/**
 * 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.security.alias;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileUtil;
import org.apache.hadoop.fs.permission.FsPermission;
import org.apache.hadoop.util.Shell;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.PosixFilePermission;
import java.nio.file.attribute.PosixFilePermissions;
import java.util.Set;
import java.util.StringTokenizer;
import java.util.EnumSet;

/**
 * CredentialProvider based on Java's KeyStore file format. The file may be
 * stored only on the local filesystem using the following name mangling:
 * localjceks://file/home/larry/creds.jceks -> file:///home/larry/creds.jceks
 */
@InterfaceAudience.Private
public final class LocalJavaKeyStoreProvider extends
    AbstractJavaKeyStoreProvider {
  public static final String SCHEME_NAME = "localjceks";
  private File file;
  private Set<PosixFilePermission> permissions;

  private LocalJavaKeyStoreProvider(URI uri, Configuration conf)
      throws IOException {
    super(uri, conf);
  }

  @Override
  protected String getSchemeName() {
    return SCHEME_NAME;
  }

  @Override
  protected OutputStream getOutputStreamForKeystore() throws IOException {
    if (LOG.isDebugEnabled()) {
      LOG.debug("using '" + file + "' for output stream.");
    }
    FileOutputStream out = new FileOutputStream(file);
    return out;
  }

  @Override
  protected boolean keystoreExists() throws IOException {
    /* The keystore loader doesn't handle zero length files. */
    return file.exists() && (file.length() > 0);
  }

  @Override
  protected InputStream getInputStreamForFile() throws IOException {
    FileInputStream is = new FileInputStream(file);
    return is;
  }

  @Override
  protected void createPermissions(String perms) throws IOException {
    int mode = 700;
    try {
      mode = Integer.parseInt(perms, 8);
    } catch (NumberFormatException nfe) {
      throw new IOException("Invalid permissions mode provided while "
          + "trying to createPermissions", nfe);
    }
    permissions = modeToPosixFilePermission(mode);
  }

  @Override
  protected void stashOriginalFilePermissions() throws IOException {
    // save off permissions in case we need to
    // rewrite the keystore in flush()
    if (!Shell.WINDOWS) {
      Path path = Paths.get(file.getCanonicalPath());
      permissions = Files.getPosixFilePermissions(path);
    } else {
      // On Windows, the JDK does not support the POSIX file permission APIs.
      // Instead, we can do a winutils call and translate.
      String[] cmd = Shell.getGetPermissionCommand();
      String[] args = new String[cmd.length + 1];
      System.arraycopy(cmd, 0, args, 0, cmd.length);
      args[cmd.length] = file.getCanonicalPath();
      String out = Shell.execCommand(args);
      StringTokenizer t = new StringTokenizer(out, Shell.TOKEN_SEPARATOR_REGEX);
      // The winutils output consists of 10 characters because of the leading
      // directory indicator, i.e. "drwx------".  The JDK parsing method expects
      // a 9-character string, so remove the leading character.
      String permString = t.nextToken().substring(1);
      permissions = PosixFilePermissions.fromString(permString);
    }
  }

  @Override
  protected void initFileSystem(URI uri)
      throws IOException {
    super.initFileSystem(uri);
    try {
      file = new File(new URI(getPath().toString()));
      if (LOG.isDebugEnabled()) {
        LOG.debug("initialized local file as '" + file + "'.");
        if (file.exists()) {
          LOG.debug("the local file exists and is size " + file.length());
          if (LOG.isTraceEnabled()) {
            if (file.canRead()) {
              LOG.trace("we can read the local file.");
            }
            if (file.canWrite()) {
              LOG.trace("we can write the local file.");
            }
          }
        } else {
          LOG.debug("the local file does not exist.");
        }
      }
    } catch (URISyntaxException e) {
      throw new IOException(e);
    }
  }

  @Override
  public void flush() throws IOException {
    super.flush();
    if (LOG.isDebugEnabled()) {
      LOG.debug("Resetting permissions to '" + permissions + "'");
    }
    if (!Shell.WINDOWS) {
      Files.setPosixFilePermissions(Paths.get(file.getCanonicalPath()),
          permissions);
    } else {
      // FsPermission expects a 10-character string because of the leading
      // directory indicator, i.e. "drwx------". The JDK toString method returns
      // a 9-character string, so prepend a leading character.
      FsPermission fsPermission = FsPermission.valueOf(
          "-" + PosixFilePermissions.toString(permissions));
      FileUtil.setPermission(file, fsPermission);
    }
  }

  /**
   * The factory to create JksProviders, which is used by the ServiceLoader.
   */
  public static class Factory extends CredentialProviderFactory {
    @Override
    public CredentialProvider createProvider(URI providerName,
        Configuration conf) throws IOException {
      if (SCHEME_NAME.equals(providerName.getScheme())) {
        return new LocalJavaKeyStoreProvider(providerName, conf);
      }
      return null;
    }
  }

  private static Set<PosixFilePermission> modeToPosixFilePermission(
      int mode) {
    Set<PosixFilePermission> perms = EnumSet.noneOf(PosixFilePermission.class);
    if ((mode & 0001) != 0) {
      perms.add(PosixFilePermission.OTHERS_EXECUTE);
    }
    if ((mode & 0002) != 0) {
      perms.add(PosixFilePermission.OTHERS_WRITE);
    }
    if ((mode & 0004) != 0) {
      perms.add(PosixFilePermission.OTHERS_READ);
    }
    if ((mode & 0010) != 0) {
      perms.add(PosixFilePermission.GROUP_EXECUTE);
    }
    if ((mode & 0020) != 0) {
      perms.add(PosixFilePermission.GROUP_WRITE);
    }
    if ((mode & 0040) != 0) {
      perms.add(PosixFilePermission.GROUP_READ);
    }
    if ((mode & 0100) != 0) {
      perms.add(PosixFilePermission.OWNER_EXECUTE);
    }
    if ((mode & 0200) != 0) {
      perms.add(PosixFilePermission.OWNER_WRITE);
    }
    if ((mode & 0400) != 0) {
      perms.add(PosixFilePermission.OWNER_READ);
    }
    return perms;
  }
}