class Base {

    constructor() {

    }

    async save() {
        if (!this.isValid()) {
            return;
        }
        try {
            const [element, created] = await (await this.getModel()).findOrCreate({
                where: await this.#createWhereClause()
            });
            if (created) {
                logger.debug('created \'' + this.tableName + '\' entry: ' + JSON.stringify(element));
            }
            if (element?.id === undefined) {
                return undefined;
            }
            this.#fillThis(element);
        } catch (error) {
            logger.error('error finding or creating \'' + this.tableName + '\' entry: \'' + JSON.stringify(this) + '\' > ' + error);
        }
    }

    async find() {
        if (!this.isValid()) {
            return;
        }
        try {
            const element = await (await this.getModel()).findOne({
                where: await this.#createWhereClause()
            });
            if (element?.id === undefined) {
                return undefined;
            }
            this.#fillThis(element);
        } catch (error) {
            logger.error('error finding \'' + this.tableName + '\' entry: \'' + JSON.stringify(this) + '\' > ' + error);
        }
    }

    async createTable() {
        return await createTable();
    }

    async createTable() {
        const model = await this.getModel();
        if (model === undefined) {
            return;
        }
        await model.sync({ alter: true });
    }

    async getModel() {
        return undefined;
    }

    isValid() {
        return false;
    }

    isRelationTable() {
        return this.relationTable === true;
    }

    #fillThis(data) {
        if (data === undefined || data.dataValues === undefined || data.dataValues.id === undefined || data.dataValues.id < 0) {
            return;
        }
        for (const key in data.dataValues) {
            this[key] = data.dataValues[key];
        }
    }

    async #createWhereClause(fields) {
        const model = await this.getModel();
        if (model === undefined || model.tableAttributes === undefined) {
            return undefined;
        }
        const where = {};
        for (const key in model.tableAttributes) {
            if (key === 'id' || key === 'createdAt' || key === 'updatedAt' || fields !== undefined && (key !== fields || !fields.includes(key))) {
                continue;
            }
            const value = this[key];
            if (value === undefined) {
                continue;
            }
            if (this.isRelationTable()) {
                const id = value.id;
                if (id === undefined) {
                    continue;
                }
                where[key] = id;
            } else {
                where[key] = value;
            }
        }
        return where;
    }

}

module.exports = Base;