/*

 * Copyright (c) 2013, 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 org.graalvm.compiler.phases.common;

import org.graalvm.compiler.core.common.type.FloatStamp;

import org.graalvm.compiler.core.common.type.Stamp;

import org.graalvm.compiler.debug.GraalError;

import org.graalvm.compiler.graph.Graph;

import org.graalvm.compiler.graph.Node;

import org.graalvm.compiler.nodes.AbstractBeginNode;

import org.graalvm.compiler.nodes.AbstractMergeNode;

import org.graalvm.compiler.nodes.BeginNode;

import org.graalvm.compiler.nodes.ConstantNode;

import org.graalvm.compiler.nodes.EndNode;

import org.graalvm.compiler.nodes.IfNode;

import org.graalvm.compiler.nodes.LogicNode;

import org.graalvm.compiler.nodes.MergeNode;

import org.graalvm.compiler.nodes.ShortCircuitOrNode;

import org.graalvm.compiler.nodes.StructuredGraph;

import org.graalvm.compiler.nodes.ValueNode;

import org.graalvm.compiler.nodes.calc.ConditionalNode;

import org.graalvm.compiler.nodes.calc.FloatEqualsNode;

import org.graalvm.compiler.nodes.calc.FloatLessThanNode;

import org.graalvm.compiler.nodes.calc.IntegerEqualsNode;

import org.graalvm.compiler.nodes.calc.IntegerLessThanNode;

import org.graalvm.compiler.nodes.calc.NormalizeCompareNode;

import org.graalvm.compiler.phases.Phase;

public class ExpandLogicPhase extends Phase {

    private static final double EPSILON = 1E-6;

    @Override

    protected void run(StructuredGraph graph) {

        for (ShortCircuitOrNode logic : graph.getNodes(ShortCircuitOrNode.TYPE)) {

            processBinary(logic);

        }

        assert graph.getNodes(ShortCircuitOrNode.TYPE).isEmpty();

        for (NormalizeCompareNode logic : graph.getNodes(NormalizeCompareNode.TYPE)) {

            processNormalizeCompareNode(logic);

        }

        graph.setAfterExpandLogic();

    }

    private static void processNormalizeCompareNode(NormalizeCompareNode normalize) {

        LogicNode equalComp;

        LogicNode lessComp;

        StructuredGraph graph = normalize.graph();

        ValueNode x = normalize.getX();

        ValueNode y = normalize.getY();

        } else {

        }

        ConditionalNode equalValue = graph.unique(

                        new ConditionalNode(equalComp, ConstantNode.forIntegerStamp(stamp, 0, graph), ConstantNode.forIntegerStamp(stamp, 1, graph)));

        ConditionalNode value = graph.unique(new ConditionalNode(lessComp, ConstantNode.forIntegerStamp(stamp, -1, graph), equalValue));

        normalize.replaceAtUsagesAndDelete(value);

    }

    private static void processBinary(ShortCircuitOrNode binary) {

        while (binary.usages().isNotEmpty()) {

            Node usage = binary.usages().first();

            if (usage instanceof ShortCircuitOrNode) {

                processBinary((ShortCircuitOrNode) usage);

            } else if (usage instanceof IfNode) {

                processIf(binary.getX(), binary.isXNegated(), binary.getY(), binary.isYNegated(), (IfNode) usage, binary.getShortCircuitProbability());

            } else if (usage instanceof ConditionalNode) {

                processConditional(binary.getX(), binary.isXNegated(), binary.getY(), binary.isYNegated(), (ConditionalNode) usage);

            } else {

                throw GraalError.shouldNotReachHere();

            }

        }

        binary.safeDelete();

    }

    private static void processIf(LogicNode x, boolean xNegated, LogicNode y, boolean yNegated, IfNode ifNode, double shortCircuitProbability) {

        /*

         * this method splits an IfNode, which has a ShortCircuitOrNode as its condition, into two

         * separate IfNodes: if(X) and if(Y)

         *

         * for computing the probabilities P(X) and P(Y), we use two different approaches. The first

         * one assumes that the shortCircuitProbability and the probability on the IfNode were

         * created with each other in mind. If this assumption does not hold, we fall back to

         * another mechanism for computing the probabilities.

         */

        AbstractBeginNode trueTarget = ifNode.trueSuccessor();

        AbstractBeginNode falseTarget = ifNode.falseSuccessor();

        // 1st approach

        // assumption: P(originalIf.trueSuccessor) == P(X) + ((1 - P(X)) * P(Y))

        double firstIfTrueProbability = shortCircuitProbability;

        double secondIfTrueProbability = sanitizeProbability((ifNode.getTrueSuccessorProbability() - shortCircuitProbability) / (1 - shortCircuitProbability));

        double expectedOriginalIfTrueProbability = firstIfTrueProbability + (1 - firstIfTrueProbability) * secondIfTrueProbability;

        if (!doubleEquals(ifNode.getTrueSuccessorProbability(), expectedOriginalIfTrueProbability)) {

            /*

             * 2nd approach

             *

             * the assumption above did not hold, so we either used an artificial probability as

             * shortCircuitProbability or the ShortCircuitOrNode was moved to some other IfNode.

             *

             * so, we distribute the if's trueSuccessorProbability between the newly generated if

             * nodes according to the shortCircuitProbability. the following invariant is always

             * true in this case: P(originalIf.trueSuccessor) == P(X) + ((1 - P(X)) * P(Y))

             */

            firstIfTrueProbability = ifNode.getTrueSuccessorProbability() * shortCircuitProbability;

            secondIfTrueProbability = sanitizeProbability(1 - (ifNode.probability(falseTarget) / (1 - firstIfTrueProbability)));

        }

        ifNode.clearSuccessors();

        Graph graph = ifNode.graph();

        AbstractMergeNode trueTargetMerge = graph.add(new MergeNode());

        trueTargetMerge.setNext(trueTarget);

        EndNode firstTrueEnd = graph.add(new EndNode());

        EndNode secondTrueEnd = graph.add(new EndNode());

        trueTargetMerge.addForwardEnd(firstTrueEnd);

        trueTargetMerge.addForwardEnd(secondTrueEnd);

        AbstractBeginNode firstTrueTarget = BeginNode.begin(firstTrueEnd);

        AbstractBeginNode secondTrueTarget = BeginNode.begin(secondTrueEnd);

        if (yNegated) {

            secondIfTrueProbability = 1.0 - secondIfTrueProbability;

        }

        if (xNegated) {

            firstIfTrueProbability = 1.0 - firstIfTrueProbability;

        }

        AbstractBeginNode secondIf = BeginNode.begin(graph.add(new IfNode(y, yNegated ? falseTarget : secondTrueTarget, yNegated ? secondTrueTarget : falseTarget, secondIfTrueProbability)));

        IfNode firstIf = graph.add(new IfNode(x, xNegated ? secondIf : firstTrueTarget, xNegated ? firstTrueTarget : secondIf, firstIfTrueProbability));

        ifNode.replaceAtPredecessor(firstIf);

        ifNode.safeDelete();

    }

    private static boolean doubleEquals(double a, double b) {

        assert !Double.isNaN(a) && !Double.isNaN(b) && !Double.isInfinite(a) && !Double.isInfinite(b);

        return a - EPSILON < b && a + EPSILON > b;

    }

    private static double sanitizeProbability(double value) {

        double newValue = Math.min(1.0, Math.max(0.0, value));

        if (Double.isNaN(newValue)) {

            newValue = 0.5;

        }

        return newValue;

    }

    private static void processConditional(LogicNode x, boolean xNegated, LogicNode y, boolean yNegated, ConditionalNode conditional) {

        ValueNode trueTarget = conditional.trueValue();

        ValueNode falseTarget = conditional.falseValue();

        Graph graph = conditional.graph();

        ConditionalNode secondConditional = graph.unique(new ConditionalNode(y, yNegated ? falseTarget : trueTarget, yNegated ? trueTarget : falseTarget));

        ConditionalNode firstConditional = graph.unique(new ConditionalNode(x, xNegated ? secondConditional : trueTarget, xNegated ? trueTarget : secondConditional));

        conditional.replaceAndDelete(firstConditional);

    }

    @Override

    public boolean checkContract() {

        return false;

    }

}