Add random command

This command simply prints a random URL. A tag may be specified to limit
the search to that tag. In the Conkeror module this command immediately
loads the random bookmark in the current buffer.

- js/clark.js: If `error' is empty, return the value of `data'. This
  makes it easier for some commands to use the result of the command.
  Add `clark-random' to `clark_keymap'.

doc/clark.texi

@@ -118,6 +118,12 @@ as when no commands are given, but filtered by either of these
 conditions.
 @end deffn
 
+@deffn Command random [TAG]
+Look through the database for a random bookmark. If @var{tag} is
+specified, limit the results to bookmarks having the given tag. Simply
+prints the url of the selected bookmark.
+@end deffn
+
 @node Management, Miscellaneous, Querying, Usage
 @section Maintaining bookmarks in the database.
 

js/clark.js

@@ -264,6 +264,22 @@ function clark_set_tags(I) {
 interactive("clark-set-tags", "Replace the tags for the bookmark of"
             + " the current URL.", clark_set_tags);
 
+function clark_random(I)
+{
+    check_buffer(I.buffer, content_buffer);
+
+    let tag = yield I.minibuffer.read($prompt="tag: ");
+    let command = clark_program + ' random';
+    if (tag != "")
+        command += ' ' + tag;
+
+    let result = yield clark_shell_command(command);
+
+    if (result)
+        I.buffer.load(result);
+}
+interactive("clark-random", "Open a random bookmark", clark_random);
+
 function clark_shell_command(command)
 {
     let data = "", error = "";
@@ -278,11 +294,12 @@ function clark_shell_command(command)
                 )}]
     );
 
-    yield co_return(error == "");
+    yield co_return(error == "" && data);
 }
 
 define_keymap("clark_keymap");
 
+define_key(clark_keymap, "#", "clark-random");
 define_key(clark_keymap, "?", "clark-exists-p");
 define_key(clark_keymap, "a", "clark-add");
 define_key(clark_keymap, "A", "clark-add-link");

lisp/clark.asd

@@ -30,4 +30,5 @@
   :serial t
   :depends-on (:sqlite)
   :components ((:file "package")
-               (:file "clark")))
+               (:file "clark")
+               (:file "queries")))

lisp/clark.lisp

@@ -330,6 +330,17 @@ list of tags."
   (clear-tags url)
   (add-tags url tags))
 
+(defun random-item (lst)
+  (nth (random (length lst) (make-random-state t)) lst))
+
+(defcommand random (&optional tag)
+  "Pick a random bookmark, possibly from TAG."
+  "Usage: clark random [<tag>]
+
+Get a random bookmark. If TAG is given limit the result to a bookmark
+having the tag TAG."
+  (format t "~a~%" (random-item (url-list tag))))
+
 (defcommand version ()
     "Show version."
     "Usage: clark version

lisp/queries.lisp

@@ -0,0 +1,46 @@
+;; Copyright (C) 2013  Tom Willemsen <tom at ryuslash dot org>
+
+;; This file is part of CLark
+
+;; CLark is free software: you can redistribute it and/or modify it
+;; under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; CLark is distributed in the hope that it will be useful, but
+;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+;; General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with CLark. If not, see <http://www.gnu.org/licenses/>.
+
+;;; Code:
+
+(in-package :org.ryuslash.clark)
+
+(defun url-list-no-tag ()
+  "Get a list of all URLs stored."
+  (mapcar #'car
+          (execute-to-list
+           *db* (sql select "url"
+                     from "bookmark"))))
+
+(defun url-list-for-tag (tag)
+  "Get a list of all the stored URLs with tag TAG."
+  (mapcar
+   #'car
+   (execute-to-list
+    *db* (sql select "url"
+              from "bookmark"
+              where ? in (select "name"
+                          from "tag"
+                          join "bookmark_tag" on ("tag_id = tag.rowid")
+                          where "bookmark_id" = "bookmark.rowid"))
+    tag)))
+
+(defun url-list (&optional tag)
+  "Get a list of URLs, possibly with tag TAG."
+  (if tag
+      (url-list-for-tag tag)
+      (url-list-no-tag)))