const INTERNAL_SECOND_MS = 60 * 1000;
const INTERNAL_MINUTE_MS = 60 * INTERNAL_SECOND_MS;
const INTERNAL_HOUR_MS = 60 * INTERNAL_MINUTE_MS;

var isIndexedDBSupported = 'indexedDB' in window;


$.dbManager = {
    openDatabases: {}
}

$.dbManager.alert = function (msg) {
    alert(msg);
}

$.dbManager.openDatabase = function (name, version, onUpgradeNeeded) {
    let dbManager = this;
    return new Promise(function (resolve, reject) {
        let db = dbManager.openDatabases[name];
        if (db !== undefined && db !== null) {
            resolve(db);
            return;
        }
        let request = indexedDB.open(name, version);
        request.onupgradeneeded = function (event) {
            //Upgrade DB? Drop DB and reload?  For now, drop db
            console.log("onupgradeneeded");

            if (onUpgradeNeeded != null) {
                onUpgradeNeeded(event);
            }
            else {
                dbManager.deleteDatabase(name).then(
                    function onSuccess(db) {
                        resolve(db);
                    },
                    function onError(error) {
                        reject(error);
                    });
            }
            //reject("Upgrade Needed");
        };

        request.onerror = function () {
            console.error("Error: ", request.error);
            reject(request.error);
        };

        request.onblocked = function () {
            console.error();
            reject("Database blocked");
        };

        request.onsuccess = function () {
            let db = request.result;

            db.onversionchange = function (event) {
                let isDeleted = event.newVersion === null;
                db.close();
                if(!isDeleted)
                    alert("Database is outdated, please reload the page: ", event.currentTarget.name)
            };

            console.log("Database opened: ", name);
            if (dbManager.openDatabases == null)
                dbManager.openDatabases = {};

            dbManager.openDatabases[name] = db;
            db.onclose = function () { //TODO: DOesn't appear to be called currently
                console.log('Database connection closed: ', name);
                dbManager.openDatabases[name] = null;
            }
            resolve(db);
        };
    });
}

$.dbManager.closeDatabase = function (name) {
    let currentDB = this;

    return new Promise(function (resolve, reject) {
        let db = currentDB.openDatabases[name];
        if (db != null) {
            db.close();
        }
        currentDB.openDatabases[name] == null;
        resolve();
    });
}

$.dbManager.deleteDatabase = function (name) {
    let currentDB = this;
    return new Promise(function (resolve, reject) {
        let request = indexedDB.deleteDatabase(name);

        request.onerror = function () {
            console.error("Error", request.error);
            reject(request.error);
        };

        request.onsuccess = function () {
            console.log("database deleted: ", name);
            currentDB.openDatabases[name] = null;
            resolve();
        };
    });
}