import * as path from 'path'

import { database as db } from './database'
import { LAST_MIGRATION_VERSION } from './constants'
import { logger, readdirPromise } from '../helpers'

async function migrate () {
  const tables = await db.sequelize.getQueryInterface().showAllTables()

  // No tables, we don't need to migrate anything
  // The installer will do that
  if (tables.length === 0) return

  let actualVersion = await db.Application.loadMigrationVersion()
  if (actualVersion === null) {
    await db.Application.create({ migrationVersion: 0 })
    actualVersion = 0
  }

  // No need migrations, abort
  if (actualVersion >= LAST_MIGRATION_VERSION) return

  // If there are a new migration scripts
  logger.info('Begin migrations.')

  const migrationScripts = await getMigrationScripts()

  for (const migrationScript of migrationScripts) {
    try {
      await executeMigration(actualVersion, migrationScript)
    } catch (err) {
      logger.error('Cannot execute migration %s.', migrationScript.version, err)
      process.exit(0)
    }
  }

  logger.info('Migrations finished. New migration version schema: %s', LAST_MIGRATION_VERSION)
}

// ---------------------------------------------------------------------------

export {
  migrate
}

// ---------------------------------------------------------------------------

async function getMigrationScripts () {
  const files = await readdirPromise(path.join(__dirname, 'migrations'))
  const filesToMigrate: {
    version: string,
    script: string
  }[] = []

  files
    .filter(file => file.endsWith('.js.map') === false)
    .forEach(file => {
      // Filename is something like 'version-blabla.js'
      const version = file.split('-')[0]
      filesToMigrate.push({
        version,
        script: file
      })
    })

  return filesToMigrate
}

async function executeMigration (actualVersion: number, entity: { version: string, script: string }) {
  const versionScript = parseInt(entity.version, 10)

  // Do not execute old migration scripts
  if (versionScript <= actualVersion) return undefined

  // Load the migration module and run it
  const migrationScriptName = entity.script
  logger.info('Executing %s migration script.', migrationScriptName)

  const migrationScript = require(path.join(__dirname, 'migrations', migrationScriptName))

  await db.sequelize.transaction(async t => {
    const options = {
      transaction: t,
      queryInterface: db.sequelize.getQueryInterface(),
      sequelize: db.sequelize,
      db
    }

    await migrationScript.up(options)

    // Update the new migration version
    await db.Application.updateMigrationVersion(versionScript, t)
  })
}