/components/camel-guice/src/main/java/org/apache/camel/guice/inject/Injectors.java

/**
 * 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.camel.guice.inject;

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Type;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.StringTokenizer;

import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
import com.google.inject.AbstractModule;
import com.google.inject.Binding;
import com.google.inject.Guice;
import com.google.inject.Injector;
import com.google.inject.Key;
import com.google.inject.Module;
import com.google.inject.Provider;
import com.google.inject.Scope;
import com.google.inject.Singleton;
import com.google.inject.TypeLiteral;
import com.google.inject.internal.BindingImpl;
import com.google.inject.internal.Scoping;
import com.google.inject.matcher.Matcher;
import com.google.inject.name.Names;
import com.google.inject.util.Modules;

import org.apache.camel.guice.jndi.GuiceInitialContextFactory;
import org.apache.camel.guice.jndi.internal.Classes;
import org.apache.camel.guice.support.CloseErrors;
import org.apache.camel.guice.support.CloseFailedException;
import org.apache.camel.guice.support.Closer;
import org.apache.camel.guice.support.Closers;
import org.apache.camel.guice.support.CompositeCloser;
import org.apache.camel.guice.support.HasScopeAnnotation;
import org.apache.camel.guice.support.internal.CloseErrorsImpl;

@SuppressWarnings({ "rawtypes", "unchecked" })
public final class Injectors {
    public static final String MODULE_CLASS_NAMES = "org.guiceyfruit.modules";

    private Injectors() {
        //Helper class
    }
    /**
     * Creates an injector from the given properties, loading any modules define
     * by the {@link #MODULE_CLASS_NAMES} property value (space separated) along
     * with any other modules passed as an argument.
     * 
     * @param environment
     *            the properties used to create the injector
     * @param overridingModules
     *            any modules which override the modules referenced in the
     *            environment such as to provide the actual JNDI context
     */
    public static Injector createInjector(final Map environment,
            Module... overridingModules) throws ClassNotFoundException,
            IllegalAccessException, InstantiationException {
        List<Module> modules = Lists.newArrayList();

        // lets bind the properties
        modules.add(new AbstractModule() {
            protected void configure() {
                Names.bindProperties(binder(), environment);
            }
        });

        Object moduleValue = environment.get(MODULE_CLASS_NAMES);
        if (moduleValue instanceof String) {
            String names = (String) moduleValue;
            StringTokenizer iter = new StringTokenizer(names);
            while (iter.hasMoreTokens()) {
                String moduleName = iter.nextToken();
                Module module = loadModule(moduleName);
                if (module != null) {
                    modules.add(module);
                }
            }
        }
        Injector injector = Guice.createInjector(Modules.override(modules)
                .with(overridingModules));
        return injector;
    }

    /**
     * Returns an instance of the given type with the
     * {@link com.google.inject.name.Named} annotation value.
     * 
     * This method allows you to switch this code
     * <code>injector.getInstance(Key.get(type, Names.named(name)));</code>
     * 
     * to the more concise
     * <code>Injectors.getInstance(injector, type, name);</code>
     */
    public static <T> T getInstance(Injector injector, java.lang.Class<T> type,
            String name) {
        return injector.getInstance(Key.get(type, Names.named(name)));
    }

    /**
     * Returns a collection of all instances of the given base type
     * 
     * @param baseClass
     *            the base type of objects required
     * @param <T>
     *            the base type
     * @return a set of objects returned from this injector
     */
    public static <T> Set<T> getInstancesOf(Injector injector,
            Class<T> baseClass) {
        Set<T> answer = Sets.newHashSet();
        Set<Entry<Key<?>, Binding<?>>> entries = injector.getBindings()
                .entrySet();
        for (Entry<Key<?>, Binding<?>> entry : entries) {
            Key<?> key = entry.getKey();
            Class<?> keyType = getKeyType(key);
            if (keyType != null && baseClass.isAssignableFrom(keyType)) {
                Binding<?> binding = entry.getValue();
                Object value = binding.getProvider().get();
                if (value != null) {
                    T castValue = baseClass.cast(value);
                    answer.add(castValue);
                }
            }
        }
        return answer;
    }

    /**
     * Returns a collection of all instances matching the given matcher
     * 
     * @param matcher
     *            matches the types to return instances
     * @return a set of objects returned from this injector
     */
    public static <T> Set<T> getInstancesOf(Injector injector,
            Matcher<Class> matcher) {
        Set<T> answer = Sets.newHashSet();
        Set<Entry<Key<?>, Binding<?>>> entries = injector.getBindings()
                .entrySet();
        for (Entry<Key<?>, Binding<?>> entry : entries) {
            Key<?> key = entry.getKey();
            Class<?> keyType = getKeyType(key);
            if (keyType != null && matcher.matches(keyType)) {
                Binding<?> binding = entry.getValue();
                Object value = binding.getProvider().get();
                answer.add((T) value);
            }
        }
        return answer;
    }

    /**
     * Returns a collection of all of the providers matching the given matcher
     * 
     * @param matcher
     *            matches the types to return instances
     * @return a set of objects returned from this injector
     */
    public static <T> Set<Provider<T>> getProvidersOf(Injector injector,
            Matcher<Class> matcher) {
        Set<Provider<T>> answer = Sets.newHashSet();
        Set<Entry<Key<?>, Binding<?>>> entries = injector.getBindings()
                .entrySet();
        for (Entry<Key<?>, Binding<?>> entry : entries) {
            Key<?> key = entry.getKey();
            Class<?> keyType = getKeyType(key);
            if (keyType != null && matcher.matches(keyType)) {
                Binding<?> binding = entry.getValue();
                answer.add((Provider<T>) binding.getProvider());
            }
        }
        return answer;
    }

    /**
     * Returns a collection of all providers of the given base type
     * 
     * @param baseClass
     *            the base type of objects required
     * @param <T>
     *            the base type
     * @return a set of objects returned from this injector
     */
    public static <T> Set<Provider<T>> getProvidersOf(Injector injector,
            Class<T> baseClass) {
        Set<Provider<T>> answer = Sets.newHashSet();
        Set<Entry<Key<?>, Binding<?>>> entries = injector.getBindings()
                .entrySet();
        for (Entry<Key<?>, Binding<?>> entry : entries) {
            Key<?> key = entry.getKey();
            Class<?> keyType = getKeyType(key);
            if (keyType != null && baseClass.isAssignableFrom(keyType)) {
                Binding<?> binding = entry.getValue();
                answer.add((Provider<T>) binding.getProvider());
            }
        }
        return answer;
    }

    /** Returns true if a binding exists for the given matcher */
    public static boolean hasBinding(Injector injector, Matcher<Class> matcher) {
        return !getBindingsOf(injector, matcher).isEmpty();
    }

    /** Returns true if a binding exists for the given base class */
    public static boolean hasBinding(Injector injector, Class<?> baseClass) {
        return !getBindingsOf(injector, baseClass).isEmpty();
    }

    /** Returns true if a binding exists for the given key */
    public static boolean hasBinding(Injector injector, Key<?> key) {
        Binding<?> binding = getBinding(injector, key);
        return binding != null;
    }

    /**
     * Returns the binding for the given key or null if there is no such binding
     */
    public static Binding<?> getBinding(Injector injector, Key<?> key) {
        Map<Key<?>, Binding<?>> bindings = injector.getBindings();
        Binding<?> binding = bindings.get(key);
        return binding;
    }

    /**
     * Returns a collection of all of the bindings matching the given matcher
     * 
     * @param matcher
     *            matches the types to return instances
     * @return a set of objects returned from this injector
     */
    public static Set<Binding<?>> getBindingsOf(Injector injector,
            Matcher<Class> matcher) {
        Set<Binding<?>> answer = Sets.newHashSet();
        Set<Entry<Key<?>, Binding<?>>> entries = injector.getBindings()
                .entrySet();
        for (Entry<Key<?>, Binding<?>> entry : entries) {
            Key<?> key = entry.getKey();
            Class<?> keyType = getKeyType(key);
            if (keyType != null && matcher.matches(keyType)) {
                answer.add(entry.getValue());
            }
        }
        return answer;
    }

    /**
     * Returns a collection of all bindings of the given base type
     * 
     * @param baseClass
     *            the base type of objects required
     * @return a set of objects returned from this injector
     */
    public static Set<Binding<?>> getBindingsOf(Injector injector,
            Class<?> baseClass) {
        Set<Binding<?>> answer = Sets.newHashSet();
        Set<Entry<Key<?>, Binding<?>>> entries = injector.getBindings()
                .entrySet();
        for (Entry<Key<?>, Binding<?>> entry : entries) {
            Key<?> key = entry.getKey();
            Class<?> keyType = getKeyType(key);
            if (keyType != null && baseClass.isAssignableFrom(keyType)) {
                answer.add(entry.getValue());
            }
        }
        return answer;
    }

    /** Returns the key type of the given key */
    public static <T> Class<?> getKeyType(Key<?> key) {
        Class<?> keyType = null;
        TypeLiteral<?> typeLiteral = key.getTypeLiteral();
        Type type = typeLiteral.getType();
        if (type instanceof Class) {
            keyType = (Class<?>) type;
        }
        return keyType;
    }

    protected static Module loadModule(String moduleName)
        throws ClassNotFoundException, IllegalAccessException,
            InstantiationException {
        Class<?> type = Classes.loadClass(moduleName,
                GuiceInitialContextFactory.class.getClassLoader());
        return (Module) type.newInstance();
    }

    /*
  */
    /**
     * Closes the given scope on this injector
     * 
     * @param injector
     *            the injector on which to close objects
     * @param scopeAnnotation
     *            the scope on which to close the objects
     * @throws CloseFailedException
     *             the exceptions caused if closing an object fails
     */
    /*
     * public static void close(Injector injector, Annotation scopeAnnotation)
     * throws CloseFailedException { Key<PreDestroyer> key =
     * Key.get(PreDestroyer.class, scopeAnnotation); if (hasBinding(injector,
     * key)) { PreDestroyer destroyer = injector.getInstance(key);
     * destroyer.close(); } }
     */

    /**
     * Closes any singleton objects in the injector using the currently
     * registered {@link Closer} implementations
     */
    public static void close(Injector injector) throws CloseFailedException {
        close(injector, new CloseErrorsImpl(Injectors.class));
    }

    /**
     * Closes objects within the given scope using the currently registered
     * {@link Closer} implementations
     */
    public static void close(Injector injector, CloseErrors errors)
        throws CloseFailedException {
        close(injector, Singleton.class, errors);
    }

    /**
     * Closes objects within the given scope using the currently registered
     * {@link Closer} implementations
     */
    public static void close(Injector injector,
            Class<? extends Annotation> scopeAnnotationToClose)
        throws CloseFailedException {
        close(injector, scopeAnnotationToClose, new CloseErrorsImpl(
                Injectors.class));
    }

    /**
     * Closes objects within the given scope using the currently registered
     * {@link Closer} implementations
     */
    public static void close(Injector injector,
            Class<? extends Annotation> scopeAnnotationToClose,
            CloseErrors errors) throws CloseFailedException {
        Set<Closer> closers = getInstancesOf(injector, Closer.class);
        Closer closer = CompositeCloser.newInstance(closers);
        if (closer == null) {
            return;
        }

        Set<Entry<Key<?>, Binding<?>>> entries = injector.getBindings()
                .entrySet();
        for (Entry<Key<?>, Binding<?>> entry : entries) {
            Key<?> key = entry.getKey();
            Binding<?> binding = entry.getValue();
            closeBinding(key, binding, scopeAnnotationToClose, closer, errors);
        }

        tryCloseJitBindings(closer, injector, scopeAnnotationToClose, errors);
        errors.throwIfNecessary();
    }

    private static void tryCloseJitBindings(Closer closer, Injector injector,
            Class<? extends Annotation> scopeAnnotationToClose,
            CloseErrors errors) {
        Class<? extends Injector> type = injector.getClass();
        Field field;
        try {
            field = type.getDeclaredField("jitBindings");
            field.setAccessible(true);
            Object bindings = field.get(injector);
            if (bindings != null) {
                if (bindings instanceof Map) {
                    Map<Key<?>, BindingImpl<?>> map = (Map<Key<?>, BindingImpl<?>>) bindings;
                    Set<Entry<Key<?>, BindingImpl<?>>> entries = map.entrySet();
                    for (Entry<Key<?>, BindingImpl<?>> entry : entries) {
                        closeBinding(entry.getKey(), entry.getValue(),
                                scopeAnnotationToClose, closer, errors);
                    }
                }
            }
        } catch (NoSuchFieldException e) {
            // ignore - Guice has refactored so we can't access the jit bindings
            // System.out.println("No such field! " + e);
        } catch (IllegalAccessException e) {
            // ignore - Guice has refactored so we can't access the jit bindings
            // System.out.println("Failed to access field: " + field +
            // ". Reason: " + e);
        }
    }

    private static void closeBinding(Key<?> key, Binding<?> binding,
            Class<? extends Annotation> scopeAnnotationToClose, Closer closer,
            CloseErrors errors) {
        Provider<?> provider = binding.getProvider();

        Class<? extends Annotation> scopeAnnotation = getScopeAnnotation(binding);
        if ((scopeAnnotation != null)
                && scopeAnnotation.equals(scopeAnnotationToClose)) {
            Object value = provider.get();
            if (value != null) {
                Closers.close(key, value, closer, errors);
            }
        }
    }

    /**
     * Returns the scope annotation for the given binding or null if there is no
     * scope
     */
    public static Class<? extends Annotation> getScopeAnnotation(
            Binding<?> binding) {
        Class<? extends Annotation> scopeAnnotation = null;
        if (binding instanceof BindingImpl) {
            BindingImpl bindingImpl = (BindingImpl) binding;
            Scoping scoping = bindingImpl.getScoping();
            if (scoping != null) {
                scopeAnnotation = scoping.getScopeAnnotation();

                // TODO not sure why we need this hack???
                if (scopeAnnotation == null) {
                    Scope scope = scoping.getScopeInstance();
                    if (scope instanceof HasScopeAnnotation) {
                        HasScopeAnnotation hasScopeAnnotation = (HasScopeAnnotation) scope;
                        scopeAnnotation = hasScopeAnnotation
                                .getScopeAnnotation();
                    }

                    if (scopeAnnotation == null
                            && (scoping == Scoping.EAGER_SINGLETON
                                    || scoping == Scoping.SINGLETON_ANNOTATION || scoping == Scoping.SINGLETON_INSTANCE)) {
                        scopeAnnotation = Singleton.class;
                    }
                }
            }
        }
        return scopeAnnotation;
    }
}