/* Copyright (c) 2006-2007 MetaCarta, Inc., published under a modified BSD license.
 * See http://svn.openlayers.org/trunk/openlayers/repository-license.txt 
 * for the full text of the license. */

/**
 * @requires OpenLayers/Util.js
 * 
 * Class: OpenLayers.Projection
 * Class for coordinate transformations between coordinate systems.
 *     Depends on the proj4js library. If proj4js is not available, 
 *     then this is just an empty stub.
 */
OpenLayers.Projection = OpenLayers.Class({
    
    /**
     * Constructor: OpenLayers.Projection
     * This class offers several methods for interacting with a wrapped 
     *     pro4js projection object. 
     *
     * Parameters:
     * options - {Object} An optional object with properties to set on the
     *     format
     *
     * Returns:
     * {<OpenLayers.Projection>} A projection object.
     */
    initialize: function(projCode, options) {
        OpenLayers.Util.extend(this, options);
        this.projCode = projCode;
        if (window.Proj4js) {
            this.proj = new Proj4js.Proj(projCode);
        }
    },
    
    /**
     * APIMethod: getCode
     * Get the string SRS code.
     *
     * Returns:
     * {String} The SRS code.
     */
    getCode: function() {
        return this.proj ? this.proj.srsCode : this.projCode;
    },
   
    /**
     * APIMethod: getUnits
     * Get the units string for the projection -- returns null if 
     *     proj4js is not available.
     *
     * Returns:
     * {String} The units abbreviation.
     */
    getUnits: function() {
        return this.proj ? this.proj.units : null;
    },

    /**
     * Method: toString
     * Convert projection to string (getCode wrapper).
     *
     * Returns:
     * {String} The projection code.
     */
    toString: function() {
        return this.getCode();
    },

    /**
     * Method: equals
     * Test equality of two projection instances.  Determines equality based
     *     soley on the projection code.
     *
     * Returns:
     * {Boolean} The two projections are equivalent.
     */
    equals: function(projection) {
        if (this.getCode() == projection.getCode()) {
            return true;
        }
        return false;
    },

    /* Method: destroy
     * Destroy projection object.
     */
    destroy: function() {
        delete this.proj;
        delete this.projCode;
    },
    
    CLASS_NAME: "OpenLayers.Projection" 
});     

/**
 * APIMethod: transform
 * Read data from a string, and return an object whose type depends on the
 * subclass. 
 * 
 * Parameters:
 * point - {object} input horizontal coodinate
 * sourceProj - {OpenLayers.Projection} source map coordinate system
 * destProj - {OpenLayers.Projection} destination map coordinate system
 *
 * Returns:
 * point - {object} trasnformed coordinate
 */
OpenLayers.Projection.transform = function(point, source, dest) {
    if (source.proj && dest.proj) {
        point = Proj4js.transform(source.proj, dest.proj, point);
    }
    return point;
};