package org.maltparser.parser.algorithm.nivre;

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 ArcEagerOracle extends Oracle {

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

    public GuideUserAction predict(DependencyStructure gold, ParserConfiguration config) throws MaltChainedException {
        final NivreConfig nivreConfig = (NivreConfig) config;
        final DependencyNode stackPeek = nivreConfig.getStack().peek();
        final int stackPeekIndex = stackPeek.getIndex();
        final int inputPeekIndex = nivreConfig.getInput().peek().getIndex();

        if (!stackPeek.isRoot() && gold.getTokenNode(stackPeekIndex).getHead().getIndex() == inputPeekIndex) {
            return updateActionContainers(ArcEager.LEFTARC, gold.getTokenNode(stackPeekIndex).getHeadEdge().getLabelSet());
        } else if (gold.getTokenNode(inputPeekIndex).getHead().getIndex() == stackPeekIndex) {
            return updateActionContainers(ArcEager.RIGHTARC, gold.getTokenNode(inputPeekIndex).getHeadEdge().getLabelSet());
        } else if (!nivreConfig.isAllowReduce() && !stackPeek.hasHead()) {
            return updateActionContainers(ArcEager.SHIFT, null);
        } else if (gold.getTokenNode(inputPeekIndex).hasLeftDependent()
                && gold.getTokenNode(inputPeekIndex).getLeftmostDependent().getIndex() < stackPeekIndex) {
            return updateActionContainers(ArcEager.REDUCE, null);
        } else if (gold.getTokenNode(inputPeekIndex).getHead().getIndex() < stackPeekIndex
                && (!gold.getTokenNode(inputPeekIndex).getHead().isRoot() || nivreConfig.isAllowRoot())) {
            return updateActionContainers(ArcEager.REDUCE, null);
        } else {
            return updateActionContainers(ArcEager.SHIFT, null);
        }
    }

    public void finalizeSentence(DependencyStructure dependencyGraph) throws MaltChainedException {
    }

    public void terminate() throws MaltChainedException {
    }
}