/*******************************************************************************
 * Copyright (c) 2007, 2010 Association for Decentralized Information Management
 * in Industry THTH ry.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     VTT Technical Research Centre of Finland - initial API and implementation
 *******************************************************************************/
package org.simantics.utils;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

public class ReflectionUtils {

    /**
     * For a class <code>C extends PC&lt;P&gt;</code>, where <code>PC</code> is
     * a class, not an interface, retrieves class <code>P</code>.
     * 
     * @param clazz
     * @return
     */
    public static Class<?> getSingleParameterType(Class<?> clazz) {

        Type t = clazz.getGenericSuperclass();
        if(t instanceof Class<?>) {
            throw new UnsupportedOperationException("Missing parameter type for input class '" + clazz.getCanonicalName() + "'");
        } else if (t instanceof ParameterizedType) {
            ParameterizedType type = (ParameterizedType)t;
            Type argType = type.getActualTypeArguments()[0];
            if (argType instanceof Class<?>) {
                return (Class<?>) argType;
            } else if (argType instanceof ParameterizedType) {
                // This happens if the input class X<T>
                // parameter T is also parameterized.
                ParameterizedType pargType = (ParameterizedType) argType;
                return (Class<?>) pargType.getRawType();
            } else {
                throw new UnsupportedOperationException("Unsupported parameter type in class '" + clazz.getCanonicalName() + "': " + argType);
            }
        } else {
            throw new UnsupportedOperationException("Unknown case in class '" + clazz.getCanonicalName() + "'");
        }

    }

    /**
     * Works like {@link #getSingleParameterType(Class)} assuming the retrieved
     * parameter class extends <code>T</code>.
     * 
     * @param clazz
     * @return
     */
    @SuppressWarnings("unchecked")
    public static <T> Class<T> getSingleParameterTypeExtending(Class<?> clazz) {

        Type t = clazz.getGenericSuperclass();
        if(t instanceof Class<?>) {
            throw new UnsupportedOperationException("Missing parameter type for input class '" + clazz.getCanonicalName() + "'");
        } else if (t instanceof ParameterizedType) {
            ParameterizedType type = (ParameterizedType)t;
            Type argType = type.getActualTypeArguments()[0];
            if (argType instanceof Class<?>) {
                return (Class<T>) argType;
            } else if (argType instanceof ParameterizedType) {
                // This happens if the input class X<T>
                // parameter T is also parameterized.
                ParameterizedType pargType = (ParameterizedType) argType;
                return (Class<T>) pargType.getRawType();
            } else {
                throw new UnsupportedOperationException("Unsupported parameter type in class '" + clazz.getCanonicalName() + "': " + argType);
            }
        } else {
            throw new UnsupportedOperationException("Unknown case in class '" + clazz.getCanonicalName() + "'");
        }

    }

}