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/**
 * Copyright (C) 2006-2015 phloc systems
 * http://www.phloc.com
 * office[at]phloc[dot]com
 *
 * Licensed 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 com.phloc.commons.xml.xpath;

import java.util.Map;

import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.NotThreadSafe;
import javax.xml.namespace.QName;
import javax.xml.xpath.XPathVariableResolver;

import com.phloc.commons.ValueEnforcer;
import com.phloc.commons.annotations.ReturnsMutableCopy;
import com.phloc.commons.collections.ContainerHelper;
import com.phloc.commons.equals.EqualsUtils;
import com.phloc.commons.hash.HashCodeGenerator;
import com.phloc.commons.state.EChange;
import com.phloc.commons.string.ToStringGenerator;

/**
 * Class is used in conjunction with {@link javax.xml.xpath.XPathExpression} to
 * resolve variable values used in XPath queries at runtime. The local part of
 * the QName to resolve is used as the key in the map.
 * 
 * @author Philip Helger
 */
@NotThreadSafe
public class MapBasedXPathVariableResolver implements XPathVariableResolver
{
  private final Map  m_aVars;

  public MapBasedXPathVariableResolver ()
  {
    this (null);
  }

  public MapBasedXPathVariableResolver (@Nullable final Map  aVars)
  {
    m_aVars = ContainerHelper.newMap (aVars);
  }

  @Nonnull
  public EChange addUniqueVariable (@Nonnull final String sName, @Nonnull final Object aValue)
  {
    ValueEnforcer.notNull (sName, "Name");
    ValueEnforcer.notNull (aValue, "Value");

    if (m_aVars.containsKey (sName))
      return EChange.UNCHANGED;
    m_aVars.put (sName, aValue);
    return EChange.CHANGED;
  }

  @Nonnull
  public EChange removeVariable (@Nullable final String sName)
  {
    return EChange.valueOf (m_aVars.remove (sName) != null);
  }

  @Nonnull
  public EChange removeVariables (@Nullable final Iterable  aNames)
  {
    EChange eChange = EChange.UNCHANGED;
    if (aNames != null)
      for (final String sName : aNames)
        eChange = eChange.or (removeVariable (sName));
    return eChange;
  }

  @Nonnull
  @ReturnsMutableCopy
  public Map  getAllVariables ()
  {
    return ContainerHelper.newMap (m_aVars);
  }

  @Nonnegative
  public int getVariableCount ()
  {
    return m_aVars.size ();
  }

  @Nonnull
  public EChange clear ()
  {
    if (m_aVars.isEmpty ())
      return EChange.UNCHANGED;
    m_aVars.clear ();
    return EChange.CHANGED;
  }

  public void setAllVariables (@Nullable final Map  aVars)
  {
    m_aVars.clear ();
    if (aVars != null)
      m_aVars.putAll (aVars);
  }

  @Nullable
  public Object resolveVariable (@Nonnull final QName aVariableName)
  {
    ValueEnforcer.notNull (aVariableName, "VariableName");

    if (m_aVars == null)
      return null;

    final String sLocalName = aVariableName.getLocalPart ();
    return m_aVars.get (sLocalName);
  }

  @Override
  public boolean equals (final Object o)
  {
    if (o == this)
      return true;
    if (o == null || !getClass ().equals (o.getClass ()))
      return false;
    final MapBasedXPathVariableResolver rhs = (MapBasedXPathVariableResolver) o;
    return EqualsUtils.equals (m_aVars, rhs.m_aVars);
  }

  @Override
  public int hashCode ()
  {
    return new HashCodeGenerator (this).append (m_aVars).getHashCode ();
  }

  @Override
  public String toString ()
  {
    return new ToStringGenerator (this).append ("vars", m_aVars).toString ();
  }
}