'use strict'

const { Client } = require('pg')

const table = process.argv[2]
const limit = parseInt(process.argv[3], 10) || 0
const st = parseInt(process.argv[4], 10) || 0

console.log(table, limit)
const db = new Client({
  host: "db2.eu.skies.zone",
  user: "postgres",
  password: "fFVejV2QgEIc7RWA5DyE",
  database: "skies_0"
})

const backup = new Client({
  host: "localhost",
  user: "postgres",
  password: "",
  database: "skies_backup"
})

async function start() {
  await db.connect()
  await backup.connect()

  let total = limit

  if (!total) {
    const count = await db.query(`SELECT COUNT(*) FROM "${ table }"`)
    total = parseInt(count.rows[0].count, 10)
  }

  console.log(`Prepare to migrate ${ total } rows`)

  let offset = st
  const ranges = []
  while (offset < total) {
    ranges.push([offset, 1])
    offset += 1
  }

  let completed = 0

  const damaged = []

  while (ranges.length) {
    const [offset, limit] = ranges.shift()

    try {
      console.log(`Checking range ${ offset }-${ offset + limit }`)
      const res = await db.query(`SELECT * FROM "${ table }" OFFSET $1::numeric LIMIT $2::numeric`, [offset, limit])
      completed += res.rows.length
      await insert(backup, table, res.rows)

      console.log(`Completed ${ completed }`)
    } catch (e) {
      console.error(e.message)
      if (limit === 1) {
        damaged.push(offset)
        continue
      }

      const l = Math.floor(limit / 2)
      ranges.unshift([offset, l], [offset + l, limit - l])
    }

  }

  console.log(`Completed: ${ completed }, damaged: ${ damaged.length }`)
  console.log(`Damaged rows: ${ damaged.join(', ') }`)

  await backup.end()
  await db.end()
}

start().catch(console.error.bind(console))

function insert(db, table, payload) {
  const keys = Object.keys(payload[0])
  const values = []
  const data = []
  let ii = 1
  for (const item of payload) {
    const chunk = []

    for (const key of keys) {
      chunk.push(`$${ ii++ }`)
      data.push(item[key])
    }

    values.push(`(${ chunk.join(', ') })`)
  }

  return db.query(`INSERT INTO ${ table }(${ keys.join(", ") }) VALUES ${ values.join(", ") }`, data)
}