db.js

const sqlite3 = require("sqlite3");

/**
 * Stores one database instance per fhir version
 */
const DB_INSTANCES = {};

function getDatabase(fhirVersion)
{
    if (!DB_INSTANCES[fhirVersion]) {
        const DB = new sqlite3.Database(
            `${__dirname}/database.r${fhirVersion}.db`
        );

        /**
         * Calls database methods and returns a promise
         * @param {String} method
         * @param {[*]} args 
         */
        Object.defineProperty(DB, "promise", {
            get() {
                return function(method, ...args) {
                    return new Promise((resolve, reject) => {
                        DB[method](...args, (error, result) => {
                            if (error) {
                                return reject(error);
                            }
                            resolve(result);
                        });
                    });
                }
            }
        });

        DB_INSTANCES[fhirVersion] = DB;
    }

    return DB_INSTANCES[fhirVersion];
}

module.exports = getDatabase;