//   Copyright 2012 Georg-August-Universität Göttingen, Germany
//
//   Licensed under the Apache License, Version 2.0 (the "License");
//   you may not use this file except in compliance with the License.
//   You may obtain a copy of the License at
//
//       http://www.apache.org/licenses/LICENSE-2.0
//
//   Unless required by applicable law or agreed to in writing, software
//   distributed under the License is distributed on an "AS IS" BASIS,
//   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//   See the License for the specific language governing permissions and
//   limitations under the License.

package de.ugoe.cs.autoquest.tasktrees.nodeequality;

import java.util.List;

import de.ugoe.cs.autoquest.tasktrees.treeifc.IEventTask;
import de.ugoe.cs.autoquest.tasktrees.treeifc.IIteration;
import de.ugoe.cs.autoquest.tasktrees.treeifc.ISelection;
import de.ugoe.cs.autoquest.tasktrees.treeifc.ISequence;
import de.ugoe.cs.autoquest.tasktrees.treeifc.ITaskTreeNode;

/**
 * <p>
 * This class is capable of comparing Iterations. Iterations equal at distinct levels
 * in distinct situations. The following table shows the results of the comparison for the
 * specific situations (the parameters are commutative). In any other situation, the comparison
 * returns <code>NodeEquality.UNEQUAL</code>:
 * </p>
 * 
 * <table border="1">
 *   <tr>
 *     <th>iteration 1</th>
 *     <th>iteration 2</th>
 *     <th>comparison result</th>
 *   </tr>
 *   <tr>
 *     <td>any iteration</td>
 *     <td>any iteration with a child that is lexically equal to the child of iteration 1</td>
 *     <td><code>NodeEquality.LEXICALLY_EQUAL</code></td>
 *   </tr>
 *   <tr>
 *     <td>any iteration</td>
 *     <td>any iteration with a child that is syntactically equal to the child of iteration 1</td>
 *     <td><code>NodeEquality.SYNTACTICALLY_EQUAL</code></td>
 *   </tr>
 *   <tr>
 *     <td>any iteration</td>
 *     <td>any iteration with a child that is semantically equal to the child of iteration 1</td>
 *     <td><code>NodeEquality.SEMANTICALLY_EQUAL</code></td>
 *   </tr>
 *   <tr>
 *     <td>an iteration with a selection of syntactically equal children</td>
 *     <td>an iteration with a child that is syntactically equal to the children of the child
 *     selection of iteration 1</td>
 *     <td><code>NodeEquality.SYNTACTICALLY_EQUAL</code></td>
 *   </tr>
 *   <tr>
 *     <td>an iteration with a selection of syntactically equal children</td>
 *     <td>an iteration with a selection of syntactically equal children that are all syntactically
 *     equal to the selection of children of iteration 1</td>
 *     <td><code>NodeEquality.SYNTACTICALLY_EQUAL</code></td>
 *   </tr>
 *   <tr>
 *     <td>an iteration with a selection of semantically equal children</td>
 *     <td>an iteration with a child that is semantically equal to the children of the child
 *     selection of iteration 1</td>
 *     <td><code>NodeEquality.SEMANTICALLY_EQUAL</code></td>
 *   </tr>
 *   <tr>
 *     <td>an iteration with a selection of semantically equal children</td>
 *     <td>an iteration with a selection of semantically equal children that are all semantically
 *     equal to the selection of children of iteration 1</td>
 *     <td><code>NodeEquality.SEMANTICALLY_EQUAL</code></td>
 *   </tr>
 * </table>
 * 
 * @version $Revision: $ $Date: 19.02.2012$
 * @author 2012, last modified by $Author: patrick$
 */
public class IterationComparisonRule implements NodeComparisonRule {
    
    /** the rule manager for internally comparing task tree nodes */
    private NodeEqualityRuleManager mRuleManager;

    /**
     * <p>
     * simple constructor to provide the rule with the node equality rule manager to be able
     * to perform comparisons of the children of provided task tree nodes
     * </p>
     * 
     * @param ruleManager the rule manager for comparing task tree nodes
     */
    IterationComparisonRule(NodeEqualityRuleManager ruleManager) {
        super();
        mRuleManager = ruleManager;
    }

    /* (non-Javadoc)
     * @see NodeComparisonRule#isApplicable(ITaskTreeNode, ITaskTreeNode)
     */
    @Override
    public boolean isApplicable(ITaskTreeNode node1, ITaskTreeNode node2) {
        return (node1 instanceof IIteration) && (node2 instanceof IIteration);
    }

    /* (non-Javadoc)
     * @see NodeComparisonRule#areLexicallyEqual(ITaskTreeNode, ITaskTreeNode)
     */
    @Override
    public boolean areLexicallyEqual(ITaskTreeNode node1, ITaskTreeNode node2) {
        List<ITaskTreeNode> children1 = node1.getChildren();
        List<ITaskTreeNode> children2 = node2.getChildren();
        
        if (children1.size() == children2.size()) {
            if (children1.size() == 0) {
                return true;
            }
            else {
                ITaskTreeNode child1 = children1.get(0);
                ITaskTreeNode child2 = children2.get(0);
                
                // iterations may have 3 different structures.
                // 1. they have one child, which is the iterated one
                // 2. they have a sequence of children, which is iterated
                // 3. they have a selection of different iterated variants (usually the variants
                //    are semantically equal)
                // check if the type of children match. If not, return false. If they match,
                // use the equality manager to perform further comparisons
                
                if (((child1 instanceof ISelection) && (child2 instanceof ISelection)) ||
                    ((child1 instanceof ISequence) && (child2 instanceof ISequence)) ||
                    ((child1 instanceof IEventTask) && (child2 instanceof IEventTask)))
                {
                    return getNodeEquality
                        (child1, child2).isAtLeast(NodeEquality.LEXICALLY_EQUAL);
                }
            }
        }
        
        return false;
    }

    /* (non-Javadoc)
     * @see NodeComparisonRule#areSyntacticallyEqual(ITaskTreeNode, ITaskTreeNode)
     */
    @Override
    public boolean areSyntacticallyEqual(ITaskTreeNode node1, ITaskTreeNode node2) {
        List<ITaskTreeNode> children1 = node1.getChildren();
        List<ITaskTreeNode> children2 = node2.getChildren();
        
        if (children1.size() == children2.size()) {
            if (children1.size() == 0) {
                return true;
            }
            else {
                ITaskTreeNode child1 = children1.get(0);
                ITaskTreeNode child2 = children2.get(0);
                
                // iterations may have 3 different structures.
                // 1. they have one child, which is the iterated one
                // 2. they have a sequence of children, which is iterated
                // 3. they have a selection of different iterated variants (usually the variants
                //    are semantically equal)
                // ignore the type of the children but check them for equality.
                
                return getNodeEquality(child1, child2).isAtLeast(NodeEquality.SYNTACTICALLY_EQUAL);
            }
        }
        
        return false;
    }

    /* (non-Javadoc)
     * @see NodeComparisonRule#areSemanticallyEqual(ITaskTreeNode, ITaskTreeNode)
     */
    @Override
    public boolean areSemanticallyEqual(ITaskTreeNode node1, ITaskTreeNode node2) {
        return compare(node1, node2).isAtLeast(NodeEquality.SEMANTICALLY_EQUAL);
    }

    /* (non-Javadoc)
     * @see NodeComparisonRule#compare(ITaskTreeNode, ITaskTreeNode)
     */
    @Override
    public NodeEquality compare(ITaskTreeNode node1, ITaskTreeNode node2) {
        List<ITaskTreeNode> children1 = node1.getChildren();
        List<ITaskTreeNode> children2 = node2.getChildren();

        // if both iterations do not have children, they are equal although this doesn't make sense
        if ((children1.size() == 0) && (children2.size() == 0)) {
            return NodeEquality.LEXICALLY_EQUAL;
        }
        else if ((children1.size() == 0) || (children2.size() == 0)) {
            return NodeEquality.UNEQUAL;
        }

        ITaskTreeNode child1 = children1.get(0);
        ITaskTreeNode child2 = children2.get(0);

        // iterations may have 3 different structures.
        // 1. they have one child, which is the iterated one
        // 2. they have a sequence of children, which is iterated
        // 3. they have a selection of different iterated variants (usually the variants are
        // semantically equal)
        //
        // the permutations of the three variants in combination must be checked

        // check if both nodes are the same variants of iterations and if their children are equal.
        // This condition matches, if both iterations are the same variants of iteration. I.e. three
        // combinations of the permutation are handled herewith.
        NodeEquality nodeEquality = getNodeEquality(child1, child2);
        
        if (nodeEquality != null) {
            return nodeEquality;
        }

        // compare one iteration with a single node as a child and another one with a selection of
        // semantically equal nodes
        return selectionChildrenSemanticallyEqualNode(child1, child2);
        
        // all other combinations (i.e. sequence with single child and sequence with selection)
        // can not match
    }

    /**
     * TODO update comment
     */
    private NodeEquality getNodeEquality(ITaskTreeNode child1, ITaskTreeNode child2) {
        NodeEquality nodeEquality = callRuleManager(child1, child2, null);

        if (nodeEquality.isAtLeast(NodeEquality.SEMANTICALLY_EQUAL)) {
            // prevent, that identical is returned, because the iterations itself are not identical
            // although the iterated tasks are
            if (nodeEquality == NodeEquality.IDENTICAL) {
                return NodeEquality.LEXICALLY_EQUAL;
            }
            else {
                return nodeEquality;
            }
        }
        
        return NodeEquality.UNEQUAL;
    }

    /**
     * <p>
     * compares two task tree nodes. One of them must be a selection, the other one can be any task
     * tree node. The method returns a node equality that is not <code>NodeEquality.UNEQUAL</code>
     * if the other node is at least semantically equal to the children of the selection. It
     * returns more concrete equalities, if the equality between the other node and the children
     * of the selection is more concrete.
     * </p> 
     * 
     * @param taskTreeNode  the first task tree node to compare
     * @param taskTreeNode2 the second task tree node to compare
     * 
     * @return as described
     */
    private NodeEquality selectionChildrenSemanticallyEqualNode(ITaskTreeNode taskTreeNode,
                                                                ITaskTreeNode taskTreeNode2)
    {
        ISelection selection = null;
        ITaskTreeNode node = null;
        if (taskTreeNode instanceof ISelection) {
            selection = (ISelection) taskTreeNode;
            node = taskTreeNode2;
        }
        else if (taskTreeNode2 instanceof ISelection) {
            selection = (ISelection) taskTreeNode2;
            node = taskTreeNode;
        }
        else {
            return NodeEquality.UNEQUAL;
        }

        // Iterations, where one has a selection and the other one not can at most be syntactically
        // equal but not identical
        NodeEquality commonDenominatorForAllComparisons = NodeEquality.SYNTACTICALLY_EQUAL;

        for (ITaskTreeNode child : selection.getChildren()) {
            NodeEquality nodeEquality =
                  callRuleManager(node, child, commonDenominatorForAllComparisons);

            if ((nodeEquality == null) || (nodeEquality == NodeEquality.UNEQUAL))
            {
                return NodeEquality.UNEQUAL;
            }
            
            commonDenominatorForAllComparisons =
                commonDenominatorForAllComparisons.getCommonDenominator(nodeEquality);
        }

        return commonDenominatorForAllComparisons;
    }

    /**
     * <p>
     * TODO: comment
     * </p>
     *
     * @param child1
     * @param child2
     * @param requiredEqualityLevel
     * @return
     */
    private NodeEquality callRuleManager(ITaskTreeNode child1,
                                         ITaskTreeNode child2,
                                         NodeEquality  requiredEqualityLevel)
    {
        if (requiredEqualityLevel == null) {
            return mRuleManager.compare(child1, child2);
        }
        else if (mRuleManager.areAtLeastEqual(child1, child2, requiredEqualityLevel)) {
            return requiredEqualityLevel;
        }
        else {
            return NodeEquality.UNEQUAL;
        }
    }
}