/*
    * 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.hbase.security.access;
  
  import com.google.common.collect.Maps;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.io.VersionedWritable;
  
  import java.io.DataInput;
  import java.io.DataOutput;
  import java.io.IOException;
  import java.util.Arrays;
  import java.util.Map;
  
  /**
   * Base permissions instance representing the ability to perform a given set
   * of actions.
   *
   * @see TablePermission
   */
  @InterfaceAudience.Public
  @InterfaceStability.Evolving
  public class Permission extends VersionedWritable {
    protected static final byte VERSION = 0;
  
    @InterfaceAudience.Public
    @InterfaceStability.Evolving
    public enum Action {
      READ('R'), WRITE('W'), EXEC('X'), CREATE('C'), ADMIN('A');
  
      private byte code;
      Action(char code) {
        this.code = (byte)code;
      }
  
      public byte code() { return code; }
    }
  
    private static final Log LOG = LogFactory.getLog(Permission.class);
    protected static final Map<Byte,Action> ACTION_BY_CODE = Maps.newHashMap();
  
    protected Action[] actions;
  
    static {
      for (Action a : Action.values()) {
        ACTION_BY_CODE.put(a.code(), a);
      }
    }
  
    /** Empty constructor for Writable implementation.  <b>Do not use.</b> */
    public Permission() {
      super();
    }
  
    public Permission(Action... assigned) {
      if (assigned != null && assigned.length > 0) {
        actions = Arrays.copyOf(assigned, assigned.length);
      }
    }
  
    public Permission(byte[] actionCodes) {
      if (actionCodes != null) {
        Action acts[] = new Action[actionCodes.length];
        int j = 0;
        for (int i=0; i<actionCodes.length; i++) {
          byte b = actionCodes[i];
          Action a = ACTION_BY_CODE.get(b);
          if (a == null) {
            LOG.error("Ignoring unknown action code '"+
                Bytes.toStringBinary(new byte[]{b})+"'");
            continue;
          }
          acts[j++] = a;
        }
        this.actions = Arrays.copyOf(acts, j);
      }
    }
  
    public Action[] getActions() {
     return actions;
   }
 
   public boolean implies(Action action) {
     if (this.actions != null) {
       for (Action a : this.actions) {
         if (a == action) {
           return true;
         }
       }
     }
 
     return false;
   }
 
   @Override
   public boolean equals(Object obj) {
     if (!(obj instanceof Permission)) {
       return false;
     }
     Permission other = (Permission)obj;
     // check actions
     if (actions == null && other.getActions() == null) {
       return true;
     } else if (actions != null && other.getActions() != null) {
       Action[] otherActions = other.getActions();
       if (actions.length != otherActions.length) {
         return false;
       }
 
       outer:
       for (Action a : actions) {
         for (Action oa : otherActions) {
           if (a == oa) continue outer;
         }
         return false;
       }
       return true;
     }
 
     return false;
   }
 
   @Override
   public int hashCode() {
     final int prime = 37;
     int result = 23;
     for (Action a : actions) {
       result = prime * result + a.code();
     }
     return result;
   }
 
   @Override
   public String toString() {
     StringBuilder str = new StringBuilder("[Permission: ")
         .append("actions=");
     if (actions != null) {
       for (int i=0; i<actions.length; i++) {
         if (i > 0)
           str.append(",");
         if (actions[i] != null)
           str.append(actions[i].toString());
         else
           str.append("NULL");
       }
     }
     str.append("]");
 
     return str.toString();
   }
 
   /** @return the object version number */
   @Override
   public byte getVersion() {
     return VERSION;
   }
 
   @Override
   public void readFields(DataInput in) throws IOException {
     super.readFields(in);
     int length = (int)in.readByte();
     if (length > 0) {
       actions = new Action[length];
       for (int i = 0; i < length; i++) {
         byte b = in.readByte();
         Action a = ACTION_BY_CODE.get(b);
         if (a == null) {
           throw new IOException("Unknown action code '"+
               Bytes.toStringBinary(new byte[]{b})+"' in input");
         }
         this.actions[i] = a;
       }
     } else {
       actions = new Action[0];
     }
   }
 
   @Override
   public void write(DataOutput out) throws IOException {
     super.write(out);
     out.writeByte(actions != null ? actions.length : 0);
     if (actions != null) {
       for (Action a: actions) {
         out.writeByte(a.code());
       }
     }
   }
 }