package org.maltparser.parser.transition;

/**
 * Transition contains one individual transition. For example, Nivre arc-eager
 * algorithms have the unlabeled transition
 * <code>SH</code>,
 * <code>RE</code> and the labeled transition<code>RA</code>,
 * <code>LA</code>. These transition will be four individual transition.
 *
 * @author Joakim Nivre
 * @author Johan Hall
 * @since 1.0
 */
public class Transition implements Comparable<Transition> {

    /**
     * Transition code
     */
    private int code;
    /**
     * Transition symbol
     */
    private String symbol;
    /**
     * <code>true</code> if the transition is labeled, otherwise
     * <code>false</code>
     */
    private boolean labeled;
    private int cachedHash;

    /**
     * Creates a transition
     *
     * @param code	Transition code
     * @param symbol	Transition name
     * @param labeled
     * <code>true</code> if the transition is labeled, otherwise
     * <code>false</code>
     */
    public Transition(int code, String symbol, boolean labeled) {
        this.code = code;
        this.symbol = symbol;
        this.labeled = labeled;
    }

    /**
     * Returns the transition code
     *
     * @return the transition code
     */
    public int getCode() {
        return code;
    }

    /**
     * Returns the transition symbol
     *
     * @return	the transition symbol
     */
    public String getSymbol() {
        return symbol;
    }

    /**
     * Returns true if the transition is labeled, otherwise false
     *
     * @return
     * <code>true</code> if the transition is labeled, otherwise
     * <code>false</code>
     */
    public boolean isLabeled() {
        return labeled;
    }

    public int compareTo(Transition that) {
        final int BEFORE = -1;
        final int EQUAL = 0;
        final int AFTER = 1;
//	    if ( this == that ) return EQUAL;
        if (this.code < that.code) {
            return BEFORE;
        }
        if (this.code > that.code) {
            return AFTER;
        }
        return EQUAL;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        Transition t = (Transition) obj;
        return (code == t.code && symbol.equals(t.symbol) && labeled == t.isLabeled());
    }

    @Override
    public int hashCode() {
        if (cachedHash == 0) {
            int hash = 31 * 7 + code;
            hash = 31 * hash + (null == symbol ? 0 : symbol.hashCode());
            hash = 31 * hash + (labeled ? 1 : 0);
            cachedHash = hash;
        }
        return cachedHash;
    }

    /*
     * (non-Javadoc) @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return symbol + " [" + code + "] " + labeled;
    }
}