Allow wikis to be redirected when deleting

Fixes #54

.gitignore

@@ -5,4 +5,5 @@ composer
 composer.lock
 vendor
 wikicache.json
+redirects.txt
 node_modules

404.php

@@ -2,9 +2,38 @@
 header( 'HTTP/1.0 404 Not Found' );
 require_once "includes.php";
 
-echo new \OOUI\MessageWidget( [
-	'type' => 'error',
-	'label' => 'Page not found. The wiki you are looking for may have been deleted.'
-] );
+// Check for redirect
+$redirects = get_if_file_exists( 'redirects.txt' );
+$redirect = false;
+if ( $redirects ) {
+	$uri = $_SERVER['REQUEST_URI'];
+	$lines = explode( "\n", $redirects );
+	foreach ( $lines as $line ) {
+		if ( !$line ) {
+			continue;
+		}
+		$parts = explode( ' ', $line );
+		if ( strpos( $uri, $parts[0] ) !== false ) {
+			$uri = str_replace( $parts[0], $parts[1], $uri );
+			$redirect = true;
+		}
+	}
+}
+
+if ( $redirect ) {
+	echo new \OOUI\MessageWidget( [
+		'type' => 'info',
+		'icon' => 'articleRedirect',
+		'label' => new \OOUI\HtmlSnippet(
+			'This wiki has been deleted. The following wiki was selected as a direct replacement: ' .
+			'<a href="' . htmlspecialchars( $uri ) . '">' . $uri . '</a>'
+		)
+	] );
+} else {
+	echo new \OOUI\MessageWidget( [
+		'type' => 'error',
+		'label' => 'Page not found. The wiki you are looking for may have been deleted.'
+	] );
+}
 
 include "footer.html";

delete.php

@@ -11,24 +11,88 @@
 }
 
 if ( !isset( $_POST['confirm' ] ) ) {
-	echo '<form method="POST">' .
-		'<p>Are you sure you want to delete this wiki: <a href="wikis/' . $wiki . '/w">' . $wiki . '</a>?</p>' .
-		'<p>This cannot be undone.</p>' .
-		new OOUI\ButtonInputWidget( [
-			'type' => 'submit',
-			'name' => 'confirm',
-			'label' => 'Delete',
-			'flags' => [ 'primary', 'destructive' ]
-		] ) .
-	'</form>';
-	die();
-}
 
-ob_implicit_flush( true );
+	$wikilist = [
+		[
+			'data' => '',
+			'label' => 'None',
+		]
+	];
+	$cache = load_wikicache();
+	if ( $cache ) {
+		$wikis = json_decode( $cache, true );
+		foreach ( $wikis as $hash => $data ) {
+			$wikilist[] = [
+				'data' => $hash,
+				'label' => $hash . ' - ' . $data['creator'] . ' (' . date( 'c', $data[ 'mtime' ] ) . ')',
+			];
+		}
+	}
+	echo new OOUI\FormLayout( [
+		'method' => 'POST',
+		'items' => [
+			new OOUI\FieldsetLayout( [
+				'label' => new OOUI\HtmlSnippet(
+					'Are you sure you want to delete this wiki: <a href="wikis/' . $wiki . '/w">' . $wiki . '</a>?<br>' .
+					'This cannot be undone.'
+				),
+				'items' => array_filter( [
+					count( $wikilist ) > 1 ?
+						new OOUI\FieldLayout(
+							new OOUI\DropdownInputWidget( [
+								'name' => 'redirect',
+								'options' => $wikilist,
+							] ),
+							[
+								'label' => 'Leave a redirect to this wiki:',
+								'align' => 'left',
+							]
+						) :
+						null,
+					new OOUI\FieldLayout(
+						new OOUI\ButtonInputWidget( [
+							'type' => 'submit',
+							'name' => 'confirm',
+							'label' => 'Delete',
+							'flags' => [ 'primary', 'destructive' ]
+						] ),
+						[
+							'label' => ' ',
+							'align' => 'left',
+						]
+					),
+				] )
+			] )
+		]
+	] );
 
-$error = delete_wiki( $wiki );
-if ( $error ) {
-	die( "Wiki not cleanly deleted, may have not been fully setup." );
-}
+} else {
+	ob_implicit_flush( true );
+
+	$error = delete_wiki( $wiki );
+	if ( $error ) {
+		echo( "Wiki not cleanly deleted, may have not been fully setup." );
+	} else {
+		echo "Wiki deleted.";
+	}
 
-echo "Wiki deleted.";
+	function isValidHash( $hash ) {
+		return preg_match( '/^[0-9a-f]{32}$/', $hash );
+	}
+
+	$redirect = $_POST['redirect'] ?? null;
+
+	if (
+		$redirect &&
+		isValidHash( $redirect ) &&
+		isValidHash( $wiki )
+	) {
+		// TODO: Avoid duplication in redirect file
+		file_put_contents(
+			'redirects.txt',
+			$wiki . ' ' . $redirect . "\n",
+			FILE_APPEND | LOCK_EX
+		);
+		echo ' Redirected to <a href="wikis/' . $redirect . '/w">' . $redirect . '</a>.';
+	}
+}

index.php

@@ -151,7 +151,6 @@
 							'classes' => [ 'form-submit' ],
 							'label' => 'Create demo',
 							'type' => 'submit',
-							// 'disabled' => true,
 							'flags' => [ 'progressive', 'primary' ]
 						] ),
 						[