/* This file is part of VoltDB.
 * Copyright (C) 2008-2010 VoltDB L.L.C.
 *
 * VoltDB is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * VoltDB 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
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with VoltDB.  If not, see <http://www.gnu.org/licenses/>.
 */

package org.voltdb.expressions;

import org.json.JSONException;
import org.json.JSONObject;
import org.json.JSONStringer;
import org.voltdb.VoltType;
import org.voltdb.catalog.Database;
import org.voltdb.types.*;

/**
 *
 */
public class ConstantValueExpression extends AbstractValueExpression {

    public enum Members {
        VALUE;
    }

    protected String m_value = null;
    protected boolean m_isNull = true;

    public ConstantValueExpression() {
        super(ExpressionType.VALUE_CONSTANT);
    }
    public ConstantValueExpression(AbstractExpression left, AbstractExpression right) {
        super(ExpressionType.VALUE_CONSTANT, null, null);
        assert(left == null);
        assert(right == null);
    }

    @Override
    public Object clone() throws CloneNotSupportedException {
        ConstantValueExpression clone = (ConstantValueExpression)super.clone();
        clone.m_value = m_value;
        clone.m_isNull = m_isNull;
        return clone;
    }

    @Override
    public void validate() throws Exception {
        super.validate();

        // Make sure our value is not null
        if (m_value == null && !m_isNull)
        {
            throw new Exception("ERROR: The constant value for '" + this +
                                "' is inconsistently null");
        // Make sure the value type is something we support here
        } else if (m_valueType == VoltType.NULL ||
                   m_valueType == VoltType.VOLTTABLE) {
            throw new Exception("ERROR: Invalid constant value type '" + m_valueType + "' for '" + this + "'");
        }
    }

    /**
     * @return the value
     */
    public String getValue() {
        return m_value;
    }

    /**
     * @param value the value to set
     */
    public void setValue(String value) {
        m_value = value;
        m_isNull = false;
        if (m_value == null || m_value.equals("NULL"))
        {
            m_isNull = true;
        }
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        
        if (obj instanceof ConstantValueExpression == false) return false;
        ConstantValueExpression expr = (ConstantValueExpression) obj;

        if (expr.m_isNull && m_isNull)
        {
            return true;
        }

        if (expr.m_isNull != m_isNull)
        {
            return false;
        }

        if (expr.m_value.equals(m_value) == false)
            return false;

        // if all seems well, defer to the superclass, which checks kids
        return super.equals(obj);
    }

    @Override
    public void toJSONString(JSONStringer stringer) throws JSONException {
        super.toJSONString(stringer);
        stringer.key(Members.VALUE.name());
        if (m_isNull)
        {
            stringer.value("NULL");
        }
        else
        {
            switch (m_valueType)
            {
            case INVALID:
                throw new JSONException("ConstantValueExpression.toJSONString(): value_type should never be VoltType.INVALID");
            case NULL:
                throw new JSONException("ConstantValueExpression.toJSONString(): And they should be never be this either! VoltType.NULL");
            case TINYINT:
                stringer.value(Long.valueOf(m_value));
                break;
            case SMALLINT:
                stringer.value(Long.valueOf(m_value));
                break;
            case INTEGER:
                stringer.value(Long.valueOf(m_value));
                break;
            case BIGINT:
                stringer.value(Long.valueOf(m_value));
                break;
            case FLOAT:
                stringer.value(Double.valueOf(m_value));
                break;
            case STRING:
                stringer.value(m_value);
                break;
            case TIMESTAMP:
                stringer.value(Long.valueOf(m_value));
                break;
            case DECIMAL:
                stringer.value(m_value);
                break;
            default:
                throw new JSONException("ConstantValueExpression.toJSONString(): Unrecognized value_type " + m_valueType);
            }
        }
    }

    @Override
    public void loadFromJSONObject(JSONObject obj, Database db) throws JSONException {
        if (!obj.isNull(Members.VALUE.name())) {
            m_value = obj.getString(Members.VALUE.name());
        }
    }
}