GoCardless Coding Challenge 1: Fraud Detection Shortest Code Challenge

Code Golf – Transaction Tally.md

Scenario

You're developing a system to analyze transactions for potential fraud.

You have a list of transactions, each with a variety of attributes like amount, currency, status, and a fraud score.

Your goal is to calculate total amounts for different currencies only for transactions flagged non clean.

You shall refactor ONLY the analyze_transactions method to be the shortest possible, without changing any other pieces of the code.

fraud_detection_shortest_code.rb

transactions = [
  { id: 1, amount: 100, currency: 'USD', status: 'potential_fraud', fraud_score: 85 },
  { id: 2, amount: 200, currency: 'EUR', status: 'potential_fraud', fraud_score: 90 },
  { id: 3, amount: 150, currency: 'USD', status: 'clean', fraud_score: 10 },
  { id: 4, amount: 300, currency: 'USD', status: 'potential_fraud', fraud_score: 88 },
  { id: 5, amount: 250, currency: 'EUR', status: 'clean', fraud_score: 5 },
  { id: 6, amount: 400, currency: 'GBP', status: 'potential_fraud', fraud_score: 92 },
  { id: 7, amount: 50,  currency: 'GBP', status: 'potential_fraud', fraud_score: 80 }
]

class Task
  def initialize(transactions)
    @transactions = transactions
  end

  def analyze_transactions
    def total_usd_fraud
      total_usd = 0
      @transactions.each do |tx|
        if tx[:currency] == 'USD' && tx[:status] == 'potential_fraud'
          total_usd += tx[:amount]
        end
      end
      total_usd
    end

    def total_eur_fraud
      total_eur = 0
      @transactions.each do |tx|
        if tx[:currency] == 'EUR' && tx[:status] == 'potential_fraud'
          total_eur += tx[:amount]
        end
      end
      total_eur
    end

    def total_gbp_fraud
      total_gbp = 0
      @transactions.each do |tx|
        if tx[:currency] == 'GBP' && tx[:status] == 'potential_fraud'
          total_gbp += tx[:amount]
        end
      end
      total_gbp
    end
  end

  def run
    analyze_transactions
    puts total_usd_fraud, total_eur_fraud, total_gbp_fraud
  end
end

class Solution
  def initialize(transactions) = @transactions = transactions

  def analyze_transactions
    def method_missing(m,*a)[email protected](&:values).map{_1[2]=~/^#{m[6]}/i&&_1[3]=~/f/?_1[1]:0}.sum
  end

  def run
    analyze_transactions
    puts total_usd_fraud, total_eur_fraud, total_gbp_fraud
  end
end

Task.new(transactions).run
Solution.new(transactions).run

This final version is the shortest I can make, but quite unreadable.

The previous version was a little longer and more readable, because it had whitespace and used .compact instead of a ternary operator.