/**
 * 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.cxf.aegis.type;

import java.beans.PropertyDescriptor;
import java.io.InputStream;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import javax.xml.namespace.QName;
import javax.xml.stream.XMLStreamException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.cxf.aegis.DatabindingException;
import org.apache.cxf.aegis.type.basic.BeanType;
import org.apache.cxf.aegis.type.basic.XMLBeanTypeInfo;
import org.apache.cxf.aegis.util.NamespaceHelper;
import org.apache.cxf.aegis.util.jdom.StaxBuilder;
import org.apache.cxf.common.classloader.ClassLoaderUtils;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.Namespace;
import org.jdom.xpath.XPath;

/**
 * Deduce mapping information from an xml file. The xml file should be in the
 * same packages as the class, with the name <code>className.aegis.xml</code>.
 * For example, given the following service interface: <p/>
 * 
 * <pre>
 * public Collection getResultsForValues(String id, Collection values); //method 1
 * 
 * public Collection getResultsForValues(int id, Collection values); //method 2
 * 
 * public String getResultForValue(String value); //method 3
 * </pre>
 * 
 * An example of the type xml is:
 * 
 * <pre>
 *  &lt;mappings&gt;
 *   &lt;mapping&gt;
 *     &lt;method name=&quot;getResultsForValues&quot;&gt;
 *       &lt;return-type componentType=&quot;com.acme.ResultBean&quot; /&gt;
 *       &lt;!-- no need to specify index 0, since it's a String --&gt;
 *       &lt;parameter index=&quot;1&quot; componentType=&quot;java.lang.String&quot; /&gt;
 *     &lt;/method&gt;
 *   &lt;/mapping&gt;
 *  &lt;/mappings&gt;
 * </pre>
 * 
 * <p/> Note that for values which can be easily deduced (such as the String
 * parameter, or the second service method) no mapping need be specified in the
 * xml descriptor, which is why no mapping is specified for method 3. <p/>
 * However, if you have overloaded methods with different semantics, then you
 * will need to specify enough parameters to disambiguate the method and
 * uniquely identify it. So in the example above, the mapping specifies will
 * apply to both method 1 and method 2, since the parameter at index 0 is not
 * specified.
 * 
 */
public class XMLTypeCreator extends AbstractTypeCreator {
    private static final Log LOG = LogFactory.getLog(XMLTypeCreator.class);
    private static List<Class> stopClasses = new ArrayList<Class>();
    static {
        stopClasses.add(Object.class);
        stopClasses.add(Exception.class);
        stopClasses.add(RuntimeException.class);
        stopClasses.add(Throwable.class);
    }

    // cache of classes to documents
    private Map<String, Document> documents = new HashMap<String, Document>();


    protected Document getDocument(Class clazz) {
        if (clazz == null) {
            return null;
        }
        Document doc = documents.get(clazz.getName());
        if (doc != null) {
            return doc;
        }
        String path = '/' + clazz.getName().replace('.', '/') + ".aegis.xml";
        InputStream is = clazz.getResourceAsStream(path);
        if (is == null) {
            LOG.debug("Mapping file : " + path + " not found.");
            return null;
        }
        LOG.debug("Found mapping file : " + path);
        try {
            doc = new StaxBuilder().build(is);
            documents.put(clazz.getName(), doc);
            return doc;
        } catch (XMLStreamException e) {
            LOG.error("Error loading file " + path, e);
        }
        return null;
    }

    @Override
    protected boolean isEnum(Class javaType) {
        Element mapping = findMapping(javaType);
        if (mapping != null) {
            return super.isEnum(javaType);
        } else {
            return nextCreator.isEnum(javaType);
        }
    }

    @Override
    public Type createEnumType(TypeClassInfo info) {
        Element mapping = findMapping(info.getTypeClass());
        if (mapping != null) {
            return super.createEnumType(info);
        } else {
            return nextCreator.createEnumType(info);
        }
    }

    @Override
    public Type createCollectionType(TypeClassInfo info) {
        if (info.getGenericType() instanceof Class || info.getGenericType() instanceof TypeClassInfo) {
            return createCollectionTypeFromGeneric(info);
        }

        return nextCreator.createCollectionType(info);
    }

    @Override
    public TypeClassInfo createClassInfo(PropertyDescriptor pd) {
        Element mapping = findMapping(pd.getReadMethod().getDeclaringClass());
        if (mapping == null) {
            return nextCreator.createClassInfo(pd);
        }

        Element propertyEl = getMatch(mapping, "./property[@name='" + pd.getName() + "']");
        if (propertyEl == null) {
            return nextCreator.createClassInfo(pd);
        }

        TypeClassInfo info = new TypeClassInfo();
        info.setTypeClass(pd.getReadMethod().getReturnType());
        readMetadata(info, mapping, propertyEl);

        return info;
    }

    protected Element findMapping(Class clazz) {
        Document doc = getDocument(clazz);
        if (doc == null) {
            return null;
        }

        Element mapping = getMatch(doc, "/mappings/mapping[@uri='" + getTypeMapping().getEncodingStyleURI()
                                        + "']");
        if (mapping == null) {
            mapping = getMatch(doc, "/mappings/mapping[not(@uri)]");
        }

        return mapping;
    }

    protected List<Element> findMappings(Class clazz) {
        List<Element> mappings = new ArrayList<Element>();

        Element top = findMapping(clazz);
        if (top != null) {
            mappings.add(top);
        }

        Class parent = clazz;
        while (true) {

            // Read mappings for interfaces as well
            Class[] interfaces = parent.getInterfaces();
            for (int i = 0; i < interfaces.length; i++) {
                Class interfaze = interfaces[i];
                List<Element> interfaceMappings = findMappings(interfaze);
                mappings.addAll(interfaceMappings);
            }

            Class sup = parent.getSuperclass();

            if (sup == null || stopClasses.contains(sup)) {
                break;
            }

            Element mapping = findMapping(sup);
            if (mapping != null) {
                mappings.add(mapping);
            }

            parent = sup;
        }

        return mappings;
    }

    @Override
    public Type createDefaultType(TypeClassInfo info) {
        Element mapping = findMapping(info.getTypeClass());
        List mappings = findMappings(info.getTypeClass());

        if (mapping != null || mappings.size() > 0) {
            String typeNameAtt = null;
            if (mapping != null) {
                typeNameAtt = mapping.getAttributeValue("name");
            }

            String extensibleElements = null;
            if (mapping != null) {
                extensibleElements = mapping.getAttributeValue("extensibleElements");
            }

            String extensibleAttributes = null;
            if (mapping != null) {
                extensibleAttributes = mapping.getAttributeValue("extensibleAttributes");
            }

            String defaultNS = NamespaceHelper.makeNamespaceFromClassName(info.getTypeClass().getName(),
                                                                          "http");
            QName name = null;
            if (typeNameAtt != null) {
                name = NamespaceHelper.createQName(mapping, typeNameAtt, defaultNS);

                defaultNS = name.getNamespaceURI();
            }

            XMLBeanTypeInfo btinfo = new XMLBeanTypeInfo(info.getTypeClass(), mappings, defaultNS);
            btinfo.setTypeMapping(getTypeMapping());
            btinfo.setDefaultMinOccurs(getConfiguration().getDefaultMinOccurs());
            btinfo.setDefaultNillable(getConfiguration().isDefaultNillable());

            if (extensibleElements != null) {
                btinfo.setExtensibleElements(Boolean.valueOf(extensibleElements).booleanValue());
            } else {
                btinfo.setExtensibleElements(getConfiguration().isDefaultExtensibleElements());
            }

            if (extensibleAttributes != null) {
                btinfo.setExtensibleAttributes(Boolean.valueOf(extensibleAttributes).booleanValue());
            } else {
                btinfo.setExtensibleAttributes(getConfiguration().isDefaultExtensibleAttributes());
            }

            BeanType type = new BeanType(btinfo);

            if (name == null) {
                name = createQName(info.getTypeClass());
            }

            type.setSchemaType(name);

            type.setTypeClass(info.getTypeClass());
            type.setTypeMapping(getTypeMapping());

            return type;
        } else {
            return nextCreator.createDefaultType(info);
        }
    }

    @Override
    public TypeClassInfo createClassInfo(Method m, int index) {
        Element mapping = findMapping(m.getDeclaringClass());

        if (mapping == null) {
            return nextCreator.createClassInfo(m, index);
        }

        // find the elements that apply to the specified method
        TypeClassInfo info = new TypeClassInfo();
        if (index >= 0) {
            if (index >= m.getParameterTypes().length) {
                throw new DatabindingException("Method " + m 
                                               + " does not have a parameter at index " 
                                               + index);
            }
            // we don't want nodes for which the specified index is not
            // specified
            List<Element> nodes = getMatches(mapping, "./method[@name='" + m.getName()
                                                      + "']/parameter[@index='" + index + "']/parent::*");
            if (nodes.size() == 0) {
                // no mapping for this method
                return nextCreator.createClassInfo(m, index);
            }
            // pick the best matching node
            Element bestMatch = getBestMatch(mapping, m, nodes);

            if (bestMatch == null) {
                // no mapping for this method
                return nextCreator.createClassInfo(m, index);
            }
            info.setTypeClass(m.getParameterTypes()[index]);
            // info.setAnnotations(m.getParameterAnnotations()[index]);
            Element parameter = getMatch(bestMatch, "parameter[@index='" + index + "']");
            readMetadata(info, mapping, parameter);
        } else {
            List<Element> nodes = getMatches(mapping, "./method[@name='" + m.getName()
                                                      + "']/return-type/parent::*");
            if (nodes.size() == 0) {
                return nextCreator.createClassInfo(m, index);
            }
            Element bestMatch = getBestMatch(mapping, m, nodes);
            if (bestMatch == null) {
                // no mapping for this method
                return nextCreator.createClassInfo(m, index);
            }
            info.setTypeClass(m.getReturnType());
            // info.setAnnotations(m.getAnnotations());
            Element rtElement = bestMatch.getChild("return-type");
            readMetadata(info, mapping, rtElement);
        }

        return info;
    }

    protected void readMetadata(TypeClassInfo info, Element mapping, Element parameter) {
        info.setTypeName(createQName(parameter, parameter.getAttributeValue("typeName")));
        info.setMappedName(createQName(parameter, parameter.getAttributeValue("mappedName")));
        setComponentType(info, mapping, parameter);
        setKeyType(info, mapping, parameter);
        setType(info, parameter);

        String min = parameter.getAttributeValue("minOccurs");
        if (min != null) {
            info.setMinOccurs(Long.parseLong(min));
        }

        String max = parameter.getAttributeValue("maxOccurs");
        if (max != null) {
            info.setMaxOccurs(Long.parseLong(max));
        }

        String flat = parameter.getAttributeValue("flat");
        if (flat != null) {
            info.setFlat(Boolean.valueOf(flat.toLowerCase()).booleanValue());
        }
    }

    @Override
    protected Type getOrCreateGenericType(TypeClassInfo info) {
        Type type = null;
        if (info.getGenericType() != null) {
            type = createTypeFromGeneric(info.getGenericType());
        }

        if (type == null) {
            type = super.getOrCreateGenericType(info);
        }

        return type;
    }

    private Type createTypeFromGeneric(Object cType) {
        if (cType instanceof TypeClassInfo) {
            return createTypeForClass((TypeClassInfo)cType);
        } else if (cType instanceof Class) {
            return createType((Class)cType);
        } else {
            return null;
        }
    }

    @Override
    protected Type getOrCreateMapKeyType(TypeClassInfo info) {
        Type type = null;
        if (info.getKeyType() != null) {
            type = createTypeFromGeneric(info.getKeyType());
        }

        if (type == null) {
            type = super.getOrCreateMapKeyType(info);
        }

        return type;
    }

    @Override
    protected Type getOrCreateMapValueType(TypeClassInfo info) {
        Type type = null;
        if (info.getGenericType() != null) {
            type = createTypeFromGeneric(info.getGenericType());
        }

        if (type == null) {
            type = super.getOrCreateMapValueType(info);
        }

        return type;
    }

    protected void setComponentType(TypeClassInfo info, Element mapping, Element parameter) {
        String componentType = parameter.getAttributeValue("componentType");
        if (componentType != null) {
            info.setGenericType(loadGeneric(info, mapping, componentType));
        }
    }

    private Object loadGeneric(TypeClassInfo info, Element mapping, String componentType) {
        if (componentType.startsWith("#")) {
            String name = componentType.substring(1);
            Element propertyEl = getMatch(mapping, "./component[@name='" + name + "']");
            if (propertyEl == null) {
                throw new DatabindingException("Could not find <component> element in mapping named '" + name
                                               + "'");
            }

            TypeClassInfo componentInfo = new TypeClassInfo();
            readMetadata(componentInfo, mapping, propertyEl);
            String className = propertyEl.getAttributeValue("class");
            if (className == null) {
                throw new DatabindingException("A 'class' attribute must be specified for <component> "
                                               + name);
            }

            componentInfo.setTypeClass(loadComponentClass(className));

            return componentInfo;
        } else {
            return loadComponentClass(componentType);
        }
    }

    private Class loadComponentClass(String componentType) {
        try {
            return ClassLoaderUtils.loadClass(componentType, getClass());
        } catch (ClassNotFoundException e) {
            throw new DatabindingException("Unable to load component type class " + componentType, e);
        }
    }

    protected void setType(TypeClassInfo info, Element parameter) {
        String type = parameter.getAttributeValue("type");
        if (type != null) {
            try {
                info.setType(ClassLoaderUtils.loadClass(type, getClass()));
            } catch (ClassNotFoundException e) {
                throw new DatabindingException("Unable to load type class " + type, e);
            }
        }
    }

    protected void setKeyType(TypeClassInfo info, Element mapping, Element parameter) {
        String componentType = parameter.getAttributeValue("keyType");
        if (componentType != null) {
            info.setKeyType(loadGeneric(info, mapping, componentType));
        }
    }

    private Element getBestMatch(Element mapping, Method method, List<Element> availableNodes) {
        // first find all the matching method names
        List<Element> nodes = getMatches(mapping, "./method[@name='" + method.getName() + "']");
        // remove the ones that aren't in our acceptable set, if one is
        // specified
        if (availableNodes != null) {
            nodes.retainAll(availableNodes);
        }
        // no name found, so no matches
        if (nodes.size() == 0) {
            return null;
        }
        // if the method has no params, then more than one mapping is pointless
        Class[] parameterTypes = method.getParameterTypes();
        if (parameterTypes.length == 0) {
            return nodes.get(0);
        }
        // here's the fun part.
        // we go through the method parameters, ruling out matches
        for (int i = 0; i < parameterTypes.length; i++) {
            Class parameterType = parameterTypes[i];
            for (Iterator iterator = nodes.iterator(); iterator.hasNext();) {
                Element element = (Element)iterator.next();
                // first we check if the parameter index is specified
                Element match = getMatch(element, "parameter[@index='" + i + "']");
                if (match != null
                    // we check if the type is specified and matches
                    && match.getAttributeValue("class") != null
                    // if it doesn't match, then we can definitely rule out
                    // this result
                    && !match.getAttributeValue("class").equals(parameterType.getName())) {
                    
                    iterator.remove();                    
                }
            }
        }
        // if we have just one node left, then it has to be the best match
        if (nodes.size() == 1) {
            return nodes.get(0);
        }
        // all remaining definitions could apply, so we need to now pick the
        // best one
        // the best one is the one with the most parameters specified
        Element bestCandidate = null;
        int highestSpecified = 0;
        for (Iterator iterator = nodes.iterator(); iterator.hasNext();) {
            Element element = (Element)iterator.next();
            int availableParameters = element.getChildren("parameter").size();
            if (availableParameters > highestSpecified) {
                bestCandidate = element;
                highestSpecified = availableParameters;
            }
        }
        return bestCandidate;
    }

    private Element getMatch(Object doc, String xpath) {
        try {
            XPath path = XPath.newInstance(xpath);
            return (Element)path.selectSingleNode(doc);
        } catch (JDOMException e) {
            throw new DatabindingException("Error evaluating xpath " + xpath, e);
        }
    }

    @SuppressWarnings("unchecked")
    private List<Element> getMatches(Object doc, String xpath) {
        try {
            XPath path = XPath.newInstance(xpath);
            return path.selectNodes(doc);
        } catch (JDOMException e) {
            throw new DatabindingException("Error evaluating xpath " + xpath, e);
        }
    }

    /**
     * Creates a QName from a string, such as "ns:Element".
     */
    protected QName createQName(Element e, String value) {
        if (value == null || value.length() == 0) {
            return null;
        }

        int index = value.indexOf(":");

        if (index == -1) {
            return new QName(getTypeMapping().getEncodingStyleURI(), value);
        }

        String prefix = value.substring(0, index);
        String localName = value.substring(index + 1);
        Namespace ns = e.getNamespace(prefix);

        if (ns == null || localName == null) {
            throw new DatabindingException("Invalid QName in mapping: " + value);
        }

        return new QName(ns.getURI(), localName, prefix);
    }
}
