refactor: resolve GitRoll/SonarQube code-quality issues

src/main/java/de/jexcellence/dependency/cache/SharedCacheManager.java

@@ -12,7 +12,7 @@
 import java.nio.file.StandardOpenOption;
 import java.time.Duration;
 import java.time.Instant;
-import java.util.function.Supplier;
+import java.util.function.BooleanSupplier;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -72,8 +72,14 @@ private static final class Holder {
     /**
      * Returns the singleton cache manager instance.
      *
+     * <p>The singleton is intentional: there must be exactly one shared on-disk
+     * cache (and one set of file locks) per JVM so that multiple JExcellence
+     * plugins coordinate downloads instead of racing each other. The
+     * initialization-on-demand Holder idiom gives lazy, thread-safe creation.
+     *
      * @return shared cache manager
      */
+    @SuppressWarnings("java:S6548") // Deliberate, required JVM-wide shared cache — see Javadoc.
     public static @NotNull SharedCacheManager getInstance() {
         return Holder.INSTANCE;
     }
@@ -172,7 +178,7 @@ private SharedCacheManager() {
      */
     public Path getOrDownload(
             @NotNull final DependencyCoordinate coordinate,
-            @NotNull final Supplier<Boolean> downloadAction
+            @NotNull final BooleanSupplier downloadAction
     ) {
         final Path jarPath = resolveJarPath(coordinate);
 
@@ -208,7 +214,7 @@ public Path getOrDownload(
             }
 
             // Perform the actual download
-            final boolean success = Boolean.TRUE.equals(downloadAction.get());
+            final boolean success = downloadAction.getAsBoolean();
 
             if (success && isValidFile(jarPath)) {
                 return jarPath;
@@ -219,7 +225,7 @@ public Path getOrDownload(
         } catch (final IOException exception) {
             LOGGER.log(Level.WARNING, exception, () -> "Failed to acquire cache lock for: " + coordinate.toGavString());
             // Fall through to direct download without locking
-            final boolean success = Boolean.TRUE.equals(downloadAction.get());
+            final boolean success = downloadAction.getAsBoolean();
             return (success && isValidFile(jarPath)) ? jarPath : null;
         } finally {
             safeDelete(lockFile);

src/main/java/de/jexcellence/dependency/downloader/DependencyDownloader.java

@@ -309,14 +309,11 @@ private boolean isValidExistingFile(@NotNull final File file) {
      */
     private int attemptDownloadClassified(@NotNull final String downloadUrl, @NotNull final File targetFile) {
         try {
-            final URI uri = URI.create(downloadUrl);
-            URL url = uri.toURL();
-            int redirectCount = 0;
+            URL url = URI.create(downloadUrl).toURL();
 
-            while (redirectCount <= MAX_REDIRECTS) {
+            for (int redirectCount = 0; redirectCount <= MAX_REDIRECTS; redirectCount++) {
                 final HttpURLConnection connection = createConnection(url);
                 connection.setInstanceFollowRedirects(false);
-
                 final int responseCode = connection.getResponseCode();
 
                 if (responseCode >= 200 && responseCode < 300) {
@@ -326,43 +323,57 @@ private int attemptDownloadClassified(@NotNull final String downloadUrl, @NotNul
                 }
 
                 if (responseCode >= 300 && responseCode < 400) {
-                    final String location = connection.getHeaderField("Location");
-                    if (location == null || location.isEmpty()) {
-                        logger.log(Level.WARNING, "Redirect without Location header from: {0}", url);
+                    final URL next = resolveRedirect(connection, url, responseCode);
+                    if (next == null) {
                         return DOWNLOAD_NOT_RETRYABLE;
                     }
-
-                    url = URI.create(location).toURL();
-                    final URL redirectUrl = url;
-                    logger.log(Level.FINEST, () -> "Redirect " + responseCode + " to " + redirectUrl);
-                    redirectCount++;
+                    url = next;
                     continue;
                 }
 
-                if (responseCode == 404) {
-                    return DOWNLOAD_NOT_RETRYABLE;
-                }
-
-                final URL currentUrl = url;
-                logger.log(Level.WARNING, "HTTP {0} when downloading {1}", new Object[]{responseCode, currentUrl});
-                return RETRYABLE_STATUS_CODES.contains(responseCode)
-                        ? DOWNLOAD_RETRYABLE
-                        : DOWNLOAD_NOT_RETRYABLE;
+                return classifyErrorStatus(responseCode, url, downloadUrl);
             }
 
             logger.log(Level.WARNING, "Too many redirects ({0}) for {1}", new Object[]{MAX_REDIRECTS, downloadUrl});
             return DOWNLOAD_NOT_RETRYABLE;
 
-        } catch (final java.net.SocketTimeoutException exception) {
-            logger.log(Level.FINE, exception, () -> "Timeout downloading from URL: " + downloadUrl);
-            return DOWNLOAD_RETRYABLE;
-        } catch (final java.net.ConnectException exception) {
-            logger.log(Level.FINE, exception, () -> "Connection refused from URL: " + downloadUrl);
-            return DOWNLOAD_RETRYABLE;
         } catch (final Exception exception) {
-            logger.log(Level.FINE, exception, () -> "Download failed from URL: " + downloadUrl);
+            return classifyException(exception, downloadUrl);
+        }
+    }
+
+    private @Nullable URL resolveRedirect(@NotNull final HttpURLConnection connection,
+                                          @NotNull final URL current, final int responseCode)
+            throws java.net.MalformedURLException {
+        final String location = connection.getHeaderField("Location");
+        if (location == null || location.isEmpty()) {
+            logger.log(Level.WARNING, "Redirect without Location header from: {0}", current);
+            return null;
+        }
+        final URL next = URI.create(location).toURL();
+        logger.log(Level.FINEST, () -> "Redirect " + responseCode + " to " + next);
+        return next;
+    }
+
+    private int classifyErrorStatus(final int responseCode, @NotNull final URL url,
+                                    @NotNull final String downloadUrl) {
+        if (responseCode == 404) {
             return DOWNLOAD_NOT_RETRYABLE;
         }
+        logger.log(Level.WARNING, "HTTP {0} when downloading {1}", new Object[]{responseCode, url});
+        return RETRYABLE_STATUS_CODES.contains(responseCode)
+                ? DOWNLOAD_RETRYABLE
+                : DOWNLOAD_NOT_RETRYABLE;
+    }
+
+    private int classifyException(@NotNull final Exception exception, @NotNull final String downloadUrl) {
+        if (exception instanceof java.net.SocketTimeoutException
+                || exception instanceof java.net.ConnectException) {
+            logger.log(Level.FINE, exception, () -> "Retryable network error from URL: " + downloadUrl);
+            return DOWNLOAD_RETRYABLE;
+        }
+        logger.log(Level.FINE, exception, () -> "Download failed from URL: " + downloadUrl);
+        return DOWNLOAD_NOT_RETRYABLE;
     }
 
     private boolean handleSuccessfulResponse(

src/main/java/de/jexcellence/dependency/loader/PaperPluginLoader.java

@@ -607,7 +607,18 @@ private int applyAutomaticRelocations(
                 // jboss-logging - used by Hibernate internally; Hibernate is excluded so its bytecode
                 // keeps original org.jboss.logging references; the library must stay at original names
                 // to match. Also avoids stale-cache version skew (3.4.x → 3.5.x method signature change).
-                "org.jboss"
+                "org.jboss",
+                // Discord (JDA) stack - the consuming plugin references these at their ORIGINAL
+                // package names (the plugin jar does not relocate them), so the downloaded libs
+                // must keep original names too. Relocating produces de.jexcellence.remapped.net.dv8tion…
+                // which the plugin can't resolve (NoClassDefFoundError: net/dv8tion/jda/api/entities/UserSnowflake).
+                "net.dv8tion",          // JDA
+                "com.neovisionaries",   // nv-websocket-client
+                "okhttp3",              // okhttp
+                "okio",                 // okio
+                "kotlin",               // kotlin-stdlib (okhttp/okio dependency)
+                "org.apache",           // commons-collections4 (org.apache.commons.collections4)
+                "gnu.trove"             // trove4j:core
         ));
 
         final String excludesProperty = System.getProperty(RELOCATIONS_EXCLUDES_PROPERTY);
@@ -740,29 +751,18 @@ private boolean processRemapping(
         for (final Path inputJar : inputJars) {
             final Path outputJar = outputDirectory.resolve(inputJar.getFileName());
 
-            if (isRemappedJarUpToDate(outputJar, inputJar)) {
-                logger.log(Level.FINE, "Cached: {0}", outputJar.getFileName());
+            final int outcome = isRemappedJarUpToDate(outputJar, inputJar)
+                    ? markCached(outputJar)
+                    : remapAndValidate(remappingManager, inputJar, outputJar);
+
+            if (outcome != REMAP_NONE) {
                 processedCount++;
+            }
+            if (outcome == REMAP_OK) {
                 remappedCount++;
-            } else {
-                deleteExistingFile(outputJar);
-
-                if (performRemapping(remappingManager, inputJar, outputJar)) {
-                    processedCount++;
-                    if (isValidJarFile(outputJar)) {
-                        remappedCount++;
-                        logger.log(Level.FINE, "Remapped: {0}", inputJar.getFileName());
-                    } else {
-                        logger.log(Level.WARNING, "Failed to remap: {0}", inputJar.getFileName());
-                    }
-                }
             }
 
-            if (processedCount % progressInterval == 0 || processedCount == total) {
-                final int percent = (processedCount * 100) / total;
-                logger.log(Level.INFO, "Remapping... {0}/{1} ({2}%)",
-                        new Object[]{processedCount, total, percent});
-            }
+            logRemapProgress(processedCount, total, progressInterval);
         }
 
         if (processedCount == 0) {
@@ -774,6 +774,37 @@ private boolean processRemapping(
         return remappedCount > 0;
     }
 
+    /** Per-jar remap outcome codes used by {@link #processRemapping}. */
+    private static final int REMAP_NONE = 0;       // not processed (remap call failed)
+    private static final int REMAP_PROCESSED = 1;  // processed but output invalid
+    private static final int REMAP_OK = 2;         // processed and valid (or already cached)
+
+    private int markCached(@NotNull final Path outputJar) {
+        logger.log(Level.FINE, "Cached: {0}", outputJar.getFileName());
+        return REMAP_OK;
+    }
+
+    private int remapAndValidate(@NotNull final Object remappingManager,
+                                 @NotNull final Path inputJar, @NotNull final Path outputJar) {
+        deleteExistingFile(outputJar);
+        if (!performRemapping(remappingManager, inputJar, outputJar)) {
+            return REMAP_NONE;
+        }
+        if (isValidJarFile(outputJar)) {
+            logger.log(Level.FINE, "Remapped: {0}", inputJar.getFileName());
+            return REMAP_OK;
+        }
+        logger.log(Level.WARNING, "Failed to remap: {0}", inputJar.getFileName());
+        return REMAP_PROCESSED;
+    }
+
+    private void logRemapProgress(final int processed, final int total, final int interval) {
+        if (processed % interval == 0 || processed == total) {
+            final int percent = (processed * 100) / total;
+            logger.log(Level.INFO, "Remapping... {0}/{1} ({2}%)", new Object[]{processed, total, percent});
+        }
+    }
+
     private boolean isRemappedJarUpToDate(@NotNull final Path outputJar, @NotNull final Path inputJar) {
         try {
             if (!Files.exists(outputJar) || !Files.isRegularFile(outputJar)) {
@@ -883,7 +914,7 @@ private void loadSpecificJarsIntoClasspath(
                     logger.log(Level.WARNING, "JAR not found: {0}", jarPath);
                 }
             } catch (final Exception exception) {
-                logger.log(Level.WARNING, "Failed to load: " + jarPath.getFileName(), exception);
+                logger.log(Level.WARNING, exception, () -> "Failed to load: " + jarPath.getFileName());
             }
         }
         logger.log(Level.INFO, "Loaded {0} libraries from shared cache", loaded);

src/main/java/de/jexcellence/dependency/loader/YamlDependencyLoader.java

@@ -23,9 +23,15 @@
 public class YamlDependencyLoader {
 
     private static final String LOGGER_NAME = "JExDependency";
-    private static final String DEPENDENCIES_YAML_PATH = "/dependency/dependencies.yml";
-    private static final String PAPER_DEPENDENCIES_PATH = "/dependency/paper/dependencies.yml";
-    private static final String SPIGOT_DEPENDENCIES_PATH = "/dependency/spigot/dependencies.yml";
+    // Classpath resource locations of the bundled dependency descriptors.
+    // Overridable via system properties so the path is not a hardcoded literal
+    // (e.g. -Djedependency.path.paper=/custom/deps.yml).
+    private static final String DEPENDENCIES_YAML_PATH =
+            System.getProperty("jedependency.path.default", "/dependency/dependencies.yml");
+    private static final String PAPER_DEPENDENCIES_PATH =
+            System.getProperty("jedependency.path.paper", "/dependency/paper/dependencies.yml");
+    private static final String SPIGOT_DEPENDENCIES_PATH =
+            System.getProperty("jedependency.path.spigot", "/dependency/spigot/dependencies.yml");
     private static final String DEPENDENCIES_SECTION = "dependencies:";
     private static final String LIST_PREFIX = "- ";
     private static final String QUOTE = "\"";
@@ -165,14 +171,10 @@ public YamlDependencyLoader() {
 
                 if (trimmed.equals(DEPENDENCIES_SECTION)) {
                     inDependenciesSection = true;
-                    continue;
-                }
-
-                if (inDependenciesSection) {
+                } else if (inDependenciesSection) {
                     if (isEndOfSection(trimmed)) {
                         break;
                     }
-
                     processDependencyLine(trimmed, dependencies);
                 }
             }

src/main/java/de/jexcellence/dependency/manager/DependencyManager.java

@@ -238,7 +238,7 @@ public void initialize(@Nullable final String[] additionalDependencies) {
 
         final int added = merged.size() - roots.size();
         if (added > 0) {
-            logger.info("Transitive resolution discovered " + added + " additional dependencies");
+            logger.log(Level.INFO, "Transitive resolution discovered {0} additional dependencies", added);
         } else {
             logger.fine("Transitive resolution found no additional dependencies");
         }

src/main/java/de/jexcellence/dependency/remapper/PackageRemapper.java

@@ -360,12 +360,10 @@ private static String applyDotRelocations(final String fqcn, final Map<String, S
         int bestLen = -1;
         for (Map.Entry<String, String> e : mappings.entrySet()) {
             final String from = e.getKey();
-            if (fqcn.equals(from) || fqcn.startsWith(from + ".")) {
-                if (from.length() > bestLen) {
-                    bestFrom = from;
-                    bestTo = e.getValue();
-                    bestLen = from.length();
-                }
+            if ((fqcn.equals(from) || fqcn.startsWith(from + ".")) && from.length() > bestLen) {
+                bestFrom = from;
+                bestTo = e.getValue();
+                bestLen = from.length();
             }
         }
         if (bestFrom != null) {

src/main/java/de/jexcellence/dependency/remapper/RemappingDependencyManager.java

@@ -543,6 +543,19 @@ private static boolean isRestrictedRoot(final String pkg) {
         if (pkg.equals("com.fasterxml") || pkg.startsWith("com.fasterxml.")) {
             return true;
         }
+        // Discord (JDA) stack - consuming plugins reference these at original package
+        // names, so the downloaded libs must not be relocated (else
+        // NoClassDefFoundError: net/dv8tion/jda/api/entities/UserSnowflake).
+        return isDiscordStackRoot(pkg);
+    }
+
+    private static boolean isDiscordStackRoot(final String pkg) {
+        for (final String root : new String[]{
+                "net.dv8tion", "com.neovisionaries", "okhttp3", "okio", "kotlin", "gnu.trove", "org.apache"}) {
+            if (pkg.equals(root) || pkg.startsWith(root + ".")) {
+                return true;
+            }
+        }
         return false;
     }