/**
    * Copyright (C) 2014-2017 Philip Helger (www.helger.com)
    * philip[at]helger[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.helger.schematron.saxon;
  
  import javax.annotation.Nonnull;
  import javax.annotation.Nullable;
  import javax.annotation.concurrent.Immutable;
  import javax.xml.transform.ErrorListener;
  import javax.xml.transform.TransformerConfigurationException;
  import javax.xml.transform.TransformerFactory;
  import javax.xml.transform.TransformerFactoryConfigurationError;
  import javax.xml.transform.URIResolver;
  
  import com.helger.commons.CGlobal;
  import com.helger.commons.exception.InitializationException;
  import com.helger.commons.lang.ClassLoaderHelper;
  import com.helger.xml.transform.DefaultTransformURIResolver;
  import com.helger.xml.transform.LoggingTransformErrorListener;
  
  import net.sf.saxon.lib.FeatureKeys;
  
  /**
   * A special {@link TransformerFactory} handler that prefers Saxon's
   * {@link TransformerFactory} before calling the SPI version
   * <code>TransformerFactory.newInstance ()</code>. This is mainly to solve the
   * interoperability issue when using Xalan and Saxon together in the class path.
   *
   * @author Philip Helger
   */
  @Immutable
  public final class SchematronTransformerFactory
  {
    public static final String SAXON_TRANSFORMER_FACTORY_CLASS = "net.sf.saxon.TransformerFactoryImpl";
    private static final TransformerFactory s_aDefaultFactory;
  
    static
    {
      s_aDefaultFactory = createTransformerFactorySaxonFirst ((ClassLoader) null,
                                                              new LoggingTransformErrorListener (CGlobal.DEFAULT_LOCALE),
                                                              new DefaultTransformURIResolver ());
    }
  
    private SchematronTransformerFactory ()
    {}
  
    /**
     * @return The default "Saxon first" {@link TransformerFactory}. Never
     *         <code>null</code>.
     */
    @Nonnull
    public static TransformerFactory getDefaultSaxonFirst ()
    {
      return s_aDefaultFactory;
    }
  
    /**
     * Create a new {@link TransformerFactory} trying to invoke the Saxon
     * implementation first using the class
     * {@value #SAXON_TRANSFORMER_FACTORY_CLASS}.
     *
     * @param aClassLoader
     *        The optional class loader to be used. May be <code>null</code>.
     * @param aErrorListener
     *        An optional XSLT error listener to be used. May be
     *        <code>null</code>.
     * @param aURIResolver
     *        An optional XSLT URI resolver to be used. May be <code>null</code>.
     * @return A new {@link TransformerFactory} and not <code>null</code>.
     * @throws InitializationException
     *         In case initialization fails.
     */
    @Nonnull
    public static TransformerFactory createTransformerFactorySaxonFirst (@Nullable final ClassLoader aClassLoader,
                                                                         @Nullable final ErrorListener aErrorListener,
                                                                         @Nullable final URIResolver aURIResolver)
    {
      TransformerFactory aFactory;
      try
      {
        // Try Saxon first
        final ClassLoader aEffectiveClassLoader = aClassLoader != null ? aClassLoader
                                                                       : ClassLoaderHelper.getContextClassLoader ();
        aFactory = TransformerFactory.newInstance (SAXON_TRANSFORMER_FACTORY_CLASS, aEffectiveClassLoader);
  
        // Debug/testing only
       if (false)
         aFactory.setFeature (FeatureKeys.TRACE_OPTIMIZER_DECISIONS, true);
       if (false)
         aFactory.setFeature (FeatureKeys.COMPILE_WITH_TRACING, true);
       if (false)
         aFactory.setAttribute (FeatureKeys.XSLT_VERSION, "2.0");
     }
     catch (final TransformerFactoryConfigurationError | TransformerConfigurationException ex)
     {
       try
       {
         // Try default afterwards
         aFactory = TransformerFactory.newInstance ();
       }
       catch (final TransformerFactoryConfigurationError ex2)
       {
         throw new InitializationException ("Failed to create XML TransformerFactory", ex2);
       }
     }
 
     if (aErrorListener != null)
       aFactory.setErrorListener (aErrorListener);
     if (aURIResolver != null)
       aFactory.setURIResolver (aURIResolver);
     return aFactory;
   }
 }