Attempt to support .gpx files.

git-svn-id: https://www.unprompted.com/svn/projects/tildefriends/trunk@4389 ed5197a5-7fde-0310-b194-c3ffbd925b24

apps/gg/gpx.js

@@ -0,0 +1,81 @@
+function xml_parse(xml) {
+	let result;
+	let path = [];
+	let tag_begin;
+	let text_begin;
+	for (let i = 0; i < xml.length; i++) {
+		let c = xml.charAt(i);
+		if (!tag_begin && c == '<') {
+			if (i > text_begin && path.length) {
+				let value = xml.substring(text_begin, i);
+				if (!/^\s*$/.test(value)) {
+					path[path.length - 1].value = value;
+				}
+			}
+			tag_begin = i + 1;
+		} else if (tag_begin && c == '>') {
+			let tag = xml.substring(tag_begin, i).trim();
+			if (tag.startsWith('?') && tag.endsWith('?')) {
+				/* Ignore directives. */
+			} else  if (tag.startsWith('/')) {
+				path.pop();
+			} else {
+				let parts = tag.split(' ');
+				let attributes = {};
+				for (let j = 1; j < parts.length; j++) {
+					let eq = parts[j].indexOf('=');
+					let value = parts[j].substring(eq + 1);
+					if (value.startsWith('"') && value.endsWith('"')) {
+						value = value.substring(1, value.length - 1);
+					}
+					attributes[parts[j].substring(0, eq)] = value;
+				}
+				let next = {name: parts[0], children: [], attributes: attributes};
+				if (path.length) {
+					path[path.length - 1].children.push(next);
+				} else {
+					result = next;
+				}
+				if (!tag.endsWith('/')) {
+					path.push(next);
+				}
+			}
+			tag_begin = undefined;
+			text_begin = i + 1;
+		}
+	}
+	return result;
+}
+
+function* xml_each(node, name) {
+	for (let child of node.children) {
+		if (child.name == name) {
+			yield child;
+		}
+	}
+}
+
+export function gpx_parse(xml) {
+	let result = {segments: []};
+	let tree = xml_parse(xml);
+	if (tree?.name == 'gpx') {
+		for (let trk of xml_each(tree, 'trk')) {
+			for (let trkseg of xml_each(trk, 'trkseg')) {
+				let segment = [];
+				for (let trkpt of xml_each(trkseg, 'trkpt')) {
+					segment.push({lat: parseFloat(trkpt.attributes.lat), lon: parseFloat(trkpt.attributes.lon)});
+				}
+				result.segments.push(segment);
+			}
+		}
+	}
+	for (let metadata of xml_each(tree, 'metadata')) {
+		for (let link of xml_each(metadata, 'link')) {
+			result.link = link.attributes.href;
+		}
+		for (let time of xml_each(metadata, 'time')) {
+			result.time = time.value;
+		}
+	}
+	return result;
+}