Subversion Repositories mkgmap

/*
 * Copyright (C) 2010.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 3 or
 * version 2 as published by the Free Software Foundation.
 *
 * 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 GNU
 * General Public License for more details.
 */
package uk.me.parabola.mkgmap.osmstyle.eval;

import uk.me.parabola.mkgmap.reader.osm.Element;

/**
 * Interface for an node in the style expression language.
 * Operations need have only one operand, use {@link BinaryOp} for
 * when they definitely have two.
 *
 * In spite of the name this covers both values and operations.
 *
 * @author Steve Ratcliffe
 */
public interface Op {

        /**
         * Evaluate the expression.
         * @param el The OSM element to be tested.
         * @return True if the expression is true for the given element.
         */
        public boolean eval(Element el);

        /**
         * Does this operation have a higher priority that the other one?
         * @param other The other operation.
         */
        public boolean hasHigherPriority(Op other);

        /**
         * Get the first operand.
         */
        public Op getFirst();

        /**
         * Set the first operand.
         */
        public void setFirst(Op first);

        /**
         * Return the second operand for a binary operation. If this is not a binary operation,
         * then null is returned.
         * @return The right hand side, or null if there is not one.
         */
        public Op getSecond();

        /** Get the operation type */
        public NodeType getType();

        /**
         * For operations that are value types this is the string value.
         *
         * Only applies to nodes of type VALUE and FUNCTION, returns null for all
         * other kinds of node.
         *
         * @return The value, or UnsupportedOperationException if it does not have a value.
         */
        public String value(Element el);

        /**
         * For a value-type node, this is a key value associated with value. For a base Value node
         * this is the same as value(), but if value() is overridden then it may not be.
         */
        public String getKeyValue();

        /**
         * Test the node type and return true if it matches the given argument.
         */
        public boolean isType(NodeType value);

        /**
         * For an operation this is a number that determines the precedence of this operation.
         * Used when building the node tree. Higher numbers bind more tightly.
         */
        public int priority();

}