Dirty Money: Code Challenge https://jorin.me/dirtymoney

follow-the-dirty-money.md

Follow the dirty money

A shady Internet business has been discovered.

The website has been made public by a whistle blower. We have enough evidence about the dirty deals they did. But to charge them we need to get hands on precise numbers about the transactions that happened on their platform.

Unfortunately no record of the transactions could be seized so far. The only hint we have is this one transaction:

fd0d929f-966f-4d1a-89cd-feee5a1c5347.json

What we need is the total of all transactions in Dollar. Can you trace down all other transactions and get the total?

Be careful to count each transaction only once, even if it is linked multiple times. You can use whatever tool works best.

Please share the total and your solution below!

Cheers, Jorin

@jorinvo

(For 2015 challenge see https://jorin.me/csv-challenge)

@jorinvo No, it's still up (it's GitHub's own link shortener). It's git.io rather than git.to, though :-)

Working PHP solution

<?php

$start = 'https://gist.githubusercontent.com/jorinvo/6f68380dd07e5db3cf5fd48b2465bb04/raw/c02b1e0b45ecb2e54b36e4410d0631a66d474323/fd0d929f-966f-4d1a-89cd-feee5a1c5347.json';
$original = fetch_and_decode($start);
$keyed_array = [];

$keyed_array = process_links($original, $keyed_array);

echo "transactions: " . count($keyed_array) . ", total: " . array_sum($keyed_array) . "\n";

//--

function process_links($payload, $keyed_array) {

  if (!array_key_exists($payload->id, $keyed_array)) {
    $keyed_array[$payload->id] = find_transaction($payload);
  }

  if (count($payload->links) == 0) return $keyed_array;

  foreach($payload->links as $link) {
    $link_fetched = fetch_and_decode($link);
    $keyed_array = process_links($link_fetched, $keyed_array);
  }

  return $keyed_array;
}


function fetch_and_decode($url) {
  return json_decode(file_get_contents($url));
}

function find_transaction($decoded_transaction) {
  preg_match('/\$(\d*(\.|,)\d*)/', $decoded_transaction->content, $matches);
  return(str_replace(',', '.', $matches[1]));
}

tested on php 5.6

transactions: 50, total: 9064.79

@chocolateboy, I see, cool :) But I won't change the links for this post anymore. Next time!

In Elixir (not concurrent yet):

defmodule DirtyMoney do
  def total(link) do
    {:ok, agent} = Agent.start_link(fn -> %{} end)

    follow(link, agent)

    Agent.get agent, fn transactions ->
      transactions
      |> Map.values
      |> Enum.sum
      |> Kernel./(100)
    end
  end

  def follow(link, agent) do
    %{"id" => id, "content" => content, "links" => links} =
      link
      |> HTTPoison.get!([], follow_redirect: true)
      |> Map.fetch!(:body)
      |> Poison.decode!

    count(agent, id, content)

    Enum.each(links, fn link ->
      follow(link, agent)
    end)
  end

  def count(agent, id, content) do
    Agent.update agent, fn transactions ->
      Map.put_new_lazy transactions, id, fn ->
        parse(content)
      end
    end
  end

  def parse(content) do
    [_, whole, part] = Regex.run(~r/\$(\d+)[,.](\d+)/, content)

    cents =
      part
      |> String.pad_trailing(2, "0")
      |> String.to_integer

    cents + String.to_integer(whole) * 100
  end
end

DirtyMoney.total("https://git.io/vDCxb")

There are more amazing answers over at dev.to!

bash, jq, wget, grep, sed, awk:

#!/bin/bash
mkdir xyz && cd xyz
echo -e '0\n1' > /tmp/count
wget https://gist.githubusercontent.com/jorinvo/6f68380dd07e5db3cf5fd48b2465bb04/raw/c02b1e0b45ecb2e54b36e4410d0631a66d474323/fd0d929f-966f-4d1a-89cd-feee5a1c5347.json > /dev/null 2> /dev/null
while [[ $(tail -1 /tmp/count) -ne $(tail -2 /tmp/count | head -1) ]]; do
  jq -r '.links[]' *.json | xargs wget -nc > /dev/null 2> /dev/null
  ls | wc -l >> /tmp/count
done
jq .content *.json | grep -Eo '\$[0-9,.]+[0-9]' | tr -d '$' | sed 's/,/./g' | awk '{sum = sum + $1} END{print sum}'
cd ..
rm -rf ./xyz /tmp/count

9064.79 😄