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+                    GNU AFFERO GENERAL PUBLIC LICENSE
+                       Version 3, 19 November 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The GNU Affero General Public License is a free, copyleft license for
+software and other kinds of works, specifically designed to ensure
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+
+  The licenses for most software and other practical works are designed
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+  When we speak of free software, we are referring to freedom, not
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+  Developers that use our General Public Licenses protect your rights
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+The GNU General Public License permits making a modified version and
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+  An older license, called the Affero General Public License and
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+                       TERMS AND CONDITIONS
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+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If your software can interact with users remotely through a computer
+network, you should also make sure that it provides a way for users to
+get its source.  For example, if your program is a web application, its
+interface could display a "Source" link that leads users to an archive
+of the code.  There are many ways you could offer source, and different
+solutions will be better for different programs; see section 13 for the
+specific requirements.
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU AGPL, see
+<https://www.gnu.org/licenses/>.
diff --git a/README.org b/README.org
new file mode 100644
index 0000000..9044fa2
--- /dev/null
+++ b/README.org
@@ -0,0 +1,66 @@
+#+title: hmm - Emacs Universal Handling System
+
+* Background
+
+In Emacs, we do things in multiple ways:
+
+1. "Oh, I would like to invoke foo command, then choose the object of
+   that command." Example: M-x eww (command), then put in the url
+   (object) we want to visit
+2. "Oh, I have this thing (object) in the current context, and I would
+   like to do something (command) about it.  Example: click a link
+   (object), which invokes eww (command) to visit open this url.
+
+More often than not, we are faced with the second scenario, where we
+have a thing at point / in region / in the buffer-local environment,
+and we want to do something about it.  Sometimes, we have multiple
+ways to handle the object, and we would like to choose the /handler/
+rather than the /object/.  For example, say we want to clone the a git
+repo <https://git.sr.ht/~bzg/org-mode> at point.  In this case, the
+default behaviour might be open the url with eww, but we want to use a
+different handler.  An adhoc way would be to implement a command that
+runs a ~git clone~ process to clone the url at point.  The problem is
+how to invoke the command?  We can do so by invoking it with M-x or
+binding it to a key.  Maybe yet another thing we may want to do urls
+is to copy it, or run a command to fetch info and capture it into an
+org entry.  It can soon be exhausting to remember these commands, and
+you might forget some useful commands you wrote a year ago!
+
+hmm is designed to fix this problem.  Depending on the context, hmm
+will guess the object, filter commands that handle the object, and
+prompt for you to choose which command to invoke.  In the previous
+example, where the point is in at a url to a git repo, you invoke
+<C-M-return>, and a list of commands show up for you to choose from.
+In a sense it is like "open with".
+
+* Install and use
+
+Clone the repo, add the path to load-path, require and update.
+
+#+begin_src elisp
+(add-to-list 'load-path "~/.emacs.d/hmm")
+(require 'hmm)
+;; set your own handlers, web browsers, search engines, external handlers,
+;; matchers etc.
+;; (add-to-list 'hmm-web-browser '(:name luwak :command luwak-open))
+;; ...
+
+;; Make the customisation come into effect.
+(hmm-update)
+#+end_src
+
+This binds <C-M-<return>> to the ~hmm~ command.
+
+* Prior art
+
+- Emacs browse-url.el has some functions and variables like
+  ~browse-url-select-handler~, ~browse-url-handlers~ and
+  ~browse-url-default-handlers~.  It handles urls, and does not prompt
+  selection of handlers.
+
+* Contact and license
+
+hmm is maintained by Yuchen Pei (id@ypei.org).  It is covered by [[https://www.gnu.org/licenses/agpl-3.0.en.html][GNU
+AGPLv3+]].  You may find the license text in a file named COPYING.agpl3
+in the project tree.
+
diff --git a/hmm.el b/hmm.el
index 6063ec2..d53c045 100644
--- a/hmm.el
+++ b/hmm.el
@@ -1,8 +1,92 @@
 ;; -*- lexical-binding: t; -*-
 
-(defvar hmm-web-search-engines nil "hmm web search engines.")
-(defvar hmm-web-browsers nil "hmm web browers.")
-(defvar hmm-handlers '(:query nil :url nil :file nil))
+;; Copyright (C) 2022 Yuchen Pei.
+;; 
+;; This file is part of hmm.el.
+;; 
+;; hmm.el is free software: you can redistribute it and/or modify it under
+;; the terms of the GNU Affero General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+;; 
+;; hmm.el is distributed in the hope that it will be useful, but WITHOUT
+;; ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+;; or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General
+;; Public License for more details.
+;; 
+;; You should have received a copy of the GNU Affero General Public
+;; License along with hmm.el.  If not, see <https://www.gnu.org/licenses/>.
+
+(defvar hmm-web-search-engines
+  '((:name ddg
+           :format "https://html.duckduckgo.com/html?q=%s")
+    (:name fsd
+           :format "https://directory.fsf.org/w/index.php?search=%s")
+    (:name ml-emacs-devel
+           :format
+           "https://lists.gnu.org/archive/cgi-bin/namazu.cgi?query=%s&idxname=emacs-devel")
+    (:name ml-help-gnu-emacs
+           :format
+           "https://lists.gnu.org/archive/cgi-bin/namazu.cgi?query=%s&idxname=help-gnu-emacs")
+    (:name wikipedia
+           :format "https://en.wikipedia.org/w/index.php?search=%s"))
+  "hmm web search engines.")
+
+(defvar hmm-web-browsers
+  '((:name eww :command eww)
+    (:name firefox :command browse-url-firefox))
+  "hmm web browers.")
+
+(defvar hmm-handlers
+  '(:query
+    ((:command locate)
+     (:command project-or-external-find-regexp))
+    :url
+    ((:schemes ("mailto") :command browse-url-mail))
+    :file
+    ((:command find-file)
+     (:command dired :mimetypes ("inode/directory"))
+     (:command byte-compile-file :mimetypes ("text/x-lisp"))
+     (:command hmm-file-mime-type)))
+  "hmm handlers.")
+
+(defvar hmm-external-handlers
+  '((:name mpv
+           :external-command "mpv %U"
+           :display-name "mpv player"
+           :description "Play url with mpv"
+           :schemes
+           ("ftp" "http" "https" "mms" "rtmp" "rtsp" "sftp" "smb" "srt")
+           :handling :url)
+    (:name wget
+           :external-command "wget %U"
+           :display-name "GNU Wget"
+           :description "The non-interactive network downloader"
+           :schemes
+           ("ftp" "http" "https")
+           :handling :url)
+    (:name torsocks-mpv
+           :external-command "torsocks mpv %U"
+           :display-name "mpv player torsocks"
+           :description "Play url with mpv over torsocks"
+           :schemes
+           ("ftp" "http" "https" "mms" "rtmp" "rtsp" "sftp" "smb" "srt")
+           :handling :url))
+  "hmm external handlers.")
+
+(defvar hmm-matchers
+  '(((thing-at-point-url-at-point) . hmm-url)
+    ((thing-at-point-file-at-point) . hmm-file)
+    ((and (derived-mode-p 'dired-mode) (dired-get-filename nil t))
+     . hmm-file)
+    ((and (derived-mode-p 'dired-mode) (expand-file-name default-directory))
+     . hmm-file)
+    ((and (derived-mode-p 'org-mode) (my-org-link-at-point)) . hmm-url)
+    ((get-text-property (point) 'shr-url) . hmm-url)
+    ((thing-at-point 'symbol) . hmm-query)
+    ((buffer-file-name) . hmm-file)
+    ((expand-file-name default-directory) . hmm-file))
+  "Matchers for 'hmm-thing-at-point'.")
 
 (defmacro hmm-define-web-search-engine (engine browser)
   (let* ((engine-name (plist-get engine :name))
@@ -51,7 +135,7 @@
 
 (defun hmm-add-handler (handler handling)
   (let ((handlers (plist-get hmm-handlers handling)))
-    (add-to-list 'handlers handler)
+    (cl-pushnew handler handlers)
     (plist-put hmm-handlers handling handlers)))
 
 (defun hmm-thing-in-region (from to)
@@ -60,34 +144,19 @@
   (let* ((query (buffer-substring from to)))
     (hmm-query query)))
 
-(defun hmm-thing-at-point ()
-  (interactive)
-  "Prompt for what to do with thing at point.
-
-If it is a file, display a list of file handlers.
-If it is a url, display a list of url handlers."
-  (let ((thing))
-    (cond ((setq thing (thing-at-point-url-at-point))
-           (hmm-url thing))
-          ((setq thing (thing-at-point-file-at-point))
-           (hmm-file thing))
-          ((and (derived-mode-p 'dired-mode)
-                (setq thing (dired-get-filename nil t)))
-           (hmm-file thing))
-          ((derived-mode-p 'dired-mode)
-           (hmm-file (expand-file-name default-directory)))
-          ((and (derived-mode-p 'org-mode)
-                (setq thing (my-org-link-at-point)))
-           (hmm-url thing))
-          ((setq thing (get-text-property (point) 'shr-url))
-           (hmm-url thing))
-          ((setq thing (thing-at-point 'symbol))
-           (hmm-query thing))
-          ((setq thing (buffer-file-name))
-           (hmm-file thing))
-          ((setq thing (expand-file-name default-directory))
-           (hmm-file thing))
-          (t (error "Cannot guess what to do with what.")))))
+(defmacro hmm-define-hmm-thing-at-point ()
+  `(defun hmm-thing-at-point ()
+     "Prompt for what to do with thing at point."
+     (interactive)
+     (let ((thing))
+       ,(cons 'cond
+              (append
+               (mapcar
+                (lambda (pair)
+                  `((setq thing ,(car pair))
+                    (,(cdr pair) thing)))
+                hmm-matchers)
+               `((t (error "Cannot guess what to do with what."))))))))
 
 (defun hmm ()
   (interactive)
@@ -99,7 +168,7 @@ If it is a url, display a list of url handlers."
 
 (defun hmm-query (query)
   (interactive "sQuery: ")
-  (hmm-open-internal query :query "Search %s using: "))
+  (hmm-handle-internal query :query "Handle query %s using: "))
 
 (defun hmm-url (url)
   (interactive (list (read-string "URL: " (thing-at-point-url-at-point))))
@@ -144,21 +213,24 @@ If it is a url, display a list of url handlers."
   (let ((regex (plist-get handler :regex)))
     (cond ((eq type :url)
            (let ((schemes (plist-get handler :schemes))
-                 (url (url-generic-parse-url thing))
-                 (url-no-scheme))
+                 (url-obj (url-generic-parse-url thing)))
              (and
               (or (null schemes)
-                  (member (url-type url) schemes))
+                  (member (url-type url-obj) schemes))
               (or (not regex)
                   (string-match
                    regex
-                   (progn
-                     (setf (url-type url) nil
-                           (url-fullness url) nil)
-                     (setq url-no-scheme (url-recreate-url url))))))))
+                   (hmm-url-no-scheme thing))))))
           (t (or (not regex)
                  (string-match regex thing))))))
 
+(defun hmm-url-no-scheme (url)
+  "Remove the scheme from a url."
+  (let ((url-obj (url-generic-parse-url url)))
+    (setf (url-type url-obj) nil
+          (url-fullness url-obj) nil)
+    (url-recreate-url url-obj)))
+
 (defun hmm-update-handlers ()
   (interactive)
   (dolist (engine hmm-web-search-engines)
@@ -174,6 +246,12 @@ If it is a url, display a list of url handlers."
            :schemes (list "http" "https"))
      :url)))
 
+(defun hmm-update ()
+  (interactive)
+  (hmm-update-handlers)
+  (hmm-define-hmm-thing-at-point)
+  (message "Updated."))
+
 (defun hmm-get-xdg-handlers ()
   (seq-filter
    (lambda (handler)