//   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.ISelection;
import de.ugoe.cs.autoquest.tasktrees.treeifc.ITaskTreeNode;

/**
 * <p>
 * This class is capable of comparing any task tree node which is not a selection with a
 * selection. This is needed, because selections may contain exactly that node. Therefore, if
 * this node is selected out of a selection the selection is equal to the node itself. 
 * The rule returns lexically equal, it the selection contains a lexically equal node. The same
 * applies for syntactical and semantical equality.
 * </p>

 * @author Patrick Harms
 */
public class NodeAndSelectionComparisonRule 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
     */
    NodeAndSelectionComparisonRule(NodeEqualityRuleManager ruleManager) {
        super();
        mRuleManager = ruleManager;
    }

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

    /* (non-Javadoc)
     * @see NodeComparisonRule#areLexicallyEqual(ITaskTreeNode, ITaskTreeNode)
     */
    @Override
    public boolean areLexicallyEqual(ITaskTreeNode node1, ITaskTreeNode node2) {
        NodeEquality equality = getEquality(node1, node2, NodeEquality.LEXICALLY_EQUAL);
        return (equality != null) && (equality.isAtLeast(NodeEquality.LEXICALLY_EQUAL));
    }

    /* (non-Javadoc)
     * @see NodeComparisonRule#areSyntacticallyEqual(ITaskTreeNode, ITaskTreeNode)
     */
    @Override
    public boolean areSyntacticallyEqual(ITaskTreeNode node1, ITaskTreeNode node2) {
        NodeEquality equality = getEquality(node1, node2, NodeEquality.SYNTACTICALLY_EQUAL);
        return (equality != null) && (equality.isAtLeast(NodeEquality.SYNTACTICALLY_EQUAL));
    }

    /* (non-Javadoc)
     * @see NodeComparisonRule#areSemanticallyEqual(ITaskTreeNode, ITaskTreeNode)
     */
    @Override
    public boolean areSemanticallyEqual(ITaskTreeNode node1, ITaskTreeNode node2) {
        NodeEquality equality = getEquality(node1, node2, NodeEquality.SEMANTICALLY_EQUAL);
        return (equality != null) && (equality.isAtLeast(NodeEquality.SEMANTICALLY_EQUAL));
    }

    /* (non-Javadoc)
     * @see NodeComparisonRule#compare(ITaskTreeNode, ITaskTreeNode)
     */
    @Override
    public NodeEquality compare(ITaskTreeNode node1, ITaskTreeNode node2) {
        return getEquality(node1, node2, null);
    }
    
    /**
     * 
     */
    private NodeEquality getEquality(ITaskTreeNode node1,
                                     ITaskTreeNode node2,
                                     NodeEquality  requiredEqualityLevel)
    {
        ISelection selection = null;
        ITaskTreeNode node = null;
        
        if (node1 instanceof ISelection) {
            if (node2 instanceof ISelection) {
                // the rule is not responsible for two selections
                return null;
            }
            
            selection = (ISelection) node1;
            node = node2;
        }
        else if (node2 instanceof ISelection) {
            if (node1 instanceof ISelection) {
                // the rule is not responsible for two selections
                return null;
            }
            
            selection = (ISelection) node2;
            node = node1;
        }
        else {
            return null;
        }

        // now, that we found the selection and the node, lets compare the children of the selection
        // with the node.
        List<ITaskTreeNode> children = selection.getChildren();
        
        if (children.size() < 1) {
            return null;
        }

        NodeEquality mostConcreteNodeEquality = null;
        
        for (ITaskTreeNode child : children) {
            NodeEquality nodeEquality = callRuleManager(child, node, requiredEqualityLevel);
            
            if (nodeEquality != NodeEquality.UNEQUAL) {
                if (mostConcreteNodeEquality == null) {
                    mostConcreteNodeEquality = nodeEquality;
                }
                else if (mostConcreteNodeEquality.isAtLeast(nodeEquality)) {
                    mostConcreteNodeEquality = nodeEquality;
                    
                }
                
                if ((requiredEqualityLevel != null) &&
                    (mostConcreteNodeEquality.isAtLeast(requiredEqualityLevel)))
                {
                    // if we found one child of the selection that is as equal as required, then
                    // we can consider the selection to be sufficiently equal to the other node.
                    // So we break up checking further children.
                    break;
                }
            }
        }
        
        // although the subtask may be identical to the node, we can not return identical, as
        // the selection is not identical to the node, but at most lexically equal
        if (mostConcreteNodeEquality == NodeEquality.IDENTICAL) {
            return NodeEquality.LEXICALLY_EQUAL;
        }
        else {
            return mostConcreteNodeEquality;
        }

    }
    
    /**
     * <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;
        }
    }
}