Redirect old posts

We have two sitautions to account for:

  1. Old posts had both uppercase and lowercase letters in slugs; and
  2. Some ids changed.

Lighttpd can't convert to lowercase and having a bunch of separate redirects
in my webserver configuration for the id changes is messy.  So, this script
is intended to be called only when a post contains an uppercase character in
the path.

I had wanted to avoid _any_ sort of dynamic scripts.  Oh well.

All other redirects are handled in the websevrer configuration (which isn't
part of this repo atm).

Makefile

@@ -56,7 +56,7 @@ srcpages = src/index.html src/about.html src/papers.html src/posts.html \
 www-pages = $(patsubst src/%, $(www-root)/%, $(srcpages))
 
 www-files = $(www-pages) $(www-root)/style.css $(www-root)/rss.xml $(www-paper) \
-            $(www-images) $(www-fonts)
+            $(www-images) $(www-fonts) $(www-root)/redirect-map.php
 
 RSS_N=10
 export WWW_URL

src/redirect-map.php

@@ -0,0 +1,69 @@
+<?php
+/**
+ * Redirect old post ("thought") pages
+ *
+ *  Copyright (C) 2019 Mike Gerwitz
+ *
+ *  This program 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.
+ *
+ *  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 General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * This script should only be invoked for post paths containing an uppercase
+ * character.
+ *
+ * When this site migrated away from repo2html, ids were changed to be all
+ * lowercase.  Further, some of the ids changed in other ways.  To handle
+ * that latter case, a manual mapping was created.
+ *
+ * This script issues permanent redirects and, for security reasons, works
+ * only for post pages.
+ */
+
+$req_path = strtolower( $_GET[ 'path' ] );
+
+// Abort immediately if this is not a blog post (prevent this script from
+// being used for arbitrary redirects)
+if ( !preg_match( '#^/\d{4}/\d{2}/#', $req_path ) ) {
+    http_response_code( 500 );
+    die( 'Unsupported redirect' );
+}
+
+// Map from old to new location
+$map = [
+ "/2012/10/digitizing-books-is-fair-use-author-s-guild-v.-hathitrust"                        => "/2012/10/digitizing-books-is-fair-use-authors-guild-v-hathitrust",
+ "/2012/10/getting-too-tired-to-hack-at-23-00"                                               => "/2012/10/getting-too-tired-to-hack-at-2300",
+ "/2012/10/jailbreaking-and-dcma-eff-touts-victory-fsf-warns-of-failure"                     => "/2012/10/jailbreaking-and-dcmaeff-touts-victory-fsf-warns-of-failure",
+ "/2012/10/openwireless.org"                                                                 => "/2012/10/openwirelessorg",
+ "/2012/10/the-use-of-trademarks-in-free-software-has-always-been-a-curious-and-unclear"     => "/2012/10/trademarks-in-free-software",
+ "/2012/10/ubuntu-12.10-privacy-amazon-ads-and-data-leaks"                                   => "/2012/10/ubuntu-1210-privacy-amazon-ads-and-data-leaks",
+ "/2012/11/copyright-reform-you-re-silly"                                                    => "/2012/11/copyright-reform-youre-silly",
+ "/2012/11/u.s.-copyright-alert-system"                                                      => "/2012/11/us-copyright-alert-system",
+ "/2012/11/vlc-s-move-to-lgpl"                                                               => "/2012/11/vlcs-move-to-lgpl",
+ "/2013/04/u.s.-house-passes-cispa"                                                          => "/2013/04/us-house-passes-cispa",
+ "/2013/08/freebsd-clang-and-gcc-copyleft-vs.-community"                                     => "/2013/08/freebsd-clang-and-gcc-copyleft-vs-community",
+ "/2013/08/windows-8.1-to-display-targeted-advertisements-on-local-system-searches"          => "/2013/08/windows-81-to-display-targeted-advertisements-on-local-system-searches",
+ "/2014/03/re-freebsd-clang-and-gcc-copyleft-vs.-community"                                  => "/2014/03/re-freebsd-clang-and-gcc-copyleft-vs-community",
+ "/2016/01/google-analytics-removed-from-gitlab.com-instance"                                => "/2016/01/google-analytics-removed-from-gitlabcom-instance",
+ "/2016/08/nso-group-pegasus-trident-ios-exploits-targeting-human-rights-activist"           => "/2016/08/nso-group-pegasus-tridentios-exploits-targeting-human-rights-activist",
+ "/2017/06/don-t-force-me-to-use-your-tools-on-the-web"                                      => "/2017/06/dont-force-me-to-use-your-tools-on-the-web",
+ "/2018/04/when-talking-about-mobile-tracking-don-t-veil-bad-actors-with-blanket-statements" => "/2018/04/when-talking-about-mobile-tracking-dont-veil-bad-actors-with-blanket-statements",
+ "/2018/10/webmasters-please-don-t-block-tor"                                                => "/2018/10/webmasters-please-dont-block-tor",
+];
+
+// Redirect either to the mapped location or to the lowercased location
+$dest_path = ( isset( $map[ $req_path ] ) )
+    ? $map[ $req_path ]
+    : $req_path;
+
+// Permanent redirect
+http_response_code( 301 );
+header( "Location: $dest_path" );