/*
 * 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.LinkedHashSet;
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 java.util.regex.Pattern;

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 volatile Set<String> originalNames = Collections.emptySet();
  private final Class<S> clazz;
  private final String[] suffixes;

  private static final Pattern SERVICE_NAME_PATTERN = Pattern.compile("^[a-zA-Z][a-zA-Z0-9_]+$");

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

  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 LinkedHashSet<String> originalNames = new LinkedHashSet<>(this.originalNames);
    final SPIClassIterator<S> loader = SPIClassIterator.get(clazz, classloader);
    while (loader.hasNext()) {
      final Class<? extends S> service = loader.next();
      String name = null;
      String originalName = null;
      try {
        originalName = AbstractAnalysisFactory.lookupSPIName(service);
        name = originalName.toLowerCase(Locale.ROOT);
        if (!isValidName(originalName)) {
          throw new ServiceConfigurationError("The name " + originalName + " for " + service.getName() +
              " is invalid: Allowed characters are (English) alphabet, digits, and underscore. It should be started with an alphabet.");
        }
      } catch (NoSuchFieldException | IllegalAccessException | IllegalStateException e) {
        // just ignore on Lucene 8.x.
        // we should properly handle these exceptions from Lucene 9.0.
      }

      // 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 (name != null && !services.containsKey(name)) {
        services.put(name, service);
        // preserve (case-sensitive) original name for reference
        originalNames.add(originalName);
      }

      // register legacy spi name for backwards compatibility.
      String legacyName = AbstractAnalysisFactory.generateLegacySPIName(service, suffixes);
      if (legacyName == null) {
        throw new ServiceConfigurationError("The class name " + service.getName() +
            " has wrong suffix, allowed are: " + Arrays.toString(suffixes));
      }
      if (!services.containsKey(legacyName)) {
        services.put(legacyName, service);
        // also register this to original name set for reference
        originalNames.add(legacyName);
      }

    }

    // make sure that the number of lookup keys is same to the number of original names.
    // in fact this constraint should be met in existence checks of the lookup map key,
    // so this is more like an assertion rather than a status check.
    if (services.keySet().size() != originalNames.size()) {
      throw new ServiceConfigurationError("Service lookup key set is inconsistent with original name set!");
    }

    this.services = Collections.unmodifiableMap(services);
    this.originalNames = Collections.unmodifiableSet(originalNames);
  }

  private boolean isValidName(String name) {
    return SERVICE_NAME_PATTERN.matcher(name).matches();
  }

  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 originalNames;
  }  
  
  
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);
    }
  }
}