convert-tab-groups-backup-to-html.js

/**
 * Converts a Tab Groups backup to HTML.
 */
function convertTabGroupsBackupToHtml(backup) {
	if (undefined === backup.version
			|| 'tabGroups' != backup.version[0] || 1 != backup.version[1]) {
		throw new Error('Unexpected input');
	}
	return [
		'<ul>',
		backup.windows.map(window => {
			// Create a map which maps group identifiers to their tabs.
			const groupIdentifierTabsMap = {};
			window.tabs.forEach(tab => {
				// Determine the group this tab is in.
				var groupIdentifier /* = undefined */;
				if (undefined !== tab.extData['tabview-tab']) {
					try {
						groupIdentifier = JSON.parse(tab.extData['tabview-tab'])['groupID'];
					} catch (error) {
						// In case the data chunk is not valid JSON (or that JSON does not represent an object or something) continue
						// as if there was no group identifier.
					}
				}
				if (undefined === groupIdentifier) {
					groupIdentifier = 'none';
				}
				// Add the tab to the map.
				if (undefined === groupIdentifierTabsMap[groupIdentifier]) {
					groupIdentifierTabsMap[groupIdentifier] = [tab];
				} else /* if (undefined !== groupIdentifierTabsMap[groupIdentifier]) */ {
					groupIdentifierTabsMap[groupIdentifier].push(tab);
				}
			});
			// Parse the map which maps group identifiers to meta data about that group.
			var groupIdentifierMetaDataMap;
			if (undefined !== window.extData['tabview-group']) {
				try {
					groupIdentifierMetaDataMap = JSON.parse(window.extData['tabview-group']);
				} catch (error) {
					// In case the data chunk is not valid JSON, continue as if there was no data.
				}
			}
			if (undefined === groupIdentifierMetaDataMap) {
				groupIdentifierMetaDataMap = {};
			}
			return [
				'<li>',
				'<ul>',
				Object.keys(groupIdentifierTabsMap).map(groupIdentifier => {
					// Fetch the title.
					var title;
					if (undefined !== groupIdentifierMetaDataMap[groupIdentifier]) {
						title = groupIdentifierMetaDataMap[groupIdentifier]['title'];
					}
					if (undefined === title
							|| 0 == title.length) {
						title = groupIdentifier;
					}
					return [
						'<li>',
						['<h4>', title, '</h4>'].join(''),
						'<ul>',
						groupIdentifierTabsMap[groupIdentifier].map(tab => {
							return [
								'<li>',
								['<a href="', tab.entries[0].url, '">', tab.entries[0].title, '</a>'].join(''),
								'</li>'
							].join('\n');
						}).join('\n'),
						'</ul>',
						'</li>'
					].join('\n');
				}).join('\n'),
				'</ul>',
				'</li>'
			].join('\n');
		}).join('\n'),
		'</ul>'
	].join('\n');
}