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/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed 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.elasticsearch.common.inject.spi;

import org.elasticsearch.common.inject.Binder;
import org.elasticsearch.common.inject.ConfigurationException;
import org.elasticsearch.common.inject.TypeLiteral;

import java.util.Set;

import static com.google.common.base.Preconditions.checkNotNull;

/**
 * A request to inject the instance fields and methods of an instance. Requests are created
 * explicitly in a module using {@link org.elasticsearch.common.inject.Binder#requestInjection(Object)
 * requestInjection()} statements:
 *  *     requestInjection(serviceInstance);
 *
 * @author [email protected] (Mike Ward)
 * @since 2.0
 */
public final class InjectionRequest implements Element {

    private final Object source;
    private final TypeLiteral type;
    private final T instance;

    public InjectionRequest(Object source, TypeLiteral type, T instance) {
        this.source = checkNotNull(source, "source");
        this.type = checkNotNull(type, "type");
        this.instance = checkNotNull(instance, "instance");
    }

    @Override
    public Object getSource() {
        return source;
    }

    public T getInstance() {
        return instance;
    }

    public TypeLiteral getType() {
        return type;
    }

    /**
     * Returns the instance methods and fields of {@code instance} that will be injected to fulfill
     * this request.
     *
     * @return a possibly empty set of injection points. The set has a specified iteration order. All
     *         fields are returned and then all methods. Within the fields, supertype fields are returned
     *         before subtype fields. Similarly, supertype methods are returned before subtype methods.
     * @throws ConfigurationException if there is a malformed injection point on the class of {@code
     *                                instance}, such as a field with multiple binding annotations. The exception's {@link
     *                                ConfigurationException#getPartialValue() partial value} is a {@code Set}
     *                                of the valid injection points.
     */
    public Set getInjectionPoints() throws ConfigurationException {
        return InjectionPoint.forInstanceMethodsAndFields(instance.getClass());
    }

    @Override
    public  R acceptVisitor(ElementVisitor visitor) {
        return visitor.visit(this);
    }

    @Override
    public void applyTo(Binder binder) {
        binder.withSource(getSource()).requestInjection(type, instance);
    }
}