/*!
 * tracker/transaction.js
 * Copyright © 2019 – Katana Cryptographic Ltd. All Rights Reserved.
 */
'use strict'

const _ = require('lodash')
const bitcoin = require('bitcoinjs-lib')
const util = require('../lib/util')
const Logger = require('../lib/logger')
const hdaHelper = require('../lib/bitcoin/hd-accounts-helper')
const db = require('../lib/db/mysql-db-wrapper')
const network = require('../lib/bitcoin/network')
const keys = require('../keys')[network.key]
const gapLimit = [keys.gap.external, keys.gap.internal]
const activeNet = network.network
const TransactionsBundle = require('./transactions-bundle')


/**
 * A class allowing to process a transaction
 */
class Transaction {

  /**
   * Constructor
   * @param {bitcoin.Transaction} tx - transaction object
   */
  constructor(tx) {
    this.tx = tx
    this.txid = this.tx.getId()   
    // Id of transaction stored in db
    this.storedTxnID = null 
    // Should this transaction be broadcast out to connected clients?
    this.doBroadcast = false
  }

  /**
   * Register transaction in db if it's a transaction of interest
   * @returns {object} returns a composite result object
   *  {
   *    tx: <transaction_as_stored_in_db>,
   *    broadcast: <boolean>
   *  }
   */
  async checkTransaction() {
    try {
      // Process transaction inputs
      await this._processInputs()

      // Process transaction outputs
      await this._processOutputs()

      // If this point reached with no errors,
      // store the fact that this transaction was checked.
      TransactionsBundle.cache.set(this.txid, Date.now())

      const tx = await db.getTransaction(this.txid)

      return {
        tx: tx,
        broadcast: this.doBroadcast
      }

    } catch(e) {
      Logger.error(e, 'Transaction.checkTransaction()')
      return Promise.reject(e)
    }
  }

  /**
   * Process transaction inputs
   * @returns {Promise}
   */
  async _processInputs() {
    // Array of inputs spent
    const spends = []
    // Store input indices, keyed by `txid-outindex` for easy retrieval
    const indexedInputs = {}
    // Store database ids of double spend transactions
    const doubleSpentTxnIDs = []
    // Store inputs of interest
    const inputs = [] 

    // Extracts inputs information
    let index = 0

    for (let input of this.tx.ins) {
      const spendTxid = Buffer.from(input.hash).reverse().toString('hex')
      spends.push({txid:spendTxid, index:input.index})
      indexedInputs[`${spendTxid}-${input.index}`] = index
      index++
    }

    // Check if we find some inputs of interest
    const results = await db.getOutputSpends(spends)

    if (results.length == 0)
      return null

    // Flag the transaction for broadcast
    this.doBroadcast = true

    // This transaction is spending an existing output.
    // This is value leaving a wallet's addresses.
    // Each result contains
    //  {outID, addrAddress, outAmount, txnTxid, outIndex, spendingTxnID/null}

    // Store the transaction in db
    await this._ensureTransaction()

    // Prepare the inputs
    for (let r of results) {
      const index = indexedInputs[`${r.txnTxid}-${r.outIndex}`]

      inputs.push({
        txnID: this.storedTxnID,
        outID: r.outID,
        inIndex: index,
        inSequence: this.tx.ins[index].sequence
      })

      // Detect potential double spends
      if (r.spendingTxnID !== null && r.spendingTxnID != this.storedTxnID) {
        Logger.info(`DOUBLE SPEND of ${r.txnTxid}-${r.outIndex} by ${this.txid}!`)
        // Delete the existing transaction that has been double-spent:
        // since the deepest block keeps its transactions, this will
        // eventually work itself out, and the wallet will not show
        // two transactions spending the same output.
        doubleSpentTxnIDs.push(r.spendingTxnID)
      }
    }

    // Record the inputs of interest in the database
    await db.addInputs(inputs)

    // Process the double spends
    if (doubleSpentTxnIDs.length > 0) {
      // Get txids to update LRU cache
      const txs = await db.getTransactionsById(doubleSpentTxnIDs)

      for (let tx of txs)
        TransactionsBundle.cache.del(tx.txnTxid)

      await db.deleteTransactionsByID(doubleSpentTxnIDs)
    }
  }

  /**
   * Process transaction outputs
   * @returns {Promise}
   */
  async _processOutputs() {
    // Store outputs, keyed by address. Values are arrays of outputs
    const indexedOutputs = {}
    
    // Extracts outputs information
    let index = 0

    for (let output of this.tx.outs) {
      try {
        const address = bitcoin.address.fromOutputScript(output.script, activeNet)
        if (!indexedOutputs[address])
          indexedOutputs[address] = []

        indexedOutputs[address].push({
          index,
          value: output.value,
          script: output.script.toString('hex'),
        })
      } catch(e) {}
      index++
    }

    // Array of addresses receiving tx outputs
    const addresses = _.keys(indexedOutputs)
    
    // Store a list of known addresses that received funds
    let fundedAddresses = []

    // Get HD Accounts that own any of the output addresses
    const result = await db.getHDAccountsByAddresses(addresses)

    // Get outputs spending to loose addresses first
    const aLooseAddr = await this._processOutputsLooseAddresses(result.loose, indexedOutputs)
    fundedAddresses = fundedAddresses.concat(aLooseAddr)

    // Get outputs spending to a tracked account
    const aHdAcctAddr = await this._processOutputsHdAccounts(result.hd, indexedOutputs)
    fundedAddresses = fundedAddresses.concat(aHdAcctAddr)

    if (fundedAddresses.length == 0)
      return null

    // Flag the transaction for broadcast
    this.doBroadcast = true

    // Add the transaction to the database
    await this._ensureTransaction()

    // Associate transaction outputs with known addresses
    const outputs = []

    for (let a of fundedAddresses) {
      outputs.push({
        txnID: this.storedTxnID, 
        addrID: a.addrID,
        outIndex: a.outIndex,
        outAmount: a.outAmount,
        outScript: a.outScript,
      })
    }

    await db.addOutputs(outputs)
  }

  /**
   * Process outputs sending to tracked loose addresses
   * @param {object[]} addresses - array of address objects
   * @param {object} indexedOutputs - outputs indexed by address
   * @returns {Promise - object[]} return an array of funded addresses
   *  {addrID: ..., outIndex: ..., outAmount: ..., outScript: ...}
   */
  async _processOutputsLooseAddresses(addresses, indexedOutputs) {
    // Store a list of known addresses that received funds
    const fundedAddresses = []

    // Get outputs spending to loose addresses first
    for (let a of addresses) {
      if (indexedOutputs[a.addrAddress]) {
        for (let output of indexedOutputs[a.addrAddress]) {
          fundedAddresses.push({
            addrID: a.addrID,
            outIndex: output.index,
            outAmount: output.value,
            outScript: output.script,
          })
        }
      }
    }

    return Promise.resolve(fundedAddresses)
  }

  /**
   * Process outputs sending to tracked hd accounts
   * @param {object[]} hdAccounts - array of hd account objects
   * @param {object} indexedOutputs - outputs indexed by address
   * @returns {Promise - object[]} return an array of funded addresses
   *  {addrID: ..., outIndex: ..., outAmount: ..., outScript: ...}
   */
  async _processOutputsHdAccounts(hdAccounts, indexedOutputs) {
    // Store a list of known addresses that received funds
    const fundedAddresses = []
    const xpubList = _.keys(hdAccounts)
    
    if (xpubList.length > 0) {
      await util.seriesCall(xpubList, async xpub => {
        const usedNewAddresses = await this._deriveNewAddresses(
          xpub,
          hdAccounts[xpub],
          indexedOutputs
        )

        const usedNewResults = await db.getAddresses(usedNewAddresses)

        // Append these address results to the hdAccount address list
        Array.prototype.push.apply(hdAccounts[xpub].addresses, usedNewResults)

        for (let entry of hdAccounts[xpub].addresses) {
          if (indexedOutputs[entry.addrAddress]) {
            for (let output of indexedOutputs[entry.addrAddress]) {
              fundedAddresses.push({
                addrID: entry.addrID,
                outIndex: output.index,
                outAmount: output.value,
                outScript: output.script,
              })
            }
          }
        }
      })
    }
    
    return fundedAddresses
  }

  /**
   * Derive new addresses for a hd account
   * Check if tx addresses are at or beyond the next unused
   * index for the HD chain. Derive additional addresses
   * to replace the gap limit and add those addresses to
   * the database. Make sure to account for tx sending to 
   * newly-derived addresses.
   *
   * @param {string} xpub
   * @param {object} hdAccount - hd account object
   * @param {object} indexedOutputs - outputs indexed by address
   * @returns {Promise - object[]} returns an array of the new addresses used
   */
  async _deriveNewAddresses(xpub, hdAccount, indexedOutputs) {
    const hdType = hdAccount.hdType

    let derivedIndices = [-1,-1]

    // Get maximum derived address indices for each chain
    derivedIndices = await db.getHDAccountDerivedIndices(xpub)

    // Get the next unused chain indices for this account
    const unusedIndices = await db.getHDAccountNextUnusedIndices(xpub)

    const newAddresses = []
    const usedNewAddresses = {}

    // Get the maximum used index in the addresses
    for (let chain of [0,1]) {
      // Get addresses for this account that are on this chain
      const chainAddresses = _.filter(hdAccount.addresses, v => {
        return v.hdAddrChain == chain
      })

      if (chainAddresses.length == 0)
        continue

      // Get the maximum used address on this chain
      const chainMaxUsed = _.maxBy(chainAddresses, a => {
        return a.hdAddrIndex
      })

      let chainMaxUsedIndex = chainMaxUsed.hdAddrIndex

      // If max used index will not advance the unused index, move on
      if (chainMaxUsedIndex < unusedIndices[chain])
        continue

      // If max derived index is beyond max used index plus gap limit.
      if (derivedIndices[chain] >= chainMaxUsedIndex + gapLimit[chain]) {
        // Check that we don't have a hole in the next <gapLimit> indices
        const nbDerivedIndicesForward = await db.getHDAccountNbDerivedIndices(
          xpub,
          chain,
          chainMaxUsedIndex,
          chainMaxUsedIndex + gapLimit[chain]
        )

        if (nbDerivedIndicesForward < gapLimit[chain] + 1) {
          // Hole detected. Force derivation.
          derivedIndices[chain] = chainMaxUsedIndex
        } else {
          // Move on
          continue
        }
      }

      let done

      do {
        done = true

        // Derive additional addresses beyond the max index...
        // ..and including the gap limit beyond the max used
        const minIdx = derivedIndices[chain] + 1
        const maxIdx = chainMaxUsedIndex + gapLimit[chain] + 1
        const indices = _.range(minIdx, maxIdx)

        const derived = await hdaHelper.deriveAddresses(xpub, chain, indices, hdType)
        Array.prototype.push.apply(newAddresses, derived)

        Logger.info(`Derived hdID(${hdAccount.hdID}) M/${chain}/${indices.join(',')}`)

        // Update view of derived address indices
        derivedIndices[chain] = chainMaxUsedIndex + gapLimit[chain]

        // Check derived addresses for use in this transaction
        for (let d of derived) {
          if (indexedOutputs[d.address]) {
            Logger.info(`Derived address already in outputs: M/${d.chain}/${d.index}`)
            // This transaction spends to an address
            // beyond the original derived gap limit!
            chainMaxUsedIndex = d.index
            usedNewAddresses[d.address] = d
            done = false
          }
        }
      } while (!done)

    }

    await db.addAddressesToHDAccount(xpub, newAddresses)
    return _.keys(usedNewAddresses)
  }
   

  /**
   * Store the transaction in database
   * @returns {Promise}
   */
  async _ensureTransaction() {
    if (this.storedTxnID == null) {
      this.storedTxnID = await db.ensureTransactionId(this.txid)

      await db.addTransaction({
        txid: this.txid,
        version: this.tx.version,
        locktime: this.tx.locktime,
      })

      Logger.info(`Storing transaction ${this.txid}`)
    }
  }

}

module.exports = Transaction