/*
 * 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.lucene.analysis.util;


import java.lang.reflect.InvocationTargetException;
import java.util.Arrays;
import java.util.Collections;
import java.util.Locale;
import java.util.Map;
import java.util.Objects;
import java.util.LinkedHashMap;
import java.util.Set;
import java.util.ServiceConfigurationError;

import org.apache.lucene.util.SPIClassIterator;

Helper class for loading named SPIs from classpath (e.g. Tokenizers, TokenStreams).
@lucene.internal
/**
 * Helper class for loading named SPIs from classpath (e.g. Tokenizers, TokenStreams).
 * @lucene.internal
 */
public final class AnalysisSPILoader<S extends AbstractAnalysisFactory> {

  private volatile Map<String,Class<? extends S>> services = Collections.emptyMap();
  private final Class<S> clazz;
  private final String[] suffixes;
  
  public AnalysisSPILoader(Class<S> clazz) {
    this(clazz, new String[] { clazz.getSimpleName() });
  }

  public AnalysisSPILoader(Class<S> clazz, ClassLoader loader) {
    this(clazz, new String[] { clazz.getSimpleName() }, loader);
  }

  public AnalysisSPILoader(Class<S> clazz, String[] suffixes) {
    this(clazz, suffixes, null);
  }
  
  public AnalysisSPILoader(Class<S> clazz, String[] suffixes, ClassLoader classloader) {
    this.clazz = clazz;
    this.suffixes = suffixes;
    // if clazz' classloader is not a parent of the given one, we scan clazz's classloader, too:
    final ClassLoader clazzClassloader = clazz.getClassLoader();
    if (classloader == null) {
      classloader = clazzClassloader;
    }
    if (clazzClassloader != null && !SPIClassIterator.isParentClassLoader(clazzClassloader, classloader)) {
      reload(clazzClassloader);
    }
    reload(classloader);
  }
  
  
Reloads the internal SPI list from the given ClassLoader. Changes to the service list are visible after the method ends, all iterators (e.g., from availableServices(),...) stay consistent. 
NOTE: Only new service providers are added, existing ones are
never removed or replaced.
This method is expensive and should only be called for discovery
of new service providers on the given classpath/classloader!
/** 
   * Reloads the internal SPI list from the given {@link ClassLoader}.
   * Changes to the service list are visible after the method ends, all
   * iterators (e.g., from {@link #availableServices()},...) stay consistent. 
   * 
   * <p><b>NOTE:</b> Only new service providers are added, existing ones are
   * never removed or replaced.
   * 
   * <p><em>This method is expensive and should only be called for discovery
   * of new service providers on the given classpath/classloader!</em>
   */
  public synchronized void reload(ClassLoader classloader) {
    Objects.requireNonNull(classloader, "classloader");
    final LinkedHashMap<String,Class<? extends S>> services =
      new LinkedHashMap<>(this.services);
    final SPIClassIterator<S> loader = SPIClassIterator.get(clazz, classloader);
    while (loader.hasNext()) {
      final Class<? extends S> service = loader.next();
      final String clazzName = service.getSimpleName();
      String name = null;
      for (String suffix : suffixes) {
        if (clazzName.endsWith(suffix)) {
          name = clazzName.substring(0, clazzName.length() - suffix.length()).toLowerCase(Locale.ROOT);
          break;
        }
      }
      if (name == null) {
        throw new ServiceConfigurationError("The class name " + service.getName() +
          " has wrong suffix, allowed are: " + Arrays.toString(suffixes));
      }
      // only add the first one for each name, later services will be ignored
      // this allows to place services before others in classpath to make 
      // them used instead of others
      //
      // TODO: Should we disallow duplicate names here?
      // Allowing it may get confusing on collisions, as different packages
      // could contain same factory class, which is a naming bug!
      // When changing this be careful to allow reload()!
      if (!services.containsKey(name)) {
        services.put(name, service);
      }
    }
    this.services = Collections.unmodifiableMap(services);
  }
  
  public S newInstance(String name, Map<String,String> args) {
    final Class<? extends S> service = lookupClass(name);
    return newFactoryClassInstance(service, args);
  }
  
  public Class<? extends S> lookupClass(String name) {
    final Class<? extends S> service = services.get(name.toLowerCase(Locale.ROOT));
    if (service != null) {
      return service;
    } else {
      throw new IllegalArgumentException("A SPI class of type "+clazz.getName()+" with name '"+name+"' does not exist. "+
          "You need to add the corresponding JAR file supporting this SPI to your classpath. "+
          "The current classpath supports the following names: "+availableServices());
    }
  }

  public Set<String> availableServices() {
    return services.keySet();
  }  
  
  
Creates a new instance of the given AbstractAnalysisFactory by invoking the constructor, passing the given argument map. /** Creates a new instance of the given {@link AbstractAnalysisFactory} by invoking the constructor, passing the given argument map. */
  public static <T extends AbstractAnalysisFactory> T newFactoryClassInstance(Class<T> clazz, Map<String,String> args) {
    try {
      return clazz.getConstructor(Map.class).newInstance(args);
    } catch (InvocationTargetException ite) {
      final Throwable cause = ite.getCause();
      if (cause instanceof RuntimeException) {
        throw (RuntimeException) cause;
      }
      if (cause instanceof Error) {
        throw (Error) cause;
      }
      throw new RuntimeException("Unexpected checked exception while calling constructor of "+clazz.getName(), cause);
    } catch (ReflectiveOperationException e) {
      throw new UnsupportedOperationException("Factory "+clazz.getName()+" cannot be instantiated. This is likely due to missing Map<String,String> constructor.", e);
    }
  }
}