Add method for retrieving XDG config directory

jib-core/src/main/java/com/google/cloud/tools/jib/api/Containerizer.java

@@ -22,7 +22,7 @@
 import com.google.cloud.tools.jib.configuration.ImageConfiguration;
 import com.google.cloud.tools.jib.docker.DockerClient;
 import com.google.cloud.tools.jib.event.EventHandlers;
-import com.google.cloud.tools.jib.filesystem.UserCacheHome;
+import com.google.cloud.tools.jib.filesystem.XdgDirectories;
 import com.google.common.base.Preconditions;
 import java.io.IOException;
 import java.nio.file.Files;
@@ -45,7 +45,7 @@ public class Containerizer {
    * home]/google-cloud-tools-java/jib}.
    */
   public static final Path DEFAULT_BASE_CACHE_DIRECTORY =
-      UserCacheHome.getCacheHome().resolve("google-cloud-tools-java").resolve("jib");
+      XdgDirectories.getCacheHome().resolve("google-cloud-tools-java").resolve("jib");
 
   private static final String DEFAULT_TOOL_NAME = "jib-core";
 

jib-core/src/main/java/com/google/cloud/tools/jib/filesystem/XdgDirectories.java

@@ -0,0 +1,174 @@
+/*
+ * Copyright 2018 Google LLC.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package com.google.cloud.tools.jib.filesystem;
+
+import com.google.common.annotations.VisibleForTesting;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Properties;
+import java.util.logging.Logger;
+
+/**
+ * Obtains OS-specific directories based on the XDG Base Directory Specification.
+ *
+ * <p>Specifically, from the specification:
+ *
+ * <ul>
+ *   <li>These directories are defined by the environment variables {@code $XDG_CACHE_HOME} and
+ *       {@code $XDG_CONFIG_HOME}.
+ *   <li>If {@code $XDG_CACHE_HOME} / {@code $XDG_CONFIG_HOME} is either not set or empty, a
+ *       platform-specific equivalent of {@code $HOME/.cache} / {@code $HOME/.config} should be
+ *       used.
+ * </ul>
+ *
+ * @see <a
+ *     href="https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html">https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html</a>
+ */
+public class XdgDirectories {
+
+  private static final Logger LOGGER = Logger.getLogger(XdgDirectories.class.getName());
+  private static final Path JIB_SUBDIRECTORY_LINUX =
+      Paths.get("google-cloud-tools-java").resolve("jib");
+  private static final Path JIB_SUBDIRECTORY_OTHER = Paths.get("Google").resolve("Jib");
+
+  public static Path getCacheHome() {
+    return getCacheHome(System.getProperties(), System.getenv());
+  }
+
+  public static Path getConfigHome() {
+    return getConfigHome(System.getProperties(), System.getenv());
+  }
+
+  /**
+   * Returns {@code $XDG_CACHE_HOME}, if available, or resolves the OS-specific user cache home
+   * based.
+   *
+   * <p>For Linux, this is {@code $HOME/.cache/}.
+   *
+   * <p>For Windows, this is {@code %LOCALAPPDATA%}.
+   *
+   * <p>For macOS, this is {@code $HOME/Library/Application Support/}.
+   */
+  @VisibleForTesting
+  static Path getCacheHome(Properties properties, Map<String, String> environment) {
+    // Use environment variable $XDG_CACHE_HOME if set and not empty.
+    String xdgCacheHome = environment.get("XDG_CACHE_HOME");
+    if (xdgCacheHome != null && !xdgCacheHome.trim().isEmpty()) {
+      return Paths.get(xdgCacheHome);
+    }
+
+    String userHome = properties.getProperty("user.home");
+    Path xdgPath = Paths.get(userHome, ".cache");
+
+    String rawOsName = properties.getProperty("os.name");
+    String osName = rawOsName.toLowerCase(Locale.ENGLISH);
+
+    if (osName.contains("linux")) {
+      return xdgPath;
+
+    } else if (osName.contains("windows")) {
+      // Use %LOCALAPPDATA% for Windows.
+      String localAppDataEnv = environment.get("LOCALAPPDATA");
+      if (localAppDataEnv == null || localAppDataEnv.trim().isEmpty()) {
+        LOGGER.warning("LOCALAPPDATA environment is invalid or missing");
+        return xdgPath;
+      }
+      Path localAppData = Paths.get(localAppDataEnv);
+      if (!Files.exists(localAppData)) {
+        LOGGER.warning(localAppData + " does not exist");
+        return xdgPath;
+      }
+      return localAppData;
+
+    } else if (osName.contains("mac") || osName.contains("darwin")) {
+      // Use '~/Library/Application Support/' for macOS.
+      Path applicationSupport = Paths.get(userHome, "Library", "Application Support");
+      if (!Files.exists(applicationSupport)) {
+        LOGGER.warning(applicationSupport + " does not exist");
+        return xdgPath;
+      }
+      return applicationSupport;
+    }
+
+    throw new IllegalStateException("Unknown OS: " + rawOsName);
+  }
+
+  /**
+   * Returns config directory based on {@code $XDG_CONFIG_HOME}, if available, or resolves the
+   * OS-specific user config directory.
+   *
+   * <p>For Linux, this is {@code $HOME/.config/google-cloud-tools-java/jib/}.
+   *
+   * <p>For Windows, this is {@code %LOCALAPPDATA%\Google\Jib/}.
+   *
+   * <p>For macOS, this is {@code $HOME/Library/Preferences/Google/Jib/}.
+   */
+  @VisibleForTesting
+  static Path getConfigHome(Properties properties, Map<String, String> environment) {
+    Path windowsSubDirectory = JIB_SUBDIRECTORY_OTHER.resolve("Config");
+    String rawOsName = properties.getProperty("os.name");
+    String osName = rawOsName.toLowerCase(Locale.ENGLISH);
+
+    // Use environment variable $XDG_CONFIG_HOME if set and not empty.
+    String xdgConfigHome = environment.get("XDG_CONFIG_HOME");
+    if (xdgConfigHome != null && !xdgConfigHome.trim().isEmpty()) {
+      if (osName.contains("linux")) {
+        return Paths.get(xdgConfigHome).resolve(JIB_SUBDIRECTORY_LINUX);
+      } else if (osName.contains("windows")) {
+        return Paths.get(xdgConfigHome).resolve(windowsSubDirectory);
+      }
+      return Paths.get(xdgConfigHome).resolve(JIB_SUBDIRECTORY_OTHER);
+    }
+
+    String userHome = properties.getProperty("user.home");
+    Path xdgPath = Paths.get(userHome, ".config");
+
+    if (osName.contains("linux")) {
+      return xdgPath.resolve(JIB_SUBDIRECTORY_LINUX);
+
+    } else if (osName.contains("windows")) {
+      // Use %LOCALAPPDATA% for Windows.
+      String localAppDataEnv = environment.get("LOCALAPPDATA");
+      if (localAppDataEnv == null || localAppDataEnv.trim().isEmpty()) {
+        LOGGER.warning("LOCALAPPDATA environment is invalid or missing");
+        return xdgPath.resolve(windowsSubDirectory);
+      }
+      Path localAppData = Paths.get(localAppDataEnv);
+      if (!Files.exists(localAppData)) {
+        LOGGER.warning(localAppData + " does not exist");
+        return xdgPath.resolve(windowsSubDirectory);
+      }
+      return localAppData.resolve(windowsSubDirectory);
+
+    } else if (osName.contains("mac") || osName.contains("darwin")) {
+      // Use '~/Library/Preferences/' for macOS.
+      Path applicationSupport = Paths.get(userHome, "Library", "Preferences");
+      if (!Files.exists(applicationSupport)) {
+        LOGGER.warning(applicationSupport + " does not exist");
+        return xdgPath.resolve(JIB_SUBDIRECTORY_OTHER);
+      }
+      return applicationSupport.resolve(JIB_SUBDIRECTORY_OTHER);
+    }
+
+    throw new IllegalStateException("Unknown OS: " + rawOsName);
+  }
+
+  private XdgDirectories() {}
+}