/**
 * 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.jaxrs.impl;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.ServiceLoader;
import java.util.Set;
import java.util.logging.Logger;
import java.util.stream.Collectors;

import javax.ws.rs.ConstrainedTo;
import javax.ws.rs.Priorities;
import javax.ws.rs.RuntimeType;
import javax.ws.rs.client.ClientRequestFilter;
import javax.ws.rs.client.ClientResponseFilter;
import javax.ws.rs.container.ContainerRequestFilter;
import javax.ws.rs.container.ContainerResponseFilter;
import javax.ws.rs.core.Configurable;
import javax.ws.rs.core.Configuration;
import javax.ws.rs.core.Feature;

import org.apache.cxf.common.logging.LogUtils;
import org.apache.cxf.jaxrs.utils.AnnotationUtils;

public class ConfigurableImpl<C extends Configurable<C>> implements Configurable<C>, AutoCloseable {
    private static final Logger LOG = LogUtils.getL7dLogger(ConfigurableImpl.class);
    
    private static final Class<?>[] RESTRICTED_CLASSES_IN_SERVER = {ClientRequestFilter.class, 
                                                                    ClientResponseFilter.class};
    private static final Class<?>[] RESTRICTED_CLASSES_IN_CLIENT = {ContainerRequestFilter.class, 
                                                                    ContainerResponseFilter.class};
    
    private ConfigurationImpl config;
    private final C configurable;
    private final ClassLoader classLoader;

    private final Class<?>[] restrictedContractTypes;

    private final Collection<Object> instantiatorInstances = new ArrayList<>();
    private volatile Instantiator instantiator;

    public interface Instantiator {
        <T> Object create(Class<T> cls);

        default void release(Object instance) {
            // no-op
        }
    }
    
    public ConfigurableImpl(C configurable, RuntimeType rt) {
        this(configurable, new ConfigurationImpl(rt));
    }
    
    public ConfigurableImpl(C configurable, Configuration config) {
        this.configurable = configurable;
        this.config = config instanceof ConfigurationImpl
            ? (ConfigurationImpl)config : new ConfigurationImpl(config);
        this.classLoader = Thread.currentThread().getContextClassLoader();
        restrictedContractTypes = RuntimeType.CLIENT == config.getRuntimeType() ? RESTRICTED_CLASSES_IN_CLIENT
            : RESTRICTED_CLASSES_IN_SERVER;
    }

    static Class<?>[] getImplementedContracts(Object provider, Class<?>[] restrictedClasses) {
        Class<?> providerClass = provider instanceof Class<?> ? ((Class<?>)provider) : provider.getClass();

        Set<Class<?>> interfaces = collectAllInterfaces(providerClass);

        List<Class<?>> implementedContracts = interfaces.stream()
            .filter(el -> Arrays.stream(restrictedClasses).noneMatch(el::equals))
            .collect(Collectors.toList());

        return implementedContracts.toArray(new Class<?>[]{});
    }

    private static Set<Class<?>> collectAllInterfaces(Class<?> providerClass) {
        Set<Class<?>> interfaces = new HashSet<>();
        do {
            for (Class<?> anInterface : providerClass.getInterfaces()) {
                collectInterfaces(interfaces, anInterface);
            }
            providerClass = providerClass.getSuperclass();
        } while (providerClass != null && providerClass != Object.class);

        return interfaces;
    }

    /**
     * internal helper function to recursively collect Interfaces.
     * This is needed since {@link Class#getInterfaces()} does only return directly implemented Interfaces,
     * But not the ones derived from those classes.
     */
    private static void collectInterfaces(Set<Class<?>> interfaces, Class<?> anInterface) {
        interfaces.add(anInterface);
        for (Class<?> superInterface : anInterface.getInterfaces()) {
            collectInterfaces(interfaces, superInterface);
        }
    }

    protected C getConfigurable() {
        return configurable;
    }

    @Override
    public void close() {
        synchronized (instantiatorInstances) {
            if (instantiatorInstances.isEmpty()) {
                return;
            }
            instantiatorInstances.forEach(instantiator::release);
            instantiatorInstances.clear();
        }
    }

    @Override
    public Configuration getConfiguration() {
        return config;
    }

    @Override
    public C property(String name, Object value) {
        config.setProperty(name, value);
        return configurable;
    }

    @Override
    public C register(Object provider) {
        return register(provider, AnnotationUtils.getBindingPriority(provider.getClass()));
    }

    @Override
    public C register(Object provider, int bindingPriority) {
        if (Instantiator.class.isInstance(provider)) {
            synchronized (this) {
                instantiator = Instantiator.class.cast(provider);
            }
            return configurable;
        }
        return doRegister(provider, bindingPriority, getImplementedContracts(provider, restrictedContractTypes));
    }

    @Override
    public C register(Object provider, Class<?>... contracts) {
        return doRegister(provider, Priorities.USER, contracts);
    }

    @Override
    public C register(Object provider, Map<Class<?>, Integer> contracts) {
        return doRegister(provider, contracts);
    }

    @Override
    public C register(Class<?> providerClass) {
        return register(providerClass, AnnotationUtils.getBindingPriority(providerClass));
    }

    @Override
    public C register(Class<?> providerClass, int bindingPriority) {
        return doRegister(createProvider(providerClass), bindingPriority,
                          getImplementedContracts(providerClass, restrictedContractTypes));
    }

    @Override
    public C register(Class<?> providerClass, Class<?>... contracts) {
        return doRegister(providerClass, Priorities.USER, contracts);
    }

    @Override
    public C register(Class<?> providerClass, Map<Class<?>, Integer> contracts) {
        return register(createProvider(providerClass), contracts);
    }

    protected Instantiator getInstantiator() {
        if (instantiator != null) {
            return instantiator;
        }
        synchronized (this) {
            if (instantiator != null) {
                return instantiator;
            }
            final Iterator<Instantiator> instantiators = ServiceLoader.load(Instantiator.class, classLoader).iterator();
            if (instantiators.hasNext()) {
                instantiator = instantiators.next();
            } else {
                instantiator = ConfigurationImpl::createProvider;
            }
        }
        return instantiator;
    }

    private C doRegister(Object provider, int bindingPriority, Class<?>... contracts) {
        if (contracts == null || contracts.length == 0) {
            LOG.warning("Null, empty or invalid contracts specified for " + provider + "; ignoring.");
            return configurable;
        }
        return doRegister(provider, ConfigurationImpl.initContractsMap(bindingPriority, contracts));
    }

    private C doRegister(Object provider, Map<Class<?>, Integer> contracts) {
        if (!checkConstraints(provider)) {
            return configurable;
        }
        if (provider instanceof Feature) {
            Feature feature = (Feature)provider;
            boolean enabled = feature.configure(new FeatureContextImpl(this));
            config.setFeature(feature, enabled);

            return configurable;
        }
        config.register(provider, contracts);
        return configurable;
    }

    private boolean checkConstraints(Object provider) {
        Class<?> providerClass = provider.getClass();
        ConstrainedTo providerConstraint = providerClass.getAnnotation(ConstrainedTo.class);
        if (providerConstraint != null) {
            RuntimeType currentRuntime = config.getRuntimeType();
            RuntimeType providerRuntime = providerConstraint.value();
            // need to check (1) whether the registration is occurring in the specified runtime type
            // and (2) does the provider implement an invalid interface based on the constrained runtime type
            if (providerRuntime != currentRuntime) {
                LOG.warning("Provider " + provider + " cannot be registered in this " + currentRuntime
                            + " runtime because it is constrained to " + providerRuntime + " runtimes.");
                return false;
            }
            
            Class<?>[] restrictedInterfaces = RuntimeType.CLIENT == providerRuntime ? RESTRICTED_CLASSES_IN_CLIENT
                                                                                         : RESTRICTED_CLASSES_IN_SERVER;
            for (Class<?> restrictedContract : restrictedInterfaces) {
                if (restrictedContract.isAssignableFrom(providerClass)) {
                    RuntimeType opposite = RuntimeType.CLIENT == providerRuntime ? RuntimeType.SERVER
                                                                                      : RuntimeType.CLIENT;
                    LOG.warning("Provider " + providerClass.getName() + " is invalid - it is constrained to "
                        + providerRuntime + " runtimes but implements a " + opposite + " interface ");
                    return false;
                }
            }
        }
        return true;
    }

    private Object createProvider(final Class<?> providerClass) {
        final Object instance = getInstantiator().create(providerClass);
        synchronized (instantiatorInstances) {
            instantiatorInstances.add(instance);
        }
        return instance;
    }
}

