Add utilities to detect and replace broken links V2

Author: barsh404error

application/src/main/java/org/togetherjava/tjbot/features/utils/LinkDetection.java

@@ -9,6 +9,7 @@
 import java.net.http.HttpRequest;
 import java.net.http.HttpResponse;
 import java.util.List;
+import java.util.Objects;
 import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.CompletableFuture;
@@ -17,6 +18,10 @@
  * Utility class to detect links.
  */
 public class LinkDetection {
+    private static final HttpClient HTTP_CLIENT = HttpClient.newHttpClient();
+
+    private static final Set<LinkFilter> DEFAULT_FILTERS =
+            Set.of(LinkFilter.SUPPRESSED, LinkFilter.NON_HTTP_SCHEME);
 
     /**
      * Possible ways to filter a link.
@@ -63,41 +68,57 @@ public static boolean containsLink(String content) {
         return !(new UrlDetector(content, UrlDetectorOptions.BRACKET_MATCH).detect().isEmpty());
     }
 
+    @SuppressWarnings("java:S2095")
     public static CompletableFuture<Boolean> isLinkBroken(String url) {
-        HttpClient client = HttpClient.newHttpClient();
-
-        HttpRequest request = HttpRequest.newBuilder(URI.create(url))
+        HttpRequest headRequest = HttpRequest.newBuilder(URI.create(url))
             .method("HEAD", HttpRequest.BodyPublishers.noBody())
             .build();
 
-        return client.sendAsync(request, HttpResponse.BodyHandlers.discarding())
-            .thenApply(response -> response.statusCode() >= 400)
-            .exceptionally(ignored -> true);
+        return HTTP_CLIENT.sendAsync(headRequest, HttpResponse.BodyHandlers.discarding())
+            .thenApply(response -> {
+                int status = response.statusCode();
+                if (status >= 200 && status < 400) {
+                    return false;
+                }
+                return status >= 400 ? true : null;
+            })
+            .exceptionally(ignored -> null)
+            .thenCompose(result -> {
+                if (result != null) {
+                    return CompletableFuture.completedFuture(result);
+                }
+                HttpRequest getRequest = HttpRequest.newBuilder(URI.create(url)).GET().build();
+
+                return HTTP_CLIENT.sendAsync(getRequest, HttpResponse.BodyHandlers.discarding())
+                    .thenApply(resp -> resp.statusCode() >= 400)
+                    .exceptionally(ignored -> true);
+            });
     }
 
     public static CompletableFuture<String> replaceDeadLinks(String text, String replacement) {
-        Set<LinkFilter> filters = Set.of(LinkFilter.SUPPRESSED, LinkFilter.NON_HTTP_SCHEME);
-
-        List<String> links = extractLinks(text, filters);
+        List<String> links = extractLinks(text, DEFAULT_FILTERS);
 
         if (links.isEmpty()) {
             return CompletableFuture.completedFuture(text);
         }
 
-        StringBuilder result = new StringBuilder(text);
-
-        List<CompletableFuture<Void>> checks =
-                links.stream().map(link -> isLinkBroken(link).thenAccept(isDead -> {
-                    if (isDead) {
-                        int index = result.indexOf(link);
-                        if (index != -1) {
-                            result.replace(index, index + link.length(), replacement);
-                        }
-                    }
-                })).toList();
+        List<CompletableFuture<String>> deadLinkFutures = links.stream()
+            .distinct()
+            .map(link -> isLinkBroken(link).thenApply(isBroken -> isBroken ? link : null))
+            .toList();
 
-        return CompletableFuture.allOf(checks.toArray(new CompletableFuture[0]))
-            .thenApply(v -> result.toString());
+        return CompletableFuture.allOf(deadLinkFutures.toArray(new CompletableFuture[0]))
+            .thenApply(ignored -> deadLinkFutures.stream()
+                .map(CompletableFuture::join)
+                .filter(Objects::nonNull)
+                .toList())
+            .thenApply(deadLinks -> {
+                String result = text;
+                for (String deadLink : deadLinks) {
+                    result = result.replace(deadLink, replacement);
+                }
+                return result;
+            });
     }
 
     private static Optional<String> toLink(Url url, Set<LinkFilter> filter) {