/*
 * Copyright (c) 2013, 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.graal.truffle;

import java.lang.reflect.*;

import sun.misc.*;

import com.oracle.graal.api.meta.*;
import com.oracle.graal.graph.Node;
import com.oracle.graal.nodes.*;
import com.oracle.graal.nodes.java.*;
import com.oracle.graal.phases.common.*;
import com.oracle.truffle.api.*;
import com.oracle.truffle.api.nodes.Node.Child;

final class PartialEvaluatorCanonicalizer implements CanonicalizerPhase.CustomCanonicalizer {

    private final MetaAccessProvider metaAccess;
    private final ConstantReflectionProvider constantReflection;

    PartialEvaluatorCanonicalizer(MetaAccessProvider metaAccess, ConstantReflectionProvider constantReflection) {
        this.metaAccess = metaAccess;
        this.constantReflection = constantReflection;
    }

    @Override
    public Node canonicalize(Node node) {
        if (node instanceof LoadFieldNode) {
            LoadFieldNode loadFieldNode = (LoadFieldNode) node;
            if (!loadFieldNode.isStatic() && loadFieldNode.object().isConstant() && !loadFieldNode.object().isNullConstant()) {
                if (Modifier.isFinal(loadFieldNode.field().getModifiers()) || (loadFieldNode.kind() == Kind.Object && loadFieldNode.field().getAnnotation(Child.class) != null) ||
                                loadFieldNode.field().getAnnotation(CompilerDirectives.CompilationFinal.class) != null) {
                    Constant constant = loadFieldNode.field().readValue(loadFieldNode.object().asConstant());
                    assert verifyFieldValue(loadFieldNode.field(), constant);
                    return ConstantNode.forConstant(constant, metaAccess, node.graph());
                }
            }
        } else if (node instanceof LoadIndexedNode) {
            LoadIndexedNode loadIndexedNode = (LoadIndexedNode) node;
            if (loadIndexedNode.array().isConstant() && !loadIndexedNode.array().isNullConstant() && loadIndexedNode.index().isConstant()) {
                Object array = loadIndexedNode.array().asConstant().asObject();
                long index = loadIndexedNode.index().asConstant().asLong();
                if (index >= 0 && index < Array.getLength(array)) {
                    int arrayBaseOffset = Unsafe.getUnsafe().arrayBaseOffset(array.getClass());
                    int arrayIndexScale = Unsafe.getUnsafe().arrayIndexScale(array.getClass());
                    Constant constant = constantReflection.readUnsafeConstant(loadIndexedNode.elementKind(), array, arrayBaseOffset + index * arrayIndexScale,
                                    loadIndexedNode.elementKind() == Kind.Object);
                    return ConstantNode.forConstant(constant, metaAccess, loadIndexedNode.graph());
                }
            }
        }
        return node;
    }

    private static boolean verifyFieldValue(ResolvedJavaField field, Constant constant) {
        assert field.getAnnotation(Child.class) == null || constant.isNull() || constant.asObject() instanceof com.oracle.truffle.api.nodes.Node : "@Child field value must be a Node: " + field +
                        ", but was: " + constant.asObject();
        return true;
    }
}