package org.maltparser.parser.algorithm.stack;

import java.util.Stack;
import org.maltparser.core.exception.MaltChainedException;
import org.maltparser.core.syntaxgraph.DependencyStructure;
import org.maltparser.core.syntaxgraph.node.DependencyNode;
import org.maltparser.parser.DependencyParserConfig;
import org.maltparser.parser.Oracle;
import org.maltparser.parser.ParserConfiguration;
import org.maltparser.parser.history.GuideUserHistory;
import org.maltparser.parser.history.action.GuideUserAction;

/**
 * @author Johan Hall
 *
 */
public class ProjectiveOracle extends Oracle {

    public ProjectiveOracle(DependencyParserConfig manager, GuideUserHistory history) throws MaltChainedException {
        super(manager, history);
        setGuideName("projective");
    }

    public GuideUserAction predict(DependencyStructure gold, ParserConfiguration configuration) throws MaltChainedException {
        StackConfig config = (StackConfig) configuration;
        Stack<DependencyNode> stack = config.getStack();

        if (stack.size() < 2) {
            return updateActionContainers(Projective.SHIFT, null);
        } else {
            DependencyNode left = stack.get(stack.size() - 2);
            int leftIndex = left.getIndex();
            int rightIndex = stack.get(stack.size() - 1).getIndex();
            if (!left.isRoot() && gold.getTokenNode(leftIndex).getHead().getIndex() == rightIndex) {
                return updateActionContainers(Projective.LEFTARC, gold.getTokenNode(leftIndex).getHeadEdge().getLabelSet());
            } else if (gold.getTokenNode(rightIndex).getHead().getIndex() == leftIndex && checkRightDependent(gold, config.getDependencyGraph(), rightIndex)) {
                return updateActionContainers(Projective.RIGHTARC, gold.getTokenNode(rightIndex).getHeadEdge().getLabelSet());
            } else {
                return updateActionContainers(Projective.SHIFT, null);
            } // Solve the problem with non-projective input.
        }
    }

    private boolean checkRightDependent(DependencyStructure gold, DependencyStructure parseDependencyGraph, int index) throws MaltChainedException {
        if (gold.getTokenNode(index).getRightmostDependent() == null) {
            return true;
        } else if (parseDependencyGraph.getTokenNode(index).getRightmostDependent() != null) {
            if (gold.getTokenNode(index).getRightmostDependent().getIndex() == parseDependencyGraph.getTokenNode(index).getRightmostDependent().getIndex()) {
                return true;
            }
        }
        return false;
    }

    public void finalizeSentence(DependencyStructure dependencyGraph) throws MaltChainedException {
    }

    public void terminate() throws MaltChainedException {
    }
}