Projective.java

package org.maltparser.parser.algorithm.stack;

import java.util.Stack;
import org.maltparser.core.exception.MaltChainedException;
import org.maltparser.core.syntaxgraph.LabelSet;
import org.maltparser.core.syntaxgraph.edge.Edge;
import org.maltparser.core.syntaxgraph.node.DependencyNode;
import org.maltparser.parser.ParserConfiguration;
import org.maltparser.parser.TransitionSystem;
import org.maltparser.parser.history.GuideUserHistory;
import org.maltparser.parser.history.History;
import org.maltparser.parser.history.action.ComplexDecisionAction;
import org.maltparser.parser.history.action.GuideUserAction;
import org.maltparser.parser.transition.TransitionTable;

/**
 * @author Johan Hall
 *
 */
public class Projective extends TransitionSystem {

    protected static final int SHIFT = 1;
    protected static final int RIGHTARC = 2;
    protected static final int LEFTARC = 3;

    public Projective() throws MaltChainedException {
        super();
    }

    public void apply(GuideUserAction currentAction, ParserConfiguration configuration) throws MaltChainedException {
        final StackConfig config = (StackConfig) configuration;
        final Stack<DependencyNode> stack = config.getStack();
        currentAction.getAction(actionContainers);
        Edge e;
        DependencyNode head;
        DependencyNode dep;
        switch (transActionContainer.getActionCode()) {
            case LEFTARC:
                head = stack.pop();
                dep = stack.pop();
                e = config.getDependencyStructure().addDependencyEdge(head.getIndex(), dep.getIndex());
                addEdgeLabels(e);
                stack.push(head);
                break;
            case RIGHTARC:
                dep = stack.pop();
                e = config.getDependencyStructure().addDependencyEdge(stack.peek().getIndex(), dep.getIndex());
                addEdgeLabels(e);
                break;
            default:
                final Stack<DependencyNode> input = config.getInput();
                if (input.isEmpty()) {
                    stack.pop();
                } else {
                    stack.push(input.pop()); // SHIFT
                }
                break;
        }
    }

    public boolean permissible(GuideUserAction currentAction, ParserConfiguration configuration) throws MaltChainedException {
        final StackConfig config = (StackConfig) configuration;
        currentAction.getAction(actionContainers);
        final int trans = transActionContainer.getActionCode();
        if ((trans == LEFTARC || trans == RIGHTARC) && !isActionContainersLabeled()) {
            return false;
        }
        final Stack<DependencyNode> stack = config.getStack();
        if ((trans == LEFTARC || trans == RIGHTARC) && stack.size() < 2) {
            return false;
        }
        if (trans == LEFTARC && stack.get(stack.size() - 2).isRoot()) {
            return false;
        }
        if (trans == SHIFT && config.getInput().isEmpty()) {
            return false;
        }

        return true;
    }

    public GuideUserAction getDeterministicAction(GuideUserHistory history, ParserConfiguration config) throws MaltChainedException {
        return null;
    }

    protected void addAvailableTransitionToTable(TransitionTable ttable) throws MaltChainedException {
        ttable.addTransition(SHIFT, "SH", false, null);
        ttable.addTransition(RIGHTARC, "RA", true, null);
        ttable.addTransition(LEFTARC, "LA", true, null);
    }

    protected void initWithDefaultTransitions(GuideUserHistory history) throws MaltChainedException {
        GuideUserAction currentAction = new ComplexDecisionAction((History) history);

        transActionContainer.setAction(SHIFT);
        for (int i = 0; i < arcLabelActionContainers.length; i++) {
            arcLabelActionContainers[i].setAction(-1);
        }
        currentAction.addAction(actionContainers);
    }

    public String getName() {
        return "projective";
    }

    public GuideUserAction defaultAction(GuideUserHistory history, ParserConfiguration configuration) throws MaltChainedException {
        if (((StackConfig) configuration).getInput().isEmpty()) {
            LabelSet labelSet = ((StackConfig) configuration).getDependencyGraph().getDefaultRootEdgeLabels();
            return updateActionContainers(history, RIGHTARC, labelSet);
        }
        return updateActionContainers(history, SHIFT, null);
    }
}