tildefriends/apps/gg/gpx.js

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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;
}