/*
    * 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.eclipse.sisu.plexus;
  
  import javax.annotation.Priority;
  import javax.inject.Inject;
  import javax.inject.Singleton;
  
  import java.io.StringReader;
  import java.lang.reflect.Array;
  import java.lang.reflect.InvocationTargetException;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Properties;
  
  import com.google.inject.Injector;
  import com.google.inject.Key;
  import com.google.inject.Module;
  import com.google.inject.TypeLiteral;
  import com.google.inject.spi.TypeConverter;
  import com.google.inject.spi.TypeConverterBinding;
  import org.apache.maven.api.xml.XmlNode;
  import org.apache.maven.internal.xml.XmlNodeBuilder;
  import org.codehaus.plexus.util.xml.Xpp3Dom;
  import org.codehaus.plexus.util.xml.Xpp3DomBuilder;
  import org.codehaus.plexus.util.xml.pull.MXParser;
  import org.codehaus.plexus.util.xml.pull.XmlPullParser;
  import org.codehaus.plexus.util.xml.pull.XmlPullParserException;
  import org.eclipse.sisu.bean.BeanProperties;
  import org.eclipse.sisu.bean.BeanProperty;
  import org.eclipse.sisu.inject.Logs;
  import org.eclipse.sisu.inject.TypeArguments;
  
  /**
   * {@link PlexusBeanConverter} {@link Module} that converts Plexus XML configuration into beans.
   */
  @Singleton
  @Priority(10)
  public final class PlexusXmlBeanConverter implements PlexusBeanConverter {
      // ----------------------------------------------------------------------
      // Constants
      // ----------------------------------------------------------------------
  
      private static final String CONVERSION_ERROR = "Cannot convert: \"%s\" to: %s";
  
      // ----------------------------------------------------------------------
      // Implementation fields
      // ----------------------------------------------------------------------
  
      private final Collection<TypeConverterBinding> typeConverterBindings;
  
      // ----------------------------------------------------------------------
      // Constructors
      // ----------------------------------------------------------------------
  
      @Inject
      PlexusXmlBeanConverter(final Injector injector) {
          typeConverterBindings = injector.getTypeConverterBindings();
      }
  
      // ----------------------------------------------------------------------
      // Public methods
      // ----------------------------------------------------------------------
  
      @SuppressWarnings({"unchecked", "rawtypes"})
      public Object convert(final TypeLiteral role, final String value) {
          if (value.trim().startsWith("<")) {
              try {
                  final MXParser parser = new MXParser();
                  parser.setInput(new StringReader(value));
                  parser.nextTag();
  
                  return parse(parser, role);
              } catch (final Exception e) {
                  throw new IllegalArgumentException(String.format(CONVERSION_ERROR, value, role), e);
              }
          }
  
          return convertText(value, role);
      }
  
     // ----------------------------------------------------------------------
     // Implementation methods
     // ----------------------------------------------------------------------
 
     /**
      * Parses a sequence of XML elements and converts them to the given target type.
      *
      * @param parser The XML parser
      * @param toType The target type
      * @return Converted instance of the target type
      */
     private Object parse(final MXParser parser, final TypeLiteral<?> toType) throws Exception {
         parser.require(XmlPullParser.START_TAG, null, null);
 
         final Class<?> rawType = toType.getRawType();
         if (XmlNode.class.isAssignableFrom(rawType)) {
             return XmlNodeBuilder.build(parser);
         }
         if (Xpp3Dom.class.isAssignableFrom(rawType)) {
             return parseXpp3Dom(parser);
         }
         if (Properties.class.isAssignableFrom(rawType)) {
             return parseProperties(parser);
         }
         if (Map.class.isAssignableFrom(rawType)) {
             return parseMap(parser, TypeArguments.get(toType.getSupertype(Map.class), 1));
         }
         if (Collection.class.isAssignableFrom(rawType)) {
             return parseCollection(parser, TypeArguments.get(toType.getSupertype(Collection.class), 0));
         }
         if (rawType.isArray()) {
             return parseArray(parser, TypeArguments.get(toType, 0));
         }
         return parseBean(parser, toType, rawType);
     }
 
     /**
      * Parses an XML subtree and converts it to the {@link Xpp3Dom} type.
      *
      * @param parser The XML parser
      * @return Converted Xpp3Dom instance
      */
     private static Xpp3Dom parseXpp3Dom(final XmlPullParser parser) throws Exception {
         return Xpp3DomBuilder.build(parser);
     }
 
     /**
      * Parses a sequence of XML elements and converts them to the appropriate {@link Properties} type.
      *
      * @param parser The XML parser
      * @return Converted Properties instance
      */
     private static Properties parseProperties(final XmlPullParser parser) throws Exception {
         final Properties properties = newImplementation(parser, Properties.class);
         while (parser.nextTag() == XmlPullParser.START_TAG) {
             parser.nextTag();
             // 'name-then-value' or 'value-then-name'
             if ("name".equals(parser.getName())) {
                 final String name = parser.nextText();
                 parser.nextTag();
                 properties.put(name, parser.nextText());
             } else {
                 final String value = parser.nextText();
                 parser.nextTag();
                 properties.put(parser.nextText(), value);
             }
             parser.nextTag();
         }
         return properties;
     }
 
     /**
      * Parses a sequence of XML elements and converts them to the appropriate {@link Map} type.
      *
      * @param parser The XML parser
      * @return Converted Map instance
      */
     private Map<String, Object> parseMap(final MXParser parser, final TypeLiteral<?> toType) throws Exception {
         @SuppressWarnings("unchecked")
         final Map<String, Object> map = newImplementation(parser, HashMap.class);
         while (parser.nextTag() == XmlPullParser.START_TAG) {
             map.put(parser.getName(), parse(parser, toType));
         }
         return map;
     }
 
     /**
      * Parses a sequence of XML elements and converts them to the appropriate {@link Collection} type.
      *
      * @param parser The XML parser
      * @return Converted Collection instance
      */
     private Collection<Object> parseCollection(final MXParser parser, final TypeLiteral<?> toType) throws Exception {
         @SuppressWarnings("unchecked")
         final Collection<Object> collection = newImplementation(parser, ArrayList.class);
         while (parser.nextTag() == XmlPullParser.START_TAG) {
             collection.add(parse(parser, toType));
         }
         return collection;
     }
 
     /**
      * Parses a sequence of XML elements and converts them to the appropriate array type.
      *
      * @param parser The XML parser
      * @return Converted array instance
      */
     private Object parseArray(final MXParser parser, final TypeLiteral<?> toType) throws Exception {
         // convert to a collection first then convert that into an array
         final Collection<?> collection = parseCollection(parser, toType);
         final Object array = Array.newInstance(toType.getRawType(), collection.size());
 
         int i = 0;
         for (final Object element : collection) {
             Array.set(array, i++, element);
         }
 
         return array;
     }
 
     /**
      * Parses a sequence of XML elements and converts them to the appropriate bean type.
      *
      * @param parser The XML parser
      * @return Converted bean instance
      */
     private Object parseBean(final MXParser parser, final TypeLiteral<?> toType, final Class<?> rawType)
             throws Exception {
         final Class<?> clazz = loadImplementation(parseImplementation(parser), rawType);
 
         // simple bean? assumes string constructor
         if (parser.next() == XmlPullParser.TEXT) {
             final String text = parser.getText();
 
             // confirm element doesn't contain nested XML
             if (parser.next() != XmlPullParser.START_TAG) {
                 return convertText(text, clazz == rawType ? toType : TypeLiteral.get(clazz));
             }
         }
 
         if (String.class == clazz) {
             // mimic plexus: discard any strings containing nested XML
             while (parser.getEventType() == XmlPullParser.START_TAG) {
                 final String pos = parser.getPositionDescription();
                 Logs.warn("Expected TEXT, not XML: {}", pos, new Throwable());
                 parser.skipSubTree();
                 parser.nextTag();
             }
             return "";
         }
 
         final Object bean = newImplementation(clazz);
 
         // build map of all known bean properties belonging to the chosen implementation
         final Map<String, BeanProperty<Object>> propertyMap = new HashMap<String, BeanProperty<Object>>();
         for (final BeanProperty<Object> property : new BeanProperties(clazz)) {
             final String name = property.getName();
             if (!propertyMap.containsKey(name)) {
                 propertyMap.put(name, property);
             }
         }
 
         while (parser.getEventType() == XmlPullParser.START_TAG) {
             // update properties inside the bean, guided by the cached property map
             final BeanProperty<Object> property = propertyMap.get(Roles.camelizeName(parser.getName()));
             if (property != null) {
                 property.set(bean, parse(parser, property.getType()));
                 parser.nextTag();
             } else {
                 throw new XmlPullParserException("Unknown bean property: " + parser.getName(), parser, null);
             }
         }
 
         return bean;
     }
 
     /**
      * Parses an XML element looking for the name of a custom implementation.
      *
      * @param parser The XML parser
      * @return Name of the custom implementation; otherwise {@code null}
      */
     private static String parseImplementation(final XmlPullParser parser) {
         return parser.getAttributeValue(null, "implementation");
     }
 
     /**
      * Attempts to load the named implementation, uses default implementation if no name is given.
      *
      * @param name The optional implementation name
      * @param defaultClazz The default implementation type
      * @return Custom implementation type if one was given; otherwise default implementation type
      */
     private static Class<?> loadImplementation(final String name, final Class<?> defaultClazz) {
         if (null == name) {
             return defaultClazz; // just use the default type
         }
 
         // TCCL allows surrounding container to influence class loading policy
         final ClassLoader tccl = Thread.currentThread().getContextClassLoader();
         if (tccl != null) {
             try {
                 return tccl.loadClass(name);
             } catch (final Exception e) {
                 // drop through...
             } catch (final LinkageError e) {
                 // drop through...
             }
         }
 
         // assume custom type is in same class space as default
         final ClassLoader peer = defaultClazz.getClassLoader();
         if (peer != null) {
             try {
                 return peer.loadClass(name);
             } catch (final Exception e) {
                 // drop through...
             } catch (final LinkageError e) {
                 // drop through...
             }
         }
 
         try {
             // last chance - classic model
             return Class.forName(name);
         } catch (final Exception e) {
             throw new TypeNotPresentException(name, e);
         } catch (final LinkageError e) {
             throw new TypeNotPresentException(name, e);
         }
     }
 
     /**
      * Creates an instance of the given implementation using the default constructor.
      *
      * @param clazz The implementation type
      * @return Instance of given implementation
      */
     private static <T> T newImplementation(final Class<T> clazz) {
         try {
             return clazz.newInstance();
         } catch (final Exception e) {
             throw new IllegalArgumentException("Cannot create instance of: " + clazz, e);
         } catch (final LinkageError e) {
             throw new IllegalArgumentException("Cannot create instance of: " + clazz, e);
         }
     }
 
     /**
      * Creates an instance of the given implementation using the given string, assumes a public string constructor.
      *
      * @param clazz The implementation type
      * @param value The string argument
      * @return Instance of given implementation, constructed using the the given string
      */
     private static <T> T newImplementation(final Class<T> clazz, final String value) {
         try {
             return clazz.getConstructor(String.class).newInstance(value);
         } catch (final Exception e) {
             final Throwable cause = e instanceof InvocationTargetException ? e.getCause() : e;
             throw new IllegalArgumentException(String.format(CONVERSION_ERROR, value, clazz), cause);
         } catch (final LinkageError e) {
             throw new IllegalArgumentException(String.format(CONVERSION_ERROR, value, clazz), e);
         }
     }
 
     /**
      * Creates an instance of the implementation named in the current XML element, or the default if no name is given.
      *
      * @param parser The XML parser
      * @param defaultClazz The default implementation type
      * @return Instance of custom implementation if one was given; otherwise instance of default type
      */
     @SuppressWarnings("unchecked")
     private static <T> T newImplementation(final XmlPullParser parser, final Class<T> defaultClazz) {
         return (T) newImplementation(loadImplementation(parseImplementation(parser), defaultClazz));
     }
 
     /**
      * Converts the given string to the target type, using {@link TypeConverter}s registered with the {@link Injector}.
      *
      * @param value The string value
      * @param toType The target type
      * @return Converted instance of the target type
      */
     private Object convertText(final String value, final TypeLiteral<?> toType) {
         final String text = value.trim();
 
         final Class<?> rawType = toType.getRawType();
         if (rawType.isAssignableFrom(String.class)) {
             return text; // compatible type => no conversion needed
         }
 
         // use temporary Key as quick way to auto-box primitive types into their equivalent object types
         final TypeLiteral<?> boxedType =
                 rawType.isPrimitive() ? Key.get(rawType).getTypeLiteral() : toType;
 
         for (final TypeConverterBinding b : typeConverterBindings) {
             if (b.getTypeMatcher().matches(boxedType)) {
                 return b.getTypeConverter().convert(text, toType);
             }
         }
 
         // last chance => attempt to create an instance of the expected type: use the string if non-empty
         return text.length() == 0 ? newImplementation(rawType) : newImplementation(rawType, text);
     }
 }