/*
 * 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.tomcat.util.modeler.modules;

import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.management.ObjectName;

import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.modeler.AttributeInfo;
import org.apache.tomcat.util.modeler.ManagedBean;
import org.apache.tomcat.util.modeler.OperationInfo;
import org.apache.tomcat.util.modeler.ParameterInfo;
import org.apache.tomcat.util.modeler.Registry;
import org.apache.tomcat.util.res.StringManager;

/**
 * Source for creating MBean descriptors through introspection.
 */
public class MbeansDescriptorsIntrospectionSource extends ModelerSource {
    /**
     * Default constructor.
     */
    public MbeansDescriptorsIntrospectionSource() {
    }

    /**
     * The log instance for this class.
     */
    private static final Log log = LogFactory.getLog(MbeansDescriptorsIntrospectionSource.class);
    private static final StringManager sm = StringManager.getManager(MbeansDescriptorsIntrospectionSource.class);

    private Registry registry;
    private String type;
    private final List<ObjectName> mbeans = new ArrayList<>();

    /**
     * Set the registry.
     *
     * @param reg the registry to set
     */
    public void setRegistry(Registry reg) {
        this.registry = reg;
    }

    /**
     * Used if a single component is loaded
     *
     * @param type The type
     */
    public void setType(String type) {
        this.type = type;
    }

    /**
     * Set the source.
     *
     * @param source the source to set
     */
    public void setSource(Object source) {
        this.source = source;
    }

    @Override
    public List<ObjectName> loadDescriptors(Registry registry, String type, Object source) throws Exception {
        setRegistry(registry);
        setType(type);
        setSource(source);
        execute();
        return mbeans;
    }

    /**
     * Execute the descriptor loading.
     *
     * @throws Exception if an error occurs
     */
    public void execute() throws Exception {
        if (registry == null) {
            registry = Registry.getRegistry(null);
        }
        try {
            ManagedBean managed = createManagedBean(registry, null, (Class<?>) source, type);
            if (managed == null) {
                return;
            }
            managed.setName(type);

            registry.addManagedBean(managed);

        } catch (Exception e) {
            log.error(sm.getString("modules.readDescriptorsError"), e);
        }
    }


    // ------------ Implementation for non-declared introspection classes

    private static final Map<String,String> specialMethods = new HashMap<>();
    static {
        specialMethods.put("preDeregister", "");
        specialMethods.put("postDeregister", "");
    }

    private static final Class<?>[] supportedTypes = new Class[] { Boolean.class, Boolean.TYPE, Byte.class, Byte.TYPE,
            Character.class, Character.TYPE, Short.class, Short.TYPE, Integer.class, Integer.TYPE, Long.class,
            Long.TYPE, Float.class, Float.TYPE, Double.class, Double.TYPE, String.class, String[].class,
            BigDecimal.class, BigInteger.class, ObjectName.class, Object[].class, java.io.File.class, };

    /**
     * Check if this class is one of the supported types. If the class is supported, returns true. Otherwise, returns
     * false.
     *
     * @param ret The class to check
     *
     * @return boolean True if class is supported
     */
    private boolean supportedType(Class<?> ret) {
        for (Class<?> supportedType : supportedTypes) {
            if (ret == supportedType) {
                return true;
            }
        }
        return isBeanCompatible(ret);
    }

    /**
     * Check if this class conforms to JavaBeans specifications. If the class is conformant, returns true.
     *
     * @param javaType The class to check
     *
     * @return boolean True if the class is compatible.
     */
    private boolean isBeanCompatible(Class<?> javaType) {
        // Must be a non-primitive and non array
        if (javaType.isArray() || javaType.isPrimitive()) {
            return false;
        }

        // Anything in the java or javax package that
        // does not have a defined mapping is excluded.
        if (javaType.getName().startsWith("java.") || javaType.getName().startsWith("javax.")) {
            return false;
        }

        try {
            javaType.getConstructor();
        } catch (NoSuchMethodException e) {
            return false;
        }

        // Make sure superclass is compatible
        Class<?> superClass = javaType.getSuperclass();
        if (superClass != null && superClass != Object.class && superClass != Exception.class &&
                superClass != Throwable.class) {
            return isBeanCompatible(superClass);
        }
        return true;
    }

    /**
     * Process the methods and extract 'attributes', methods, etc.
     *
     * @param realClass     The class to process
     * @param attNames      The attribute name (complete)
     * @param getAttMap     The readable attributes map
     * @param setAttMap     The settable attributes map
     * @param invokeAttList The invokable attributes list
     */
    private void initMethods(Class<?> realClass, Set<String> attNames, Map<String,Method> getAttMap,
            Map<String,Method> setAttMap, List<Method> invokeAttList) {

        Method[] methods = realClass.getMethods();
        for (Method method : methods) {
            String name = method.getName();

            if (Modifier.isStatic(method.getModifiers())) {
                continue;
            }
            if (!Modifier.isPublic(method.getModifiers())) {
                if (log.isTraceEnabled()) {
                    log.trace("Not public " + method);
                }
                continue;
            }
            if (method.getDeclaringClass() == Object.class) {
                continue;
            }
            Class<?>[] params = method.getParameterTypes();

            if (name.startsWith("get") && params.length == 0) {
                Class<?> ret = method.getReturnType();
                if (!supportedType(ret)) {
                    if (log.isTraceEnabled()) {
                        log.trace("Unsupported type " + method);
                    }
                    continue;
                }
                name = unCapitalize(name.substring(3));

                getAttMap.put(name, method);
                attNames.add(name);
            } else if (name.startsWith("is") && params.length == 0) {
                Class<?> ret = method.getReturnType();
                if (Boolean.TYPE != ret) {
                    if (log.isTraceEnabled()) {
                        log.trace("Unsupported type " + method + " " + ret);
                    }
                    continue;
                }
                name = unCapitalize(name.substring(2));

                getAttMap.put(name, method);
                attNames.add(name);

            } else if (name.startsWith("set") && params.length == 1) {
                if (!supportedType(params[0])) {
                    if (log.isTraceEnabled()) {
                        log.trace("Unsupported type " + method + " " + params[0]);
                    }
                    continue;
                }
                name = unCapitalize(name.substring(3));
                setAttMap.put(name, method);
                attNames.add(name);
            } else {
                if (params.length == 0) {
                    if (specialMethods.get(name) != null) {
                        continue;
                    }
                    invokeAttList.add(method);
                } else {
                    boolean supported = true;
                    for (Class<?> param : params) {
                        if (!supportedType(param)) {
                            supported = false;
                            break;
                        }
                    }
                    if (supported) {
                        invokeAttList.add(method);
                    }
                }
            }
        }
    }

    /**
     * XXX Find if the 'className' is the name of the MBean or the real class ( I suppose first ) XXX Read (optional)
     * descriptions from a .properties, generated from source XXX Deal with constructors
     *
     * @param registry  The Bean registry (not used)
     * @param domain    The bean domain (not used)
     * @param realClass The class to analyze
     * @param type      The bean type
     *
     * @return ManagedBean The create MBean
     */
    public ManagedBean createManagedBean(Registry registry, String domain, Class<?> realClass, String type) {
        ManagedBean mbean = new ManagedBean();


        Set<String> attrNames = new HashSet<>();
        // key: attribute val: getter method
        Map<String,Method> getAttMap = new HashMap<>();
        // key: attribute val: setter method
        Map<String,Method> setAttMap = new HashMap<>();
        // key: operation val: invoke method
        List<Method> invokeAttList = new ArrayList<>();

        initMethods(realClass, attrNames, getAttMap, setAttMap, invokeAttList);

        try {
            for (String name : attrNames) {
                AttributeInfo ai = new AttributeInfo();
                ai.setName(name);
                Method gm = getAttMap.get(name);
                if (gm != null) {
                    ai.setGetMethod(gm.getName());
                    Class<?> t = gm.getReturnType();
                    ai.setType(t.getName());
                }
                Method sm = setAttMap.get(name);
                if (sm != null) {
                    Class<?> t = sm.getParameterTypes()[0];
                    ai.setType(t.getName());
                    ai.setSetMethod(sm.getName());
                }
                ai.setDescription("Introspected attribute " + name);
                if (log.isTraceEnabled()) {
                    log.trace("Introspected attribute " + name + " " + gm + " " + sm);
                }
                if (gm == null) {
                    ai.setReadable(false);
                }
                if (sm == null) {
                    ai.setWriteable(false);
                }
                if (sm != null || gm != null) {
                    mbean.addAttribute(ai);
                }
            }

            for (Method method : invokeAttList) {
                String name = method.getName();
                OperationInfo op = new OperationInfo();
                op.setName(name);
                op.setReturnType(method.getReturnType().getName());
                op.setDescription("Introspected operation " + name);
                Class<?>[] params = method.getParameterTypes();
                for (int i = 0; i < params.length; i++) {
                    ParameterInfo pi = new ParameterInfo();
                    pi.setType(params[i].getName());
                    pi.setName(("param" + i).intern());
                    pi.setDescription(("Introspected parameter param" + i).intern());
                    op.addParameter(pi);
                }
                mbean.addOperation(op);
            }

            if (log.isTraceEnabled()) {
                log.trace("Setting name: " + type);
            }
            mbean.setName(type);

            return mbean;
        } catch (Exception e) {
            log.error(sm.getString("source.introspectionError", realClass.getName()), e);
            return null;
        }
    }


    // -------------------- Utils --------------------
    /**
     * Converts the first character of the given String into lower-case.
     *
     * @param name The string to convert
     *
     * @return String
     */
    private static String unCapitalize(String name) {
        if (name == null || name.isEmpty()) {
            return name;
        }
        char[] chars = name.toCharArray();
        chars[0] = Character.toLowerCase(chars[0]);
        return new String(chars);
    }

}

