const { pipe, transform } = require('bluestream')
const mysql = require('mysql')
const { createWriteStream } = require('fs')
const connection = mysql.createConnection({
  socketPath: '/var/run/mysqld/mysqld.sock',
  user: 'root',
  password: 'root',
  dateStrings: true,
})


const asyncQuery = (...args) => {
  return new Promise((resolve, reject) => {
    connection.query(...args, (error, data) => (error ? reject(error) : resolve(data)))
  })
}

async function getTableIds() {
  const rows = await asyncQuery('SELECT table_schema, table_name FROM information_schema.tables')
  return rows
    .filter(({ table_schema: db }) => db !== 'test' && db !== 'vividcortex' && db !== 'information_schema')
    .map(({ table_schema: db, table_name: tableName }) => `${db}.${tableName}`)
}

async function writeTableToFile(tableID) {
  console.log(`Loading ${tableID}`)
  const query = connection.query(`SELECT * from ${tableID}`).stream({ highWaterMark: 100 })
  const serialize = transform(row => JSON.stringify(row) + '\n')
  const file = createWriteStream(`./${tableID}.ndjson`)
  await pipe(
    query,
    serialize,
    file
  )
  console.log(`Done loading ${tableID}`)
}

async function run() {
  connection.connect()
  const tableIds = await getTableIds()
  for (const tableId of tableIds) {
    await writeTableToFile(tableId)
  }
  connection.end()
}

run()