Added repository fallback and resolution mode

Author: AlessioDP

core/src/main/java/com/alessiodp/libby/Library.java

@@ -34,6 +34,12 @@ public class Library {
      */
     @NotNull
     private final Collection<String> repositories;
+    
+    /**
+     * Fallback repository URLs for this library
+     */
+    @NotNull
+    private final Collection<String> fallbackRepositories;
 
     /**
      * Maven group ID
@@ -128,6 +134,7 @@ public class Library {
      */
     private Library(@Nullable Collection<String> urls,
                     @Nullable Collection<String> repositories,
+                    @Nullable Collection<String> fallbackRepositories,
                     @NotNull String groupId,
                     @NotNull String artifactId,
                     @NotNull String version,
@@ -151,6 +158,7 @@ private Library(@Nullable Collection<String> urls,
         this.path = craftPath(this.partialPath, this.artifactId, this.version, this.classifier);
 
         this.repositories = repositories != null ? Collections.unmodifiableList(new LinkedList<>(repositories)) : Collections.emptyList();
+        this.fallbackRepositories = fallbackRepositories != null ? Collections.unmodifiableList(new LinkedList<>(fallbackRepositories)) : Collections.emptyList();
         relocatedPath = hasRelocations() ? path + "-relocated-" + Math.abs(this.relocations.hashCode()) + ".jar" : null;
         this.isolatedLoad = isolatedLoad;
         this.loaderId = loaderId;
@@ -169,14 +177,24 @@ public Collection<String> getUrls() {
     }
 
     /**
-     * Gets the repositories URLs for this library.
+     * Gets the repository URLs for this library.
      *
-     * @return repositories URLs
+     * @return repository URLs
      */
     @NotNull
     public Collection<String> getRepositories() {
         return repositories;
     }
+    
+    /**
+     * Gets the fallback repository URLs for this library.
+     *
+     * @return fallback repository URLs
+     */
+    @NotNull
+    public Collection<String> getFallbackRepositories() {
+        return fallbackRepositories;
+    }
 
     /**
      * Gets the Maven group ID for this library.
@@ -380,6 +398,11 @@ public static class Builder {
          * Repository URLs for this library
          */
         private final Collection<String> repositories = new LinkedList<>();
+        
+        /**
+         * Fallback repository URLs for this library
+         */
+        private final Collection<String> fallbackRepositories = new LinkedList<>();
 
         /**
          * Maven group ID
@@ -456,6 +479,18 @@ public Builder repository(@NotNull String url) {
             repositories.add(requireNonNull(url, "repository").endsWith("/") ? url : url + '/');
             return this;
         }
+        
+        /**
+         * Adds a fallback repository URL for this library. See {@link #repository(String)}.
+         *
+         * @param url fallback repository URL
+         * @return this builder
+         */
+        @NotNull
+        public Builder fallbackRepository(@NotNull String url) {
+            fallbackRepositories.add(requireNonNull(url, "fallbackRepository").endsWith("/") ? url : url + '/');
+            return this;
+        }
 
         /**
          * Sets the Maven group ID for this library.
@@ -642,7 +677,7 @@ public Builder excludeTransitiveDependency(@NotNull String groupId, @NotNull Str
          */
         @NotNull
         public Library build() {
-            return new Library(urls, repositories, groupId, artifactId, version, classifier, checksum, relocations, isolatedLoad, loaderId, resolveTransitiveDependencies, excludedTransitiveDependencies);
+            return new Library(urls, repositories, fallbackRepositories, groupId, artifactId, version, classifier, checksum, relocations, isolatedLoad, loaderId, resolveTransitiveDependencies, excludedTransitiveDependencies);
         }
     }
 }

core/src/main/java/com/alessiodp/libby/LibraryManager.java

@@ -47,6 +47,8 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import static java.util.Objects.requireNonNull;
 
@@ -107,6 +109,11 @@ public abstract class LibraryManager {
      * Map of isolated class loaders and theirs id
      */
     protected final Map<String, IsolatedClassLoader> isolatedLibraries = new HashMap<>();
+    
+    /**
+     * Repository resolution mode for libraries
+     */
+    protected RepositoryResolutionMode repositoryResolutionMode = RepositoryResolutionMode.DEFAULT;
 
     /**
      * Creates a new library manager.
@@ -282,6 +289,24 @@ public void addJitPack() {
         addRepository(Repositories.JITPACK);
     }
 
+    /**
+     * Get the repository resolution mode.
+     *
+     * @return the repository resolution mode
+     */
+    public RepositoryResolutionMode getRepositoryResolutionMode() {
+        return repositoryResolutionMode;
+    }
+    
+    /**
+     * Set the repository resolution mode.
+     *
+     * @param repositoryResolutionMode the repository resolution mode
+     */
+    public void setRepositoryResolutionMode(RepositoryResolutionMode repositoryResolutionMode) {
+        this.repositoryResolutionMode = repositoryResolutionMode;
+    }
+    
     /**
      * Gets all the possible download URLs for this library. Entries are
      * ordered by direct download URLs first and then repository download URLs.
@@ -294,19 +319,9 @@ public void addJitPack() {
     public Collection<String> resolveLibrary(@NotNull Library library) {
         Set<String> urls = new LinkedHashSet<>(requireNonNull(library, "library").getUrls());
         boolean snapshot = library.isSnapshot();
+        Collection<String> repos = resolveRepositories(library);
 
-        // Try from library-declared repos first
-        for (String repository : library.getRepositories()) {
-            if (snapshot) {
-                String url = resolveSnapshot(repository, library);
-                if (url != null)
-                    urls.add(repository + url);
-            } else {
-                urls.add(repository + library.getPath());
-            }
-        }
-
-        for (String repository : getRepositories()) {
+        for (String repository : repos) {
             if (snapshot) {
                 String url = resolveSnapshot(repository, library);
                 if (url != null)
@@ -318,6 +333,36 @@ public Collection<String> resolveLibrary(@NotNull Library library) {
 
         return Collections.unmodifiableSet(urls);
     }
+    
+    /**
+     * Resolves the repository URLs for this library.
+     *
+     * @param library the library to resolve repositories for
+     * @return the resolved repositories
+     */
+    protected Collection<String> resolveRepositories(@NotNull Library library) {
+        switch (getRepositoryResolutionMode()) {
+            case GLOBAL_FIRST:
+                return Stream.of(
+                        getRepositories(),
+                        library.getRepositories(),
+                        library.getFallbackRepositories()
+                ).flatMap(Collection::stream).collect(Collectors.toCollection(LinkedHashSet::new));
+            case LIBRARY_FIRST:
+                return Stream.of(
+                        library.getRepositories(),
+                        library.getFallbackRepositories(),
+                        getRepositories()
+                ).flatMap(Collection::stream).collect(Collectors.toCollection(LinkedHashSet::new));
+            case DEFAULT:
+            default:
+                return Stream.of(
+                        library.getRepositories(),
+                        getRepositories(),
+                        library.getFallbackRepositories()
+                ).flatMap(Collection::stream).collect(Collectors.toCollection(LinkedHashSet::new));
+        }
+    }
 
     /**
      * Resolves the URL of the artifact of a snapshot library.

core/src/main/java/com/alessiodp/libby/RepositoryResolutionMode.java

@@ -0,0 +1,19 @@
+package com.alessiodp.libby;
+
+/**
+ * Enum representing the resolution mode of repositories, determining the order in which repositories are searched when resolving dependencies.
+ */
+public enum RepositoryResolutionMode {
+	/**
+	 * The default resolution mode searches for library repositories first, followed by global repositories, and then library fallback repositories if necessary.
+	 */
+	DEFAULT,
+	/**
+	 * With GLOBAL_FIRST, global repositories are searched first, followed by library repositories, and then library fallback repositories if necessary.
+	 */
+	GLOBAL_FIRST,
+	/**
+	 * With LIBRARY_FIRST, library repositories are searched first, followed by library fallback repositories, and then global repositories if necessary.
+	 */
+	LIBRARY_FIRST
+}