/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.hadoop.mrunit.testutil;

import java.io.File;
import java.io.IOException;
import java.util.Set;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.junit.Rule;
import org.junit.rules.ExternalResource;
import org.junit.rules.TemporaryFolder;
import org.junit.runner.Description;
import org.junit.runners.model.Statement;

import com.google.common.collect.ImmutableSet;
import com.google.common.io.Files;
import com.google.common.io.Resources;

/**
 * A JUnit {@link Rule} that creates a managed temporary directory for a test case and
 * destroys it afterwards. This works much like JUnit's {@link TemporaryFolder} but is
 * geared towards Hadoop applications. The temporary directory is deleted after each test
 * case, no matter if the test case succeeded or failed.
 * 
 * <p>This is how it works:</p>
 *
 * <pre><tt>
 * public class TestExample {
 *   {@literal @Rule}
 *   public TemporaryPath tmpDir = new TemporaryPath();
 *   
 *   {@literal @Test}
 *   public void testSomething() {
 *     Path input = tmpDir.copyResourcePath("my-test-data");
 *     Path output = tmpDir.getPath("output");
 *     
 *     // create and run a Hadoop job reading from input and writing to output
 *   }
 * }
 * </tt></pre>
 * 
 * <p>In some cases, the frameworks you use in your tests use temporary directories
 * internally. If those directories are configurable via Hadoop properties, you can
 * let {@link TemporaryPath#overridePathProperties(Configuration)} override them
 * so that they point to your managed temporary directory. You have to specify the
 * properties to override via the constructor.</p> 
 */
public final class TemporaryPath extends ExternalResource {
  private final TemporaryFolder tmp = new TemporaryFolder();
  private final Set<String> confKeys;

  /**
   * Construct {@link TemporaryPath}.
   * @param confKeys {@link Configuration} keys containing directories to override
   */
  public TemporaryPath(String... confKeys) {
    if (confKeys != null) {
      this.confKeys = ImmutableSet.copyOf(confKeys);
    } else {
      this.confKeys = ImmutableSet.of();
    }
  }

  /**
   * Used by JUnit internally.
   */
  @Override
  public Statement apply(Statement base, Description description) {
    return tmp.apply(base, description);
  }

  /**
   * Get the root directory which will be deleted automatically.
   */
  public File getRootFile() {
    return tmp.getRoot();
  }

  /**
   * Get the root directory as a {@link Path}.
   */
  public Path getRootPath() {
    return toPath(tmp.getRoot());
  }

  /**
   * Get the root directory as an absolute file name.
   */
  public String getRootFileName() {
    return tmp.getRoot().getAbsolutePath();
  }

  /**
   * Get a {@link File} below the temporary directory.
   */
  public File getFile(String fileName) {
    return new File(getRootFile(), fileName);
  }

  /**
   * Get a {@link Path} below the temporary directory.
   */
  public Path getPath(String fileName) {
    return toPath(getFile(fileName));
  }

  /**
   * Get an absolute file name below the temporary directory.
   */
  public String getFileName(String fileName) {
    return getFile(fileName).getAbsolutePath();
  }

  /**
   * Copy a classpath resource to {@link File}.
   */
  public File copyResourceFile(String resourceName) throws IOException {
    File dest = new File(tmp.getRoot(), new File(resourceName).getName());
    copy(resourceName, dest);
    return dest;
  }

  /**
   * Copy a classpath resource to a {@link Path}.
   */
  public Path copyResourcePath(String resourceName) throws IOException {
    return toPath(copyResourceFile(resourceName));
  }
  

  /**
   * Get a new {@link Configuration} instance.
   */
  public Configuration getDefaultConfiguration() {
    return overridePathProperties(new Configuration());
  }

  /**
   * Set all keys specified in the constructor to temporary directories.
   */
  public Configuration overridePathProperties(Configuration conf) {
    for (String name : confKeys) {
      conf.set(name, getFileName("tmp-" + name));
    }
    return conf;
  }

  /**
   * Copy a classpath resource returning its absolute file name.
   */
  public String copyResourceFileName(String resourceName) throws IOException {
    return copyResourceFile(resourceName).getAbsolutePath();
  }

  private void copy(String resourceName, File dest) throws IOException {
    Files.copy(Resources.newInputStreamSupplier(Resources.getResource(resourceName)), dest);
  }

  private static Path toPath(File file) {
    return new Path(file.getAbsolutePath());
  }
}