/*******************************************************************************
 * Copyright (c) 2000, 2007 IBM Corporation and others.
 * 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:
 *     IBM Corporation - initial API and implementation
 *     
 * Port to the D Programming language:
 *     Jacob Carlborg <jacob.carlborg@gmail.com>
 *******************************************************************************/
module dwt.internal.Callback;

import dwt.dwthelper.utils;
import dwt.internal.C;

/**
 * Instances of this class represent entry points into Java
 * which can be invoked from operating system level callback
 * routines.
 * <p>
 * IMPORTANT: A callback is only valid when invoked on the
 * thread which created it. The results are undefined (and
 * typically bad) when a callback is passed out to the 
 * operating system (or other code) in such a way that the
 * callback is called from a different thread.
 */

public class Callback
{

    Object object;
    String method, signature;
    int argCount;
    int /*long*/address, errorResult;
    bool isStatic, isArrayBased;

    static const String PTR_SIGNATURE = C.PTR_SIZEOF is 4 ? "I" : "J"; //$NON-NLS-1$  //$NON-NLS-2$
    static const String SIGNATURE_0 = getSignature(0);
    static const String SIGNATURE_1 = getSignature(1);
    static const String SIGNATURE_2 = getSignature(2);
    static const String SIGNATURE_3 = getSignature(3);
    static const String SIGNATURE_4 = getSignature(4);
    static const String
            SIGNATURE_N = "([" + PTR_SIGNATURE + ")" + PTR_SIGNATURE; //$NON-NLS-1$  //$NON-NLS-2$

    /**
     * Constructs a new instance of this class given an object
     * to send the message to, a string naming the method to
     * invoke and an argument count. Note that, if the object
     * is an instance of <code>Class</code> it is assumed that
     * the method is a static method on that class.
     *
     * @param object the object to send the message to
     * @param method the name of the method to invoke
     * @param argCount the number of arguments that the method takes
     */
    public this (Object object, String method, int argCount)
    {
        this(object, method, argCount, false);
    }

    /**
     * Constructs a new instance of this class given an object
     * to send the message to, a string naming the method to
     * invoke, an argument count and a flag indicating whether
     * or not the arguments will be passed in an array. Note 
     * that, if the object is an instance of <code>Class</code>
     * it is assumed that the method is a static method on that
     * class.
     *
     * @param object the object to send the message to
     * @param method the name of the method to invoke
     * @param argCount the number of arguments that the method takes
     * @param isArrayBased <code>true</code> if the arguments should be passed in an array and false otherwise
     */
    public this (Object object, String method, int argCount, bool isArrayBased)
    {
        this(object, method, argCount, isArrayBased, 0);
    }

    /**
     * Constructs a new instance of this class given an object
     * to send the message to, a string naming the method to
     * invoke, an argument count, a flag indicating whether
     * or not the arguments will be passed in an array and a value
     * to return when an exception happens. Note that, if
     * the object is an instance of <code>Class</code>
     * it is assumed that the method is a static method on that
     * class.
     *
     * @param object the object to send the message to
     * @param method the name of the method to invoke
     * @param argCount the number of arguments that the method takes
     * @param isArrayBased <code>true</code> if the arguments should be passed in an array and false otherwise
     * @param errorResult the return value if the java code throws an exception
     */
    public this (Object object, String method, int argCount, bool isArrayBased,
            int /*long*/errorResult)
    {

        /* Set the callback fields */
        this.object = object;
        this.method = method;
        this.argCount = argCount;
        this.isStatic = cast(ClassInfo) object;
        this.isArrayBased = isArrayBased;
        this.errorResult = errorResult;

        /* Inline the common cases */
        if (isArrayBased)
        {
            signature = SIGNATURE_N;
        }
        else
        {
            switch (argCount)
            {
                case 0:
                    signature = SIGNATURE_0;
                break; //$NON-NLS-1$
                case 1:
                    signature = SIGNATURE_1;
                break; //$NON-NLS-1$
                case 2:
                    signature = SIGNATURE_2;
                break; //$NON-NLS-1$
                case 3:
                    signature = SIGNATURE_3;
                break; //$NON-NLS-1$
                case 4:
                    signature = SIGNATURE_4;
                break; //$NON-NLS-1$
                default:
                    signature = getSignature(argCount);
            }
        }

        /* Bind the address */
        address = bind(this, object, method, signature, argCount, isStatic,
                isArrayBased, errorResult);
    }

    /**
     * Allocates the native level resources associated with the
     * callback. This method is only invoked from within the
     * constructor for the argument.
     *
     * @param callback the callback to bind
     * @param object the callback's object
     * @param method the callback's method
     * @param signature the callback's method signature
     * @param argCount the callback's method argument count
     * @param isStatic whether the callback's method is static
     * @param isArrayBased whether the callback's method is array based
     * @param errorResult the callback's error result
     */
    static synchronized int /*long*/ bind (Callback callback, Object object, String method, String signature, int argCount, bool isStatic, bool isArrayBased, int /*long*/ errorResult)
    {
        
    }
    
    /**
     * Releases the native level resources associated with the callback,
     * and removes all references between the callback and
     * other objects. This helps to prevent (bad) application code
     * from accidentally holding onto extraneous garbage.
     */
    public void dispose ()
    {
        if (object is null)
            return;
        unbind(this);
        object = method = signature = null;
        address = 0;
    }

    /**
     * Returns the address of a block of machine code which will
     * invoke the callback represented by the receiver.
     *
     * @return the callback address
     */
    public int /*long*/getAddress ()
    {
        return address;
    }

    /**
     * Returns the DWT platform name.
     *
     * @return the platform name of the currently running DWT
     */
    //public static native String getPlatform ();
    /**
     * Returns the number of times the system has been recursively entered
     * through a callback.
     * <p>
     * Note: This should not be called by application code.
     * </p>
     * 
     * @return the entry count
     * 
     * @since 2.1
     */
    //public static native int getEntryCount ();
    static String getSignature (int argCount)
    {
        String signature = "("; //$NON-NLS-1$
        for (int i = 0; i < argCount; i++)
            signature += PTR_SIGNATURE;
        signature += ")" + PTR_SIGNATURE; //$NON-NLS-1$
        return signature;
    }

    /**
     * Indicates whether or not callbacks which are triggered at the
     * native level should cause the messages described by the matching
     * <code>Callback</code> objects to be invoked. This method is used
     * to safely shut down DWT when it is run within environments
     * which can generate spurious events.
     * <p>
     * Note: This should not be called by application code.
     * </p>
     *
     * @param enable true if callbacks should be invoked
     */
    //public static final native synchronized void setEnabled (bool enable);
    /**
     * Returns whether or not callbacks which are triggered at the
     * native level should cause the messages described by the matching
     * <code>Callback</code> objects to be invoked. This method is used
     * to safely shut down DWT when it is run within environments
     * which can generate spurious events.
     * <p>
     * Note: This should not be called by application code.
     * </p>
     *
     * @return true if callbacks should not be invoked
     */
    //public static final native synchronized bool getEnabled ();
    /**
     * This might be called directly from native code in environments
     * which can generate spurious events. Check before removing it.
     *
     * @deprecated
     *
     * @param ignore true if callbacks should not be invoked
     */
    static final void ignoreCallbacks (bool ignore)
    {
        setEnabled(!ignore);
    }

    /**
     * Immediately wipes out all native level state associated
     * with <em>all</em> callbacks.
     * <p>
     * <b>WARNING:</b> This operation is <em>extremely</em> dangerous,
     * and should never be performed by application code.
     * </p>
     */
    //public static final native synchronized void reset ();
    /**
     * Releases the native level resources associated with the callback.
     *
     * @see #dispose
     */
    //static final native synchronized void unbind (Callback callback);
}