task.php

task.php

<?php

/**
 * we have a cart with coupon and we need to calculate the discount amount
 *
 * Note:
 * - the coupon support multiple conditions
 * - the included and excluded are optional
 */
// Order Data
$order                        = new stdClass();
$order->total_cart            = 175;
$order->shipping_cost         = 50;
$order->customer_id           = 101;
$order->cart_content          = [
    ['product_id' => 1, 'product_name' => 'Book', 'product_price' => 5, 'category_id' => 10],
    ['product_id' => 2, 'product_name' => 'Pen', 'product_price' => 1, 'category_id' => 20],
    ['product_id' => 3, 'product_name' => 'Bag', 'product_price' => 120, 'category_id' => 30],
    ['product_id' => 4, 'product_name' => 'Notebook', 'product_price' => 35, 'category_id' => 40],
    ['product_id' => 5, 'product_name' => 'Pencil Case', 'product_price' => 14, 'category_id' => 50]
];
// Coupon Data
$coupon                        = new stdClass();
$coupon->type                  = 'percentage';         // fixed, percentage
$coupon->amount                = 20;                   // Based on type
$coupon->end_date              = strtotime("+1 day");
$coupon->minimum_amount        = 100;
$coupon->free_shipping         = false;                // true, false
$coupon->included_categories   = [10, 20];
$coupon->excluded_categories   = [50];
$coupon->included_products     = [3];
$coupon->excluded_products     = [4, 1];

function calculate_coupon_discount($order, $coupon)
{
    $discounted_amount = 0;

    if ($coupon->end_date < strtotime('now')) {
        return $discounted_amount;
    }

    if ($coupon->free_shipping) {
        $discounted_amount += $order->shipping_cost;
    }

    $included_products = get_included_products($order, $coupon);
    $total_price_of_included_products = array_sum(array_column($included_products, 'product_price'));

    if ($total_price_of_included_products >= $coupon->minimum_amount) {
        $discounted_amount += calculate_discount_amount($total_price_of_included_products, $coupon);
    }

    return $discounted_amount;
}

function calculate_discount_amount($price, $coupon)
{
    return $coupon->type === 'percentage' ?
        ($price * $coupon->amount / 100) :
        $coupon->amount;
}

function get_included_products($order, $coupon)
{
    $included_products = [];

    foreach ($order->cart_content as $product) {
        if (in_array($product['category_id'], array_get($coupon->included_categories))) {
            $included_products[$product['product_id']] = $product;
        }

        if (in_array($product['category_id'], array_get($coupon->excluded_categories))) {
            unset($included_products[$product['product_id']]);
        }

        if (in_array($product['product_id'], array_get($coupon->included_products))) {
            $included_products[$product['product_id']] = $product;
        }

        if (in_array($product['product_id'], array_get($coupon->excluded_products))) {
            unset($included_products[$product['product_id']]);
        }
    }
    return $included_products;
}

function array_get($array, $default = [])
{
    return $array ?? $default;
}

echo calculate_coupon_discount($order, $coupon);