Use a utility method to copy file hiearchy from classpath (#23)

Author: EtienneMiret

src/functionalTest/java/io/miret/etienne/gradle/sass/MultiProjectTest.java

@@ -83,26 +83,14 @@ void stopServer() {
 
   @BeforeEach
   void setupProject() throws IOException {
-    List<String> directories = ImmutableList.of(
-        "app",
-        "lib"
-    );
     List<String> files = ImmutableList.of(
         "app/build.gradle",
         "lib/build.gradle",
         "build.gradle",
         "settings.gradle"
     );
 
-    for (String subDir : directories) {
-      Files.createDirectories(projectDir.resolve(subDir));
-    }
-    for (String resource : files) {
-      try (InputStream input = MultiProjectTest.class.getResourceAsStream("multi-project/" + resource)) {
-        requireNonNull(input, "Missing resource: " + resource);
-        Files.copy(input, projectDir.resolve(resource));
-      }
-    }
+    Utils.copy("/io/miret/etienne/gradle/sass/multi-project", files, projectDir);
   }
 
   @Test

src/functionalTest/java/io/miret/etienne/gradle/sass/Utils.java

@@ -0,0 +1,50 @@
+package io.miret.etienne.gradle.sass;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Collection;
+import java.util.Objects;
+
+public class Utils {
+
+  /**
+   * Copies classpath resources to a directory.
+   * <p>
+   * Each resource will be searched in the classpath from {@code base} and
+   * copied to {@code destination}. That is, for {@code base = "/io/miret/"},
+   * {@code destination = "/var/tmp"} and a {@code foo/bar.txt} resource,
+   * the {@code /io/miret/foo/bar.txt} classpath resource will be copied
+   * to {@code /var/tmp/foo/bar.txt}.
+   * <p>
+   * Intermediate directories will be created as needed.
+   *
+   * @param base base name for the resources, must include the starting '/'.
+   * @param resources the set of file resources to copy, relative to base.
+   * @param destination a path that points to an existing directory.
+   */
+  public static void copy(
+      String base,
+      Collection<String> resources,
+      Path destination
+  ) throws IOException {
+    if (!base.startsWith("/")) {
+      throw new IllegalArgumentException("Base resource name must start with a '/'");
+    }
+    for (String resourceStr : resources) {
+      Path resourcePath = Paths.get(resourceStr);
+      if (resourcePath.isAbsolute()) {
+        throw new IllegalArgumentException("Absolute path provided: " + resourceStr);
+      }
+      Path target = destination.resolve(resourcePath);
+      Files.createDirectories(target.getParent());
+      try (InputStream input = Utils.class.getResourceAsStream(base + "/" + resourceStr)) {
+        Objects.requireNonNull(input, "No such resource: " + resourceStr);
+        Files.copy(input, target);
+      }
+    }
+  }
+
+}