// @flow

import "@babel/polyfill"

import _ from 'lodash'

import { gzipCompress } from './compressionUtils'
import { sleep } from './asyncUtils'
import System from "./System"
import Module from "./Module"
import { ExtendedError, throwUnsetArg } from './errorUtils' // eslint-disable-line no-unused-vars

import type AWSClient from './AWSClient'

const { log, warn, error, noteGauge, noteCount, noteTimer, trackOp } = new Module(__filename) // eslint-disable-line no-unused-vars

const MAX_PARTITION_CACHE_SIZE = 1000

export default class AthenaClient {

  _awsClient: AWSClient
  _addedPartitions: Array<string>


  constructor(dependencies: { awsClient: AWSClient }) {
    this._awsClient = dependencies.awsClient
    this._addedPartitions = []
  }


  writeAthenaFile = async (items: Array<Object>, options: {|
    bucket: string,
    dirPath: string,
    fileName: string,
    athenaFullTableName?: ?string,
    noLog?: ?boolean,
  |}): Promise<void> => {
    await Promise.all([
  
      // persist data to S3
      (async () => {
        const gzippedBody = await gzipCompress(items.map(item => JSON.stringify(item)).join('\n'))
        await this._awsClient.runS3(s3 => s3.putObject({
          Bucket: options.bucket,
          Key: `${options.dirPath}/${options.fileName}.jsons.gz`,
          Body: gzippedBody, 
          ContentType: 'text/plain',
          ContentEncoding: 'gzip',
          Metadata: {
            'x-amz-meta-items': items.length.toString(),
          },
        }), {
          noLog: true,
        })
      })(),
  
      // create athena partition
      (async () => {
        const athenaFullTableName = options.athenaFullTableName
        if (!athenaFullTableName)
          return
          
        const partitionDesc = options.dirPath
          .split('/')
          .map(part => part.split('='))
          .filter(partParts => partParts.length === 2)
          .map(([ field, value ])=> `${field} = '${value}'`)
          .join(', ')

        const existingPartition = this._addedPartitions.find(p => p === partitionDesc)
        if (!existingPartition) {
          const query = `ALTER TABLE ${athenaFullTableName} ADD IF NOT EXISTS PARTITION (${partitionDesc}) LOCATION 's3://${options.bucket}/${options.dirPath}';`     
          await this.executeAthenaQuery(query, 'add-athena-partition', { dontWaitForCompletion: true, noLog: true })
          
          // maintain partition cache
          this._addedPartitions.unshift(partitionDesc)
          if (this._addedPartitions.length > MAX_PARTITION_CACHE_SIZE)
            this._addedPartitions.pop()
        }
      })(),
      
    ])
  }
  
  executeAthenaQuery = async (query: string, queryName: string, options: ?{ dontWaitForCompletion?: boolean, maxResults?: number, noLog?: boolean }): Promise<Array<Object>> => {
    options = options || {}
    const opts = {
      dontWaitForCompletion: options.dontWaitForCompletion || false,
      maxResults: options.maxResults || 0,
      noLog: options.noLog || false,
    }
    
    return await trackOp(async () => {
      try {     
        let results: Array<Object> = []
        const asyncIterator = await this.executeAthenaQueryAndGetResultIterator(query, queryName)
        if (opts.dontWaitForCompletion)
          return []
        for await (const items of asyncIterator) {
          const reachedMaxResults = opts.maxResults > 0 && results.length + items.length > opts.maxResults
          const itemsToAdd = reachedMaxResults ? items.slice(0, opts.maxResults - results.length) : items
          results = [ ...results, ...itemsToAdd ]
          if (reachedMaxResults)
            break
        }
        return results
      } catch (err) {
        error('Athena query execution failed', { queryName: queryName, query: query, err })
        throw err
      }
    }, `athena-query-${queryName}`, null, { log: !opts.noLog })
  }
  
  executeAthenaQueryAndGetResultIterator = async (query: string, queryName: string): Promise<AsyncGenerator<Array<Object>, void, any>> => {
    try {
      const awsConfig = System.getConfig().aws
      if (!awsConfig)
        throw new Error('aws config not set in system config')
  
      const startMS = Date.now()
      const OUTPUT_LOCATION = `s3://aws-athena-query-results-${ awsConfig.accountId || throwUnsetArg('systemConfig.aws.accountId') }-${ awsConfig.defaultRegion || throwUnsetArg('systemConfig.aws.defaultRegion') }/${System.getConfig().env}/${queryName}/`
  
      // execute query
      const startRes = await this._awsClient.runAthena(athena => athena.startQueryExecution({
        QueryString: query,
        ResultConfiguration: {
          OutputLocation: OUTPUT_LOCATION,
        },
      }))
  
      return iterateAthenaQueryResults(this._awsClient, startRes.result.QueryExecutionId, queryName, query, startMS)
    } catch (err) {
      error('Athena query execution failed', { queryName: queryName, query: query, err })
      throw err
    }
  }
}



async function* iterateAthenaQueryResults(awsClient: AWSClient, queryExecutionId: string, queryName: string, query: string, startMS: number): AsyncGenerator<Array<Object>, void, any> {
  try {
    // wait for query execution to end
    let dataScannedInBytes = 0
    while (true) {
      const statusRes = await awsClient.runAthena(athena => athena.getQueryExecution({
        QueryExecutionId: queryExecutionId,
      }))
      
      const { State, StateChangeReason } = statusRes.result.QueryExecution.Status
      if (State === 'SUCCEEDED') {
        dataScannedInBytes = _.get(statusRes.result.QueryExecution, 'Statistics.DataScannedInBytes')
        break
      } else if (['QUEUED', 'RUNNING'].includes(State)) {
        await sleep(500)
      } else {
        throw new ExtendedError('Athena query failed', { queryName: queryName, state: State, reason: StateChangeReason, query: query })
      }
    }

    const kbScanned = Math.round(dataScannedInBytes / 1000)
    const kbCharged = Math.max(kbScanned, 10 * 1000) // Athena charges a minimum of 10mb for every query
    const costDollar = 5 * kbCharged / 1000000000 // Athena charges 5$ for a TB of data
    noteCount(`${queryName}.kbScanned`, kbScanned)
    noteCount(`${queryName}.kbCharged`, kbCharged)
    noteCount(`${queryName}.dollarsCharged`, costDollar)

    // fetch response
    let nextToken: ?string = null
    do {
      const resultsRes = await awsClient.runAthena(athena => athena.getQueryResults({
        QueryExecutionId: queryExecutionId,
        MaxResults: Infinity,
        NextToken: nextToken,
      }))

      const athenaResults = getAthenaQueryResultLines(resultsRes.result)
      const newResultObjects = csvArrayToObjects(athenaResults)

      yield newResultObjects

      nextToken = resultsRes.result.NextToken      
    } while (nextToken)

    const durationMS = Date.now() - startMS
    // log(`Athena query complete`, { queryName, kbScanned, kbCharged, costDollar, resultsLoaded: resultObjects.length, durationMS: durationMS })
    noteTimer(`${queryName}.duration`, durationMS)
  } catch (err) {
    error('Athena query execution failed', { queryName: queryName, query: query, err })
    throw err
  }
}

function stripQuotes(input: *): * {
  if (typeof input !== 'string')
    return input
  if (input === '')
    return null
  const length = input.length
  if (length < 2 || !input.startsWith('"') || !input.endsWith('"'))
    return input
  return input.substr(1, length - 2)
}

function getAthenaQueryResultLines(res: Object): Array<Array<string>> {
  const rolloutLines: Array<Array<string>> = []     
  const numericTypeNames = ['integer', 'bigint', 'double']
  const columnMetas = res.ResultSet.ResultSetMetadata.ColumnInfo
  rolloutLines.push(columnMetas.map(cm => cm.Name))
  res.ResultSet.Rows
    .splice(1) // skip header
    .forEach(
      row => rolloutLines.push(
        row.Data.map(
          (datum, i) => numericTypeNames
            .includes(columnMetas[i].Type) ? 
            (datum.VarCharValue === undefined ? null : Number(datum.VarCharValue)) : 
            (datum.VarCharValue === undefined ? null : `"${datum.VarCharValue}"`)
        )
      )
    )
  const csvContent = rolloutLines
  return csvContent
}

function csvArrayToObjects(csvArray: Array<Array<string>>) {
  const propNames = csvArray[0]
  const valueLines = csvArray.slice(1)
  const objects = valueLines.map(valueLine => {
    const obj = {}
    valueLine.forEach((value, i) => obj[propNames[i]] = stripQuotes(value))
    return obj
  })
  return objects
}