terriajs/lib/Models/OpenStreetMapCatalogItem.js

Geospatial data visualization platform.

'use strict';

/*global require*/
var URI = require('urijs');
var defined = require('terriajs-cesium/Source/Core/defined');
var UrlTemplateImageryProvider = require('terriajs-cesium/Source/Scene/UrlTemplateImageryProvider');
var defineProperties = require('terriajs-cesium/Source/Core/defineProperties');
var knockout = require('terriajs-cesium/Source/ThirdParty/knockout');
var ImageryLayerCatalogItem = require('./ImageryLayerCatalogItem');
var inherit = require('../Core/inherit');
var proxyCatalogItemUrl = require('./proxyCatalogItemUrl');
var WebMercatorTilingScheme = require('terriajs-cesium/Source/Core/WebMercatorTilingScheme');

/**
 * A {@link ImageryLayerCatalogItem} representing a layer from the Open Street Map server.
 *
 * @alias OpenStreetMapCatalogItem
 * @constructor
 * @extends ImageryLayerCatalogItem
 *
 * @param {Terria} terria The Terria instance.
 */
var OpenStreetMapCatalogItem = function(terria) {
    ImageryLayerCatalogItem.call(this, terria);

    /**
     * Gets or sets the file extension used to retrieve Open Street Map data
     * This property is observable.
     * @type {String}
     */
    this.fileExtension = 'png';

    /**
     * Gets or sets the maximum tile level to retrieve from Open Street Map data
     * This property is observable.
     * @type {String}
     */
    this.maximumLevel = 25;

    /**
     * Gets or sets the attribution to display with the data
     * This property is observable.
     * @type {String}
     */
    this.attribution = undefined;

    /**
     * Gets or sets the array of subdomains, one of which will be prepended to each tile URL.
     * This property is observable.
     * @type {Array}
     */
     this.subdomains = undefined;

    knockout.track(this, ['fileExtension', 'maximumLevel', 'attribution']);
};

inherit(ImageryLayerCatalogItem, OpenStreetMapCatalogItem);

defineProperties(OpenStreetMapCatalogItem.prototype, {
    /**
     * Gets the type of data item represented by this instance.
     * @memberOf OpenStreetMapCatalogItem.prototype
     * @type {String}
     */
    type : {
        get : function() {
            return 'open-street-map';
        }
    },

    /**
     * Gets a human-readable name for this type of data source, 'OpenStreet Map'.
     * @memberOf OpenStreetMapCatalogItem.prototype
     * @type {String}
     */
    typeName : {
        get : function() {
            return 'Open Street Map';
        }
    }
});

OpenStreetMapCatalogItem.prototype._createImageryProvider = function() {
    var uri = new URI(this.url);

    if (defined(this.subdomains) && this.url.indexOf('{s}') < 0) {
        uri.hostname('{s}.' + uri.hostname());
    }

    // Don't use URIjs to add this part of the path, because it has an annoying habit of
    // encoding the `{` and `}` characters (i.e. they become `%7B` and `%7D`)
    var templateUrl = uri.toString();
    if (templateUrl[templateUrl.length - 1] !== '/') {
        templateUrl += '/';
    }

    templateUrl += '{z}/{x}/{y}.' + this.fileExtension;

    return new UrlTemplateImageryProvider({
        url : cleanAndProxyUrl(this, templateUrl),
        credit: this.attribution,
        tilingScheme: new WebMercatorTilingScheme(),
        tileWidth: 256,
        tileHeight: 256,
        minimumLevel: 0,
        maximumLevel: this.maximumLevel,
        rectangle: this.clipToRectangle ? this.rectangle : undefined,
        subdomains: this.subdomains
    });
};

function cleanAndProxyUrl(catalogItem, url) {
    return proxyCatalogItemUrl(catalogItem, cleanUrl(url));
}

function cleanUrl(url) {
    // Strip off the search portion of the URL
    var uri = new URI(url);
    uri.search('');
    return uri.toString();
}

module.exports = OpenStreetMapCatalogItem;