stuff.js

import groupby from 'https://esm.sh/lodash.groupby'
import moment from 'https://esm.sh/moment'
import { Transaction } from '../types.ts'

export function calculateTransactionTotals(content: Transaction[]) {
  groupTransactionsByUserAndCurrency(content)
  return prepareData(groupTransactionsByUserAndCurrency(content), content)
}

const calculateTotalAmountsPerCurrency = (transactions) => {
  const result = {}
  Object.keys(transactions).forEach((currency) => {
    result[currency] = transactions[currency].reduce(
      (previous, current) =>
        previous.amount
          ? (parseFloat(previous.amount) * 100 + parseFloat(current.amount) * 100) / 100
          : (parseFloat(previous) * 100 + parseFloat(current.amount) * 100) / 100,
      0,
    )
  })
  return result
}

const groupTransactionsByUser = (content: Transaction) => {
  return groupby(content, 'user_id')
}

const getLastTransactions = (transactionsGroupedByUser) => {
  const lastTransactions = {}
  for (const [userId, transactions] of Object.entries(transactionsGroupedByUser)) {
    lastTransactions[userId] = transactions.reduce((previous, current, index, transaction) => {
      if (moment(previous.timestamp).isBefore(current.timestamp) || moment(previous).isBefore(current.timestamp)) {
        return current.timestamp
      }
      return previous
    }, transactions[0].timestamp)
  }
  return lastTransactions
}

const groupTransactionsByUserAndCurrency = (content) => {
  const transactionsGroupedByUserIdAndCurrency = {}

  for (const [userId, transactions] of Object.entries(groupTransactionsByUser(content))) {
    transactionsGroupedByUserIdAndCurrency[userId] = groupby(transactions, 'currency')
  }
  return transactionsGroupedByUserIdAndCurrency
}

const prepareData = (transactionsGroupedByUserIdAndCurrency, content) => {
  const result = {}
  for (const [userId, transactions] of Object.entries(transactionsGroupedByUserIdAndCurrency)) {
    result[userId] = calculateTotalAmountsPerCurrency(transactions)
    result[userId]['last-activity'] = moment(getLastTransactions(groupTransactionsByUser(content))[userId]).format('YYYY-MM-DD')
  }
  printTable(result)
  return result
}

const printTable = (result) => {
  console.table(result, ['GBP', 'EUR', 'USD', 'last-activity'])
}