/**
 * 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.fs.permission;

import java.util.List;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;

import com.google.common.base.Objects;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;

/**
 * An AclStatus contains the ACL information of a specific file. AclStatus
 * instances are immutable. Use a {@link Builder} to create a new instance.
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class AclStatus {
  private final String owner;
  private final String group;
  private final boolean stickyBit;
  private final List<AclEntry> entries;
  private final FsPermission permission;

  /**
   * Returns the file owner.
   *
   * @return String file owner
   */
  public String getOwner() {
    return owner;
  }

  /**
   * Returns the file group.
   *
   * @return String file group
   */
  public String getGroup() {
    return group;
  }

  /**
   * Returns the sticky bit.
   * 
   * @return boolean sticky bit
   */
  public boolean isStickyBit() {
    return stickyBit;
  }

  /**
   * Returns the list of all ACL entries, ordered by their natural ordering.
   *
   * @return List<AclEntry> unmodifiable ordered list of all ACL entries
   */
  public List<AclEntry> getEntries() {
    return entries;
  }

  /**
   * Returns the permission set for the path
   * @return {@link FsPermission} for the path
   */
  public FsPermission getPermission() {
    return permission;
  }

  @Override
  public boolean equals(Object o) {
    if (o == null) {
      return false;
    }
    if (getClass() != o.getClass()) {
      return false;
    }
    AclStatus other = (AclStatus)o;
    return Objects.equal(owner, other.owner)
        && Objects.equal(group, other.group)
        && stickyBit == other.stickyBit
        && Objects.equal(entries, other.entries);
  }

  @Override
  public int hashCode() {
    return Objects.hashCode(owner, group, stickyBit, entries);
  }

  @Override
  public String toString() {
    return new StringBuilder()
      .append("owner: ").append(owner)
      .append(", group: ").append(group)
      .append(", acl: {")
      .append("entries: ").append(entries)
      .append(", stickyBit: ").append(stickyBit)
      .append('}')
      .toString();
  }

  /**
   * Builder for creating new Acl instances.
   */
  public static class Builder {
    private String owner;
    private String group;
    private boolean stickyBit;
    private List<AclEntry> entries = Lists.newArrayList();
    private FsPermission permission = null;

    /**
     * Sets the file owner.
     *
     * @param owner String file owner
     * @return Builder this builder, for call chaining
     */
    public Builder owner(String owner) {
      this.owner = owner;
      return this;
    }

    /**
     * Sets the file group.
     *
     * @param group String file group
     * @return Builder this builder, for call chaining
     */
    public Builder group(String group) {
      this.group = group;
      return this;
    }

    /**
     * Adds an ACL entry.
     *
     * @param e AclEntry entry to add
     * @return Builder this builder, for call chaining
     */
    public Builder addEntry(AclEntry e) {
      this.entries.add(e);
      return this;
    }

    /**
     * Adds a list of ACL entries.
     *
     * @param entries AclEntry entries to add
     * @return Builder this builder, for call chaining
     */
    public Builder addEntries(Iterable<AclEntry> entries) {
      for (AclEntry e : entries)
        this.entries.add(e);
      return this;
    }

    /**
     * Sets sticky bit. If this method is not called, then the builder assumes
     * false.
     *
     * @param stickyBit
     *          boolean sticky bit
     * @return Builder this builder, for call chaining
     */
    public Builder stickyBit(boolean stickyBit) {
      this.stickyBit = stickyBit;
      return this;
    }

    /**
     * Sets the permission for the file.
     * @param permission
     */
    public Builder setPermission(FsPermission permission) {
      this.permission = permission;
      return this;
    }

    /**
     * Builds a new AclStatus populated with the set properties.
     *
     * @return AclStatus new AclStatus
     */
    public AclStatus build() {
      return new AclStatus(owner, group, stickyBit, entries, permission);
    }
  }

  /**
   * Private constructor.
   *
   * @param file Path file associated to this ACL
   * @param owner String file owner
   * @param group String file group
   * @param stickyBit the sticky bit
   * @param entries the ACL entries
   * @param permission permission of the path
   */
  private AclStatus(String owner, String group, boolean stickyBit,
      Iterable<AclEntry> entries, FsPermission permission) {
    this.owner = owner;
    this.group = group;
    this.stickyBit = stickyBit;
    this.entries = Lists.newArrayList(entries);
    this.permission = permission;
  }

  /**
   * Get the effective permission for the AclEntry
   * @param entry AclEntry to get the effective action
   */
  public FsAction getEffectivePermission(AclEntry entry) {
    return getEffectivePermission(entry, permission);
  }

  /**
   * Get the effective permission for the AclEntry. <br>
   * Recommended to use this API ONLY if client communicates with the old
   * NameNode, needs to pass the Permission for the path to get effective
   * permission, else use {@link AclStatus#getEffectivePermission(AclEntry)}.
   * @param entry AclEntry to get the effective action
   * @param permArg Permission for the path. However if the client is NOT
   *          communicating with old namenode, then this argument will not have
   *          any preference.
   * @return Returns the effective permission for the entry.
   * @throws IllegalArgumentException If the client communicating with old
   *           namenode and permission is not passed as an argument.
   */
  public FsAction getEffectivePermission(AclEntry entry, FsPermission permArg)
      throws IllegalArgumentException {
    // At least one permission bits should be available.
    Preconditions.checkArgument(this.permission != null || permArg != null,
        "Permission bits are not available to calculate effective permission");
    if (this.permission != null) {
      // permission bits from server response will have the priority for
      // accuracy.
      permArg = this.permission;
    }
    if ((entry.getName() != null || entry.getType() == AclEntryType.GROUP)) {
      if (entry.getScope() == AclEntryScope.ACCESS) {
        FsAction entryPerm = entry.getPermission();
        return entryPerm.and(permArg.getGroupAction());
      } else {
        Preconditions.checkArgument(this.entries.contains(entry)
            && this.entries.size() >= 3,
            "Passed default ACL entry not found in the list of ACLs");
        // default mask entry for effective permission calculation will be the
        // penultimate entry. This can be mask entry in case of extended ACLs.
        // In case of minimal ACL, this is the owner group entry, and we end up
        // intersecting group FsAction with itself, which is a no-op.
        FsAction defaultMask = this.entries.get(this.entries.size() - 2)
            .getPermission();
        FsAction entryPerm = entry.getPermission();
        return entryPerm.and(defaultMask);
      }
    } else {
      return entry.getPermission();
    }
  }
}