildly incomplete regexp used to strip out some troublesome ANSI escape sequences.")
+  "Incomplete regexp used to strip out some troublesome ANSI escape sequences.")

 
 (defun elpher-process-text-for-display (string)
   "Perform any desired processing of STRING prior to display as text.
 Currently includes buttonifying URLs and processing ANSI escape codes."
   (elpher-buttonify-urls (if elpher-filter-ansi-from-text
 
 (defun elpher-process-text-for-display (string)
   "Perform any desired processing of STRING prior to display as text.
 Currently includes buttonifying URLs and processing ANSI escape codes."
   (elpher-buttonify-urls (if elpher-filter-ansi-from-text

-                             (ansi-color-filter-apply string)
-                           (ansi-color-apply string))))
+                             (elpher-color-filter-apply string)
+                           (elpher-color-apply string))))

 
 (defun elpher-render-text (data &optional _mime-type-string)
   "Render DATA as text.  MIME-TYPE-STRING is unused."
 
 (defun elpher-render-text (data &optional _mime-type-string)
   "Render DATA as text.  MIME-TYPE-STRING is unused."


@@ -818,9 +1115,9 @@ Currently includes buttonifying URLs and processing ANSI escape codes."
 (defun elpher-get-gopher-query-page (renderer)
   "Getter for gopher addresses requiring input.
 The response is rendered using the rendering function RENDERER."
 (defun elpher-get-gopher-query-page (renderer)
   "Getter for gopher addresses requiring input.
 The response is rendered using the rendering function RENDERER."

-   (let* ((address (elpher-page-address elpher-current-page))
-          (content (elpher-get-cached-content address))
-          (aborted t))
+  (let* ((address (elpher-page-address elpher-current-page))
+         (content (elpher-get-cached-content address))
+         (aborted t))

     (if (and content (funcall renderer nil))
         (elpher-with-clean-buffer
          (insert content)
     (if (and content (funcall renderer nil))
         (elpher-with-clean-buffer
          (insert content)


@@ -838,10 +1135,10 @@ The response is rendered using the rendering function RENDERER."
 
             (elpher-with-clean-buffer
              (insert "LOADING RESULTS... (use 'u' to cancel)"))
 
             (elpher-with-clean-buffer
              (insert "LOADING RESULTS... (use 'u' to cancel)"))

-            (elpher-get-selector search-address renderer))
+            (elpher-get-gopher-response search-address renderer))

         (if aborted
             (elpher-visit-previous-page))))))
         (if aborted
             (elpher-visit-previous-page))))))

- 
+

 ;; Raw server response rendering
 
 (defun elpher-render-raw (data &optional mime-type-string)
 ;; Raw server response rendering
 
 (defun elpher-render-raw (data &optional mime-type-string)


@@ -893,87 +1190,13 @@ The response is rendered using the rendering function RENDERER."
 
 (defvar elpher-gemini-redirect-chain)
 
 
 (defvar elpher-gemini-redirect-chain)
 

-(defun elpher-get-gemini-response (address renderer &optional force-ipv4)
-  "Retrieve gemini ADDRESS, then render using RENDERER.
-If FORCE-IPV4 is non-nil, explicitly look up and use IPv4 address corresponding
-to ADDRESS."
-  (unless elpher-gemini-TLS-cert-checks
-    (setq-local network-security-level 'low))
-  (if (not (gnutls-available-p))
-      (error "Cannot establish gemini connection: GnuTLS not available")
-    (unless (< (elpher-address-port address) 65536)
-      (error "Cannot establish gemini connection: port number > 65536"))
-    (defvar gnutls-verify-error)
-    (condition-case nil
-        (let* ((kill-buffer-query-functions nil)
-               (gnutls-verify-error nil) ; We use the NSM for verification
-               (port (elpher-address-port address))
-               (host (elpher-address-host address))
-               (response-string-parts nil)
-               (bytes-received 0)
-               (hkbytes-received 0)
-               (proc (open-network-stream "elpher-process"
-                                          nil
-                                          (if (or elpher-ipv4-always force-ipv4)
-                                              (dns-query host)
-                                            host)
-                                          (if (> port 0) port 1965)
-                                          :type 'tls
-                                          :nowait t))
-               (timer (run-at-time elpher-connection-timeout nil
-                                   (lambda ()
-                                     (elpher-process-cleanup)
-                                     (unless (or elpher-ipv4-always force-ipv4)
-                                        ; Try again with IPv4
-                                       (message "Connection timed out.  Retrying with IPv4.")
-                                       (elpher-get-gemini-response address renderer t))))))
-          (setq elpher-network-timer timer)
-          (set-process-coding-system proc 'binary)
-          (set-process-filter proc
-                              (lambda (_proc string)
-                                (when timer
-                                  (cancel-timer timer)
-                                  (setq timer nil))
-                                (setq bytes-received (+ bytes-received (length string)))
-                                (let ((new-hkbytes-received (/ bytes-received 102400)))
-                                  (when (> new-hkbytes-received hkbytes-received)
-                                    (setq hkbytes-received new-hkbytes-received)
-                                    (with-current-buffer "*elpher*"
-                                      (let ((inhibit-read-only t))
-                                        (goto-char (point-min))
-                                        (beginning-of-line 2)
-                                        (delete-region (point) (point-max))
-                                        (insert "("
-                                                (number-to-string (/ hkbytes-received 10.0))
-                                                " MB read)")))))
-                                (setq response-string-parts
-                                      (cons string response-string-parts))))
-          (set-process-sentinel proc
-                                (lambda (proc event)
-                                  (condition-case the-error
-                                      (cond
-                                       ((string-prefix-p "open" event)    ; request URL
-                                        (let ((inhibit-eol-conversion t))
-                                          (process-send-string
-                                           proc
-                                           (concat (elpher-address-to-url address)
-                                                   "\r\n"))))
-                                       ((string-prefix-p "deleted" event)) ; do nothing
-                                       ((and (not response-string-parts)
-                                             (not (or elpher-ipv4-always force-ipv4)))
-                                        ; Try again with IPv4
-                                        (message "Connection failed. Retrying with IPv4.")
-                                        (cancel-timer timer)
-                                        (elpher-get-gemini-response address renderer t))
-                                       (t
-                                        (funcall #'elpher-process-gemini-response
-                                                 (apply #'concat (reverse response-string-parts))
-                                                 renderer)
-                                        (elpher-restore-pos)))
-                                    (error
-                                     (elpher-network-error address the-error))))))
-      (error
-       (error "Error initiating connection to server")))))
+(defun elpher-get-gemini-response (address renderer)
+  "Get response string from gemini server at ADDRESS and render using RENDERER."
+  (elpher-get-host-response address 1965
+                            (concat (elpher-address-to-url address) "\r\n")
+                            (lambda (response-string)
+                              (elpher-process-gemini-response response-string renderer))
+                            'gemini))

 
 (defun elpher-parse-gemini-response (response)
   "Parse the RESPONSE string and return a list of components.
 
 (defun elpher-parse-gemini-response (response)
   "Parse the RESPONSE string and return a list of components.


@@ -1000,9 +1223,14 @@ that the response was malformed."
         (?1 ; Input required
          (elpher-with-clean-buffer
           (insert "Gemini server is requesting input."))
         (?1 ; Input required
          (elpher-with-clean-buffer
           (insert "Gemini server is requesting input."))

-         (let* ((query-string (read-string (concat response-meta ": ")))
-                (url (elpher-address-to-url (elpher-page-address elpher-current-page)))
-                (query-address (elpher-address-from-url (concat url "?" query-string))))
+         (let* ((query-string
+                 (if (eq (elt response-code 1) ?1)
+                     (read-passwd (concat response-meta ": "))
+                   (read-string (concat response-meta ": "))))
+                (query-address (seq-copy (elpher-page-address elpher-current-page)))
+                (old-fname (url-filename query-address)))
+           (setf (url-filename query-address)
+                 (concat old-fname "?" (url-build-query-string `((,query-string)))))

            (elpher-get-gemini-response query-address renderer)))
         (?2 ; Normal response
          (funcall renderer response-body response-meta))
            (elpher-get-gemini-response query-address renderer)))
         (?2 ; Normal response
          (funcall renderer response-body response-meta))


@@ -1027,11 +1255,73 @@ that the response was malformed."
          (error "Gemini server reports PERMANENT FAILURE for this request: %s %s"
                 response-code response-meta))
         (?6 ; Client certificate required
          (error "Gemini server reports PERMANENT FAILURE for this request: %s %s"
                 response-code response-meta))
         (?6 ; Client certificate required

-         (error "Gemini server requires client certificate (unsupported at this time)"))
+         (elpher-with-clean-buffer
+          (if elpher-client-certificate
+              (insert "Gemini server does not recognise the provided TLS certificate:\n\n")
+            (insert "Gemini server is requesting a valid TLS certificate:\n\n"))
+          (auto-fill-mode 1)
+          (elpher-gemini-insert-text response-meta))
+         (let ((chosen-certificate (elpher-choose-client-certificate)))
+           (unless chosen-certificate
+             (error "Gemini server requires a client certificate and none was provided"))
+           (setq elpher-client-certificate chosen-certificate))
+         (elpher-with-clean-buffer)
+         (elpher-get-gemini-response (elpher-page-address elpher-current-page) renderer))

         (_other
          (error "Gemini server response unknown: %s %s"
                 response-code response-meta))))))
 
         (_other
          (error "Gemini server response unknown: %s %s"
                 response-code response-meta))))))
 

+(unless (fboundp 'read-answer)
+  (defun read-answer (question answers)
+    "Backfill for the new read-answer code."
+    (completing-read question (mapcar 'identity answers))))
+
+(defun elpher-choose-client-certificate ()
+  "Prompt for a client certificate to use to establish a TLS connection."
+  (let* ((read-answer-short t))
+    (pcase (read-answer "What do you want to do? "
+                        '(("throwaway" ?t
+                           "generate and use throw-away certificate")
+                          ("persistent" ?p
+                           "generate new or use existing persistent certificate")
+                          ("abort" ?a
+                           "stop immediately")))
+      ("throwaway"
+       (setq elpher-client-certificate (elpher-generate-throwaway-certificate)))
+      ("persistent"
+       (let* ((existing-certificates (elpher-list-existing-certificates))
+              (file-base (completing-read
+                          "Nickname for new or existing certificate (autocompletes, empty response aborts): "
+                          existing-certificates)))
+         (if (string-empty-p (string-trim file-base))
+             nil
+           (if (member file-base existing-certificates)
+               (setq elpher-client-certificate
+                     (elpher-get-existing-certificate file-base))
+             (pcase (read-answer "Generate new certificate or install externally-generated one? "
+                                 '(("new" ?n
+                                    "generate new certificate")
+                                   ("install" ?i
+                                    "install existing certificate")
+                                   ("abort" ?a
+                                    "stop immediately")))
+               ("new"
+                (let ((common-name (read-string "Common Name field for new certificate: "
+                                                file-base)))
+                  (message "New key and self-signed certificate written to %s"
+                           elpher-certificate-directory)
+                  (elpher-generate-persistent-certificate file-base common-name)))
+               ("install"
+                (let* ((cert-file (read-file-name "Certificate file: " nil nil t))
+                       (key-file (read-file-name "Key file: " nil nil t)))
+                  (message "Key and certificate installed in %s for future use"
+                           elpher-certificate-directory)
+                  (elpher-install-and-use-existing-certificate key-file
+                                                               cert-file
+                                                               file-base)))
+               ("abort" nil))))))
+      ("abort" nil))))
+

 (defun elpher-get-gemini-page (renderer)
   "Getter which retrieves and renders a Gemini page and renders it using RENDERER."
   (let* ((address (elpher-page-address elpher-current-page))
 (defun elpher-get-gemini-page (renderer)
   "Getter which retrieves and renders a Gemini page and renders it using RENDERER."
   (let* ((address (elpher-page-address elpher-current-page))


@@ -1039,8 +1329,8 @@ that the response was malformed."
     (condition-case the-error
         (if (and content (funcall renderer nil))
             (elpher-with-clean-buffer
     (condition-case the-error
         (if (and content (funcall renderer nil))
             (elpher-with-clean-buffer

-              (insert content)
-              (elpher-restore-pos))
+             (insert content)
+             (elpher-restore-pos))

           (elpher-with-clean-buffer
            (insert "LOADING GEMINI... (use 'u' to cancel)\n"))
           (setq elpher-gemini-redirect-chain nil)
           (elpher-with-clean-buffer
            (insert "LOADING GEMINI... (use 'u' to cancel)\n"))
           (setq elpher-gemini-redirect-chain nil)


@@ -1048,7 +1338,6 @@ that the response was malformed."
       (error
        (elpher-network-error address the-error)))))
 
       (error
        (elpher-network-error address the-error)))))
 

-

 (defun elpher-render-gemini (body &optional mime-type-string)
   "Render gemini response BODY with rendering MIME-TYPE-STRING."
   (if (not body)
 (defun elpher-render-gemini (body &optional mime-type-string)
   "Render gemini response BODY with rendering MIME-TYPE-STRING."
   (if (not body)


@@ -1115,25 +1404,29 @@ For instance, the filename /a/b/../c/./d will reduce to /a/c/d"
     (string-join (reverse path-reversed-normalized) "/")))
 
 (defun elpher-address-from-gemini-url (url)
     (string-join (reverse path-reversed-normalized) "/")))
 
 (defun elpher-address-from-gemini-url (url)

-  "Extract address from URL with defaults as per gemini map files."
-  (let ((address (url-generic-parse-url url)))
+  "Extract address from URL with defaults as per gemini map files.
+While there's obviously some redundancy here between this function and
+`elpher-address-from-url', gemini map file URLs require enough special
+treatment that a separate function is warranted."
+  (let ((address (url-generic-parse-url url))
+        (current-address (elpher-page-address elpher-current-page)))

     (unless (and (url-type address) (not (url-fullness address))) ;avoid mangling mailto: urls
       (setf (url-fullness address) t)
       (if (url-host address) ;if there is an explicit host, filenames are absolute
           (if (string-empty-p (url-filename address))
               (setf (url-filename address) "/")) ;ensure empty filename is marked as absolute
     (unless (and (url-type address) (not (url-fullness address))) ;avoid mangling mailto: urls
       (setf (url-fullness address) t)
       (if (url-host address) ;if there is an explicit host, filenames are absolute
           (if (string-empty-p (url-filename address))
               (setf (url-filename address) "/")) ;ensure empty filename is marked as absolute

-        (setf (url-host address) (url-host (elpher-page-address elpher-current-page)))
+        (setf (url-host address) (url-host current-address))
+        (setf (url-port address) (url-port current-address))

         (unless (string-prefix-p "/" (url-filename address)) ;deal with relative links
           (setf (url-filename address)
         (unless (string-prefix-p "/" (url-filename address)) ;deal with relative links
           (setf (url-filename address)

-                (concat (file-name-directory
-                         (url-filename (elpher-page-address elpher-current-page)))
+                (concat (file-name-directory (url-filename current-address))

                         (url-filename address)))))
       (unless (url-type address)
         (setf (url-type address) "gemini"))
                         (url-filename address)))))
       (unless (url-type address)
         (setf (url-type address) "gemini"))

-      (if (equal (url-type address) "gemini")
-          (setf (url-filename address)
-                (elpher-collapse-dot-sequences (url-filename address)))))
-    address))
+      (when (equal (url-type address) "gemini")
+        (setf (url-filename address)
+              (elpher-collapse-dot-sequences (url-filename address)))))
+    (elpher-remove-redundant-ports address)))

 
 (defun elpher-gemini-insert-link (link-line)
   "Insert link described by LINK-LINE into a text/gemini document."
 
 (defun elpher-gemini-insert-link (link-line)
   "Insert link described by LINK-LINE into a text/gemini document."


@@ -1142,11 +1435,12 @@ For instance, the filename /a/b/../c/./d will reduce to /a/c/d"
          (address (elpher-address-from-gemini-url url))
          (type (if address (elpher-address-type address) nil))
          (type-map-entry (cdr (assoc type elpher-type-map))))
          (address (elpher-address-from-gemini-url url))
          (type (if address (elpher-address-type address) nil))
          (type-map-entry (cdr (assoc type elpher-type-map))))

+    (setq elpher--gemini-page-links (append elpher--gemini-page-links `(,address)))

     (when display-string
       (insert elpher-gemini-link-string)
       (if type-map-entry
           (let* ((face (elt type-map-entry 3))
     (when display-string
       (insert elpher-gemini-link-string)
       (if type-map-entry
           (let* ((face (elt type-map-entry 3))

-                 (filtered-display-string (ansi-color-filter-apply display-string))
+                 (filtered-display-string (elpher-color-filter-apply display-string))

                  (page (elpher-make-page filtered-display-string address)))
             (insert-text-button filtered-display-string
                                 'face face
                  (page (elpher-make-page filtered-display-string address)))
             (insert-text-button filtered-display-string
                                 'face face


@@ -1156,60 +1450,87 @@ For instance, the filename /a/b/../c/./d will reduce to /a/c/d"
                                 'help-echo #'elpher--page-button-help))
         (insert (propertize display-string 'face 'elpher-unknown)))
       (insert "\n"))))
                                 'help-echo #'elpher--page-button-help))
         (insert (propertize display-string 'face 'elpher-unknown)))
       (insert "\n"))))

-  
+

 (defun elpher-gemini-insert-header (header-line)
   "Insert header described by HEADER-LINE into a text/gemini document.
 The gemini map file line describing the header is given
 by HEADER-LINE."
   (when (string-match "^\\(#+\\)[ \t]*" header-line)
 (defun elpher-gemini-insert-header (header-line)
   "Insert header described by HEADER-LINE into a text/gemini document.
 The gemini map file line describing the header is given
 by HEADER-LINE."
   (when (string-match "^\\(#+\\)[ \t]*" header-line)

-    (let ((level (length (match-string 1 header-line)))
-          (header (substring header-line (match-end 0))))
+    (let* ((level (length (match-string 1 header-line)))
+           (header (substring header-line (match-end 0)))
+           (face (pcase level
+                   (1 'elpher-gemini-heading1)
+                   (2 'elpher-gemini-heading2)
+                   (3 'elpher-gemini-heading3)
+                   (_ 'default)))
+           (fill-column (if (display-graphic-p)
+                            (/ (* fill-column
+                                  (font-get (font-spec :name (face-font 'default)) :size))
+                               (font-get (font-spec :name (face-font face)) :size)) fill-column)))
+      (setq elpher--gemini-page-headings (cons (cons header (point))
+                                               elpher--gemini-page-headings))

       (unless (display-graphic-p)
         (insert (make-string level ?#) " "))
       (unless (display-graphic-p)
         (insert (make-string level ?#) " "))

-      (insert (propertize header 'face
-                          (pcase level
-                            (1 'elpher-gemini-heading1)
-                            (2 'elpher-gemini-heading2)
-                            (3 'elpher-gemini-heading3)
-                            (_ 'default)))
-              "\n"))))
+      (insert (propertize header 'face face))
+      (newline))))

 
 (defun elpher-gemini-insert-text (text-line)
   "Insert a plain non-preformatted TEXT-LINE into a text/gemini document.
 This function uses Emacs' auto-fill to wrap text sensibly to a maximum
 
 (defun elpher-gemini-insert-text (text-line)
   "Insert a plain non-preformatted TEXT-LINE into a text/gemini document.
 This function uses Emacs' auto-fill to wrap text sensibly to a maximum

-width defined by elpher-gemini-max-fill-width."
-  (string-match "\\(^[ \t]*\\)\\(\*[ \t]\\)?" text-line)
-  (let* ((processed-text-line (if (match-string 2 text-line)
-                                  (concat
-                                   (replace-regexp-in-string "\*"
-                                                             elpher-gemini-bullet-string
-                                                             (match-string 0 text-line))
-                                   (substring text-line (match-end 0)))
-                                text-line))
-         (fill-prefix (if (match-string 1 text-line)
-                          (replace-regexp-in-string "\*" " " (match-string 0 text-line))
-                        nil)))
+width defined by `elpher-gemini-max-fill-width'."
+  (string-match "\\(^[ \t]*\\)\\(\\*[ \t]+\\|>[ \t]*\\)?" text-line)
+  (let* ((line-prefix (match-string 2 text-line))
+         (processed-text-line
+          (if line-prefix
+              (cond ((string-prefix-p "*" line-prefix)
+                     (concat
+                      (replace-regexp-in-string "\\*"
+                                                elpher-gemini-bullet-string
+                                                (match-string 0 text-line))
+                      (substring text-line (match-end 0))))
+                    ((string-prefix-p ">" line-prefix)
+                     (propertize text-line 'face 'elpher-gemini-quoted))
+                    (t text-line))
+            text-line))
+         (adaptive-fill-mode t))

     (insert (elpher-process-text-for-display processed-text-line))
     (newline)))
 
 (defun elpher-render-gemini-map (data _parameters)
   "Render DATA as a gemini map file, PARAMETERS is currently unused."
   (elpher-with-clean-buffer
     (insert (elpher-process-text-for-display processed-text-line))
     (newline)))
 
 (defun elpher-render-gemini-map (data _parameters)
   "Render DATA as a gemini map file, PARAMETERS is currently unused."
   (elpher-with-clean-buffer

-   (let ((preformatted nil))
+   (setq elpher--gemini-page-headings nil)
+   (let ((preformatted nil)
+         (link-counter 1))

      (auto-fill-mode 1)
      (setq-local fill-column (min (window-width) elpher-gemini-max-fill-width))
      (auto-fill-mode 1)
      (setq-local fill-column (min (window-width) elpher-gemini-max-fill-width))

+     (setq elpher--gemini-page-links '())

      (dolist (line (split-string data "\n"))
        (cond
         ((string-prefix-p "```" line) (setq preformatted (not preformatted)))
         (preformatted (insert (elpher-process-text-for-display
                                (propertize line 'face 'elpher-gemini-preformatted))
                               "\n"))
      (dolist (line (split-string data "\n"))
        (cond
         ((string-prefix-p "```" line) (setq preformatted (not preformatted)))
         (preformatted (insert (elpher-process-text-for-display
                                (propertize line 'face 'elpher-gemini-preformatted))
                               "\n"))

-        ((string-prefix-p "=>" line) (elpher-gemini-insert-link line))
+        ((string-prefix-p "=>" line)
+         (progn
+           (if elpher-gemini-number-links
+               (insert
+                (concat
+                 "["
+                 (number-to-string link-counter)
+                 "] ")))
+           (setq link-counter (1+ link-counter))
+           (elpher-gemini-insert-link line)))

         ((string-prefix-p "#" line) (elpher-gemini-insert-header line))
         (t (elpher-gemini-insert-text line)))))
         ((string-prefix-p "#" line) (elpher-gemini-insert-header line))
         (t (elpher-gemini-insert-text line)))))

+   (setq elpher--gemini-page-headings (nreverse elpher--gemini-page-headings))

    (elpher-cache-content
     (elpher-page-address elpher-current-page)
    (elpher-cache-content
     (elpher-page-address elpher-current-page)

-    (buffer-string))))
+    (buffer-string))
+   (puthash
+    (elpher-page-address elpher-current-page)
+    elpher--gemini-page-links
+    elpher--gemini-page-links-cache)))

 
 (defun elpher-render-gemini-plain-text (data _parameters)
   "Render DATA as plain text file.  PARAMETERS is currently unused."
 
 (defun elpher-render-gemini-plain-text (data _parameters)
   "Render DATA as plain text file.  PARAMETERS is currently unused."


@@ -1219,14 +1540,12 @@ width defined by elpher-gemini-max-fill-width."
     (elpher-page-address elpher-current-page)
     (buffer-string))))
 
     (elpher-page-address elpher-current-page)
     (buffer-string))))
 

+

 ;; Finger page connection
 
 ;; Finger page connection
 

-(defun elpher-get-finger-page (renderer &optional force-ipv4)
+(defun elpher-get-finger-page (renderer)

   "Opens a finger connection to the current page address.
   "Opens a finger connection to the current page address.

-The result is rendered using RENDERER.  When the optional argument
-FORCE-IPV4 or the variable `elpher-ipv4-always' are non-nil, the
-IPv4 address returned by a DNS lookup will be used explicitly in
-making the connection."
+The result is rendered using RENDERER."

   (let* ((address (elpher-page-address elpher-current-page))
          (content (elpher-get-cached-content address)))
     (if (and content (funcall renderer nil))
   (let* ((address (elpher-page-address elpher-current-page))
          (content (elpher-get-cached-content address)))
     (if (and content (funcall renderer nil))


@@ -1240,58 +1559,30 @@ making the connection."
                  (user (let ((filename (elpher-address-filename address)))
                          (if (> (length filename) 1)
                              (substring filename 1)
                  (user (let ((filename (elpher-address-filename address)))
                          (if (> (length filename) 1)
                              (substring filename 1)

-                           (elpher-address-user address))))
-                 (port (let ((given-port (elpher-address-port address)))
-                         (if (> given-port 0) given-port 79)))
-                 (host (elpher-address-host address))
-                 (selector-string-parts nil)
-                 (proc (open-network-stream "elpher-process"
-                                            nil
-                                            (if (or elpher-ipv4-always force-ipv4)
-                                                (dns-query host)
-                                              host)
-                                            port
-                                            :type 'plain
-                                            :nowait t))
-                 (timer (run-at-time elpher-connection-timeout
-                                     nil
-                                     (lambda ()
-                                       (pcase (process-status proc)
-                                         ('connect
-                                          (elpher-process-cleanup)
-                                          (unless (or elpher-ipv4-always force-ipv4)
-                                            (message "Connection timed out. Retrying with IPv4 address.")
-                                            (elpher-get-finger-page renderer t))))))))
-            (setq elpher-network-timer timer)
-            (set-process-coding-system proc 'binary)
-            (set-process-filter proc
-                                (lambda (_proc string)
-                                  (when timer
-                                    (cancel-timer timer)
-                                    (setq timer nil))
-                                  (setq selector-string-parts
-                                        (cons string selector-string-parts))))
-            (set-process-sentinel proc
-                                  (lambda (_proc event)
-                                    (condition-case _the-error
-                                        (cond
-                                         ((string-prefix-p "deleted" event))
-                                         ((string-prefix-p "open" event)
-                                          (let ((inhibit-eol-conversion t))
-                                            (process-send-string
-                                             proc
-                                             (concat user "\r\n"))))
-                                         (t
-                                          (when timer
-                                            (cancel-timer timer)
-                                            (setq timer nil))
-                                          (funcall renderer (apply #'concat
-                                                                   (reverse selector-string-parts)))
-                                          (elpher-restore-pos)))))))
+                           (elpher-address-user address)))))
+            (elpher-get-host-response address 79
+                                      (concat user "\r\n")
+                                      renderer))

         (error
          (elpher-network-error address the-error))))))
 
 
         (error
          (elpher-network-error address the-error))))))
 
 

+;; Telnet page connection
+
+(defun elpher-get-telnet-page (renderer)
+  "Opens a telnet connection to the current page address (RENDERER must be nil)."
+  (when renderer
+    (elpher-visit-previous-page)
+    (error "Command not supported for telnet URLs"))
+  (let* ((address (elpher-page-address elpher-current-page))
+         (host (elpher-address-host address))
+         (port (elpher-address-port address)))
+    (elpher-visit-previous-page)
+    (if (> port 0)
+        (telnet host port)
+      (telnet host))))
+
+

 ;; Other URL page opening
 
 (defun elpher-get-other-url-page (renderer)
 ;; Other URL page opening
 
 (defun elpher-get-other-url-page (renderer)


@@ -1308,20 +1599,6 @@ making the connection."
           (browse-web url)
         (browse-url url)))))
 
           (browse-web url)
         (browse-url url)))))
 

-;; Telnet page connection
-
-(defun elpher-get-telnet-page (renderer)
-  "Opens a telnet connection to the current page address (RENDERER must be nil)."
-  (when renderer
-    (elpher-visit-previous-page)
-    (error "Command not supported for telnet URLs"))
-  (let* ((address (elpher-page-address elpher-current-page))
-         (host (elpher-address-host address))
-         (port (elpher-address-port address)))
-    (elpher-visit-previous-page)
-    (if (> port 0)
-        (telnet host port)
-      (telnet host))))

 
 ;; Start page page retrieval
 
 
 ;; Start page page retrieval
 


@@ -1344,6 +1621,7 @@ making the connection."
            " - u/mouse-3/U: return to previous page or to the start page\n"
            " - o/O: visit different selector or the root menu of the current server\n"
            " - g: go to a particular address (gopher, gemini, finger)\n"
            " - u/mouse-3/U: return to previous page or to the start page\n"
            " - o/O: visit different selector or the root menu of the current server\n"
            " - g: go to a particular address (gopher, gemini, finger)\n"

+           " - v: visit a numbered link on a gemini page\n"

            " - d/D: download item under cursor or current page\n"
            " - i/I: info on item under cursor or current page\n"
            " - c/C: copy URL representation of item under cursor or current page\n"
            " - d/D: download item under cursor or current page\n"
            " - i/I: info on item under cursor or current page\n"
            " - c/C: copy URL representation of item under cursor or current page\n"


@@ -1354,6 +1632,7 @@ making the connection."
            " - R: reload current page (regenerates cache)\n"
            " - S: set character coding system for gopher (default is to autodetect)\n"
            " - T: toggle TLS gopher mode\n"
            " - R: reload current page (regenerates cache)\n"
            " - S: set character coding system for gopher (default is to autodetect)\n"
            " - T: toggle TLS gopher mode\n"

+           " - F: forget/discard current TLS client certificate\n"

            " - .: display the raw server response for the current page\n"
            "\n"
            "Start your exploration of gopher space and gemini:\n")
            " - .: display the raw server response for the current page\n"
            "\n"
            "Start your exploration of gopher space and gemini:\n")


@@ -1365,8 +1644,8 @@ making the connection."
            "Alternatively, select a search engine and enter some search terms:\n")
    (elpher-insert-index-record "Gopher Search Engine (Veronica-2)"
                                (elpher-make-gopher-address ?7 "/v2/vs" "gopher.floodgap.com" 70))
            "Alternatively, select a search engine and enter some search terms:\n")
    (elpher-insert-index-record "Gopher Search Engine (Veronica-2)"
                                (elpher-make-gopher-address ?7 "/v2/vs" "gopher.floodgap.com" 70))

-   (elpher-insert-index-record "Gemini Search Engine (GUS)"
-                               (elpher-address-from-url "gemini://gus.guru/search"))
+   (elpher-insert-index-record "Gemini Search Engine (geminispace.info)"
+                               (elpher-address-from-url "gemini://geminispace.info/search"))

    (insert "\n"
            "This page contains your bookmarked sites (also visit with B):\n")
    (elpher-insert-index-record "Your Bookmarks" 'bookmarks)
    (insert "\n"
            "This page contains your bookmarked sites (also visit with B):\n")
    (elpher-insert-index-record "Your Bookmarks" 'bookmarks)


@@ -1428,7 +1707,7 @@ making the connection."
                          'help-echo help-string))
    (insert "\n")
    (elpher-restore-pos)))
                          'help-echo help-string))
    (insert "\n")
    (elpher-restore-pos)))

-  
+

 
 ;;; Bookmarks
 ;;
 
 ;;; Bookmarks
 ;;


@@ -1438,7 +1717,7 @@ making the connection."
 DISPLAY-STRING determines how the bookmark will appear in the
 bookmark list, while URL is the url of the entry."
   (list display-string url))
 DISPLAY-STRING determines how the bookmark will appear in the
 bookmark list, while URL is the url of the entry."
   (list display-string url))

-  
+

 (defun elpher-bookmark-display-string (bookmark)
   "Get the display string of BOOKMARK."
   (elt bookmark 0))
 (defun elpher-bookmark-display-string (bookmark)
   "Get the display string of BOOKMARK."
   (elt bookmark 0))


@@ -1454,6 +1733,9 @@ bookmark list, while URL is the url of the entry."
 (defun elpher-save-bookmarks (bookmarks)
   "Record the bookmark list BOOKMARKS to the user's bookmark file.
 Beware that this completely replaces the existing contents of the file."
 (defun elpher-save-bookmarks (bookmarks)
   "Record the bookmark list BOOKMARKS to the user's bookmark file.
 Beware that this completely replaces the existing contents of the file."

+  (let ((bookmark-dir (file-name-directory elpher-bookmarks-file)))
+    (unless (file-directory-p bookmark-dir)
+      (make-directory bookmark-dir)))

   (with-temp-file elpher-bookmarks-file
     (erase-buffer)
     (insert "; Elpher bookmarks file\n\n"
   (with-temp-file elpher-bookmarks-file
     (erase-buffer)
     (insert "; Elpher bookmarks file\n\n"


@@ -1499,6 +1781,128 @@ If ADDRESS is already bookmarked, update the label only."
                    (not (equal (elpher-bookmark-url bookmark) url)))
                  (elpher-load-bookmarks)))))
 
                    (not (equal (elpher-bookmark-url bookmark) url)))
                  (elpher-load-bookmarks)))))
 

+;;; Integrations
+;;
+
+;;; Org
+
+;; Avoid byte compilation warnings.
+(eval-when-compile
+  (declare-function org-link-store-props "ol")
+  (declare-function org-link-set-parameters "ol"))
+
+(defun elpher-org-export-link (link description format protocol)
+  "Export a LINK with DESCRIPTION for the given PROTOCOL and FORMAT.
+
+FORMAT is an Org export backend.  DESCRIPTION may be nil.  PROTOCOL may be one
+of gemini, gopher or finger."
+  (let* ((url (if (equal protocol "elpher")
+                  (string-remove-prefix "elpher:" link)
+                (format "%s:%s" protocol link)))
+         (desc (or description url)))
+    (pcase format
+      (`gemini (format "=> %s %s" url desc))
+      (`html (format "<a href=\"%s\">%s</a>" url desc))
+      (`latex (format "\\href{%s}{%s}" url desc))
+      (_ (if (not description)
+             url
+           (format "%s (%s)" desc url))))))
+
+(defun elpher-org-store-link ()
+  "Store link to an `elpher' page in Org."
+  (when (eq major-mode 'elpher-mode)
+    (let* ((url (elpher-info-current))
+           (desc (car elpher-current-page))
+           (protocol (cond
+                      ((string-prefix-p "gemini:" url) "gemini")
+                      ((string-prefix-p "gopher:" url) "gopher")
+                      ((string-prefix-p "finger:" url) "finger")
+                      (t "elpher"))))
+      (when (equal "elpher" protocol)
+        ;; Weird link. Or special inner link?
+        (setq url (concat "elpher:" url)))
+      (org-link-store-props :type protocol :link url :description desc)
+      t)))
+
+(defun elpher-org-follow-link (link protocol)
+  "Visit a LINK for the given PROTOCOL.
+
+PROTOCOL may be one of gemini, gopher or finger.  This method also
+supports the old protocol elpher, where the link is self-contained."
+  (let ((url (if (equal protocol "elpher")
+                 (string-remove-prefix "elpher:" link)
+               (format "%s:%s" protocol link))))
+    (elpher-go url)))
+
+(with-eval-after-load 'org
+  (org-link-set-parameters
+   "elpher"
+   :store #'elpher-org-store-link
+   :export (lambda (link description format _plist)
+             (elpher-org-export-link link description format "elpher"))
+   :follow (lambda (link _arg) (elpher-org-follow-link link "elpher")))
+  (org-link-set-parameters
+   "gemini"
+   :export (lambda (link description format _plist)
+             (elpher-org-export-link link description format "gemini"))
+   :follow (lambda (link _arg) (elpher-org-follow-link link "gemini")))
+  (org-link-set-parameters
+   "gopher"
+   :export (lambda (link description format _plist)
+             (elpher-org-export-link link description format "gopher"))
+   :follow (lambda (link _arg) (elpher-org-follow-link link "gopher")))
+  (org-link-set-parameters
+   "finger"
+   :export (lambda (link description format _plist)
+             (elpher-org-export-link link description format "finger"))
+   :follow (lambda (link _arg) (elpher-org-follow-link link "finger"))))
+
+;;; Browse URL
+
+;; Avoid byte compilation warnings.
+(eval-when-compile
+  (defvar thing-at-point-uri-schemes))
+
+;;;###autoload
+(defun elpher-browse-url-elpher (url &rest _args)
+  "Browse URL using Elpher.  This function is used by `browse-url'."
+  (interactive (browse-url-interactive-arg "Elpher URL: "))
+  (elpher-go url))
+
+;; Use elpher to open gopher, finger and gemini links
+;; For recent version of `browse-url' package
+(if (boundp 'browse-url-default-handlers)
+    (add-to-list
+     'browse-url-default-handlers
+     '("^\\(gopher\\|finger\\|gemini\\)://" . elpher-browse-url-elpher))
+  ;; Patch `browse-url-browser-function' for older ones. The value of
+  ;; that variable is `browse-url-default-browser' by default, so
+  ;; that's the function that gets advised.
+  (advice-add browse-url-browser-function :before-while
+              (lambda (url &rest _args)
+               "Handle gemini, gopher, and finger schemes using Elpher."
+                (let ((scheme (downcase (car (split-string url ":" t)))))
+                  (if (member scheme '("gemini" "gopher" "finger"))
+                      ;; `elpher-go' always returns nil, which will stop the
+                      ;; advice chain here in a before-while
+                      (elpher-go url)
+                    ;; chain must continue, then return t.
+                    t)))))
+
+;; Register "gemini://" as a URI scheme so `browse-url' does the right thing
+(with-eval-after-load 'thingatpt
+  (add-to-list 'thing-at-point-uri-schemes "gemini://"))
+
+;;; Mu4e:
+
+(eval-when-compile
+  (defvar mu4e~view-beginning-of-url-regexp))
+
+(with-eval-after-load 'mu4e-view
+  ;; Make mu4e aware of the gemini world
+  (setq mu4e~view-beginning-of-url-regexp
+        "\\(?:https?\\|gopher\\|finger\\|gemini\\)://\\|mailto:"))
+

 ;;; Interactive procedures
 ;;
 
 ;;; Interactive procedures
 ;;
 


@@ -1517,24 +1921,35 @@ If ADDRESS is already bookmarked, update the label only."
   (interactive)
   (push-button))
 
   (interactive)
   (push-button))
 

+;;;###autoload

 (defun elpher-go (host-or-url)
   "Go to a particular gopher site HOST-OR-URL.
 When run interactively HOST-OR-URL is read from the minibuffer."
   (interactive "sGopher or Gemini URL: ")
 (defun elpher-go (host-or-url)
   "Go to a particular gopher site HOST-OR-URL.
 When run interactively HOST-OR-URL is read from the minibuffer."
   (interactive "sGopher or Gemini URL: ")

-  (let ((page (elpher-make-page host-or-url
-                                (elpher-address-from-url host-or-url))))
-    (switch-to-buffer "*elpher*")
+  (let* ((cleaned-host-or-url (string-trim host-or-url))
+         (address (elpher-address-from-url cleaned-host-or-url))
+         (page (elpher-make-page cleaned-host-or-url address)))
+    (switch-to-buffer elpher-buffer-name)

     (elpher-visit-page page)
     (elpher-visit-page page)

-    '()))
+    nil))

 
 (defun elpher-go-current ()
   "Go to a particular site read from the minibuffer, initialized with the current URL."
   (interactive)
   (let ((address (elpher-page-address elpher-current-page)))
 
 (defun elpher-go-current ()
   "Go to a particular site read from the minibuffer, initialized with the current URL."
   (interactive)
   (let ((address (elpher-page-address elpher-current-page)))

-    (if (elpher-address-special-p address)
-        (error "Command invalid for this page")
-      (let ((url (read-string "Gopher or Gemini URL: " (elpher-address-to-url address))))
-        (elpher-visit-page (elpher-make-page url (elpher-address-from-url url)))))))
+    (let ((url (read-string "Gopher or Gemini URL: "
+                            (unless (elpher-address-special-p address)
+                              (elpher-address-to-url address)))))
+      (elpher-visit-page (elpher-make-page url (elpher-address-from-url url))))))
+
+(defun elpher-visit-gemini-numbered-link (n)
+  "Visit link designated by a number N."
+  (interactive "nLink number: ")
+  (if (or (> n (length elpher--gemini-page-links))
+          (< n 1))
+      (user-error "Invalid link number"))
+  (let ((address (nth (1- n) elpher--gemini-page-links)))
+    (elpher-go (url-recreate-url address))))

 
 (defun elpher-redraw ()
   "Redraw current page."
 
 (defun elpher-redraw ()
   "Redraw current page."


@@ -1573,8 +1988,8 @@ When run interactively HOST-OR-URL is read from the minibuffer."
 (defun elpher-back-to-start ()
   "Go all the way back to the start page."
   (interactive)
 (defun elpher-back-to-start ()
   "Go all the way back to the start page."
   (interactive)

-  (setq elpher-current-page nil)
-  (setq elpher-history nil)
+  (setq-local elpher-current-page nil)
+  (setq-local elpher-history nil)

   (let ((start-page (elpher-make-page "Elpher Start Page"
                                       (elpher-make-special-address 'start))))
     (elpher-visit-page start-page)))
   (let ((start-page (elpher-make-page "Elpher Start Page"
                                       (elpher-make-special-address 'start))))
     (elpher-visit-page start-page)))


@@ -1701,10 +2116,11 @@ When run interactively HOST-OR-URL is read from the minibuffer."
             (message "Bookmark removed.")))
       (error "No link selected"))))
 
             (message "Bookmark removed.")))
       (error "No link selected"))))
 

+;;;###autoload

 (defun elpher-bookmarks ()
   "Visit bookmarks page."
   (interactive)
 (defun elpher-bookmarks ()
   "Visit bookmarks page."
   (interactive)

-  (switch-to-buffer "*elpher*")
+  (switch-to-buffer elpher-buffer-name)

   (elpher-visit-page
    (elpher-make-page "Bookmarks Page" (elpher-make-special-address 'bookmarks))))
 
   (elpher-visit-page
    (elpher-make-page "Bookmarks Page" (elpher-make-special-address 'bookmarks))))
 


@@ -1723,7 +2139,7 @@ When run interactively HOST-OR-URL is read from the minibuffer."
     (if button
         (elpher-info-page (button-get button 'elpher-page))
       (error "No item selected"))))
     (if button
         (elpher-info-page (button-get button 'elpher-page))
       (error "No item selected"))))

-  
+

 (defun elpher-info-current ()
   "Display information on current page."
   (interactive)
 (defun elpher-info-current ()
   "Display information on current page."
   (interactive)


@@ -1792,33 +2208,40 @@ When run interactively HOST-OR-URL is read from the minibuffer."
     (define-key map (kbd "X") 'elpher-unbookmark-current)
     (define-key map (kbd "B") 'elpher-bookmarks)
     (define-key map (kbd "S") 'elpher-set-gopher-coding-system)
     (define-key map (kbd "X") 'elpher-unbookmark-current)
     (define-key map (kbd "B") 'elpher-bookmarks)
     (define-key map (kbd "S") 'elpher-set-gopher-coding-system)

+    (define-key map (kbd "F") 'elpher-forget-current-certificate)
+    (define-key map (kbd "v") 'elpher-visit-gemini-numbered-link)

     (when (fboundp 'evil-define-key*)
     (when (fboundp 'evil-define-key*)

-      (evil-define-key* 'motion map
-        (kbd "TAB") 'elpher-next-link
-        (kbd "C-") 'elpher-follow-current-link
-        (kbd "C-t") 'elpher-back
-        (kbd "u") 'elpher-back
-        (kbd "U") 'elpher-back-to-start
-        [mouse-3] 'elpher-back
-        (kbd "g") 'elpher-go
-        (kbd "o") 'elpher-go-current
-        (kbd "r") 'elpher-redraw
-        (kbd "R") 'elpher-reload
-        (kbd "T") 'elpher-toggle-tls
-        (kbd ".") 'elpher-view-raw
-        (kbd "d") 'elpher-download
-        (kbd "D") 'elpher-download-current
-        (kbd "m") 'elpher-jump
-        (kbd "i") 'elpher-info-link
-        (kbd "I") 'elpher-info-current
-        (kbd "c") 'elpher-copy-link-url
-        (kbd "C") 'elpher-copy-current-url
-        (kbd "a") 'elpher-bookmark-link
-        (kbd "A") 'elpher-bookmark-current
-        (kbd "x") 'elpher-unbookmark-link
-        (kbd "X") 'elpher-unbookmark-current
-        (kbd "B") 'elpher-bookmarks
-        (kbd "S") 'elpher-set-gopher-coding-system))
+      (evil-define-key*
+       'motion map
+       (kbd "TAB") 'elpher-next-link
+       (kbd "C-") 'elpher-follow-current-link
+       (kbd "C-t") 'elpher-back
+       (kbd "u") 'elpher-back
+       (kbd "-") 'elpher-back
+       (kbd "^") 'elpher-back
+       (kbd "U") 'elpher-back-to-start
+       [mouse-3] 'elpher-back
+       (kbd "o") 'elpher-go
+       (kbd "O") 'elpher-go-current
+       (kbd "r") 'elpher-redraw
+       (kbd "R") 'elpher-reload
+       (kbd "T") 'elpher-toggle-tls
+       (kbd ".") 'elpher-view-raw
+       (kbd "d") 'elpher-download
+       (kbd "D") 'elpher-download-current
+       (kbd "J") 'elpher-jump
+       (kbd "i") 'elpher-info-link
+       (kbd "I") 'elpher-info-current
+       (kbd "c") 'elpher-copy-link-url
+       (kbd "C") 'elpher-copy-current-url
+       (kbd "a") 'elpher-bookmark-link
+       (kbd "A") 'elpher-bookmark-current
+       (kbd "x") 'elpher-unbookmark-link
+       (kbd "X") 'elpher-unbookmark-current
+       (kbd "B") 'elpher-bookmarks
+       (kbd "S") 'elpher-set-gopher-coding-system
+       (kbd "F") 'elpher-forget-current-certificate
+       (kbd "v") 'elpher-visit-gemini-numbered-link))

     map)
   "Keymap for gopher client.")
 
     map)
   "Keymap for gopher client.")
 


@@ -1827,7 +2250,15 @@ When run interactively HOST-OR-URL is read from the minibuffer."
 
 This mode is automatically enabled by the interactive
 functions which initialize the gopher client, namely
 
 This mode is automatically enabled by the interactive
 functions which initialize the gopher client, namely

-`elpher', `elpher-go' and `elpher-bookmarks'.")
+`elpher', `elpher-go' and `elpher-bookmarks'."
+  (setq-local elpher--gemini-page-headings nil)
+  (setq-local elpher-current-page nil)
+  (setq-local elpher-history nil)
+  (setq-local elpher-buffer-name (buffer-name))
+
+  (setq-local imenu-create-index-function
+              (lambda ()
+                elpher--gemini-page-headings)))

 
 (when (fboundp 'evil-set-initial-state)
   (evil-set-initial-state 'elpher-mode 'motion))
 
 (when (fboundp 'evil-set-initial-state)
   (evil-set-initial-state 'elpher-mode 'motion))


@@ -1837,17 +2268,30 @@ functions which initialize the gopher client, namely
 ;;
 
 ;;;###autoload
 ;;
 
 ;;;###autoload

-(defun elpher ()
-  "Start elpher with default landing page."
-  (interactive)
-  (if (get-buffer "*elpher*")
-      (switch-to-buffer "*elpher*")
-    (switch-to-buffer "*elpher*")
-    (setq elpher-current-page nil)
-    (setq elpher-history nil)
-    (let ((start-page (elpher-make-page "Elpher Start Page"
-                                        (elpher-make-special-address 'start))))
-      (elpher-visit-page start-page)))
-  "Started Elpher.") ; Otherwise (elpher) evaluates to start page string.
+(defun elpher (&optional arg)
+  "Start elpher with default landing page.
+The buffer used for Elpher sessions is determined by the value of
+‘elpher-buffer-name’.  If there is already an Elpher session active in
+that buffer, Emacs will simply switch to it.  Otherwise, a new session
+will begin.  A numeric prefix ARG (as in ‘\\[universal-argument] 42
+\\[execute-extended-command] elpher RET’) switches to the session with
+that number, creating it if necessary.  A non numeric prefix ARG means
+to create a new session.  Returns the buffer selected (or created)."
+  (interactive "P")
+  (let* ((name (default-value 'elpher-buffer-name))
+         (buf (cond ((numberp arg)
+                     (get-buffer-create (format "%s<%d>" name arg)))
+                    (arg
+                     (generate-new-buffer name))
+                    (t
+                     (get-buffer-create name)))))
+    (pop-to-buffer-same-window buf)
+    (unless (buffer-modified-p)
+      (elpher-mode)
+      (let ((start-page (elpher-make-page
+                         "Elpher Start Page"
+                         (elpher-make-special-address 'start))))
+        (elpher-visit-page start-page))
+      "Started Elpher."))); Otherwise (elpher) evaluates to start page string.

 
 ;;; elpher.el ends here
 
 ;;; elpher.el ends here