const EventEmitter = require('safe-event-emitter')
const log = require('loglevel')
const EthQuery = require('ethjs-query')

/**

  Event emitter utility class for tracking the transactions as they<br>
  go from a pending state to a confirmed (mined in a block) state<br>
<br>
  As well as continues broadcast while in the pending state
<br>
@param config {object} - non optional configuration object consists of:
    @param {Object} config.provider - A network provider.
    @param {Object} config.nonceTracker see nonce tracker
    @param {function} config.getPendingTransactions a function for getting an array of transactions,
    @param {function} config.publishTransaction a async function for publishing raw transactions,


@class
*/

class PendingTransactionTracker extends EventEmitter {
  constructor (config) {
    super()
    this.droppedBuffer = {}
    this.query = new EthQuery(config.provider)
    this.nonceTracker = config.nonceTracker
    this.getPendingTransactions = config.getPendingTransactions
    this.getCompletedTransactions = config.getCompletedTransactions
    this.publishTransaction = config.publishTransaction
    this.approveTransaction = config.approveTransaction
    this.confirmTransaction = config.confirmTransaction
  }

  /**
    checks the network for signed txs and releases the nonce global lock if it is
  */
  async updatePendingTxs () {
    // in order to keep the nonceTracker accurate we block it while updating pending transactions
    const nonceGlobalLock = await this.nonceTracker.getGlobalLock()
    try {
      const pendingTxs = this.getPendingTransactions()
      await Promise.all(pendingTxs.map((txMeta) => this._checkPendingTx(txMeta)))
    } catch (err) {
      log.error('PendingTransactionTracker - Error updating pending transactions')
      log.error(err)
    }
    nonceGlobalLock.releaseLock()
  }

  /**
    Will resubmit any transactions who have not been confirmed in a block
    @param block {object} - a block object
    @emits tx:warning
  */
  resubmitPendingTxs (blockNumber) {
    const pending = this.getPendingTransactions()
    // only try resubmitting if their are transactions to resubmit
    if (!pending.length) return
    pending.forEach((txMeta) => this._resubmitTx(txMeta, blockNumber).catch((err) => {
      /*
      Dont marked as failed if the error is a "known" transaction warning
      "there is already a transaction with the same sender-nonce
      but higher/same gas price"

      Also don't mark as failed if it has ever been broadcast successfully.
      A successful broadcast means it may still be mined.
      */
      const errorMessage = err.message.toLowerCase()
      const isKnownTx = (
        // geth
        errorMessage.includes('replacement transaction underpriced') ||
        errorMessage.includes('known transaction') ||
        // parity
        errorMessage.includes('gas price too low to replace') ||
        errorMessage.includes('transaction with the same hash was already imported') ||
        // other
        errorMessage.includes('gateway timeout') ||
        errorMessage.includes('nonce too low')
      )
      // ignore resubmit warnings, return early
      if (isKnownTx) return
      // encountered real error - transition to error state
      txMeta.warning = {
        error: errorMessage,
        message: 'There was an error when resubmitting this transaction.',
      }
      this.emit('tx:warning', txMeta, err)
    }))
  }

  /**
    resubmits the individual txMeta used in resubmitPendingTxs
    @param txMeta {Object} - txMeta object
    @param latestBlockNumber {string} - hex string for the latest block number
    @emits tx:retry
    @returns txHash {string}
  */
  async _resubmitTx (txMeta, latestBlockNumber) {
    if (!txMeta.firstRetryBlockNumber) {
      this.emit('tx:block-update', txMeta, latestBlockNumber)
    }

    const firstRetryBlockNumber = txMeta.firstRetryBlockNumber || latestBlockNumber
    const txBlockDistance = Number.parseInt(latestBlockNumber, 16) - Number.parseInt(firstRetryBlockNumber, 16)

    const retryCount = txMeta.retryCount || 0

    // Exponential backoff to limit retries at publishing
    if (txBlockDistance <= Math.pow(2, retryCount) - 1) return

    // Only auto-submit already-signed txs:
    if (!('rawTx' in txMeta)) return this.approveTransaction(txMeta.id)

    const rawTx = txMeta.rawTx
    const txHash = await this.publishTransaction(rawTx)

    // Increment successful tries:
    this.emit('tx:retry', txMeta)
    return txHash
  }

  /**
    Ask the network for the transaction to see if it has been include in a block
    @param txMeta {Object} - the txMeta object
    @emits tx:failed
    @emits tx:confirmed
    @emits tx:warning
  */
  async _checkPendingTx (txMeta) {
    const txHash = txMeta.hash
    const txId = txMeta.id

    // Only check submitted txs
    if (txMeta.status !== 'submitted') return

    // extra check in case there was an uncaught error during the
    // signature and submission process
    if (!txHash) {
      const noTxHashErr = new Error('We had an error while submitting this transaction, please try again.')
      noTxHashErr.name = 'NoTxHashError'
      this.emit('tx:failed', txId, noTxHashErr)

      return
    }

    // If another tx with the same nonce is mined, set as dropped.
    const taken = await this._checkIfNonceIsTaken(txMeta)
    let dropped
    try {
      // check the network if the nonce is ahead the tx
      // and the tx has not been mined into a block

      dropped = await this._checkIftxWasDropped(txMeta)
      // the dropped buffer is in case we ask a node for the tx
      // that is behind the node we asked for tx count
      // IS A SECURITY FOR HITTING NODES IN INFURA THAT COULD GO OUT
      // OF SYNC.
      // on the next block event it will return fire as dropped
      if (dropped && !this.droppedBuffer[txHash]) {
        this.droppedBuffer[txHash] = true
        dropped = false
      } else if (dropped && this.droppedBuffer[txHash]) {
        // clean up
        delete this.droppedBuffer[txHash]
      }

    } catch (e) {
      log.error(e)
    }
    if (taken || dropped) {
      return this.emit('tx:dropped', txId)
    }

    // get latest transaction status
    try {
      const { blockNumber } = await this.query.getTransactionByHash(txHash) || {}
      if (blockNumber) {
        this.emit('tx:confirmed', txId)
      }
    } catch (err) {
      txMeta.warning = {
        error: err.message,
        message: 'There was a problem loading this transaction.',
      }
      this.emit('tx:warning', txMeta, err)
    }
  }
  /**
    checks to see if if the tx's nonce has been used by another transaction
    @param txMeta {Object} - txMeta object
    @emits tx:dropped
    @returns {boolean}
  */

  async _checkIftxWasDropped (txMeta) {
    const { txParams: { nonce, from }, hash } = txMeta
    const nextNonce = await this.query.getTransactionCount(from)
    const { blockNumber } = await this.query.getTransactionByHash(hash) || {}
    if (!blockNumber && parseInt(nextNonce) > parseInt(nonce)) {
      return true
    }
    return false
  }

  /**
    checks to see if a confirmed txMeta has the same nonce
    @param txMeta {Object} - txMeta object
    @returns {boolean}
  */


  async _checkIfNonceIsTaken (txMeta) {
    const address = txMeta.txParams.from
    const completed = this.getCompletedTransactions(address)
    const sameNonce = completed.filter((otherMeta) => {
      return otherMeta.txParams.nonce === txMeta.txParams.nonce
    })
    return sameNonce.length > 0
  }
}

module.exports = PendingTransactionTracker