/*
 * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
 * (the "License"). You may not use this work except in compliance with the License, which is
 * available at www.apache.org/licenses/LICENSE-2.0
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied, as more fully set forth in the License.
 *
 * See the NOTICE file distributed with this work for information regarding copyright ownership.
 */

package alluxio.underfs;

import alluxio.Configuration;
import alluxio.PropertyKey;

import java.util.Collections;
import java.util.Map;

/**
 * A class that gets the value of the given key in the given UFS configuration or the global
 * configuration (in case the key is not found in the UFS configuration), throw
 * {@link RuntimeException} if the key is not found in both configurations..
 */
public final class UnderFileSystemConfiguration {
  private final boolean mReadOnly;
  private final boolean mShared;
  private final Map<String, String> mUfsConf;

  private static final UnderFileSystemConfiguration DEFAULTS = new UnderFileSystemConfiguration();

  /**
   * Constructs a new instance of the configuration for a UFS.
   *
   * @param readOnly whether only read operations are permitted to UFS
   * @param shared whether the mount point is shared with all Alluxio users
   * @param ufsConf the user-specified UFS configuration as a map
   */
  public UnderFileSystemConfiguration(boolean readOnly, boolean shared,
      Map<String, String> ufsConf) {
    mReadOnly = readOnly;
    mShared = shared;
    mUfsConf = ufsConf;
  }

  /**
   * Constructs a new instance of {@link UnderFileSystemConfiguration} with defaults.
   */
  private UnderFileSystemConfiguration() {
    mReadOnly = false;
    mShared = false;
    mUfsConf = Collections.EMPTY_MAP;
  }

  /**
   * @return default UFS configuration
   */
  public static UnderFileSystemConfiguration defaults() {
    return DEFAULTS;
  }

  /**
   * @param key property key
   * @return true if the key is contained in the given UFS configuration or global configuration
   */
  public boolean containsKey(PropertyKey key) {
    return (mUfsConf != null && mUfsConf.containsKey(key.toString()))
        || Configuration.containsKey(key);
  }

  /**
   * Gets the value of the given key in the given UFS configuration or the global configuration
   * (in case the key is not found in the UFS configuration), throw {@link RuntimeException} if the
   * key is not found in both configurations.
   *
   * @param key property key
   * @return the value associated with the given key
   */
  public String getValue(PropertyKey key) {
    if (mUfsConf != null && mUfsConf.containsKey(key.toString())) {
      return mUfsConf.get(key.toString());
    }
    if (Configuration.containsKey(key)) {
      return Configuration.get(key);
    }
    throw new RuntimeException("key " + key + " not found");
  }

  /**
   * @return the map of user-customized configuration
   */
  public Map<String, String> getUserSpecifiedConf() {
    if (mUfsConf == null) {
      return Collections.emptyMap();
    }
    return Collections.unmodifiableMap(mUfsConf);
  }

  /**
   * @return whether only read operations are permitted to the {@link UnderFileSystem}
   */
  public boolean isReadOnly() {
    return mReadOnly;
  }

  /**
   * @return whether the mounted UFS is shared with all Alluxio users
   */
  public boolean isShared() {
    return mShared;
  }
}