/*
 * Copyright (c) 2012, 2014, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package com.oracle.truffle.sl.nodes.local;

import com.oracle.truffle.api.*;
import com.oracle.truffle.api.dsl.*;
import com.oracle.truffle.api.frame.*;
import com.oracle.truffle.sl.nodes.*;

/**
 * Node to write a local variable to a function's {@link VirtualFrame frame}. The Truffle frame API
 * allows to store primitive values of all Java primitive types, and Object values.
 */
@NodeChild(value = "valueNode")
@NodeField(name = "slot", type = FrameSlot.class)
public abstract class SLWriteLocalVariableNode extends SLExpressionNode {

    /**
     * Returns the descriptor of the accessed local variable. The implementation of this method is
     * created by the Truffle DSL based on the {@link NodeField} annotation on the class.
     */
    protected abstract FrameSlot getSlot();

    /**
     * Specialized method to write a primitive {@code long} value. This is only possible if the
     * local variable also has currently the type {@code long}, therefore a Truffle DSL
     * {@link #isLongKind() custom guard} is specified.
     */
    @Specialization(guards = "isLongKind")
    protected long write(VirtualFrame frame, long value) {
        frame.setLong(getSlot(), value);
        return value;
    }

    @Specialization(guards = "isBooleanKind")
    protected boolean write(VirtualFrame frame, boolean value) {
        frame.setBoolean(getSlot(), value);
        return value;
    }

    /**
     * Generic write method that works for all possible types.
     * <p>
     * Why is this method annotated with {@link Specialization} and not {@link Generic}? For a
     * {@link Generic} method, the Truffle DSL generated code would try all other specializations
     * first before calling this method. We know that all these specializations would fail their
     * guards, so there is no point in calling them. Since this method takes a value of type
     * {@link Object}, it is guaranteed to never fail, i.e., once we are in this specialization the
     * node will never be re-specialized.
     */
    @Specialization
    protected Object write(VirtualFrame frame, Object value) {
        if (getSlot().getKind() != FrameSlotKind.Object) {
            /*
             * The local variable has still a primitive type, we need to change it to Object. Since
             * the variable type is important when the compiler optimizes a method, we also discard
             * compiled code.
             */
            CompilerDirectives.transferToInterpreterAndInvalidate();
            getSlot().setKind(FrameSlotKind.Object);
        }
        frame.setObject(getSlot(), value);
        return value;
    }

    /**
     * Guard function that the local variable has the type {@code long}.
     */
    protected boolean isLongKind() {
        return isKind(FrameSlotKind.Long);
    }

    protected boolean isBooleanKind() {
        return isKind(FrameSlotKind.Boolean);
    }

    private boolean isKind(FrameSlotKind kind) {
        if (getSlot().getKind() == kind) {
            /* Success: the frame slot has the expected kind. */
            return true;
        } else if (getSlot().getKind() == FrameSlotKind.Illegal) {
            /*
             * This is the first write to this local variable. We can set the type to the one we
             * expect. Since the variable type is important when the compiler optimizes a method, we
             * also discard compiled code.
             */
            CompilerDirectives.transferToInterpreterAndInvalidate();
            getSlot().setKind(kind);
            return true;
        } else {
            /*
             * Failure: the frame slot has the wrong kind, the Truffle DSL generated code will
             * choose a different specialization.
             */
            return false;
        }
    }
}