package org.infinispan.cdi.common.util;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import javax.enterprise.context.spi.CreationalContext;
import javax.enterprise.inject.spi.AnnotatedMethod;
import javax.enterprise.inject.spi.Bean;
import javax.enterprise.inject.spi.BeanManager;
import javax.enterprise.inject.spi.InjectionPoint;

/**
 * <p>
 * Allows an {@link AnnotatedMethod} to be injected using the CDI type safe
 * resolution rules.
 * </p>
 * <p/>
 * <p>
 * {@link ParameterValueRedefiner} allows the default value to be overridden by
 * the caller of
 * {@link #invoke(Object, CreationalContext, ParameterValueRedefiner)}.
 * </p>
 *
 * @param <X> the declaring type
 * @author Pete Muir
 */
public class InjectableMethod<X> {

    private final AnnotatedMethod<X> method;
    private final List<InjectionPoint> parameters;
    private final BeanManager beanManager;

    /**
     * Instantiate a new {@link InjectableMethod}.
     *
     * @param method      the method which will be injected upon a call to
     *                    {@link #invoke(Object, CreationalContext)}
     * @param bean        the bean which defines the injectable method
     * @param beanManager the {@link BeanManager} to use to obtain the parameter
     *                    values
     */
    public InjectableMethod(AnnotatedMethod<X> method, Bean<?> declaringBean, BeanManager beanManager) {
        this(method, Beans.createInjectionPoints(method, declaringBean, beanManager), beanManager);
    }

    /**
     * Instantiate a new {@link InjectableMethod}.
     *
     * @param method      the method which will be injected upon a call to
     *                    {@link #invoke(Object, CreationalContext)}
     * @param parameters  a collection of injection points representing the
     *                    parameters of the method
     * @param beanManager the {@link BeanManager} to use to obtain the parameter
     *                    values
     */
    public InjectableMethod(AnnotatedMethod<X> method, Collection<InjectionPoint> parameters, BeanManager beanManager) {
        this.method = method;
        this.parameters = new ArrayList<InjectionPoint>(parameters);
        this.beanManager = beanManager;
    }

    /**
     * Get the bean manager used by this injectable method.
     *
     * @return the bean manager in use
     */
    protected BeanManager getBeanManager() {
        return beanManager;
    }

    /**
     * Get the injectable parameters of this method.
     *
     * @return a collection of injection points representing the parameters of
     *         this method
     */
    protected List<InjectionPoint> getParameters() {
        return parameters;
    }

    /**
     * Invoke the method, causing all parameters to be injected according to the
     * CDI type safe resolution rules.
     *
     * @param <T>               the return type of the method
     * @param receiver          the instance upon which to call the method
     * @param creationalContext the creational context to use to obtain
     *                          injectable references for each parameter
     * @return the result of invoking the method or null if the method's return
     *         type is void
     * @throws RuntimeException            if this <code>Method</code> object enforces Java
     *                                     language access control and the underlying method is
     *                                     inaccessible or if the underlying method throws an exception or
     *                                     if the initialization provoked by this method fails.
     * @throws IllegalArgumentException    if the method is an instance method and
     *                                     the specified <code>receiver</code> argument is not an instance
     *                                     of the class or interface declaring the underlying method (or
     *                                     of a subclass or implementor thereof); if an unwrapping
     *                                     conversion for primitive arguments fails; or if, after possible
     *                                     unwrapping, a parameter value cannot be converted to the
     *                                     corresponding formal parameter type by a method invocation
     *                                     conversion.
     * @throws NullPointerException        if the specified <code>receiver</code> is
     *                                     null and the method is an instance method.
     * @throws ExceptionInInitializerError if the initialization provoked by this
     *                                     method fails.
     */
    public <T> T invoke(Object receiver, CreationalContext<T> creationalContext) {
        return invoke(receiver, creationalContext, null);
    }

    /**
     * Invoke the method, calling the parameter redefiner for each parameter,
     * allowing the caller to override the default value obtained via the CDI
     * type safe resolver.
     *
     * @param <T>               the return type of the method
     * @param receiver          the instance upon which to call the method
     * @param creationalContext the creational context to use to obtain
     *                          injectable references for each parameter
     * @return the result of invoking the method or null if the method's return
     *         type is void
     * @throws RuntimeException            if this <code>Method</code> object enforces Java
     *                                     language access control and the underlying method is
     *                                     inaccessible or if the underlying method throws an exception or
     *                                     if the initialization provoked by this method fails.
     * @throws IllegalArgumentException    if the method is an instance method and
     *                                     the specified <code>receiver</code> argument is not an instance
     *                                     of the class or interface declaring the underlying method (or
     *                                     of a subclass or implementor thereof); if an unwrapping
     *                                     conversion for primitive arguments fails; or if, after possible
     *                                     unwrapping, a parameter value cannot be converted to the
     *                                     corresponding formal parameter type by a method invocation
     *                                     conversion.
     * @throws NullPointerException        if the specified <code>receiver</code> is
     *                                     null and the method is an instance method.
     * @throws ExceptionInInitializerError if the initialization provoked by this
     *                                     method fails.
     */
    public <T> T invoke(Object receiver, CreationalContext<T> creationalContext, ParameterValueRedefiner redefinition) {
        List<Object> parameterValues = new ArrayList<Object>();
        for (int i = 0; i < getParameters().size(); i++) {
            if (redefinition != null) {
                ParameterValueRedefiner.ParameterValue value = new ParameterValueRedefiner.ParameterValue(i, getParameters().get(i), getBeanManager());
                parameterValues.add(redefinition.redefineParameterValue(value));
            } else {
                parameterValues.add(getBeanManager().getInjectableReference(getParameters().get(i), creationalContext));
            }
        }

        @SuppressWarnings("unchecked")
        T result = (T) Reflections.invokeMethod(true, method.getJavaMember(), receiver, parameterValues.toArray(Reflections.EMPTY_OBJECT_ARRAY));

        return result;
    }

}
