let UpdateMsg = {};

module.exports = (app) => {
    const maxQueryPerTransaction = 1000;
    let count = 0;
    let HowManyUpdatesWereFinished = 0;

    const countWrongData = () => {
        let query = "SELECT count(1) " +
        " FROM child_table ct " +
        " INNER JOIN main_table mt " +
        " ON( " +
        "    mt.id = ct.fk_id  " +
        " AND ct.msg <> mt.msg";
        return new Promise( (resolve, reject) => {
            app.db.query(query)
                .then(res => {
                    resolve(+res.rows[0].count);
                })
                .catch(err => {
                    reject(err);
                })
        })
    }

    const hasWrongData = () =>{
        return new Promise((resolve, reject) => {
            if(count > 0) {
                resolve(true);
                return ;
            }

            console.log('Check if exists data to fix');
            countWrongData()
                .then(countWrongData => {
                    console.log('exists %d data to fix', countWrongData);
                    count = countWrongData;
                    if(countWrongData === 0){
                        resolve(false);
                        return ;
                    }

                    resolve(true);
                    return ;
                })
                .catch(err => {
                    reject(err);
                    return ;
                });
        })
    }

    const shouldAbort = (err) => {
        if (err) {
        console.error('Error in transaction', err.stack)
        app.db.query('ROLLBACK', (err) => {
            if (err) {
                console.error('Error rolling back client', err.stack)
            }

            done()
            })
        }
        return !!err
    }

    const updateWrongData = function(){
        hasWrongData()
            .then(hasDateToUpdate => {
                if(!hasDateToUpdate){
                    console.log("Finish Process");
                    return ;
                }

                app.db.query('BEGIN', (err) => {
                    if (shouldAbort(err)) return;

                    app.db.query(
                        "UPDATE child_table ct " +
                        " SET msg = mt.msg " +
                        " FROM main_table mt " +
                        " WHERE mt.id = ct.fk_id " +
                        " AND ct.id IN ( " +
                        " SELECT cts.id " +
                        " FROM child_table cts " +
                        " INNER JOIN main_table mts " +
                        " ON( " +
                        " mts.id = cts.fk_id " +
                        " AND AND cts.msg <> mts.msg " +
                        " ) " +
                        " LIMIT " + maxQueryPerTransaction +
                        " )",
                        (err, res) => {
                            if (shouldAbort(err)) return;

                            app.db.query('COMMIT', (err) => {
                                if (err) {
                                    console.error('Error committing transaction', err.stack)
                                }

                                HowManyUpdatesWereFinished += res.rowCount;
                                console.log("How many updates were finished so far? %d", HowManyUpdatesWereFinished)
                                count -= res.rowCount;
                                updateWrongData();
                            })
                        }
                    )
                })
            })
            .catch(err => {
                console.error('Error on check if exists data to update')
            })
        ;
    }

    UpdateMsg = {
        updateWrongData: updateWrongDate
    }

    return UpdateMsg;
}