const Flume = require('flumedb')
const Reduce = require('flumeview-reduce')
const FlumeLog = require('flumelog-memory')
const {pull, drain} = require('pull-stream')

function ledger (state, emitter) {
  state.accounts = {}
  state.entries = []

  const db = Flume(FlumeLog())
    .use('entries', Reduce(1, entriesReducer, null, null, state.entries))
    .use('accounts', Reduce(1, accountReducer, null, null, state.accounts))
    .use('balances', Reduce(1, accountBalanceReducer, null, null, state.accounts))

  state.db = db
  state.helpers = {pull, drain}

  pull(db.accounts.stream({live: true}), drain(acct => console.log('added:', acct)))

  function onLoad () {
    emitter.on('accounts', onEvent)
    emitter.on('entries', onEvent)
  }

  function onEvent (data) {
    db.append(data, (err, seq) => {
      if (err) throw err
      emitter.emit(state.events.RENDER)
    })
  }

  emitter.on('DOMContentLoaded', onLoad)
}

function accountBalanceReducer (acc, item) {
  if (item.type !== 'entries') return acc
  const {msg} = item

  acc[msg.debit].debit += msg.amount
  acc[msg.credit].credit += msg.amount
  return acc
}

function entriesReducer (acc, item) {
  if (item.type !== 'entries') return acc
  acc.push(item)
  return acc
}

function accountReducer (acc, item) { // TODO account for account creation of existing account
  if (item.type !== 'accounts') return acc
  const { msg } = item

  if (!acc[msg.name]) {
    acc[msg.name] = msg
    return acc
  }

  Object.assign(acc[msg.name], msg)
  return acc
}

module.exports = ledger