settings_migrator.js

"use strict"
const DefaultSettings = {
    "enabled": true,
    "systemNotice": false,
    "notice": false,
    "stream": false,
	"cc": [
		"</font><font color=\"#ffff00\">"
	],
	"rate": [
		1
	],	
	 "speaks": true,	
    "chat-name": "Guide"	
};

module.exports = function MigrateSettings(from_ver, to_ver, settings) {
    if (from_ver === undefined) {
        // Migrate legacy config file
        return Object.assign(Object.assign({}, DefaultSettings), settings);
    } else if (from_ver === null) {
        // No config file exists, use default settings
        return DefaultSettings;
    } else {
        // Migrate from older version (using the new system) to latest one
        if (from_ver + 1 < to_ver) {
            // Recursively upgrade in one-version steps
            settings = MigrateSettings(from_ver, from_ver + 1, settings);
            return MigrateSettings(from_ver + 1, to_ver, settings);
        }
        
        // If we reach this point it's guaranteed that from_ver === to_ver - 1, so we can implement
        // a switch for each version step that upgrades to the next version. This enables us to
        // upgrade from any version to the latest version without additional effort!
        switch(to_ver) {
            default:
                let oldsettings = settings
                
                settings = Object.assign(DefaultSettings, {});
                
                for(let option in oldsettings) {
                    if(settings[option]) {
                        settings[option] = oldsettings[option]
                    }
                }
                
                break;
        }
        
        return settings;
    }
}