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/*******************************************************************************
 *  Copyright (C) 2007, 2014:
 *  
 *    - Ferdinando Villa 
 *    - integratedmodelling.org
 *    - any other authors listed in @author annotations
 *
 *    All rights reserved. This file is part of the k.LAB software suite,
 *    meant to enable modular, collaborative, integrated 
 *    development of interoperable data and model components. For
 *    details, see http://integratedmodelling.org.
 *    
 *    This program is free software; you can redistribute it and/or
 *    modify it under the terms of the Affero General Public License 
 *    Version 3 or any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but without any warranty; without even the implied warranty of
 *    merchantability or fitness for a particular purpose.  See the
 *    Affero General Public License for more details.
 *  
 *     You should have received a copy of the Affero General Public License
 *     along with this program; if not, write to the Free Software
 *     Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *     The license is also available at: https://www.gnu.org/licenses/agpl.html
 *******************************************************************************/
package org.integratedmodelling.lang;

import org.integratedmodelling.exceptions.KlabValidationException;

/**
 * A logical connector, representing one of the possible four connectors (union (or), intersection (and), 
 *    exclusion (not), disjunction (xor)).

 * A bit complicated as a wrapper for an int, but it solves several problems related to string conversions and
 * equality. Private constructors force use of parseLogicalConnector to obtain one of the four possible static
 * instances. Because only the static members are used, == can be used to check for equality, although equals()
 * can be also used with both integers, LogicalConnectors and Strings. toString() will work properly.
 * 
 * @author Ferdinando Villa
 */
public class LogicalConnector {

    static public final int _UNION          = 0;
    static public final int _INTERSECTION   = 1;
    static public final int _EXCLUSION      = 2;
    static public final int _DISJOINT_UNION = 3;

    static public LogicalConnector UNION          = new LogicalConnector(_UNION);
    static public LogicalConnector INTERSECTION   = new LogicalConnector(_INTERSECTION);
    static public LogicalConnector EXCLUSION      = new LogicalConnector(_EXCLUSION);
    static public LogicalConnector DISJOINT_UNION = new LogicalConnector(_DISJOINT_UNION);

    /**
     * The value of a connector. Use this one in switch statements, or use equality 
     * with static connector members in if statements.
     */
    public int value;

    /**
     * Checks if string is a valid representation of a logical connector.
     * @param s a string
     * @return true if string represents a connector.
     */
    public static boolean isLogicalConnector(String s) {
        // TODO
        boolean ret = true;
        try {
            parseLogicalConnector(s);
        } catch (KlabValidationException e) {
            ret = false;
        }
        return ret;
    }

    /**
     * Parses string into connector and returns result. Will never allocate new connectors, but only
     * return the static instance corresponding to the string. 
     * @param s A string representing a logical connector.
     * @return a LogicalConnector
     * @throws KlabValidationException if string is silly.
     */
    public static LogicalConnector parseLogicalConnector(String s) throws KlabValidationException {

        LogicalConnector value = null;

        s = s.trim().toLowerCase();

        // TODO support formal notation quantifiers too
        if (s.equals("and") || s.equals("intersection"))
            value = INTERSECTION;
        else if (s.equals("or") || s.equals("union"))
            value = UNION;
        else if (s.equals("not") || s.equals("exclusion"))
            value = EXCLUSION;
        else if (s.equals("xor") || s.equals("disjoint-union"))
            value = DISJOINT_UNION;
        else
            throw new KlabValidationException(s + " is not a valid logical connector");

        return value;
    }

    private LogicalConnector(int i) {
        value = i;
    }

    /**
     * 
     * @param c
     * @return true if same
     */
    public boolean equals(LogicalConnector c) {
        return c.value == value;
    }

    public boolean equals(int c) {
        return value == c;
    }

    public boolean equals(String s) throws KlabValidationException {
        return value == parseLogicalConnector(s).value;
    }

    @Override
    public String toString() {

        String ret = "";
        switch (value) {
        case _UNION:
            ret = "or";
            break;
        case _INTERSECTION:
            ret = "and";
            break;
        case _EXCLUSION:
            ret = "not";
            break;
        case _DISJOINT_UNION:
            ret = "xor";
            break;
        }

        return ret;
    }
}