From 1cb4cbfe2438b6b6a1c0b726ac5200aa20e4e82a Mon Sep 17 00:00:00 2001
From: Alex Cabal <alex@alexcabal.com>
Date: Sun, 5 Jan 2025 13:52:09 -0600
Subject: [PATCH] Redirect ebook searches for only one tag to the
 /subjects/<TAG endpoint

---
 config/apache/rewrites/ebooks.conf | 14 ++++----
 www/ebooks/index.php               | 51 ++++++++++++++++++++----------
 2 files changed, 42 insertions(+), 23 deletions(-)

diff --git a/config/apache/rewrites/ebooks.conf b/config/apache/rewrites/ebooks.conf
index 617cacaf..fc620da6 100644
--- a/config/apache/rewrites/ebooks.conf
+++ b/config/apache/rewrites/ebooks.conf
@@ -11,13 +11,13 @@ RewriteRule	^/images/covers/(.+?)\-[a-z0-9]{8}\-(cover|hero)(@2x)?\.(jpg|avif)$
 RewriteRule	^/ebooks/(.+?)/download$		/ebooks/download.php?url-path=$1 [QSA]
 
 # Misc ebook rewrites.
-RewriteRule	^/subjects/([^\./]+?)$			/ebooks/index.php?tags[]=$1 [QSA]
-RewriteRule	^/ebooks/([^\./]+?)$			/authors/get.php?url-path=$1 [QSA]
-RewriteRule	^/ebooks/([^\./]+?)/downloads$		/bulk-downloads/get.php?author=$1 [QSA]
-RewriteRule	^/ebooks/([^\./]+?)/feeds$		/feeds/get.php?author=$1 [QSA]
-RewriteRule	^/collections/([^\./]+?)$		/collections/get.php?collection=$1 [QSA]
-RewriteRule	^/collections/([^/]+?)/downloads$	/bulk-downloads/get.php?collection=$1
-RewriteRule	^/collections/([^/]+?)/feeds$		/feeds/get.php?collection=$1
+RewriteRule	^/subjects/([^\./]+?)$			/ebooks/index.php?tags[]=$1 [B,QSA]
+RewriteRule	^/ebooks/([^\./]+?)$			/authors/get.php?url-path=$1 [B,QSA]
+RewriteRule	^/ebooks/([^\./]+?)/downloads$		/bulk-downloads/get.php?author=$1 [B,QSA]
+RewriteRule	^/ebooks/([^\./]+?)/feeds$		/feeds/get.php?author=$1 [B,QSA]
+RewriteRule	^/collections/([^\./]+?)$		/collections/get.php?collection=$1 [B,QSA]
+RewriteRule	^/collections/([^/]+?)/downloads$	/bulk-downloads/get.php?collection=$1 [B]
+RewriteRule	^/collections/([^/]+?)/feeds$		/feeds/get.php?collection=$1 [B]
 
 RewriteRule	^/ebooks/(.+?)/edit$			/ebooks/edit.php?url-path=$1 [L]
 RewriteRule	^/ebooks/(.+?)/delete$			/ebooks/delete.php?url-path=$1 [L]
diff --git a/www/ebooks/index.php b/www/ebooks/index.php
index 6254efcc..c48ea1e8 100644
--- a/www/ebooks/index.php
+++ b/www/ebooks/index.php
@@ -11,6 +11,7 @@ $sort = Enums\EbookSortType::tryFrom(HttpInput::Str(GET, 'sort') ?? '');
 $queryString = '';
 $queryStringParams = [];
 $queryStringWithoutPage = '';
+$pageUrl = '/ebooks';
 
 try{
 	if($page <= 0){
@@ -34,17 +35,6 @@ try{
 		$tags = [];
 	}
 
-	$result = Ebook::GetAllByFilter($query != '' ? $query : null, $tags, $sort, $page, $perPage, Enums\EbookReleaseStatusFilter::All);
-	$ebooks = $result['ebooks'];
-	$totalEbooks = $result['ebooksCount'];
-	$pageTitle = 'Browse Standard Ebooks';
-	$pageHeader = 'Browse Ebooks';
-	$pages = ceil($totalEbooks / $perPage);
-
-	if($page > 1){
-		$pageTitle .= ', page ' . $page;
-	}
-
 	$pageDescription = 'Page ' . $page . ' of the Standard Ebooks free ebook library';
 
 	if($query != ''){
@@ -73,15 +63,44 @@ try{
 
 	ksort($queryStringParams);
 
+	// If all we did was select one tag, redirect the user to `/subjects/<TAG>` instead of `/ebooks?tag[0]=<TAG>`.
+	if(sizeof($tags) == 1 && $query == '' && preg_match('|^/ebooks|iu', $_SERVER['REQUEST_URI'] ?? '')){
+		unset($queryStringParams['tags']);
+		$queryStringWithoutTags = http_build_query($queryStringParams);
+		$url = '/subjects/' . $tags[0];
+		if($queryStringWithoutTags != ''){
+			$url .= '?' . $queryStringWithoutTags;
+		}
+		header('Location: ' . $url);
+		exit();
+	}
+
+	// We only have one tag, change the page URL used for back/next links to `/subjects/<TAG>`.
+	if(sizeof($tags) == 1 && $query == ''){
+		$pageUrl = '/subjects/' . $tags[0];
+		unset($queryStringParams['tags']);
+	}
+
 	$queryString = http_build_query($queryStringParams);
 
 	unset($queryStringParams['page']);
 	$queryStringWithoutPage = http_build_query($queryStringParams);
 
-	$canonicalUrl = SITE_URL . '/ebooks';
+	$canonicalUrl = SITE_URL . $pageUrl;
 
 	if($queryString != ''){
-		$canonicalUrl .=  '?' . $queryString;
+		$canonicalUrl .= '?' . $queryString;
+	}
+
+	$result = Ebook::GetAllByFilter($query != '' ? $query : null, $tags, $sort, $page, $perPage, Enums\EbookReleaseStatusFilter::All);
+	$ebooks = $result['ebooks'];
+	$totalEbooks = $result['ebooksCount'];
+	$pageTitle = 'Browse Standard Ebooks';
+	$pageHeader = 'Browse Ebooks';
+	$pages = ceil($totalEbooks / $perPage);
+
+	if($page > 1){
+		$pageTitle .= ', page ' . $page;
 	}
 
 	if($pages > 0 && $page > $pages){
@@ -119,15 +138,15 @@ catch(Exceptions\AppException $ex){
 	<? } ?>
 	<? if(sizeof($ebooks) > 0){ ?>
 		<nav class="pagination">
-			<a<? if($page > 1){ ?> href="/ebooks?page=<?= $page - 1 ?><? if($queryStringWithoutPage != ''){ ?>&amp;<?= Formatter::EscapeHtml($queryStringWithoutPage) ?><? } ?>" rel="prev"<? }else{ ?> aria-disabled="true"<? } ?>>Back</a>
+			<a<? if($page > 1){ ?> href="<?= $pageUrl ?>?page=<?= $page - 1 ?><? if($queryStringWithoutPage != ''){ ?>&amp;<?= Formatter::EscapeHtml($queryStringWithoutPage) ?><? } ?>" rel="prev"<? }else{ ?> aria-disabled="true"<? } ?>>Back</a>
 			<ol>
 			<? for($i = 1; $i < $pages + 1; $i++){ ?>
 				<li<? if($page == $i){ ?> class="highlighted"<? } ?>>
-					<a href="/ebooks?page=<?= $i ?><? if($queryStringWithoutPage != ''){ ?>&amp;<?= Formatter::EscapeHtml($queryStringWithoutPage) ?><? } ?>"><?= $i ?></a>
+					<a href="<?= $pageUrl ?>?page=<?= $i ?><? if($queryStringWithoutPage != ''){ ?>&amp;<?= Formatter::EscapeHtml($queryStringWithoutPage) ?><? } ?>"><?= $i ?></a>
 				</li>
 			<? } ?>
 			</ol>
-			<a<? if($page < ceil($totalEbooks / $perPage)){ ?> href="/ebooks?page=<?= $page + 1 ?><? if($queryStringWithoutPage != ''){ ?>&amp;<?= Formatter::EscapeHtml($queryStringWithoutPage) ?><? } ?>" rel="next"<? }else{ ?> aria-disabled="true"<? } ?>>Next</a>
+			<a<? if($page < ceil($totalEbooks / $perPage)){ ?> href="<?= $pageUrl ?>?page=<?= $page + 1 ?><? if($queryStringWithoutPage != ''){ ?>&amp;<?= Formatter::EscapeHtml($queryStringWithoutPage) ?><? } ?>" rel="next"<? }else{ ?> aria-disabled="true"<? } ?>>Next</a>
 		</nav>
 	<? } ?>