/**
 *
 * 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.filter;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.hbase.DeserializationException;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.protobuf.generated.ComparatorProtos;
import org.apache.hadoop.hbase.util.Bytes;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.google.protobuf.InvalidProtocolBufferException;

import java.nio.charset.Charset;
import java.nio.charset.IllegalCharsetNameException;
import java.util.regex.Pattern;

/**
 * This comparator is for use with {@link CompareFilter} implementations, such
 * as {@link RowFilter}, {@link QualifierFilter}, and {@link ValueFilter}, for
 * filtering based on the value of a given column. Use it to test if a given
 * regular expression matches a cell value in the column.
 * <p>
 * Only EQUAL or NOT_EQUAL comparisons are valid with this comparator.
 * <p>
 * For example:
 * <p>
 * <pre>
 * ValueFilter vf = new ValueFilter(CompareOp.EQUAL,
 *     new RegexStringComparator(
 *       // v4 IP address
 *       "(((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3,3}" +
 *         "(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))(\\/[0-9]+)?" +
 *         "|" +
 *       // v6 IP address
 *       "((([\\dA-Fa-f]{1,4}:){7}[\\dA-Fa-f]{1,4})(:([\\d]{1,3}.)" +
 *         "{3}[\\d]{1,3})?)(\\/[0-9]+)?"));
 * </pre>
 * <p>
 * Supports {@link java.util.regex.Pattern} flags as well:
 * <p>
 * <pre>
 * ValueFilter vf = new ValueFilter(CompareOp.EQUAL,
 *     new RegexStringComparator("regex", Pattern.CASE_INSENSITIVE | Pattern.DOTALL));
 * </pre>
 * @see java.util.regex.Pattern;
 */
@InterfaceAudience.Public
@InterfaceStability.Stable
public class RegexStringComparator extends ByteArrayComparable {

  private static final Log LOG = LogFactory.getLog(RegexStringComparator.class);

  private Charset charset = Charset.forName(HConstants.UTF8_ENCODING);

  private Pattern pattern;

  /**
   * Constructor
   * Adds Pattern.DOTALL to the underlying Pattern
   * @param expr a valid regular expression
   */
  public RegexStringComparator(String expr) {
    this(expr, Pattern.DOTALL);
  }

  /**
   * Constructor
   * @param expr a valid regular expression
   * @param flags java.util.regex.Pattern flags
   */
  public RegexStringComparator(String expr, int flags) {
    super(Bytes.toBytes(expr));
    this.pattern = Pattern.compile(expr, flags);
  }

  /**
   * Specifies the {@link Charset} to use to convert the row key to a String.
   * <p>
   * The row key needs to be converted to a String in order to be matched
   * against the regular expression.  This method controls which charset is
   * used to do this conversion.
   * <p>
   * If the row key is made of arbitrary bytes, the charset {@code ISO-8859-1}
   * is recommended.
   * @param charset The charset to use.
   */
  public void setCharset(final Charset charset) {
    this.charset = charset;
  }

  @Override
  public int compareTo(byte[] value, int offset, int length) {
    // Use find() for subsequence match instead of matches() (full sequence
    // match) to adhere to the principle of least surprise.
    return pattern.matcher(new String(value, offset, length, charset)).find() ? 0
        : 1;
  }

  /**
   * @return The comparator serialized using pb
   */
  public byte [] toByteArray() {
    ComparatorProtos.RegexStringComparator.Builder builder =
      ComparatorProtos.RegexStringComparator.newBuilder();
    builder.setPattern(pattern.toString());
    builder.setPatternFlags(pattern.flags());
    builder.setCharset(charset.name());
    return builder.build().toByteArray();
  }

  /**
   * @param pbBytes A pb serialized {@link RegexStringComparator} instance
   * @return An instance of {@link RegexStringComparator} made from <code>bytes</code>
   * @throws DeserializationException
   * @see {@link #toByteArray()}
   */
  public static RegexStringComparator parseFrom(final byte [] pbBytes)
  throws DeserializationException {
    ComparatorProtos.RegexStringComparator proto;
    try {
      proto = ComparatorProtos.RegexStringComparator.parseFrom(pbBytes);
    } catch (InvalidProtocolBufferException e) {
      throw new DeserializationException(e);
    }

    RegexStringComparator comparator =
      new RegexStringComparator(proto.getPattern(), proto.getPatternFlags());
    final String charset = proto.getCharset();
    if (charset.length() > 0) {
      try {
        comparator.setCharset(Charset.forName(charset));
      } catch (IllegalCharsetNameException e) {
        LOG.error("invalid charset", e);
      }
    }
    return comparator;
  }

  /**
   * @param other
   * @return true if and only if the fields of the comparator that are serialized
   * are equal to the corresponding fields in other.  Used for testing.
   */
  boolean areSerializedFieldsEqual(ByteArrayComparable other) {
    if (other == this) return true;
    if (!(other instanceof RegexStringComparator)) return false;

    RegexStringComparator comparator = (RegexStringComparator)other;
    return super.areSerializedFieldsEqual(comparator)
      && this.pattern.toString().equals(comparator.pattern.toString())
      && this.pattern.flags() == comparator.pattern.flags()
      && this.charset.equals(comparator.charset);
  }
}