Research Square exercise

orders.php

<?php

///////////////////////////////////////////////////////////////////////////////
//
// RESEARCH SQUARE CODING EXERCISE
//
// In this exercise, we would like you to write PHP code capable of solving the
// problems below. To begin, please make a local copy of this file and open it
// using your favorite code editor.
//
// We have designed this exercise to mimic the types of problems we solve on a
// daily basis. It is intended for engineers who are proficient in PHP and we
// expect it will take approximately 30 minutes to complete. The code you write
// will be used solely for evaluation purposes.
//
// During the exercise, you may look for help on Google, php.net, and other
// publicly available resources. However, please do *NOT* ask your friends or
// colleagues for help. We want to see *your* solution.
//
// When you are finished, please paste your solution in the questionnaire form
// OR provide a link to your solution using a tool like GitHub Gist. We will
// run your code on the command line using PHP 7.4.
//
// Your solution will be evaluated using the following criteria:
// - Does it output the correct results?
// - Are there any potential bugs or defects?
// - Is the code pragmatic and easy to understand?
// - Does it continue to work when new inputs are provided?
//
// Good luck!
//
///////////////////////////////////////////////////////////////////////////////


///////////////////////////////////////////////////////////////////////////////
//
// TASK #1
//
// Summary:
//
//   The data file below contains a list of customers and their orders. Use
//   these data to find and print the price of the most expensive order.
//
//   Hint: Open the data file and look at its contents. The `total_price` field
//   holds the price of an order.
//
// Expected output:
//
//   Most expensive order = 500.00
//
///////////////////////////////////////////////////////////////////////////////

$url = 'https://rs-coding-exercise.s3.amazonaws.com/2020/orders-2020-02-10.json';
$response = json_decode(file_get_contents($url), true);

function mostExpensiveOrder(array $orders): string
{
    // sort desc on total_price
    usort($orders, fn(array $a, array $b) => $b['total_price'] <=> $a['total_price']);

    $highestOrderTotal = $orders[0]['total_price'] ?? 0.0;

    return 'Most expensive order = ' . number_format($highestOrderTotal, 2);
}

echo mostExpensiveOrder($response['orders']) . PHP_EOL;

///////////////////////////////////////////////////////////////////////////////
//
// TASK #2
//
// Summary:
//
//   Using this same data file, calculate and print the sum of prices for all
//   orders created in the previous three years, grouped by year.
//
// Expected output:
//
//   Total price of orders in 2018 = 275.00
//   Total price of orders in 2019 = 860.00
//   Total price of orders in 2020 =  20.00
//
///////////////////////////////////////////////////////////////////////////////

function aggregateOrdersByYear(array $orders): array
{
    $summary = [];
    foreach ($orders as $order) {
        if (!isset($order['created_date'])) {
            continue;
        }

        $year = (new \DateTime($order['created_date']))->format('Y');
        $summary[$year] = $order['total_price'] + ($summary[$year] ?? 0);
    }

    return $summary;
}

function reportOrderTotalsByYear(array $reportingYears, array $orders): string
{
    $aggregated = aggregateOrdersByYear($orders);
    $report = '';
    foreach ($reportingYears as $year) {
        $total = $aggregated[$year] ?? 0.0;
        $report .= "Total price of orders in {$year} = " . number_format($total, 2) . PHP_EOL;
    }

    return $report;
}

echo reportOrderTotalsByYear(['2018', '2019', '2020'], $response['orders']);


///////////////////////////////////////////////////////////////////////////////
//
// TASK #3
//
// Summary:
//
//   Using the same data file, find and print the ID and name of the customer
//   with the most orders.
//
// Expected output:
//
//   Customer with the most orders = [CUST-0001] Yoda
//
///////////////////////////////////////////////////////////////////////////////

function countOrdersByCustomer(array $orders = []): array
{
    $summary = [];
    foreach ($orders as $order) {
        if (!isset($order['customer_id'])) {
            continue;
        }

        $summary[$order['customer_id']] = 1 + ($summary[$order['customer_id']] ?? 0);
    }

    return $summary;
}

function customerWithMostOrders(array $orders, array $customers): string
{
    $countByCustomer = countOrdersByCustomer($orders);

    // sort by count desc
    arsort($countByCustomer);
    $mostOrdersCustomerId = array_key_first($countByCustomer) ?? '';

    // reshape customers into [id => name] for easier lookup
    $customerNamesById = array_column($customers, 'name', 'id');
    $mostOrdersCustomerName = $customerNamesById[$mostOrdersCustomerId] ?? '<No Name Found>';

    return "Customer with the most orders = [{$mostOrdersCustomerId}] {$mostOrdersCustomerName}";
}

echo customerWithMostOrders($response['orders'], $response['customers']) . PHP_EOL;