split-layers.js

#!/usr/bin/env node
module.exports = {
	splitLayers : function(xmlData, outputDir, outputPrefix, callback) {
		splitLayers2(xmlData, outputDir, outputPrefix, callback);
	}
};

var tilelive = require('tilelive');
var path = require('path');
var fs = require("fs");
var zlib = require("zlib");
var xml2js = require('xml2js');
require('tilelive-bridge').registerProtocols(tilelive);
var XMLWriter = require('xml-writer');

if (require.main == module) {
	main();
}

function main() {
	var args = process.argv;
	args.splice(0, 2); // Remove 'node' and the name of the script

	if (args.length < 1) {
		console.error('Usage: tile-layer-conv.js <Mapnik xml file>');
		process.exit(1);
	}

	var mapnikFile = path.resolve(__dirname, args[0]);
	var outputPrefix = path.parse(mapnikFile).name;

	fs.readFile(mapnikFile, 'utf8', function(err, data) {
		splitLayers2(data, 'out/', outputPrefix, function() {
			process.exit(0);
		});
	});
}

function splitLayers2(mapnikXmlData, outputDir, outputPrefix, callback) {
	xml2js.parseString(mapnikXmlData, function(err, json) {
		output = [];
		json.Map.Layer.forEach(function(layer) {
			var layerName = layer.$.name;
			var layerXml = createLayerXml(json, layer);
			output.push({
				name : layerName,
				xml : layerXml
			});
		});
		var counter = output.length;
		output.forEach(function(layer) {
			var outputFile = path.resolve(__dirname, outputDir + outputPrefix + '-' + layer.name + '.xml');
			fs.writeFile(outputFile, layer.xml, 'utf8', function() {
				counter--;
				if (counter == 0) {
					callback();
				}
			});
		});
	});
}

function createLayerXml(fullJson, layerJson) {
	var xml = new XMLWriter(true);
	xml.startDocument();
	xml.startElement('Map');
	forEachAttribute(fullJson.Map.$, function(key, value) {
		xml.writeAttribute(key, value);
	});
	// Map parameters
	fullJson.Map.Parameters.forEach(function(param) {
		json2xml(xml, param, 'Parameters');
	});
	// The layer itself
	json2xml(xml, layerJson, 'Layer');
	xml.endDocument();
	return xml.toString();
}

function findLayer(layerName, layers) {
	var foundLayer = null;
	layers.some(function(layer) {
		if (layer.$.name == layerName) {
			foundLayer = layer;
			return true;
		}
	});
	if (foundLayer == null) {
		throw new Error('Could not find layer: ' + layerName);
	}
	return foundLayer;
}

function json2xml(writer, object, rootName) {
	// Simple object
	if (typeof object == 'string') {
		writer.writeElement(rootName, object);
		return;
	}
	// Json object
	writer.startElement(rootName);
	if (object.hasOwnProperty('$')) {
		forEachAttribute(object.$, function(key, value) {
			writer.writeAttribute(key, value);
		});
	}
	if (object.hasOwnProperty('_')) {
		writer.text(object._);
	}
	forEachAttribute(object, function(key, value) {
		if (key != '_' && key != '$') {
			if (value.constructor === Array) {
				value.forEach(function(repeatedVal) {
					json2xml(writer, repeatedVal, key);
				});
			} else {
				json2xml(writer, value, key);
			}
		}
	});
	writer.endElement();
}

function forEachAttribute(object, callback) {
	for ( var key in object) {
		if (object.hasOwnProperty(key)) {
			callback(key, object[key]);
		}
	}
}