import { QueueObject, queue } from 'async'
import { inspect } from 'util'
import { logger } from '../../../helpers/logger'
import { CONFIG, INDEXER_QUEUE_CONCURRENCY } from '../../../initializers/constants'
import { IndexableDoc } from '../../../types/indexable-doc.model'
import { client } from '../../../helpers/meilisearch'
import { buildInValuesArray } from '../../meilisearch/meilisearch-queries'
import { EnqueuedTask } from 'meilisearch'

// identifier could be an uuid, an handle or a url for example
export type QueueParam = { host: string, identifier: string }

export abstract class AbstractIndexer <T extends IndexableDoc, DB> {
  protected readonly indexQueue: QueueObject<QueueParam>

  protected abstract readonly primaryKey: keyof DB
  protected abstract readonly filterableAttributes: string[]
  protected abstract readonly sortableAttributes: string[]
  protected abstract readonly searchableAttributes: string[]

  protected readonly rankingRules: string[]

  private elementsToBulkIndex: T[] = []
  private bulkIndexationTimer: any
  private bulkProcessEnqueuedTask: EnqueuedTask

  abstract indexSpecificElement (host: string, uuid: string): Promise<void>

  constructor (
    protected readonly indexName: string,
    protected readonly formatterFn: (o: T) => DB
  ) {
    this.indexQueue = queue<QueueParam, Error>(async (task, cb) => {
      try {
        await this.indexSpecificElement(task.host, task.identifier)

        return cb()
      } catch (err) {
        logger.error(
          { err: inspect(err) },
          'Error in index specific element %s of %s in index %s.', task.identifier, task.host, this.indexName
        )
        cb()
      }
    }, INDEXER_QUEUE_CONCURRENCY)
  }

  async initIndex () {
    const { results } = await client.getIndexes()

    if (!CONFIG.MEILISEARCH.FORCE_SETTINGS_UPDATE_AT_STARTUP && results.some(r => r.uid === this.indexName)) {
      logger.info(this.indexName + ' already exists, skipping configuration')
      return
    }

    logger.info(`Creating/updating "${this.indexName}" index settings`)

    await client.index(this.indexName).updateSearchableAttributes(this.searchableAttributes)
    await client.index(this.indexName).updateFilterableAttributes(this.filterableAttributes)
    await client.index(this.indexName).updateSortableAttributes(this.sortableAttributes)
    await client.index(this.indexName).updateFaceting({ maxValuesPerFacet: 10_000 })
    await client.index(this.indexName).updatePagination({ maxTotalHits: 10_000 })

    if (this.rankingRules) {
      await client.index(this.indexName).updateRankingRules(this.rankingRules)
    }
  }

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

  removeNotExisting (host: string, existingPrimaryKeys: Set<string>) {
    return client.index(this.indexName).deleteDocuments({
      filter: `${this.primaryKey.toString()} NOT IN ${buildInValuesArray(Array.from(existingPrimaryKeys))} AND host = ${host}`
    })
  }

  removeFromHosts (existingHosts: string[]) {
    return client.index(this.indexName).deleteDocuments({
      filter: 'host NOT IN ' + buildInValuesArray(Array.from(existingHosts))
    })
  }

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

  scheduleParallelIndexation (host: string, identifier: string) {
    this.indexQueue.push({ identifier, host })
      .catch(err => logger.error({ err: inspect(err) }, 'Cannot schedule indexation of %s for %s', identifier, host))
  }

  async waitForBulkIndexation () {
    if (!this.bulkProcessEnqueuedTask) return

    await this.waitForTask(this.bulkProcessEnqueuedTask.taskUid, 1000)

    this.bulkProcessEnqueuedTask = undefined
  }

  addElementsToBulkIndex (elements: T[]) {
    this.elementsToBulkIndex = this.elementsToBulkIndex.concat(elements)

    this.scheduleBulkIndexationProcess()
  }

  private scheduleBulkIndexationProcess () {
    if (this.bulkIndexationTimer) return

    this.bulkIndexationTimer = setTimeout(async () => {
      try {
        const elements = this.elementsToBulkIndex
        this.elementsToBulkIndex = []

        logger.info(`Bulk indexing ${elements.length} elements in ${this.indexName}`)

        this.bulkProcessEnqueuedTask = await this.indexElements(elements)

        this.bulkIndexationTimer = undefined
      } catch (err) {
        logger.error({ err }, 'Cannot schedule bulk indexation')
      }
    }, CONFIG.INDEXER.BULK_INDEXATION_INTERVAL_MS)
  }

  private async indexElements (elements: T[]) {
    const documents = elements.map(e => this.formatterFn(e))

    const result = await client.index(this.indexName).updateDocuments(documents, { primaryKey: this.primaryKey.toString() })
    logger.debug(result, 'Indexed ' + documents.length + ' documents in ' + this.indexName)

    return result
  }

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

  private waitForTask (taskId: number, intervalMs?: number) {
    return client.index(this.indexName).waitForTask(taskId, { timeOutMs: 1000 * 60 * 5, intervalMs })
  }
}