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package com.sap.it.commons.structure;

import com.sap.it.commons.lang.Checks;

public class StructureTools {
    private static final String HOST_MUST_NOT_BE_NULL = "Host must not be null";

    private StructureTools() {

    }

    /**
     * Peek for an adapter of an {@link Adaptable} object.
     * 
     * @param host
     *            Adaptable object that can be {@code null}.
     * @param adapterClass
     *            class to adapt to.
     * @return {@code null} if host is {@code null} else the result is
     *         {@link Adaptable#getAdapter(Class)}.
     */
    public static  T peekAdapter(Adaptable host, Class adapterClass) {
        return host != null ? host.getAdapter(adapterClass) : null;
    }

    /**
     * Peek for an adapter for an object that potentially implements
     * {@link Adaptable} interface.
     * 
     * @param host
     *            any object that can be {@code null}.
     * @param adapterClass
     *            class to adapt to.
     * @return {@code null} if host is {@code null} or the object does not
     *         implement the {@link Adaptable} interface else the result is
     *         {@link Adaptable#getAdapter(Class)}.
     */
    public static  T peekAdapter(Object potentialHost, Class adapterClass) {
        if (potentialHost instanceof Adaptable) {
            Adaptable adaptable = (Adaptable) potentialHost;
            return adaptable.getAdapter(adapterClass);
        } else {
            return null;
        }
    }

    /**
     * Get an adapter for an {@link Adaptable} object. Result is never
     * {@code null}.
     * 
     * @param host
     *            any object. Throws IllegalArgumentException if {@code null}.
     * @param adapterClass
     *            class to adapt to.
     * @return the adapter object. Is never {@code null}.
     * @throws IllegalArgumentException
     *             if host is {@code null} or no adapter has been found.
     */
    public static  T grantAdapter(Adaptable host, Class adapterClass) {
        Checks.nonNullArgument(host, HOST_MUST_NOT_BE_NULL);
        return returnAdapter(host.getAdapter(adapterClass), adapterClass);
    }

    /**
     * Get an adapter for an object that potentially implements
     * {@link Adaptable} interface. Result is never {@code null}.
     * 
     * @param host
     *            any object. Throws IllegalArgumentException if {@code null}.
     * @param adapterClass
     *            class to adapt to.
     * @return the adapter object. Is never {@code null}.
     * @throws IllegalArgumentException
     *             if host is {@code null} or no adapter has been found.
     */
    public static  T grantAdapter(Object potentialHost, Class adapterClass) {
        if (potentialHost instanceof Adaptable) {
            Adaptable adaptable = (Adaptable) potentialHost;
            return returnAdapter(adaptable.getAdapter(adapterClass), adapterClass);
        } else {
            Checks.nonNullArgument(potentialHost, HOST_MUST_NOT_BE_NULL);
            throw new IllegalArgumentException("Host is not adaptable");
        }
    }

    private static final  T returnAdapter(T t, Class adapterClass) {
        if (t != null) {
            return t;
        }
        throw new IllegalArgumentException("Host does not provide adapter for type: "
                + (adapterClass != null ? adapterClass.getName() : "null"));
    }
}