2 files changed, 80 insertions, 0 deletions
diff --git a/Digitigrade/FormattingProvider/CommonMark.php b/Digitigrade/FormattingProvider/CommonMark.php
new file mode 100644
index 0000000..d90ca17
--- /dev/null
+++ b/Digitigrade/FormattingProvider/CommonMark.php
@@ -0,0 +1,49 @@
+<?php
+namespace Digitigrade\FormattingProvider;
+
+use Digitigrade\FormattingProvider;
+use Digitigrade\GlobalConfig;
+use Digitigrade\Singleton;
+use League\CommonMark\Environment\Environment;
+use League\CommonMark\Extension\Autolink\AutolinkExtension;
+use League\CommonMark\Extension\CommonMark\CommonMarkCoreExtension;
+use League\CommonMark\Extension\ExternalLink\ExternalLinkExtension;
+use League\CommonMark\Extension\Strikethrough\StrikethroughExtension;
+use League\CommonMark\MarkdownConverter;
+
+class CommonMark extends Singleton implements FormattingProvider {
+    private MarkdownConverter $converter;
+
+    protected function __construct() {
+        $env = new Environment([
+            'html_input' => 'escape',
+            'renderer' => [
+                'soft_break' => '<br>'
+            ],
+            'autolink' => [
+                'allowed_protocols' => SanitisedHtml::ALLOWED_URL_SCHEMES
+            ],
+            'external_link' => [
+                'internal_hosts' => [GlobalConfig::getInstance()->getCanonicalHost()],
+                'open_in_new_window' => true,
+                'nofollow' => 'all',
+                'noopener' => 'all',
+                'noreferrer' => 'external'
+            ]
+        ]);
+        $env->addExtension(new CommonMarkCoreExtension);
+        $env->addExtension(new AutolinkExtension);
+        $env->addExtension(new ExternalLinkExtension);
+        $env->addExtension(new StrikethroughExtension);
+        $this->converter = new MarkdownConverter($env);
+    }
+
+    public function renderToHtml(string $input): string {
+        return $this->converter->convert($input);
+    }
+
+    public function renderToPlainText(string $input): string {
+        // TODO: somehow remove markup and leave the unformatted content behind
+        return htmlspecialchars($input);
+    }
+}
+\ No newline at end of file
diff --git a/Digitigrade/FormattingProvider/SanitisedHtml.php b/Digitigrade/FormattingProvider/SanitisedHtml.php
new file mode 100644
index 0000000..fa2e5eb
--- /dev/null
+++ b/Digitigrade/FormattingProvider/SanitisedHtml.php
@@ -0,0 +1,31 @@
+<?php
+namespace Digitigrade\FormattingProvider;
+
+use Digitigrade\FormattingProvider;
+use Digitigrade\Singleton;
+use Symfony\Component\HtmlSanitizer\HtmlSanitizer;
+use Symfony\Component\HtmlSanitizer\HtmlSanitizerConfig;
+
+class SanitisedHtml extends Singleton implements FormattingProvider {
+    private HtmlSanitizer $sanitiser;
+
+    public const ALLOWED_URL_SCHEMES = [
+        'http', 'https', 'ftp', 'gopher', 'gemini', 'web+pawpub', 'web+ap', 'matrix', 'xmpp', 'mailto'
+    ];
+
+    protected function __construct() {
+        $this->sanitiser = new HtmlSanitizer((new HtmlSanitizerConfig())
+            ->allowSafeElements()
+            ->allowLinkSchemes(self::ALLOWED_URL_SCHEMES)
+        );
+    }
+
+    public function renderToHtml(string $input): string {
+        return $this->sanitiser->sanitize($input);
+    }
+
+    public function renderToPlainText(string $input): string {
+        // TODO: somehow remove tags and leave the unformatted content behind
+        return htmlspecialchars($input);
+    }
+}
+\ No newline at end of file