fix: links in the post could be relative links (#47)

app/src/main/java/run/halo/feed/RelativeLinkProcessor.java

@@ -0,0 +1,121 @@
+package run.halo.feed;
+
+import com.google.common.base.Throwables;
+import lombok.extern.slf4j.Slf4j;
+import org.apache.commons.lang3.StringUtils;
+import org.jsoup.Jsoup;
+import org.jsoup.nodes.Element;
+import org.jsoup.select.Elements;
+import org.springframework.util.Assert;
+import org.springframework.web.util.UriComponentsBuilder;
+import org.springframework.web.util.UriUtils;
+import run.halo.app.core.attachment.ThumbnailSize;
+import run.halo.app.infra.utils.PathUtils;
+import run.halo.feed.telemetry.TelemetryEndpoint;
+
+import java.net.URI;
+import java.nio.charset.StandardCharsets;
+
+@Slf4j
+public class RelativeLinkProcessor {
+    private final URI externalUri;
+
+    public RelativeLinkProcessor(String externalUrl) {
+        Assert.notNull(externalUrl, "External URL must not be null");
+        this.externalUri = URI.create(externalUrl);
+    }
+
+    public String processForHtml(String html) {
+        try {
+            return doProcessForHtml(html);
+        } catch (Throwable e) {
+            log.warn("Failed to process relative links for HTML", Throwables.getRootCause(e));
+        }
+        return html;
+    }
+
+    private String doProcessForHtml(String html) {
+        var document = Jsoup.parse(html);
+
+        // Process all links
+        var links = document.select("a[href]");
+        processElementAttr(links, "href", false);
+        // process all images
+        var images = document.select("img[src]");
+        processElementAttr(images, "src", true);
+        // video/audio source src
+        var sources = document.select("source[src]");
+        processElementAttr(sources, "src", false);
+        // video src
+        var videos = document.select("video[src]");
+        processElementAttr(videos, "src", false);
+        // link href
+        var linksHref = document.select("link[href]");
+        processElementAttr(linksHref, "href", false);
+        // script src
+        var scripts = document.select("script[src]");
+        processElementAttr(scripts, "src", false);
+        // iframe src
+        var iframes = document.select("iframe[src]");
+        processElementAttr(iframes, "src", false);
+        // frame src
+        var frames = document.select("frame[src]");
+        processElementAttr(frames, "src", false);
+        // embed src
+        var embeds = document.select("embed[src]");
+        processElementAttr(embeds, "src", false);
+
+        return document.body().html();
+//        var outputHtml = document.body().html();
+//        return StringEscapeUtils.unescapeHtml4(outputHtml);
+    }
+
+    private void processElementAttr(Elements elements, String attrKey, boolean canThumb) {
+        for (Element link : elements) {
+            String src = link.attr(attrKey);
+            if (canThumb && isNotTelemetryLink(src)) {
+                var thumb = genThumbUrl(src, ThumbnailSize.M);
+                var absoluteUrl = processLink(thumb);
+                link.attr(attrKey, absoluteUrl);
+            } else {
+                var absoluteUrl = processLink(src);
+                link.attr(attrKey, absoluteUrl);
+            }
+        }
+    }
+
+    boolean isNotTelemetryLink(String uri) {
+        return uri != null && !uri.contains(TelemetryEndpoint.TELEMETRY_PATH);
+    }
+
+    private String genThumbUrl(String url, ThumbnailSize size) {
+        return processLink("/apis/api.storage.halo.run/v1alpha1/thumbnails/-/via-uri?uri="
+                + UriUtils.encode(url, StandardCharsets.UTF_8)
+                + "&size=" + size.name().toLowerCase()
+        );
+    }
+
+    private String processLink(String link) {
+        if (StringUtils.isBlank(link) || PathUtils.isAbsoluteUri(link)) {
+            return link;
+        }
+        var contextPath = StringUtils.defaultIfBlank(externalUri.getPath(), "/");
+        var linkUri = UriComponentsBuilder.fromUriString(URI.create(link).toASCIIString())
+                .build(true);
+        var builder = UriComponentsBuilder.fromUriString(externalUri.toString());
+        if (shouldAppendPath(contextPath, link)) {
+            builder.pathSegment(linkUri.getPathSegments().toArray(new String[0]));
+        } else {
+            builder.replacePath(linkUri.getPath());
+        }
+        return builder.query(linkUri.getQuery())
+                .fragment(linkUri.getFragment())
+                .build(true)
+                .toUri()
+                .toString();
+    }
+
+    private static boolean shouldAppendPath(String contextPath, String link) {
+        return !"/".equals(contextPath) && !link.startsWith(contextPath);
+    }
+}

app/src/main/java/run/halo/feed/RssXmlBuilder.java

@@ -152,6 +152,13 @@ private void createItemElementToChannel(Element channel, RSS2.Item item) {
         itemElement.addElement("link").addText(item.getLink());
 
         var description = Optional.of(getDescriptionWithTelemetry(item))
+            .map(content -> {
+                if (externalUrl != null) {
+                    return new RelativeLinkProcessor(externalUrl)
+                        .processForHtml(content);
+                }
+                return content;
+            })
             .map(XmlCharUtils::removeInvalidXmlChar)
             .orElseThrow();
         itemElement.addElement("description").addCDATA(description);

app/src/test/java/run/halo/feed/RSS2Test.java

@@ -142,7 +142,7 @@ void invalidCharTest() {
                 RSS2.Item.builder()
                     .title("title1")
                     .description("""
-                        <p>并且会保留处理后的图片以供后面的访问。</p>
+                        <p>&并且会保留处理后的图片以供后面的访问。</p>
                         """)
                     .link("link1")
                     .pubDate(Instant.EPOCH)
@@ -175,7 +175,7 @@ void invalidCharTest() {
             			</title>
             			<link>link1</link>
             			<description>
-            				<![CDATA[<p>并且会保留处理后的图片以供后面的访问。</p>]]>
+            				<![CDATA[<p>&并且会保留处理后的图片以供后面的访问。</p>]]>
             			</description>
             			<guid isPermaLink="false">guid1</guid>
             			<pubDate>Thu, 1 Jan 1970 00:00:00 GMT</pubDate>

app/src/test/java/run/halo/feed/RelativeLinkProcessorTest.java

@@ -0,0 +1,39 @@
+package run.halo.feed;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link RelativeLinkProcessor}.
+ *
+ * @author guqing
+ * @since 1.4.1
+ */
+class RelativeLinkProcessorTest {
+    private final RelativeLinkProcessor linkProcessor =
+            new RelativeLinkProcessor("http://localhost:8090");
+
+    @Test
+    void textContent() {
+        var content = "hello world";
+        var processed = linkProcessor.processForHtml(content);
+        assertThat(processed).isEqualTo(content);
+    }
+
+    @Test
+    void testProcessForHtmlIncludeATag() {
+        var content = "<a href=\"/hello\">hello</a>";
+        var processed = linkProcessor.processForHtml(content);
+        assertThat(processed).isEqualTo("<a href=\"http://localhost:8090/hello\">hello</a>");
+    }
+
+    @Test
+    void processForHtmlIncludeImgTag() {
+        var content = "<img src=\"/hello.jpg\"/>";
+        var processed = linkProcessor.processForHtml(content);
+        assertThat(processed).isEqualTo(
+                "<img src=\"http://localhost:8090/apis/api.storage.halo"
+                        + ".run/v1alpha1/thumbnails/-/via-uri?uri=%2Fhello.jpg&amp;size=m\">");
+    }
+}