HeliosLauncher/app/assets/js/preloader.js

const {ipcRenderer}  = require('electron')
const fs             = require('fs-extra')
const os             = require('os')
const path           = require('path')

const ConfigManager  = require('./configmanager')
const DistroManager  = require('./distromanager')
const LangLoader     = require('./langloader')
const { LoggerUtil } = require('helios-core')

const logger = LoggerUtil.getLogger('Preloader')

logger.info('Loading..')

// Load ConfigManager
ConfigManager.load()

// Load Strings
LangLoader.loadLanguage('en_US')

function onDistroLoad(data){
    if(data != null){
        
        // Resolve the selected server if its value has yet to be set.
        if(ConfigManager.getSelectedServer() == null || data.getServer(ConfigManager.getSelectedServer()) == null){
            logger.info('Determining default selected server..')
            ConfigManager.setSelectedServer(data.getMainServer().getID())
            ConfigManager.save()
        }
    }
    ipcRenderer.send('distributionIndexDone', data != null)
}

// Ensure Distribution is downloaded and cached.
DistroManager.pullRemote().then((data) => {
    logger.info('Loaded distribution index.')

    onDistroLoad(data)

}).catch((err) => {
    logger.info('Failed to load distribution index.')
    logger.error(err)

    logger.info('Attempting to load an older version of the distribution index.')
    // Try getting a local copy, better than nothing.
    DistroManager.pullLocal().then((data) => {
        logger.info('Successfully loaded an older version of the distribution index.')

        onDistroLoad(data)


    }).catch((err) => {

        logger.info('Failed to load an older version of the distribution index.')
        logger.info('Application cannot run.')
        logger.error(err)

        onDistroLoad(null)

    })

})

// Clean up temp dir incase previous launches ended unexpectedly. 
fs.remove(path.join(os.tmpdir(), ConfigManager.getTempNativeFolder()), (err) => {
    if(err){
        logger.warn('Error while cleaning natives directory', err)
    } else {
        logger.info('Cleaned natives directory.')
    }
})