package api;

// BEGIN: instanceof.class.InstanceProvider2

import java.util.Arrays;

import java.util.HashSet;

import java.util.Set;

import java.util.concurrent.Callable;

public final class InstanceProvider {

    private final Callable<Object> instance;

    private final Set<String> types;

    public InstanceProvider(Callable<Object> instance) {

        this.instance = instance;

        this.types = null;

    }

    /** Specifies not only a factory for creating objects, but

     * also additional information about them.

     * @param instance the factory to create the object

     * @param type the class that the create object will be instance of

     * @since 2.0 

     */

    public InstanceProvider(Callable<Object> instance, String... types) {

        this.instance = instance;

        this.types = new HashSet<String>();

        this.types.addAll(Arrays.asList(types));

    }

    public Class<?> instanceClass() throws Exception {

        return instance.call().getClass();

    }

    public Object instanceCreate() throws Exception {

        return instance.call();

    }

    /** Allows to find out if the InstanceProvider creates object of given

     * type. This check can be done without loading the actual object or

     * its implementation class into memory.

     * 

     * @param c class to test 

     * @return if the instances produced by this provider is instance of c

     * @since 2.0 

     */

    public boolean isInstanceOf(Class<?> c) throws Exception {

        if (types != null) {

            return types.contains(c.getName());

        } else {

            // fallback

            return c.isAssignableFrom(instanceClass());

        }

    }

}

// END: instanceof.class.InstanceProvider2